Precipitation strengthening is a crucial microscopic mechanism for enhancing the strength of magnesium alloys. In order to elucidate the influence of precipitation on the microscopic deformation mechanisms and macrosc...Precipitation strengthening is a crucial microscopic mechanism for enhancing the strength of magnesium alloys. In order to elucidate the influence of precipitation on the microscopic deformation mechanisms and macroscopic mechanical response of magnesium alloys under cyclic loading conditions, we employed a crystal plasticity model to analyze the stress-strain curves, specific crystal plane diffraction intensities, and the temporal evolution of various microscopic deformation mechanisms and twinning volume fractions for an extruded magnesium alloy, AXM10304, containing coherent precipitates. The research findings indicate that precipitation does not fundamentally alter the microscopic mechanisms of this alloy. However, it hinders twinning during the compression stage, mildly promotes detwinning during the tension stage, and enhances tension secondary hardening by elevating the difficulty of activation of the prismatic slip.展开更多
Zr was added to Ti−Nb−Fe alloys to develop low elastic modulus and high strengthβ-Ti alloys for biomedical applications.Ingots of Ti−12Nb−2Fe−(2,4,6,8,10)Zr(at.%)were prepared by arc melting and then subjected to hom...Zr was added to Ti−Nb−Fe alloys to develop low elastic modulus and high strengthβ-Ti alloys for biomedical applications.Ingots of Ti−12Nb−2Fe−(2,4,6,8,10)Zr(at.%)were prepared by arc melting and then subjected to homogenization,cold rolling,and solution treatments.The phases and microstructures of the alloys were analyzed by optical microscopy,X-ray diffraction,and transmission electron microscopy.The mechanical properties were measured by tensile tests.The results indicate that Zr and Fe cause a remarkable solid-solution strengthening effect on the alloys;thus,all the alloys show yield and ultimate tensile strengths higher than 510 MPa and 730 MPa,respectively.Zr plays a weak role in the deformation mechanism.Further,twinning occurs in all the deformed alloys and is beneficial to both strength and plasticity.Ti−12Nb−2Fe−(8,10)Zr alloys with metastableβphases show low elastic modulus,high tensile strength,and good plasticity and are suitable candidate materials for biomedical implants.展开更多
A new metastable dual-phase Fe59 Cr13 Ni18 Al10 medium entropy alloy(MEA)with hierarchically heteroge-neous microstructure from micro-to nano-scale was designed in this work.Partially recrystallized FCC phase and lots...A new metastable dual-phase Fe59 Cr13 Ni18 Al10 medium entropy alloy(MEA)with hierarchically heteroge-neous microstructure from micro-to nano-scale was designed in this work.Partially recrystallized FCC phase and lots of NiAl-rich B2 precipitates are obtained by annealing and aging treatment.The yield strength of the MEA at room temperature(298 K)and liquid nitrogen temperature(77 K)increased from∼910 MPa and∼1250 MPa in the annealed state,respectively,to∼1145 MPa and∼1520 MPa in the aged state,while the uniform elongation maintained more than 15%.The excellent mechanical properties of the MEA both at 298 and 77 K are attributed to the co-activation of multiple strengthening mech-anisms,including fine grain,dislocation,precipitation,transformation-induced plasticity,stacking faults,and nano-twins.展开更多
The localized plastic flow auto-waves observed for the stages of easy glide and linear work hardening in a number of metals are considered. The propagation rates were determined expe- rimentally for the auto-waves in ...The localized plastic flow auto-waves observed for the stages of easy glide and linear work hardening in a number of metals are considered. The propagation rates were determined expe- rimentally for the auto-waves in question with the aid of focused-image holography. The dispersion relation of quadratic form derived for localized plastic flow auto-waves and the dependencies of phase and group rates on wave number are discussed. A detailed comparison of the quantitative characteristics of phase and group waves has revealed that the two types of wave are closely related. An invariant is introduced for localized plastic flow phenomena occurring on the micro-and macro-scale levels in the deforming solid.展开更多
This paper suggests a new method of determining residual strain in the welding seals. Method is based on the speed of Rayleigh waves with measurements of strain changes σ1 + σ2. According to results of experiments d...This paper suggests a new method of determining residual strain in the welding seals. Method is based on the speed of Rayleigh waves with measurements of strain changes σ1 + σ2. According to results of experiments described in the paper, author finds correlations for the two types of steels. The paper also reports on the experimentally obtained values of strain in the areas around welding seals and tee joints. Research indicates that under the influence of external loadings, residual strain doesn’t cause significant changes in the epures of strain.展开更多
The precipitation behavior of topological close-packed（TCP）μphase in powder metallurgy（P/M）nickelbased superalloy FGH97 was investigated.The results showed that proper addition of solution strengthening elements,...The precipitation behavior of topological close-packed（TCP）μphase in powder metallurgy（P/M）nickelbased superalloy FGH97 was investigated.The results showed that proper addition of solution strengthening elements,such as Co,Cr,W,Mo,improved tensile strength,while excessive addition of those elements facilitated the precipitation ofμphase,which seriously aggravated the plasticity of the P/M superalloy.For the heat-treated specimens,the relationship between critical aging time（whenμstarted to precipitate）,aging temperature,and the average electron vacancy number ofγmatrix was established.展开更多
文摘Precipitation strengthening is a crucial microscopic mechanism for enhancing the strength of magnesium alloys. In order to elucidate the influence of precipitation on the microscopic deformation mechanisms and macroscopic mechanical response of magnesium alloys under cyclic loading conditions, we employed a crystal plasticity model to analyze the stress-strain curves, specific crystal plane diffraction intensities, and the temporal evolution of various microscopic deformation mechanisms and twinning volume fractions for an extruded magnesium alloy, AXM10304, containing coherent precipitates. The research findings indicate that precipitation does not fundamentally alter the microscopic mechanisms of this alloy. However, it hinders twinning during the compression stage, mildly promotes detwinning during the tension stage, and enhances tension secondary hardening by elevating the difficulty of activation of the prismatic slip.
基金the Natural Science Foundation of Shanghai,China(No.15ZR1428400)Shanghai Engineering Research Center of High-Performance Medical Device Materials,China(No.20DZ2255500)the Project of Creation of Life Innovation Materials for Interdisciplinary and International Researcher Development,Tohoku University,sponsored by Ministry,Education,Culture,Sports,Science and Technology,Japan,and the Grant-in Aid for Scientific Research(C)(No.20K05139)from JSPS(Japan Society for the Promotion of Science),Tokyo,Japan.
文摘Zr was added to Ti−Nb−Fe alloys to develop low elastic modulus and high strengthβ-Ti alloys for biomedical applications.Ingots of Ti−12Nb−2Fe−(2,4,6,8,10)Zr(at.%)were prepared by arc melting and then subjected to homogenization,cold rolling,and solution treatments.The phases and microstructures of the alloys were analyzed by optical microscopy,X-ray diffraction,and transmission electron microscopy.The mechanical properties were measured by tensile tests.The results indicate that Zr and Fe cause a remarkable solid-solution strengthening effect on the alloys;thus,all the alloys show yield and ultimate tensile strengths higher than 510 MPa and 730 MPa,respectively.Zr plays a weak role in the deformation mechanism.Further,twinning occurs in all the deformed alloys and is beneficial to both strength and plasticity.Ti−12Nb−2Fe−(8,10)Zr alloys with metastableβphases show low elastic modulus,high tensile strength,and good plasticity and are suitable candidate materials for biomedical implants.
基金supported by the National Natural Science Foundation of China(Nos.52101053 and 52274399)the Henan Provincial Science and Technology Research Project(No.232102231025).
文摘A new metastable dual-phase Fe59 Cr13 Ni18 Al10 medium entropy alloy(MEA)with hierarchically heteroge-neous microstructure from micro-to nano-scale was designed in this work.Partially recrystallized FCC phase and lots of NiAl-rich B2 precipitates are obtained by annealing and aging treatment.The yield strength of the MEA at room temperature(298 K)and liquid nitrogen temperature(77 K)increased from∼910 MPa and∼1250 MPa in the annealed state,respectively,to∼1145 MPa and∼1520 MPa in the aged state,while the uniform elongation maintained more than 15%.The excellent mechanical properties of the MEA both at 298 and 77 K are attributed to the co-activation of multiple strengthening mech-anisms,including fine grain,dislocation,precipitation,transformation-induced plasticity,stacking faults,and nano-twins.
文摘The localized plastic flow auto-waves observed for the stages of easy glide and linear work hardening in a number of metals are considered. The propagation rates were determined expe- rimentally for the auto-waves in question with the aid of focused-image holography. The dispersion relation of quadratic form derived for localized plastic flow auto-waves and the dependencies of phase and group rates on wave number are discussed. A detailed comparison of the quantitative characteristics of phase and group waves has revealed that the two types of wave are closely related. An invariant is introduced for localized plastic flow phenomena occurring on the micro-and macro-scale levels in the deforming solid.
文摘This paper suggests a new method of determining residual strain in the welding seals. Method is based on the speed of Rayleigh waves with measurements of strain changes σ1 + σ2. According to results of experiments described in the paper, author finds correlations for the two types of steels. The paper also reports on the experimentally obtained values of strain in the areas around welding seals and tee joints. Research indicates that under the influence of external loadings, residual strain doesn’t cause significant changes in the epures of strain.
基金Item Sponsored by International Science and Technology Cooperation Program of China(2014DFR50330)
文摘The precipitation behavior of topological close-packed（TCP）μphase in powder metallurgy（P/M）nickelbased superalloy FGH97 was investigated.The results showed that proper addition of solution strengthening elements,such as Co,Cr,W,Mo,improved tensile strength,while excessive addition of those elements facilitated the precipitation ofμphase,which seriously aggravated the plasticity of the P/M superalloy.For the heat-treated specimens,the relationship between critical aging time（whenμstarted to precipitate）,aging temperature,and the average electron vacancy number ofγmatrix was established.
