High-resolution transmission electron microscopy(TEM),X-ray diffractometry(XRD),energy dispersive spectroscopy(EDS)and hardness test were used to study the re-dissolution and re-precipitation behavior of nano-precipit...High-resolution transmission electron microscopy(TEM),X-ray diffractometry(XRD),energy dispersive spectroscopy(EDS)and hardness test were used to study the re-dissolution and re-precipitation behavior of nano-precipitates of the spray-formed fine-grained Al-Cu-Mg alloy during rapid cold stamping deformation.Results show that the extruded Al-Cu-Mg alloy undergoes obvious re-dissolution and re-precipitation during the rapid cold-stamping deformation process.The plasticθ′phase has a slower re-dissolution rate than the brittle S′phase.The long strip-shaped S′phases and the acicularθ′phases in Al-Cu-Mg alloy after three passes of cold stamping basically re-dissolved to form a supersaturated solid solution.A large number of fine granular balanceθphases precipitate after four passes of rapid cold-stamping deformation.Rapid cold stamping deformation causes the S′phase andθ′phase to break and promote the nano-precipitate phases to re-dissolve.The high distortion free energy of the matrix promotes the precipitation of the equilibriumθphase,and the hardness of the alloy obviously increases from HB 55 to HB 125 after the rapid cold stamping process.展开更多
In the present study, an Al/Cu/Mg multi-layered composite was produced by accumulative roll bonding(ARB) through seven passes, and its microstructure and mechanical properties were evaluated. The microstructure invest...In the present study, an Al/Cu/Mg multi-layered composite was produced by accumulative roll bonding(ARB) through seven passes, and its microstructure and mechanical properties were evaluated. The microstructure investigations show that plastic instability occurred in both the copper and magnesium reinforcements in the primary sandwich. In addition, a composite with a perfectly uniform distribution of copper and magnesium reinforcing layers was produced during the last pass. By increasing the number of ARB cycles, the microhardness of the layers including aluminum, copper, and magnesium was significantly increased. The ultimate tensile strength of the sandwich was enhanced continually and reached a maximum value of 355.5 MPa. This strength value was about 3.2, 2, and 2.1 times higher than the initial strength values for the aluminum, copper, and magnesium sheets, respectively. Investigation of tensile fracture surfaces during the ARB process indicated that the fracture mechanism changed to shear ductile at the seventh pass.展开更多
Corrosion behavior of 2024 Al-Cu-Mg alloy of different tempers was assessed by potentiodynamic polarization studies in 3.5% NaCl solution, 3.5% NaCI＋I.0% H2O2 solution and 3.5% NaCl solution at pH 12. Polarization cu...Corrosion behavior of 2024 Al-Cu-Mg alloy of different tempers was assessed by potentiodynamic polarization studies in 3.5% NaCl solution, 3.5% NaCI＋I.0% H2O2 solution and 3.5% NaCl solution at pH 12. Polarization curves showed shifting of corrosion potential （φPcor） towards more negative potential with increasing ageing time and shifting of φcorr in the positive direction with the addition of H2O2 in NaCl solution. Polarization curves in 3.5% NaCl solution at pH 12 exhibited distinct passivity phenomenon. Optical micrographs of the corroded surfaces showed general corrosion, extensive pitting and intergranular corrosion as well. Cyclic potentiodynamic polarization curves exhibited wide hysteresis loop and the mode of corrosion attack confirmed that the alloy states are susceptible to pit growth damage. Attempts were made to explain the observed corrosion behavior of the alloy of various tempers in different electrolytes with the help of microstructural features.展开更多
The microstructure evolution of spray formed and rapidly solidified Al-Cu-Mg alloy with fine grains during rapid cold punching and recrystallization annealing was investigated by transmission electron microscopy(TEM)....The microstructure evolution of spray formed and rapidly solidified Al-Cu-Mg alloy with fine grains during rapid cold punching and recrystallization annealing was investigated by transmission electron microscopy(TEM). The results show that the precipitates of fine-grained Al-Cu-Mg alloy during rapid cold punching and recrystallization annealing mainly consist of S phase and a small amount of coarse Al6Mn phase. With the increase of deformation passes, the density of precipitates increases, the size of precipitates decreases significantly, and the deformation and transition bands disappear gradually. In addition, the grains are refined and tend to be uniform. Defects introduced by rapid cold punching contribute to the precipitation and recrystallization, and promote nucleation and growth of S phase and recrystallization. Deformation and transition bands in the coarse grains transform into deformation-induced grain boundary during the deformation and recrystallization, which refine grains, obtain uniform nanocrystalline structure and promote homogeneous distribution of S phase.展开更多
The properties of modified conventional wrought aluminum alloys cannot be significantly enhanced by normal post-heat treatment in that the fine-grained strengthening,arising from high cooling rate in SLM,is underutili...The properties of modified conventional wrought aluminum alloys cannot be significantly enhanced by normal post-heat treatment in that the fine-grained strengthening,arising from high cooling rate in SLM,is underutilized.In this work,compared with the normal T6 heat treatment,a novel simple direct aging regime was proposed to maintain the grain-boundary strengthening and to utilize the precipitation strengthening of secondary AlZr.It was found that a heterogeneous grain structure,which consisted of ultrafine equiaxed(~0.82μm)and columnar(~1.80μm)grains at the bottom and top of molten pool,respectively,was formed in the SLM processed sample.After direct aging(DA),the ultrafine grains were maintained and a mass of spherical coherent L1-AlZr particles with a mean radius of approximately1.15 nm was precipitated.In contrast,after solution treatment and aging(STA),a significant grain coarsening occurred in the equiaxed grain region.Meanwhile,the coarsening L1-AlZr particles,nano-sized S phases and GPB zones were detected in the STA sample.This subsequently induced that the yield strength of the DA sample(~435 MPa)was higher than that of the STA sample(~402 MPa)owing to the grain boundary strengthening and precipitation strengthening.Both the STA and DA samples exhibited a higher strength than that of the other SLMed Al-Cu-Mg series alloys;this was comparable to that of the wrought AA2024-T6 alloy(~393 MPa).Both the STA and DA samples exhibited a higher strength than that of the other SLMed Al-Cu-Mg series alloys;this was comparable to that of the wrought AA2024-T6alloy(~393 MPa).展开更多
In this work,the Al-Cu-Mg alloy with different Y(0-0.2 wt%)and Ce(0.5-1.5 wt%)are designed.The effect of mixed addition of Y and Ce on the grain structure and hot tearing for Al-4.4Cu-1.5Mg-0.15Zr alloy was investigat...In this work,the Al-Cu-Mg alloy with different Y(0-0.2 wt%)and Ce(0.5-1.5 wt%)are designed.The effect of mixed addition of Y and Ce on the grain structure and hot tearing for Al-4.4Cu-1.5Mg-0.15Zr alloy was investigated using"cross"hot tearing mould.The results indicate that as rare earth Y and Ce increases,the grain size becomes finer,the grain morphology changes from dendrite to equiaxed grain,and effectively reduce the hot tearing sensitivity coefficient(HTS1)and crack susceptibility coefficient(CSC)of the alloy.With the increase of Ce element(0.5-1.5 wt%),the hot tearing susceptibility of the alloy decreases first and then increases.With the increase of Y element(0-0.2 wt%),the hot tearing sensitivity of the alloy decreases.When the content of rare earth is 0.2 wt%Y+1.0 wt%Ce,the minimum HTS1 value and CSC value of the alloy are 68 and 0.53,respectively.Rare earth Ce refines the alloy microstructure,shortens the feeding channel,and reduces the hot tearing initiation.Meanwhile,the rare earth Y can form Al6Cu6Y phase at the grain boundary,improve the feeding capacity of the alloy.Therefore,appropriate addition of rare earth Y and Ce can effectively reduce the hot tearing tendency of the alloy.展开更多
Transmission electron microscopy(TEM),X-ray diffraction(XRD),electron backscattered diffraction(EBSD),and tensile tests were used to study the effects of strain rates(0.1,1 and 9.1 s^(-1))on the microstructure and mec...Transmission electron microscopy(TEM),X-ray diffraction(XRD),electron backscattered diffraction(EBSD),and tensile tests were used to study the effects of strain rates(0.1,1 and 9.1 s^(-1))on the microstructure and mechanical properties of spray-formed Al-Cu-Mg alloys during large-strain rolling at 420℃.Results show that during hot rolling,the proportion of high-angle grain boundaries(HAGBs)and the degree of dynamic recrystallization(DRX)initially increase and then decrease,whereas the average grain size and dislocation density show the opposite trend with the increase of the strain rate.In addition,the number of S′phases in the matrix decreases,and the grain boundary precipitates(GBPs)become coarser and more discontinuous as the strain rate increases.When the strain rate increases from 0.1 to 9.1 s^(-1),the tensile strength of the alloy decreases from 492.45 to 427.63 MPa,whereas the elongation initially increases from 12.1%to 21.8%and then decreases to 17.7%.展开更多
The mechanical properties and microstructures of Al-8Cu-0.5Mg alloy with and without Ag addition were studied at both room- and elevated-temperatures. The results show that the alloy with Ag is strengthened by a homog...The mechanical properties and microstructures of Al-8Cu-0.5Mg alloy with and without Ag addition were studied at both room- and elevated-temperatures. The results show that the alloy with Ag is strengthened by a homogeneous distribution of coexistent θ′ and ? precipitates on the matrix (001) and (111) planes, respectively, whereas the alloy without Ag by θ′ precipitates only. The small size and high volume fraction of θ′ and ? precipitates in the Ag-containing alloy improve the tensile strength and yield strength, especially those at the elevated temperatures. However, it is also responsible for the decrease in elongation, compared with the alloy without Ag, which is due to the microcracks initiated from the inherent incompatibility between the particles and the Al matrix during deformation.展开更多
Zr modification is an effective method for improving hot-cracking resistance and elevated-temperature mechanical properties during laser powder bed fusion(L-PBF)of traditional medium and high strength wrought aluminum...Zr modification is an effective method for improving hot-cracking resistance and elevated-temperature mechanical properties during laser powder bed fusion(L-PBF)of traditional medium and high strength wrought aluminum alloys.This study investigated the l-PBF processability and elevated-temperature mechanical properties of a Zr-modified 2024Al alloy.It was found that the hot-cracking susceptibility increased with the increased scanning speed,which was in reasonable agreement with the modified Rappaz-Drezet-Gremaud criterion.Furthermore,the primary L1_(2)-Al_(3)Zr precipitates,which acted as ef-ficient nucleation sites,precipitated at the fusion boundary of the melt pool,leading to the formation of a heterogeneous grain structure.The yield strength(YS)of the as-fabricated samples at 150,250,and 350℃was 363,210,and 48 MPa,respectively.Despite the slight decrease to 360 MPa of the YS when tested at 150℃,owing to the additional precipitate strengthening from the L1_(2)-Al_(3)Zr precipitates,the YS achieved yield strengths of 253 and 69 MPa,an increase of 20.5%and 30.4%,when tested at 250 and 350℃,respectively.The yield strengths in both the as-fabricated and T6-treated conditions tested at 150 and 250℃were comparable to those of casting Al-Cu-Mg-Ag alloys and superior to those of traditionally heat-resistant 2219-T6 and 2618-T6 of Al-Cu alloys.展开更多
In present work,a novel crack-free Al-Cu-Mg-Si-Ti alloy with synchronous improved tensile properties and hot-cracking resistance was proposed and successfully manufactured by laser powder bed fusion(LPBF).The microstr...In present work,a novel crack-free Al-Cu-Mg-Si-Ti alloy with synchronous improved tensile properties and hot-cracking resistance was proposed and successfully manufactured by laser powder bed fusion(LPBF).The microstructure evolution behaviors and the corresponding strengthening mechanisms were investigated in detail.The LPBF-processed Al-Cu-Mg-Si-Ti alloy presents a heterogeneous microstructure consisting of ultrafine equiaxed grains(UFGs)at the boundary and coarse columnar grains(CGs)at the center of the single molten pool.Pre-precipitated D022-Al 3 Ti particles were found to act as the nuclei to refine the grains at the boundary of the molten pool during solidification process,which is attributed to the low cooling rate providing the sufficient incubation time for the precipitation of D022-Al 3 Ti.There are two orientation relationships(ORs)betweenα-Al and D022-Al 3 Ti,i.e.[001]α-Al//[001]D022-Al3Ti,(200)α-Al//(200)D022-Al3Ti and[1¯1¯2]α-Al//[¯111]D022-Al3Ti,(1¯11)α-Al//(¯11¯2)D022-Al3Ti,which are two of the eight ORs predicted with the E2EM model.Refined grains in present alloy,no matter for UFGs or CG,exhibited high critical hot-cracking stress,which means a strong hot-cracking resistance.Dual-nanoprecipitation of Cu-,Mg-,and Si-rich Q’and S’phases was introduced to enhance the mechanical performance ofα-Al matrix.The as-built sample exhibits superior tensile properties,with the yield strength(YS)of 473±8 MPa,ultimate tensile strength(UTS)of 541±2 MPa and elongation(EI)of 10.9%±1.2%.展开更多
The effects of pre-deformation following solution treatment on the microstructure and mechanical properties of aged high purity Al-Cu-Mg alloy were studied by tensile test, micro-hardness measurements, transmission el...The effects of pre-deformation following solution treatment on the microstructure and mechanical properties of aged high purity Al-Cu-Mg alloy were studied by tensile test, micro-hardness measurements, transmission electron microscopy and scanning electron microscopy. The micro-hardness measurements indicate that compared with un-deformed samples, the peak hardness is increased and the time to reach peak hardness is reduced with increasing pre-strain. Additionally, a double-peak hardness evolution behavior of cold-rolled （CR） samples was observed during aging. The results of TEM observation show that the number density of S′（Al2CuMg） phase is increased and the size is decreased in CR alloy with increase of pre-strain. The peak hardness and peak strength of the CR alloy are increased because of quantity increasing and refinement of S′ phase and high density dislocation.展开更多
The quench sensitivity of Al-Cu-Mg alloy was investigated at different thicknesses of the thick plate.The quenching process was simulated via finite element analysis(FEA);time-temperature-property(TTP)curves and time-...The quench sensitivity of Al-Cu-Mg alloy was investigated at different thicknesses of the thick plate.The quenching process was simulated via finite element analysis(FEA);time-temperature-property(TTP)curves and time-temperature-transformation(TTT)curves were obtained through hardness test and differential scanning calorimetry(DSC)test;and the microstructural observation was carried out by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).Experimental results exhibit that the quench cooling rate decreases dramatically from the surface to the center of the plate,and the inhomogeneous quenching causes the difference in microstructure.With the decrease in quench cooling rate,constituent particles are coarsening gradually;the quantity of T-phase(Al_(20)Cu_(2)Mn_(3))increases and the S-phase(Al_(2)Cu Mg)decreases.According to the precipitation kinetics analysis,the decrease in S-phase is caused by the increase in precipitate activation energy.So that the center of the plate shows the highest quenching sensitivity,which is consistent with the analysis of time-temperature-property curves and time-temperature-transformation curves.展开更多
To obtain better comprehensive properties of cast Al-Cu-Mg alloys,the secondary aging(T6I6)process(including initial aging,interrupted aging and re-aging stages)was optimized by an orthogonal method.The microstructure...To obtain better comprehensive properties of cast Al-Cu-Mg alloys,the secondary aging(T6I6)process(including initial aging,interrupted aging and re-aging stages)was optimized by an orthogonal method.The microstructures of the optimized Al-Cu-Mg alloy were observed by means of scanning electron microscopy and transmission electron microscopy,and the properties were investigated by hardness measurements,tensile tests,exfoliation corrosion tests,and intergranular corrosion tests.Results show that the S phase andθ’phase simultaneously exist in the T6I6 treated alloy.Appropriately increasing the temperature of the interrupted aging in the T6I6 process can improve the mechanical properties and corrosion resistance of Al-Cu-Mg alloy.The optimal comprehensive properties(tensile strength of 443.6 MPa,hardness of 161.6 HV)of the alloy are obtained by initial aging at 180℃for 2 h,interrupted aging at 90℃for 30 min,and re-aging at 170℃for 4 h.展开更多
The effect of Bagasse ash （BAp） particle reinforcement on the wear behavior of Al-Cu- Mg alloy has been studied. Bagasse ash particles were varied from 0 wt pct-10 wt pct with interval of 2 wt pct. Unlubricated pin-...The effect of Bagasse ash （BAp） particle reinforcement on the wear behavior of Al-Cu- Mg alloy has been studied. Bagasse ash particles were varied from 0 wt pct-10 wt pct with interval of 2 wt pct. Unlubricated pin-on disc tests were conducted to examine the wear behaviour of the aluminium alloy/Bagasse ash particulate composites. The tests were conducted at varying loads, from 5 to 20 N and sliding speeds of 1.26 m/s, 2.51 m/s, 3.77 m/s and 5.02 m/s for a constant sliding distance of 5000 m. The results showed that the wear rates of the A1-Cu-Mg/BAp composites are lower than that of the matrix alloy and further decrease with increasing Bagasse ash content. Wear rate increases as the sliding speed and applied load increase. The microstructure of the worn surface revealed that a large amount of plastic deformation appeared on the surface of the unreinforced alloy. While Bagasse ash reinforced Al-Cu-Mg alloy showed worn out surface that is not smooth, and grooves, scratches and parallel lines were observed. A combination of adhesion and delamination wear was in operation. These results show that improve wear properties is achievable for the aluminium alloy by the addition of Bagasse ash particles as reinforcement material.展开更多
基金Project(2019JJ60050) supported by the Natural Science Foundation of Hunan Province,China
文摘High-resolution transmission electron microscopy(TEM),X-ray diffractometry(XRD),energy dispersive spectroscopy(EDS)and hardness test were used to study the re-dissolution and re-precipitation behavior of nano-precipitates of the spray-formed fine-grained Al-Cu-Mg alloy during rapid cold stamping deformation.Results show that the extruded Al-Cu-Mg alloy undergoes obvious re-dissolution and re-precipitation during the rapid cold-stamping deformation process.The plasticθ′phase has a slower re-dissolution rate than the brittle S′phase.The long strip-shaped S′phases and the acicularθ′phases in Al-Cu-Mg alloy after three passes of cold stamping basically re-dissolved to form a supersaturated solid solution.A large number of fine granular balanceθphases precipitate after four passes of rapid cold-stamping deformation.Rapid cold stamping deformation causes the S′phase andθ′phase to break and promote the nano-precipitate phases to re-dissolve.The high distortion free energy of the matrix promotes the precipitation of the equilibriumθphase,and the hardness of the alloy obviously increases from HB 55 to HB 125 after the rapid cold stamping process.
文摘In the present study, an Al/Cu/Mg multi-layered composite was produced by accumulative roll bonding(ARB) through seven passes, and its microstructure and mechanical properties were evaluated. The microstructure investigations show that plastic instability occurred in both the copper and magnesium reinforcements in the primary sandwich. In addition, a composite with a perfectly uniform distribution of copper and magnesium reinforcing layers was produced during the last pass. By increasing the number of ARB cycles, the microhardness of the layers including aluminum, copper, and magnesium was significantly increased. The ultimate tensile strength of the sandwich was enhanced continually and reached a maximum value of 355.5 MPa. This strength value was about 3.2, 2, and 2.1 times higher than the initial strength values for the aluminum, copper, and magnesium sheets, respectively. Investigation of tensile fracture surfaces during the ARB process indicated that the fracture mechanism changed to shear ductile at the seventh pass.
文摘Corrosion behavior of 2024 Al-Cu-Mg alloy of different tempers was assessed by potentiodynamic polarization studies in 3.5% NaCl solution, 3.5% NaCI＋I.0% H2O2 solution and 3.5% NaCl solution at pH 12. Polarization curves showed shifting of corrosion potential （φPcor） towards more negative potential with increasing ageing time and shifting of φcorr in the positive direction with the addition of H2O2 in NaCl solution. Polarization curves in 3.5% NaCl solution at pH 12 exhibited distinct passivity phenomenon. Optical micrographs of the corroded surfaces showed general corrosion, extensive pitting and intergranular corrosion as well. Cyclic potentiodynamic polarization curves exhibited wide hysteresis loop and the mode of corrosion attack confirmed that the alloy states are susceptible to pit growth damage. Attempts were made to explain the observed corrosion behavior of the alloy of various tempers in different electrolytes with the help of microstructural features.
基金Project(2019JJ60050)supported by the Natural Science Foundation of Hunan Province,China
文摘The microstructure evolution of spray formed and rapidly solidified Al-Cu-Mg alloy with fine grains during rapid cold punching and recrystallization annealing was investigated by transmission electron microscopy(TEM). The results show that the precipitates of fine-grained Al-Cu-Mg alloy during rapid cold punching and recrystallization annealing mainly consist of S phase and a small amount of coarse Al6Mn phase. With the increase of deformation passes, the density of precipitates increases, the size of precipitates decreases significantly, and the deformation and transition bands disappear gradually. In addition, the grains are refined and tend to be uniform. Defects introduced by rapid cold punching contribute to the precipitation and recrystallization, and promote nucleation and growth of S phase and recrystallization. Deformation and transition bands in the coarse grains transform into deformation-induced grain boundary during the deformation and recrystallization, which refine grains, obtain uniform nanocrystalline structure and promote homogeneous distribution of S phase.
基金financially supported by the National Key R&D Program of China(No.2018YFB1106300)the National Natural Science Foundation of China(No.51604227)the Fundamental Research Funds for the Central Universities(No.31020180QD130)。
文摘The properties of modified conventional wrought aluminum alloys cannot be significantly enhanced by normal post-heat treatment in that the fine-grained strengthening,arising from high cooling rate in SLM,is underutilized.In this work,compared with the normal T6 heat treatment,a novel simple direct aging regime was proposed to maintain the grain-boundary strengthening and to utilize the precipitation strengthening of secondary AlZr.It was found that a heterogeneous grain structure,which consisted of ultrafine equiaxed(~0.82μm)and columnar(~1.80μm)grains at the bottom and top of molten pool,respectively,was formed in the SLM processed sample.After direct aging(DA),the ultrafine grains were maintained and a mass of spherical coherent L1-AlZr particles with a mean radius of approximately1.15 nm was precipitated.In contrast,after solution treatment and aging(STA),a significant grain coarsening occurred in the equiaxed grain region.Meanwhile,the coarsening L1-AlZr particles,nano-sized S phases and GPB zones were detected in the STA sample.This subsequently induced that the yield strength of the DA sample(~435 MPa)was higher than that of the STA sample(~402 MPa)owing to the grain boundary strengthening and precipitation strengthening.Both the STA and DA samples exhibited a higher strength than that of the other SLMed Al-Cu-Mg series alloys;this was comparable to that of the wrought AA2024-T6 alloy(~393 MPa).Both the STA and DA samples exhibited a higher strength than that of the other SLMed Al-Cu-Mg series alloys;this was comparable to that of the wrought AA2024-T6alloy(~393 MPa).
基金supported by the National Natural Science Foundation of China(No.51875365)the Liaoning Province Science and Technology Plan Joint Fund Project(Nos.2023-BSBA-248 and 2023-MSLH-265)the Scientific Research Fund of Liaoning Provincial Education Department(No.LJKZ0122).
文摘In this work,the Al-Cu-Mg alloy with different Y(0-0.2 wt%)and Ce(0.5-1.5 wt%)are designed.The effect of mixed addition of Y and Ce on the grain structure and hot tearing for Al-4.4Cu-1.5Mg-0.15Zr alloy was investigated using"cross"hot tearing mould.The results indicate that as rare earth Y and Ce increases,the grain size becomes finer,the grain morphology changes from dendrite to equiaxed grain,and effectively reduce the hot tearing sensitivity coefficient(HTS1)and crack susceptibility coefficient(CSC)of the alloy.With the increase of Ce element(0.5-1.5 wt%),the hot tearing susceptibility of the alloy decreases first and then increases.With the increase of Y element(0-0.2 wt%),the hot tearing sensitivity of the alloy decreases.When the content of rare earth is 0.2 wt%Y+1.0 wt%Ce,the minimum HTS1 value and CSC value of the alloy are 68 and 0.53,respectively.Rare earth Ce refines the alloy microstructure,shortens the feeding channel,and reduces the hot tearing initiation.Meanwhile,the rare earth Y can form Al6Cu6Y phase at the grain boundary,improve the feeding capacity of the alloy.Therefore,appropriate addition of rare earth Y and Ce can effectively reduce the hot tearing tendency of the alloy.
基金financially supported by the Major Special Projects in Anhui Province,China(No.202003c08020005)the Key Projects in Hunan Province,China(No.2020GK2045)。
文摘Transmission electron microscopy(TEM),X-ray diffraction(XRD),electron backscattered diffraction(EBSD),and tensile tests were used to study the effects of strain rates(0.1,1 and 9.1 s^(-1))on the microstructure and mechanical properties of spray-formed Al-Cu-Mg alloys during large-strain rolling at 420℃.Results show that during hot rolling,the proportion of high-angle grain boundaries(HAGBs)and the degree of dynamic recrystallization(DRX)initially increase and then decrease,whereas the average grain size and dislocation density show the opposite trend with the increase of the strain rate.In addition,the number of S′phases in the matrix decreases,and the grain boundary precipitates(GBPs)become coarser and more discontinuous as the strain rate increases.When the strain rate increases from 0.1 to 9.1 s^(-1),the tensile strength of the alloy decreases from 492.45 to 427.63 MPa,whereas the elongation initially increases from 12.1%to 21.8%and then decreases to 17.7%.
基金Project(2005CB623704) supported by the State Key Fundamental Research Project on Al, China
文摘The mechanical properties and microstructures of Al-8Cu-0.5Mg alloy with and without Ag addition were studied at both room- and elevated-temperatures. The results show that the alloy with Ag is strengthened by a homogeneous distribution of coexistent θ′ and ? precipitates on the matrix (001) and (111) planes, respectively, whereas the alloy without Ag by θ′ precipitates only. The small size and high volume fraction of θ′ and ? precipitates in the Ag-containing alloy improve the tensile strength and yield strength, especially those at the elevated temperatures. However, it is also responsible for the decrease in elongation, compared with the alloy without Ag, which is due to the microcracks initiated from the inherent incompatibility between the particles and the Al matrix during deformation.
基金The work was financially supported by the National Key R&D Program of China(No.2016YFB1100100)the Research Fund of the State Key Laboratory of Solidification Processing(NPU),China(No.2020-TZ-02)+3 种基金the Advance Research Projects in the Field of Manned Spaceflight(No.040302)the Shanghai Aerospace Science and Technology Innovation Fund Project(No.SAST2018-066)This work was also supported by the“Fundamental Research Funds for the Central Universities”(No.G2021KY05104)the“Natural Science Basis Research Plan in Shaanxi Province of China”(No.2022JQ-479).We would like to thank Editage(www.editage.com)for En-glish language editing.
文摘Zr modification is an effective method for improving hot-cracking resistance and elevated-temperature mechanical properties during laser powder bed fusion(L-PBF)of traditional medium and high strength wrought aluminum alloys.This study investigated the l-PBF processability and elevated-temperature mechanical properties of a Zr-modified 2024Al alloy.It was found that the hot-cracking susceptibility increased with the increased scanning speed,which was in reasonable agreement with the modified Rappaz-Drezet-Gremaud criterion.Furthermore,the primary L1_(2)-Al_(3)Zr precipitates,which acted as ef-ficient nucleation sites,precipitated at the fusion boundary of the melt pool,leading to the formation of a heterogeneous grain structure.The yield strength(YS)of the as-fabricated samples at 150,250,and 350℃was 363,210,and 48 MPa,respectively.Despite the slight decrease to 360 MPa of the YS when tested at 150℃,owing to the additional precipitate strengthening from the L1_(2)-Al_(3)Zr precipitates,the YS achieved yield strengths of 253 and 69 MPa,an increase of 20.5%and 30.4%,when tested at 250 and 350℃,respectively.The yield strengths in both the as-fabricated and T6-treated conditions tested at 150 and 250℃were comparable to those of casting Al-Cu-Mg-Ag alloys and superior to those of traditionally heat-resistant 2219-T6 and 2618-T6 of Al-Cu alloys.
基金supported by the National Key R&D Program of China(No.2016YFB1100100)the National Natural Sci-ence Foundation of China(No.52005411)the Research Fund of the State Key Laboratory of Solidification Processing(NPU),China(No.2020-TZ-02).One of the authors,Q.Z.Wang,is grateful for the fi-nancial supports provided by the China Scholarship Council(Grant No.202106290075).
文摘In present work,a novel crack-free Al-Cu-Mg-Si-Ti alloy with synchronous improved tensile properties and hot-cracking resistance was proposed and successfully manufactured by laser powder bed fusion(LPBF).The microstructure evolution behaviors and the corresponding strengthening mechanisms were investigated in detail.The LPBF-processed Al-Cu-Mg-Si-Ti alloy presents a heterogeneous microstructure consisting of ultrafine equiaxed grains(UFGs)at the boundary and coarse columnar grains(CGs)at the center of the single molten pool.Pre-precipitated D022-Al 3 Ti particles were found to act as the nuclei to refine the grains at the boundary of the molten pool during solidification process,which is attributed to the low cooling rate providing the sufficient incubation time for the precipitation of D022-Al 3 Ti.There are two orientation relationships(ORs)betweenα-Al and D022-Al 3 Ti,i.e.[001]α-Al//[001]D022-Al3Ti,(200)α-Al//(200)D022-Al3Ti and[1¯1¯2]α-Al//[¯111]D022-Al3Ti,(1¯11)α-Al//(¯11¯2)D022-Al3Ti,which are two of the eight ORs predicted with the E2EM model.Refined grains in present alloy,no matter for UFGs or CG,exhibited high critical hot-cracking stress,which means a strong hot-cracking resistance.Dual-nanoprecipitation of Cu-,Mg-,and Si-rich Q’and S’phases was introduced to enhance the mechanical performance ofα-Al matrix.The as-built sample exhibits superior tensile properties,with the yield strength(YS)of 473±8 MPa,ultimate tensile strength(UTS)of 541±2 MPa and elongation(EI)of 10.9%±1.2%.
基金Project(51301209)supported by the National Natural Science Foundation of China
文摘The effects of pre-deformation following solution treatment on the microstructure and mechanical properties of aged high purity Al-Cu-Mg alloy were studied by tensile test, micro-hardness measurements, transmission electron microscopy and scanning electron microscopy. The micro-hardness measurements indicate that compared with un-deformed samples, the peak hardness is increased and the time to reach peak hardness is reduced with increasing pre-strain. Additionally, a double-peak hardness evolution behavior of cold-rolled （CR） samples was observed during aging. The results of TEM observation show that the number density of S′（Al2CuMg） phase is increased and the size is decreased in CR alloy with increase of pre-strain. The peak hardness and peak strength of the CR alloy are increased because of quantity increasing and refinement of S′ phase and high density dislocation.
基金financially supported by the National Defense Supporting Research Program(No.JPPT-125GJGG-08-01)。
文摘The quench sensitivity of Al-Cu-Mg alloy was investigated at different thicknesses of the thick plate.The quenching process was simulated via finite element analysis(FEA);time-temperature-property(TTP)curves and time-temperature-transformation(TTT)curves were obtained through hardness test and differential scanning calorimetry(DSC)test;and the microstructural observation was carried out by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).Experimental results exhibit that the quench cooling rate decreases dramatically from the surface to the center of the plate,and the inhomogeneous quenching causes the difference in microstructure.With the decrease in quench cooling rate,constituent particles are coarsening gradually;the quantity of T-phase(Al_(20)Cu_(2)Mn_(3))increases and the S-phase(Al_(2)Cu Mg)decreases.According to the precipitation kinetics analysis,the decrease in S-phase is caused by the increase in precipitate activation energy.So that the center of the plate shows the highest quenching sensitivity,which is consistent with the analysis of time-temperature-property curves and time-temperature-transformation curves.
基金financially supported by the Program for National Key Research and Development Plan(No.2017YFB1104000)the National Natural Science Foundation of China(No.51574167)+1 种基金the Liaoning Natural Science Foundation(No.2021-MS-235)the Science and Technology Program of Liaoning Provincial Department of Education(No.LJGD2020010)。
文摘To obtain better comprehensive properties of cast Al-Cu-Mg alloys,the secondary aging(T6I6)process(including initial aging,interrupted aging and re-aging stages)was optimized by an orthogonal method.The microstructures of the optimized Al-Cu-Mg alloy were observed by means of scanning electron microscopy and transmission electron microscopy,and the properties were investigated by hardness measurements,tensile tests,exfoliation corrosion tests,and intergranular corrosion tests.Results show that the S phase andθ’phase simultaneously exist in the T6I6 treated alloy.Appropriately increasing the temperature of the interrupted aging in the T6I6 process can improve the mechanical properties and corrosion resistance of Al-Cu-Mg alloy.The optimal comprehensive properties(tensile strength of 443.6 MPa,hardness of 161.6 HV)of the alloy are obtained by initial aging at 180℃for 2 h,interrupted aging at 90℃for 30 min,and re-aging at 170℃for 4 h.
文摘The effect of Bagasse ash （BAp） particle reinforcement on the wear behavior of Al-Cu- Mg alloy has been studied. Bagasse ash particles were varied from 0 wt pct-10 wt pct with interval of 2 wt pct. Unlubricated pin-on disc tests were conducted to examine the wear behaviour of the aluminium alloy/Bagasse ash particulate composites. The tests were conducted at varying loads, from 5 to 20 N and sliding speeds of 1.26 m/s, 2.51 m/s, 3.77 m/s and 5.02 m/s for a constant sliding distance of 5000 m. The results showed that the wear rates of the A1-Cu-Mg/BAp composites are lower than that of the matrix alloy and further decrease with increasing Bagasse ash content. Wear rate increases as the sliding speed and applied load increase. The microstructure of the worn surface revealed that a large amount of plastic deformation appeared on the surface of the unreinforced alloy. While Bagasse ash reinforced Al-Cu-Mg alloy showed worn out surface that is not smooth, and grooves, scratches and parallel lines were observed. A combination of adhesion and delamination wear was in operation. These results show that improve wear properties is achievable for the aluminium alloy by the addition of Bagasse ash particles as reinforcement material.
