The influence of rolling at liquid nitrogen temperature and annealing on the microstructure and mechanical properties of Al 5083 alloy was studied in this paper. Cryorolled samples of Al 5083 show significant improvem...The influence of rolling at liquid nitrogen temperature and annealing on the microstructure and mechanical properties of Al 5083 alloy was studied in this paper. Cryorolled samples of Al 5083 show significant improvements in strength and hardness. The ultimate tensile strength increases up to 340 MPa and 390 MPa for the 30% and 50% cryorolled samples, respectively. The cryorolled samples, with 30% and 50% reduction, were subjected to Charpy impact testing at various temperatures from 190℃ to 100℃. It is observed that increasing the percentage of reduction of samples during cryorolling has significant effect on decreasing impact toughness at all temperatures by increasing yield strength and decreasing ductility. Annealing of samples after cryorolling shows remarkable increment in impact toughness through recovery and recrystallization. The average grain size of the 50% cryorolled sample （14 μm） after annealing at 350℃ for 1 h is found to be finer than that of the 30% cryorolled sample （25 μm）. The scanning electron microscopy （SEM） analysis of fractured surfaces shows a large-size dimpled morphology, resembling the ductile fracture mechanism in the starting material and fibrous structure with very fine dimples in cryorolled samples corresponding to the brittle fracture mechanism.展开更多
To investigate the effect of post cryorolling treatments on simultaneous enhancement in strength and ductility of ultrafine grained material （UFG）, AI 6061 alloy was subjected to cryorolling followed by warm rolling...To investigate the effect of post cryorolling treatments on simultaneous enhancement in strength and ductility of ultrafine grained material （UFG）, AI 6061 alloy was subjected to cryorolling followed by warm rolling （CR ＋ WR） and compared with cryorolling followed by short annealing （CR ＋ SA） at the same temperature. Transmission electron microscopy （TEM） was used to characterize the microstructural features of the processed material. The mechanical properties were investigated through Vickers hardness testing and tensile testing at room temperature. TEM, X-ray diffraction （XRD） and differential scanning calorimetry （DSC） were used to investigate the precipitation evolution in UFG material. Results indicated that the alloy subjected to CR ＋ WR has shown improved mechanical properties （114 HV, ultimate tensile strength （UTS）： 350 MPa） as compared to that in the case of CR ＋ SA （105 HV, UTS： 285 MPa）. The size of the precipitates observed in CR ＋ WR sample after peak ageing treatment is finer than that of peak aged CR ＋ SA sample. The UTS of peak aged CR ＋ WR sample （UTS： 390 MPa） was found to be higher than that of peak aged CR ＋ SA sample （UTS： 355 MPa）, without decrease in ductility.展开更多
Nanocomposite Ti-Si-N thin films have been deposited on Si （100） substrate by direct current/radio frequency （DC/RF） magnetron sputtering. The effect of varying deposition parameters on the structure and mechanica...Nanocomposite Ti-Si-N thin films have been deposited on Si （100） substrate by direct current/radio frequency （DC/RF） magnetron sputtering. The effect of varying deposition parameters on the structure and mechanical properties of Ti-Si-N films has been investigated by characterization techniques such as X-ray dif- fraction （XRD）, field emission scanning electron microscopy （FE-SEM）, atomic force microscopy （AFM） and nanoindentation, respectively. XRD analysis of the thin films exhibit all （111）, （200） and （220） peaks initially with varying sputtering pressure, but （111） peak dominates at higher sputtering pressure. The crystallite size calculated from XRD peaks shows that it increases with increasing sputtering pressure. Microstructural analy- sis reveals that the dense blurred grains transform into uniform grains in the films and shows porosity with increasing sputtering pressure. The surface roughness of the Ti-Si-N films increases with varying sputtering pressure. The hardness and Youngrs modulus values of Ti-Si-N films are 33.7 and 278.6 GPa, respectively, with 0.7 Pa sputtering pressure but it decreases with further increase in sputtering pressure due to an increase in porosity of the films.展开更多
The mechanical properties and microstructural evolution of zircaloy-4 subjected to cumulative strains of 1.48,2.96,4.44 and 5.91 through multiaxial forging（MAF） at cryogenic temperature（77 K） were investigated.The...The mechanical properties and microstructural evolution of zircaloy-4 subjected to cumulative strains of 1.48,2.96,4.44 and 5.91 through multiaxial forging（MAF） at cryogenic temperature（77 K） were investigated.The mechanical properties of the MAF treated alloy were measured through universal tensile testing and Vickers hardness testing equipment.The zircaloy-4 deformed up to a cumulative strain of 5.91 showed improvement in both ultimate tensile strength and hardness from 474 MPa to 717 MPa and from HV 190 to HV 238,respectively,as compared with the as-received alloy.However,there was a noticeable decrement in ductility（from 18%to 3.5%） due to the low strain hardening ability of deformed zircaloy-4.The improvement in strength and hardness of the deformed alloy is attributed to the grain size effect and higher dislocation density generated during multiaxial forging.The microstructural evolutions of deformed samples were characterized by optical microscopy and transmission electron microscopy（TEM）.The evolved microstructure at a cumulative strain of 5.91 obtained after MAF up to 12 cycles depicted the formation of ultrafine grains with an average size of 150-250 nm.展开更多
This study deals with the development of drum brake liner for a multi-utility vehicle possessing a hydraulic brake system by varying 7 weight%of steel fiber and stainless steel fiber each,in friction composite formula...This study deals with the development of drum brake liner for a multi-utility vehicle possessing a hydraulic brake system by varying 7 weight%of steel fiber and stainless steel fiber each,in friction composite formulations.The developed friction composites were tested for physical,chemical,corrosion,mechanical,thermal properties,and tribological characteristics,under near-actual conditions using an inertia dynamometer as per industrial standards.Finite element analysis software(ANSYS)analysis was performed to show the thermal stress distribution of the developed friction composites at the maximum temperature rise due to heat generated during brake stops,and an extensive evaluation method was used to rank the composites.The study concludes that the brake factor of the stainless steel fiber-based friction composite produces stable performance in all conditions with a lower liner temperature rise of 340°C and lower thermal stress at 4.255294 MPa.However,the steel fiber-based composites produced high performance at the beginning but deteriorated after a certain period due to higher levels of corrosion and a high temperature rise of 361°C resulting in a negative fade(-0.84%)and more thermal stress(5.619102 MPa).The primary plateau,secondary plateau,back transfer of drum wear debris,and the distribution of constituents on the worn surface of the developed composites in a resin matrix were identified and studied using a scanning electron microscope(SEM)equipped with energy-dispersive spectroscopy.展开更多
In the present work, 6082 Al alloy has been rolled to 40% and 70% thickness reductions at the cryogenic and room temperatures for the improvement in mechanical and fracture toughness properties. All cryorolled samples...In the present work, 6082 Al alloy has been rolled to 40% and 70% thickness reductions at the cryogenic and room temperatures for the improvement in mechanical and fracture toughness properties. All cryorolled samples are subjected to aging at different temperatures, i.e., 140, 160, and 190 ℃ to improve the strength, ductility, and fracture toughness. The microstructures of the cryorolled （CR） and room temperature rolled （RTR） alloy after 40% and 70% thickness reductions are characterized by FE-SEM to reveal the modes of failure. The results show that the starting bulk Al alloy specimen is fractured in total ductile manner, consisting of well-developed dimples over the entire surface. The mechanical properties and fracture toughness of the 70% CR alloy are found better than 70% RTR alloy due to higher dislocations density and formation of sub-grain structures in the CR alloy.展开更多
FeCrBMnSi alloy coating on steel substrate（310S） was fabricated by a high-velocity arc spraying（HVAS） process. Degradation behavior of the coatings at temperatures of 700℃ and 900℃ in air and in the coal fired b...FeCrBMnSi alloy coating on steel substrate（310S） was fabricated by a high-velocity arc spraying（HVAS） process. Degradation behavior of the coatings at temperatures of 700℃ and 900℃ in air and in the coal fired boiler at（700±10）℃ was studied. X-ray difraction（XRD） and scanning electron microscopy/energydisperse spectroscopy（SEM/EDS） were used to characterize the coating as well as to analyze the corrosion products for elucidating the corrosion mechanisms.Coating exhibited dense and globular morphology and the splats were interconnected as evident from SEM analysis. The maximum microhardness of the coating was found to be 630–1060 HV. The FeCrBMnSi alloy coating has imparted necessary resistance to oxidation and showed good adherence to the 310S substrate during the exposures with no tendency for spallation of its oxide scale.展开更多
The texture and mechanical properties of cross-rolled zircaloy-2 at 77 and 300 K were investigated.Crossrolling at 77 K was performed to impart different thickness reductions of 25% and 50%,while at 300 K with 25%,50%...The texture and mechanical properties of cross-rolled zircaloy-2 at 77 and 300 K were investigated.Crossrolling at 77 K was performed to impart different thickness reductions of 25% and 50%,while at 300 K with 25%,50%,75% and 85% reductions to the sample.EBSD analysis of deformed sample showed that near-basal orientation is not deformed completely after 50% rolling reduction.The activation of prismatic silp,{1122} contraction twin and {1012} extension twin were evident from the deformed microstructure at 77 K.The propensity for activation of basal slip〈a〉 at77 K was also observed.The deformation of the sample at 300 K occurs by prismatic,basal 〈a〉 and pyramidal 〈c＋a〉slips,which were predicted by pole figures.After annealing,the tensile strengths（735 and 710 MPa） are almost the same for 50% cryo-cross-rolled and room-temperature cross-rolled zircaloy-2 with almost 2.7% difference in their ductility.KAM analysis of the deformed samples was made to estimate the stored strain energy and dislocation density.Annealing of deformed sample at 673 K for 30 min results in recrystallization,which leads to the formation of ultrafine grains.展开更多
The influence of cryorolling(CR),room temperature rolling(RTR)and post annealing on precipitation,microstructuralevolution(recovery,recrystallisation and grain growth),mechanical and corrosion behavior,was investigate...The influence of cryorolling(CR),room temperature rolling(RTR)and post annealing on precipitation,microstructuralevolution(recovery,recrystallisation and grain growth),mechanical and corrosion behavior,was investigated in the present work.The precipitation kinetics and microstructural morphology of CR,RTR,and post annealed samples were investigated by differentialscanning calorimetry(DSC),transmission electron microscopy(TEM),and electron back scattered diffraction(EBSD)to elucidatethe observed mechanical properties.After annealing at200°C,UTS and hardness of CR samples(345MPa and HV127)wereimproved as compared to RTR samples(320MPa and HV115).The increase in hardness and UTS of CR samples after annealing at200°C was due to precipitation ofβ''from Al matrix,which imparted higher Zener drag effect as compared to RTR samples.Theimprovement in corrosion and pitting potentials was observed for CR samples(?1.321V and?700mV)as compared to RTRsamples(?1.335V and?710mV).In CR samples,heavy dislocation density and dissolution of Mg4Al3Si4-precipitates in the Almatrix have improved corrosion resistance of the alloy through formation of protective passive layer and suppression of galvanic cell,respectively.展开更多
The objective of the present work is to investigate the effect of various sputtering parameters such as nitrogen flow rate, deposition time and sputtering pressure on structural, wettability and optical properties of ...The objective of the present work is to investigate the effect of various sputtering parameters such as nitrogen flow rate, deposition time and sputtering pressure on structural, wettability and optical properties of titanium oxynitride films deposited on glass substrate by reactive magnetron sputtering. The X-ray diffraction graphs of titanium oxynitride films show evolution of various textures of TiO=N and TiN phases with increasing nitrogen flow rate and deposition time, but an increase in sputtering pressure from 4.0 to 8.0 Pa results in decline of various textures observed for TiO=Ny and TiN phases. The stress and strain calculated by sin2~ method are compressive, which decrease with increasing nitrogen flow rate from 55 to I00 sccm （standard cubic centimeter per minute） and increase with increasing deposition time from 80 to I40 min due to atomic penning effect and increasing thickness of the deposited films. The titanium oxynitride films have contact angle values above 90 deg., indicating that films are hydrophobic. The maximum contact angle of I09.1 deg. is observed at deposition time of 140 min. This water repellent property can add value to potential protective, wear and corrosion resistant application of titanium oxynitride films. The band gap decreases from 1.98 to 1.83 eV as nitrogen flow rate is increased from 55 to 100 sccm; it decreases from 1.93 to 1.79 eV as deposition time is increased from 80 to 140 min as more nitrogen incorporation results in higher negative potential of valence band N2p orbital. But it increases from 2.26 to 2.34 eV for titanium oxynitride films as sputtering pressure increases from 4.0 to 8.0 Pa.展开更多
基金One of the authors (R. Jayaganthan) thanks DST,New Delhi for the financial support of this work throughgrant No. DST-462-MMD
文摘The influence of rolling at liquid nitrogen temperature and annealing on the microstructure and mechanical properties of Al 5083 alloy was studied in this paper. Cryorolled samples of Al 5083 show significant improvements in strength and hardness. The ultimate tensile strength increases up to 340 MPa and 390 MPa for the 30% and 50% cryorolled samples, respectively. The cryorolled samples, with 30% and 50% reduction, were subjected to Charpy impact testing at various temperatures from 190℃ to 100℃. It is observed that increasing the percentage of reduction of samples during cryorolling has significant effect on decreasing impact toughness at all temperatures by increasing yield strength and decreasing ductility. Annealing of samples after cryorolling shows remarkable increment in impact toughness through recovery and recrystallization. The average grain size of the 50% cryorolled sample （14 μm） after annealing at 350℃ for 1 h is found to be finer than that of the 30% cryorolled sample （25 μm）. The scanning electron microscopy （SEM） analysis of fractured surfaces shows a large-size dimpled morphology, resembling the ductile fracture mechanism in the starting material and fibrous structure with very fine dimples in cryorolled samples corresponding to the brittle fracture mechanism.
文摘To investigate the effect of post cryorolling treatments on simultaneous enhancement in strength and ductility of ultrafine grained material （UFG）, AI 6061 alloy was subjected to cryorolling followed by warm rolling （CR ＋ WR） and compared with cryorolling followed by short annealing （CR ＋ SA） at the same temperature. Transmission electron microscopy （TEM） was used to characterize the microstructural features of the processed material. The mechanical properties were investigated through Vickers hardness testing and tensile testing at room temperature. TEM, X-ray diffraction （XRD） and differential scanning calorimetry （DSC） were used to investigate the precipitation evolution in UFG material. Results indicated that the alloy subjected to CR ＋ WR has shown improved mechanical properties （114 HV, ultimate tensile strength （UTS）： 350 MPa） as compared to that in the case of CR ＋ SA （105 HV, UTS： 285 MPa）. The size of the precipitates observed in CR ＋ WR sample after peak ageing treatment is finer than that of peak aged CR ＋ SA sample. The UTS of peak aged CR ＋ WR sample （UTS： 390 MPa） was found to be higher than that of peak aged CR ＋ SA sample （UTS： 355 MPa）, without decrease in ductility.
文摘Nanocomposite Ti-Si-N thin films have been deposited on Si （100） substrate by direct current/radio frequency （DC/RF） magnetron sputtering. The effect of varying deposition parameters on the structure and mechanical properties of Ti-Si-N films has been investigated by characterization techniques such as X-ray dif- fraction （XRD）, field emission scanning electron microscopy （FE-SEM）, atomic force microscopy （AFM） and nanoindentation, respectively. XRD analysis of the thin films exhibit all （111）, （200） and （220） peaks initially with varying sputtering pressure, but （111） peak dominates at higher sputtering pressure. The crystallite size calculated from XRD peaks shows that it increases with increasing sputtering pressure. Microstructural analy- sis reveals that the dense blurred grains transform into uniform grains in the films and shows porosity with increasing sputtering pressure. The surface roughness of the Ti-Si-N films increases with varying sputtering pressure. The hardness and Youngrs modulus values of Ti-Si-N films are 33.7 and 278.6 GPa, respectively, with 0.7 Pa sputtering pressure but it decreases with further increase in sputtering pressure due to an increase in porosity of the films.
基金BRNS,Bombay for their financial grant to this work through grant No.BRN-577-MMD
文摘The mechanical properties and microstructural evolution of zircaloy-4 subjected to cumulative strains of 1.48,2.96,4.44 and 5.91 through multiaxial forging（MAF） at cryogenic temperature（77 K） were investigated.The mechanical properties of the MAF treated alloy were measured through universal tensile testing and Vickers hardness testing equipment.The zircaloy-4 deformed up to a cumulative strain of 5.91 showed improvement in both ultimate tensile strength and hardness from 474 MPa to 717 MPa and from HV 190 to HV 238,respectively,as compared with the as-received alloy.However,there was a noticeable decrement in ductility（from 18%to 3.5%） due to the low strain hardening ability of deformed zircaloy-4.The improvement in strength and hardness of the deformed alloy is attributed to the grain size effect and higher dislocation density generated during multiaxial forging.The microstructural evolutions of deformed samples were characterized by optical microscopy and transmission electron microscopy（TEM）.The evolved microstructure at a cumulative strain of 5.91 obtained after MAF up to 12 cycles depicted the formation of ultrafine grains with an average size of 150-250 nm.
文摘This study deals with the development of drum brake liner for a multi-utility vehicle possessing a hydraulic brake system by varying 7 weight%of steel fiber and stainless steel fiber each,in friction composite formulations.The developed friction composites were tested for physical,chemical,corrosion,mechanical,thermal properties,and tribological characteristics,under near-actual conditions using an inertia dynamometer as per industrial standards.Finite element analysis software(ANSYS)analysis was performed to show the thermal stress distribution of the developed friction composites at the maximum temperature rise due to heat generated during brake stops,and an extensive evaluation method was used to rank the composites.The study concludes that the brake factor of the stainless steel fiber-based friction composite produces stable performance in all conditions with a lower liner temperature rise of 340°C and lower thermal stress at 4.255294 MPa.However,the steel fiber-based composites produced high performance at the beginning but deteriorated after a certain period due to higher levels of corrosion and a high temperature rise of 361°C resulting in a negative fade(-0.84%)and more thermal stress(5.619102 MPa).The primary plateau,secondary plateau,back transfer of drum wear debris,and the distribution of constituents on the worn surface of the developed composites in a resin matrix were identified and studied using a scanning electron microscope(SEM)equipped with energy-dispersive spectroscopy.
文摘In the present work, 6082 Al alloy has been rolled to 40% and 70% thickness reductions at the cryogenic and room temperatures for the improvement in mechanical and fracture toughness properties. All cryorolled samples are subjected to aging at different temperatures, i.e., 140, 160, and 190 ℃ to improve the strength, ductility, and fracture toughness. The microstructures of the cryorolled （CR） and room temperature rolled （RTR） alloy after 40% and 70% thickness reductions are characterized by FE-SEM to reveal the modes of failure. The results show that the starting bulk Al alloy specimen is fractured in total ductile manner, consisting of well-developed dimples over the entire surface. The mechanical properties and fracture toughness of the 70% CR alloy are found better than 70% RTR alloy due to higher dislocations density and formation of sub-grain structures in the CR alloy.
文摘FeCrBMnSi alloy coating on steel substrate（310S） was fabricated by a high-velocity arc spraying（HVAS） process. Degradation behavior of the coatings at temperatures of 700℃ and 900℃ in air and in the coal fired boiler at（700±10）℃ was studied. X-ray difraction（XRD） and scanning electron microscopy/energydisperse spectroscopy（SEM/EDS） were used to characterize the coating as well as to analyze the corrosion products for elucidating the corrosion mechanisms.Coating exhibited dense and globular morphology and the splats were interconnected as evident from SEM analysis. The maximum microhardness of the coating was found to be 630–1060 HV. The FeCrBMnSi alloy coating has imparted necessary resistance to oxidation and showed good adherence to the 310S substrate during the exposures with no tendency for spallation of its oxide scale.
基金BRNS,Bombay for their financial grant to this work (No.BRN-577-MMD)
文摘The texture and mechanical properties of cross-rolled zircaloy-2 at 77 and 300 K were investigated.Crossrolling at 77 K was performed to impart different thickness reductions of 25% and 50%,while at 300 K with 25%,50%,75% and 85% reductions to the sample.EBSD analysis of deformed sample showed that near-basal orientation is not deformed completely after 50% rolling reduction.The activation of prismatic silp,{1122} contraction twin and {1012} extension twin were evident from the deformed microstructure at 77 K.The propensity for activation of basal slip〈a〉 at77 K was also observed.The deformation of the sample at 300 K occurs by prismatic,basal 〈a〉 and pyramidal 〈c＋a〉slips,which were predicted by pole figures.After annealing,the tensile strengths（735 and 710 MPa） are almost the same for 50% cryo-cross-rolled and room-temperature cross-rolled zircaloy-2 with almost 2.7% difference in their ductility.KAM analysis of the deformed samples was made to estimate the stored strain energy and dislocation density.Annealing of deformed sample at 673 K for 30 min results in recrystallization,which leads to the formation of ultrafine grains.
文摘The influence of cryorolling(CR),room temperature rolling(RTR)and post annealing on precipitation,microstructuralevolution(recovery,recrystallisation and grain growth),mechanical and corrosion behavior,was investigated in the present work.The precipitation kinetics and microstructural morphology of CR,RTR,and post annealed samples were investigated by differentialscanning calorimetry(DSC),transmission electron microscopy(TEM),and electron back scattered diffraction(EBSD)to elucidatethe observed mechanical properties.After annealing at200°C,UTS and hardness of CR samples(345MPa and HV127)wereimproved as compared to RTR samples(320MPa and HV115).The increase in hardness and UTS of CR samples after annealing at200°C was due to precipitation ofβ''from Al matrix,which imparted higher Zener drag effect as compared to RTR samples.Theimprovement in corrosion and pitting potentials was observed for CR samples(?1.321V and?700mV)as compared to RTRsamples(?1.335V and?710mV).In CR samples,heavy dislocation density and dissolution of Mg4Al3Si4-precipitates in the Almatrix have improved corrosion resistance of the alloy through formation of protective passive layer and suppression of galvanic cell,respectively.
基金supported by the Council of Scientific and Industrial Research (CSIR)(Grant No.03(1148)/09/EMR-II)the Defence Research and Development Organisation (DRDO) (Grant No.ERIP/ER/0800354/M/011125)
文摘The objective of the present work is to investigate the effect of various sputtering parameters such as nitrogen flow rate, deposition time and sputtering pressure on structural, wettability and optical properties of titanium oxynitride films deposited on glass substrate by reactive magnetron sputtering. The X-ray diffraction graphs of titanium oxynitride films show evolution of various textures of TiO=N and TiN phases with increasing nitrogen flow rate and deposition time, but an increase in sputtering pressure from 4.0 to 8.0 Pa results in decline of various textures observed for TiO=Ny and TiN phases. The stress and strain calculated by sin2~ method are compressive, which decrease with increasing nitrogen flow rate from 55 to I00 sccm （standard cubic centimeter per minute） and increase with increasing deposition time from 80 to I40 min due to atomic penning effect and increasing thickness of the deposited films. The titanium oxynitride films have contact angle values above 90 deg., indicating that films are hydrophobic. The maximum contact angle of I09.1 deg. is observed at deposition time of 140 min. This water repellent property can add value to potential protective, wear and corrosion resistant application of titanium oxynitride films. The band gap decreases from 1.98 to 1.83 eV as nitrogen flow rate is increased from 55 to 100 sccm; it decreases from 1.93 to 1.79 eV as deposition time is increased from 80 to 140 min as more nitrogen incorporation results in higher negative potential of valence band N2p orbital. But it increases from 2.26 to 2.34 eV for titanium oxynitride films as sputtering pressure increases from 4.0 to 8.0 Pa.
