Wire-arc additive manufacture(WAAM)has great potential for manufacturing of Al-Cu components.However,inferior mechanical properties of WAAM deposited material restrict its industrial application.Inter-layer cold rolli...Wire-arc additive manufacture(WAAM)has great potential for manufacturing of Al-Cu components.However,inferior mechanical properties of WAAM deposited material restrict its industrial application.Inter-layer cold rolling and thermo-mechanical heat treatment(T8)with pre-stretching deformation between solution and aging treatment were adopted in this study.Their effects on hardness,mechanical properties and microstructure were analyzed and compared to the conventional heat treatment(T6).The results show that cold rolling increases the hardness and strengths,which further increase with T8 treatment.The ultimate tensile strength(UTS)of 513 MPa and yield stress(YS)of 413 MPa can be obtained in the inter-layer cold-rolled sample with T8 treatment,which is much higher than that in the as-deposited samples.The cold-rolled samples show higher elongation than that of as-deposited ones due to significant elimination of porosity in cold rolling;while both the T6 and T8 treatments decrease the elongation.The cold rolling and pre-stretching deformation both contribute to the formation of dense and dispersive precipitatedθ′phases,which inhibits the dislocation movement and enhances the strengths;as a result,T8 treatment shows better strengthening effect than the T6 treatment.The strengthening mechanism was analyzed and it was mainly related to work hardening and precipitation strengthening.展开更多
The flow stress behavior and microstructure development of Al-5Zn-2Mg (7005) aluminum alloy were studied by hot compression tests at deformation temperatures between 300-500 °C and strain rates between 0.05-50...The flow stress behavior and microstructure development of Al-5Zn-2Mg (7005) aluminum alloy were studied by hot compression tests at deformation temperatures between 300-500 °C and strain rates between 0.05-50 s-1. The deformed structures of the samples were observed by optical microscopy (OM), transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD) analysis. The calculated activation energy is 147 kJ/mol, which is very close to the activation energy for lattice self-diffusion in aluminum (142 kJ/mol). Dynamic recovery is the dominant restoration mechanism during the deformation. At high strain rate of 50 s-1, temperature rise due to deformation heating leads to a significant flow softening. Microstructure observations indicated that the remaining softening after deformation heating correction at high strain rate and the softening observed at high temperature are associated with grain coarsening induced by grain boundary migration during dynamic recovery process.展开更多
Hot deformation behavior and microstructure evolution of TC11(Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) alloy with equiaxed structure were investigated in the two-phase field at temperatures in the range of 980-800 ℃ and at stra...Hot deformation behavior and microstructure evolution of TC11(Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) alloy with equiaxed structure were investigated in the two-phase field at temperatures in the range of 980-800 ℃ and at strain rates of 0.001 s-1,0.01 s-1,0.1 s-1.Effects of thermo-mechanical parameters on both of the stress—strain curves and microstructure evolution were analyzed.Grain boundary characteristics of deformation microstructures were tested by electron backscattered diffraction(EBSD).The results reveal that β-phase dominates the deformation and presents discontinuous dynamic recrystallization at 980 ℃;meanwhile,α-phase coarsens at lower strain rates and dissolves at higher strain rates,and α-phase volume fraction and grain size decrease with increasing strain rate.Super-plastic deformation occurs at 950-900 ℃ and strain rate of 0.001 s-1.And the deformation is dominated by soft β-phase,phase interfaces and grain boundaries.Microstructural mechanism operated at 850 ℃ is continuous dynamic recrystallization of α-phase that dominates the deformation,and β-phase deforms to match the deformation of α-phase.展开更多
The hot deformation behavior of Al-Zn-Mg-0.25Sc-Zr alloy and its microstructural evolution were investigated by isothermal axisymmetric hot compression tests at temperatures from 340 to 500°C and strain rates ran...The hot deformation behavior of Al-Zn-Mg-0.25Sc-Zr alloy and its microstructural evolution were investigated by isothermal axisymmetric hot compression tests at temperatures from 340 to 500°C and strain rates ranging from 0.001 to 10 s -1 .The steady flow stress increased with increasing the strain rate or decreasing the deformation temperature,which can be described by a hyperbolic-sine constitutive equation with the deformation activation energy of 150.25 kJ/mol.The tendency of dynamic recrystallization enhanced at high deforming temperatures and low strain rates,which corresponded to low Z values.With decreasing Z value,the main softening mechanism of the alloy transformed from dynamic recovery to dynamic recrystallization, correspondingly,the subgrain size increased and the dislocation density decreased.展开更多
A sloping semisolid rheo-rolling process of Mg-3Sn-1Mn alloy was developed, and the effects of process parameters on the microstructure and mechanical properties of Mg-3Sn-lMn alloy strip were studied. The results sho...A sloping semisolid rheo-rolling process of Mg-3Sn-1Mn alloy was developed, and the effects of process parameters on the microstructure and mechanical properties of Mg-3Sn-lMn alloy strip were studied. The results show that the primary grain average diameter of the strip increases with the increase of the roll speed. The primary grain average diameter decreases firstly and then increases with the increase of the vibration frequency, and the tensile strength and elongation of the strip increase firstly and then decrease with the increase of the vibration frequency. The primary grain average diameter increases with the increase of casting temperature, and the tensile strength and elongation of the strip decrease correspondingly. When the casting temperature is 670℃, the roll speed is 52 mm/s, and the vibration frequency is 60 Hz, Mg-3Sn-1Mn alloy strip with good properties is produced. The mechanical properties of the present product are higher than those of Mg-3Sn-lMn alloy casting with the addition of 0.87% Ce (mass fraction).展开更多
Asymmetric rolling (ASR), as one of severe plastic deformation (SPD) methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achie...Asymmetric rolling (ASR), as one of severe plastic deformation (SPD) methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achieved by adjusting the diameters of the upper roll and the bottom roll and was used to prepare hot-rolled thick plate of 5182 aluminium alloy. The shear deformation and plate shape control were experimentally studied. The experimental results show that asymmetrical rolling has a significant effect on metal deformation stream and can somehow refine microstructure and improve the uniformity of microstructure and properties. The asymmetrical rolling process can also reduce the rolling force. However, bending of rolling plate often happens during asymmetrical rolling process. The factors affecting the bending were discussed.展开更多
The effects of T916 thermo-mechanical process on microstructures, mechanical properties and ballistic resistance of 2519A aluminum alloy were investigated by optical microscopy (OM), transmission electron microscopy...The effects of T916 thermo-mechanical process on microstructures, mechanical properties and ballistic resistance of 2519A aluminum alloy were investigated by optical microscopy (OM), transmission electron microscopy (TEM), tensile tests and ballistic resistance test. After T916 treatment, the yield strength, tensile strength and elongation rate of 2519A aluminum alloy reach 501 MPa, 540 MPa and 14%, respectively. And the ballistic limit velocity of 2519A-T916 alloy (30 mm in thickness) is 715 rn/s. The microstructure varies near the sidewalls of crater. The interrupted ageing contributes to these excellent properties of the alloy. During T916 process, the precipitation of Guinier Preston (GP) zone is finer and denser during the interrupted ageing, thus resulting in well precipitated strengthening phase.展开更多
The microstructure evolution of 7A85 aluminum alloy at the conditions of strain rate(0.001−1 s^(−1))and deformation temperature(250−450°C)was studied by optical microscopy(OM)and electron back scattering diffract...The microstructure evolution of 7A85 aluminum alloy at the conditions of strain rate(0.001−1 s^(−1))and deformation temperature(250−450°C)was studied by optical microscopy(OM)and electron back scattering diffraction(EBSD).Based on the K-M dislocation density model,a two-stage K-M dislocation density model of 7A85 aluminum alloy was established.The results reveal that dynamic recovery(DRV)and dynamic recrystallization(DRX)are the main mechanisms of microstructure evolution during thermal deformation of 7A85 aluminum alloy.350−400°C is the transformation zone from dynamic recovery to dynamic recrystallization.At low temperature(≤350°C),DRV is the main mechanism,while DRX mostly occurs at high temperature(≥400°C).At this point,the sensitivity of microstructure evolution to temperature is relatively high.As the temperature increased,the average misorientation angle(θˉ_(c))increased significantly,ranging from 0.93°to 7.13°.Meanwhile,the f_(LAGBs) decreased with the highest decrease of 24%.展开更多
Al-Mn alloys containing similar amounts of solutes but various dispersoid densities were cold rolled. The grain subdivision and micro-texture were examined by electron backscatter diffraction and orientation imaging m...Al-Mn alloys containing similar amounts of solutes but various dispersoid densities were cold rolled. The grain subdivision and micro-texture were examined by electron backscatter diffraction and orientation imaging microscopy. Macro-texture was measured by X-ray diffraction. It is found that a high density of fine dispersoids enhances the development of the copper and S textures at large strains (~3), and also induces a higher fraction of high-angle grain boundaries. At smaller strains, the texture and high-angle grain boundaries are not evidently influenced by the density of dispersoids. It is suggested that the texture evolution, which is enhanced by dispersoid pinning effect, contributes to the grain subdivision and the formation of high-angle grain boundaries.展开更多
Hot compression of 7050 aluminum alloy was performed on Gleeble 1500D thermo-mechanical simulator at 350 ℃ and 450 ℃ with a constant strain rate of 0.1 s-1 to different nominal strains of 0.1, 0.3 and 0.7. Microstru...Hot compression of 7050 aluminum alloy was performed on Gleeble 1500D thermo-mechanical simulator at 350 ℃ and 450 ℃ with a constant strain rate of 0.1 s-1 to different nominal strains of 0.1, 0.3 and 0.7. Microstructures of 7050 alloy under various compression conditions were observed by TEM to investigate the microstructure evolution process of the alloy deformed at various temperatures. The microstructure evolves from dislocation tangles to cell structure and subgrain structure when being deformed at 350 ℃, of which dynamic recovery is the softening mechanism. However, continuous dynamic recrystallization (DRX) occurs during hot deformation at 450 ℃, in which the main nucleation mechanisms of DRX are subgrain growth and subgrain coalescence rather than particle-simulated nucleation (PSN).展开更多
Deformation behavior and microstructure of AlMg6Mn alloy subjected to shear spinning were studied by means of mechanical characterization, optical and SEM+EDS microscopy. Specimens were shear spun on an industrial sp...Deformation behavior and microstructure of AlMg6Mn alloy subjected to shear spinning were studied by means of mechanical characterization, optical and SEM+EDS microscopy. Specimens were shear spun on an industrial spinning machine using different mandrels, providing reductions of wall thickness of 30%, 50% and 68%. The grain structure developed during shear spinning refines gradually. The grains elongate in axial direction with increase of reduction, and also stretches along circumferencial direction. Optimal combination of strength and elongation is observed. This is attributed to grain refinement and dislocation reactions with particles and atoms of Mg and Mn in solid solution.展开更多
The effect of temperature in range of 155-175 ℃ on the creep behavior, microstructural evolution, and precipitation of an Al-Cu-Li alloy was experimentally investigated during creep ageing deformation under 180 MPa f...The effect of temperature in range of 155-175 ℃ on the creep behavior, microstructural evolution, and precipitation of an Al-Cu-Li alloy was experimentally investigated during creep ageing deformation under 180 MPa for 20 h. Increasing temperature resulted in a noteworthy change in creep ageing behaviour, including a variation in creep curves, an improvement in creep rate during early creep ageing, and an increased creep strain. Tensile tests indicate that the specimen aged at higher temperature reached peak strength within a shorter time. Transmission electron microscopy(TEM) was employed to explore the effect of temperature on the microstructural evolution of the AA2198 during creep ageing deformation. Many larger dislocations and even tangled dislocation structures were observed in the sample aged at higher temperature. The number of T1 precipitates increased at higher ageing temperature at the same ageing time. Based on the analysed results, a new mechanism, considering the combined effects of the formation of larger dislocation structures induced by higher temperature and diffusion of solute atoms towards these larger or tangled dislocations, was proposed to explain the effect of temperature on microstructural evolution and creep behaviour.展开更多
The deformation behavior and microstructure of the Zr50Ti50 alloy in β phase field were investigated by isothermal compression tests at temperatures ranging from 700 to 850 °C and strain rates ranging from 0.001...The deformation behavior and microstructure of the Zr50Ti50 alloy in β phase field were investigated by isothermal compression tests at temperatures ranging from 700 to 850 °C and strain rates ranging from 0.001 to 1 s?1. The flow curves exhibited typical flow softening. The initial discontinuous yielding behavior was observed at higher strain rates, which was not found in other traditional Zr alloys. The apparent deformation activation energy was calculated to be 103 kJ/mol and constitutive equationdescribing the flow stress as a function of the strain rate and deformation temperature was proposed. The analysis indicated that the hot deformation mechanism was mainly dominated by dynamic recovery. However, dynamic recrystallization was delayed by dynamic recovery. Thereafter, the processing map was calculated to evaluate the efficiency of the forging process at the temperatures and strain rates investigated and to optimize processing parameters of hot deformation. The optimum processing parameters were found to be 830?850 °C and 0.56?1 s?1 for hot the deformation of Zr50Ti50 alloy in the β phase region.展开更多
基金Project(ZZYJKT2024-08)supported by the State Key Laboratory of Precision Manufacturing for Extreme Service Performance,ChinaProject(2022JB11GX004)supported by Selection of the best Candidates to Undertake Key Research Projects by Dalian City,ChinaProject(201806835007)supported by China Scholarship Council。
文摘Wire-arc additive manufacture(WAAM)has great potential for manufacturing of Al-Cu components.However,inferior mechanical properties of WAAM deposited material restrict its industrial application.Inter-layer cold rolling and thermo-mechanical heat treatment(T8)with pre-stretching deformation between solution and aging treatment were adopted in this study.Their effects on hardness,mechanical properties and microstructure were analyzed and compared to the conventional heat treatment(T6).The results show that cold rolling increases the hardness and strengths,which further increase with T8 treatment.The ultimate tensile strength(UTS)of 513 MPa and yield stress(YS)of 413 MPa can be obtained in the inter-layer cold-rolled sample with T8 treatment,which is much higher than that in the as-deposited samples.The cold-rolled samples show higher elongation than that of as-deposited ones due to significant elimination of porosity in cold rolling;while both the T6 and T8 treatments decrease the elongation.The cold rolling and pre-stretching deformation both contribute to the formation of dense and dispersive precipitatedθ′phases,which inhibits the dislocation movement and enhances the strengths;as a result,T8 treatment shows better strengthening effect than the T6 treatment.The strengthening mechanism was analyzed and it was mainly related to work hardening and precipitation strengthening.
基金Project(51075132)supported by the National Natural Science Foundation of ChinaProject(20090161110027)supported by the Doctoral Fund of Ministry of Education of ChinaProject(2011BAG03B02)supported by National Key Technology R&D Program during the 12th Five-Year Plan Period,China
文摘The flow stress behavior and microstructure development of Al-5Zn-2Mg (7005) aluminum alloy were studied by hot compression tests at deformation temperatures between 300-500 °C and strain rates between 0.05-50 s-1. The deformed structures of the samples were observed by optical microscopy (OM), transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD) analysis. The calculated activation energy is 147 kJ/mol, which is very close to the activation energy for lattice self-diffusion in aluminum (142 kJ/mol). Dynamic recovery is the dominant restoration mechanism during the deformation. At high strain rate of 50 s-1, temperature rise due to deformation heating leads to a significant flow softening. Microstructure observations indicated that the remaining softening after deformation heating correction at high strain rate and the softening observed at high temperature are associated with grain coarsening induced by grain boundary migration during dynamic recovery process.
基金Project(2008011045) supported by the Natural Science Foundation of Shanxi Province,China
文摘Hot deformation behavior and microstructure evolution of TC11(Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) alloy with equiaxed structure were investigated in the two-phase field at temperatures in the range of 980-800 ℃ and at strain rates of 0.001 s-1,0.01 s-1,0.1 s-1.Effects of thermo-mechanical parameters on both of the stress—strain curves and microstructure evolution were analyzed.Grain boundary characteristics of deformation microstructures were tested by electron backscattered diffraction(EBSD).The results reveal that β-phase dominates the deformation and presents discontinuous dynamic recrystallization at 980 ℃;meanwhile,α-phase coarsens at lower strain rates and dissolves at higher strain rates,and α-phase volume fraction and grain size decrease with increasing strain rate.Super-plastic deformation occurs at 950-900 ℃ and strain rate of 0.001 s-1.And the deformation is dominated by soft β-phase,phase interfaces and grain boundaries.Microstructural mechanism operated at 850 ℃ is continuous dynamic recrystallization of α-phase that dominates the deformation,and β-phase deforms to match the deformation of α-phase.
基金Project(2012CB619503)supported by the High-tech Research and Development Program of China
文摘The hot deformation behavior of Al-Zn-Mg-0.25Sc-Zr alloy and its microstructural evolution were investigated by isothermal axisymmetric hot compression tests at temperatures from 340 to 500°C and strain rates ranging from 0.001 to 10 s -1 .The steady flow stress increased with increasing the strain rate or decreasing the deformation temperature,which can be described by a hyperbolic-sine constitutive equation with the deformation activation energy of 150.25 kJ/mol.The tendency of dynamic recrystallization enhanced at high deforming temperatures and low strain rates,which corresponded to low Z values.With decreasing Z value,the main softening mechanism of the alloy transformed from dynamic recovery to dynamic recrystallization, correspondingly,the subgrain size increased and the dislocation density decreased.
基金Project(51222405) supported by the National Science Foundation of Outstanding Young Scholars of ChinaProject(51034002) supported by the National Natural Science Foundation of China+1 种基金Project(132002) supported by the Fok Ying Tong Education FoundationProject (2011CB610405) supported by the National Basic Research Program of China
文摘A sloping semisolid rheo-rolling process of Mg-3Sn-1Mn alloy was developed, and the effects of process parameters on the microstructure and mechanical properties of Mg-3Sn-lMn alloy strip were studied. The results show that the primary grain average diameter of the strip increases with the increase of the roll speed. The primary grain average diameter decreases firstly and then increases with the increase of the vibration frequency, and the tensile strength and elongation of the strip increase firstly and then decrease with the increase of the vibration frequency. The primary grain average diameter increases with the increase of casting temperature, and the tensile strength and elongation of the strip decrease correspondingly. When the casting temperature is 670℃, the roll speed is 52 mm/s, and the vibration frequency is 60 Hz, Mg-3Sn-1Mn alloy strip with good properties is produced. The mechanical properties of the present product are higher than those of Mg-3Sn-lMn alloy casting with the addition of 0.87% Ce (mass fraction).
基金Projects(51104043,51374067)supported by the National Natural Science Foundation of ChinaProject(2012CB619506)supported by the National Basic Research Program of ChinaProject(N120409002)supported by the Fundamental Research Funds for the Central Universities,China
文摘Asymmetric rolling (ASR), as one of severe plastic deformation (SPD) methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achieved by adjusting the diameters of the upper roll and the bottom roll and was used to prepare hot-rolled thick plate of 5182 aluminium alloy. The shear deformation and plate shape control were experimentally studied. The experimental results show that asymmetrical rolling has a significant effect on metal deformation stream and can somehow refine microstructure and improve the uniformity of microstructure and properties. The asymmetrical rolling process can also reduce the rolling force. However, bending of rolling plate often happens during asymmetrical rolling process. The factors affecting the bending were discussed.
基金Project(2012CB619501)supported by the National Basic Research Program of China
文摘The effects of T916 thermo-mechanical process on microstructures, mechanical properties and ballistic resistance of 2519A aluminum alloy were investigated by optical microscopy (OM), transmission electron microscopy (TEM), tensile tests and ballistic resistance test. After T916 treatment, the yield strength, tensile strength and elongation rate of 2519A aluminum alloy reach 501 MPa, 540 MPa and 14%, respectively. And the ballistic limit velocity of 2519A-T916 alloy (30 mm in thickness) is 715 rn/s. The microstructure varies near the sidewalls of crater. The interrupted ageing contributes to these excellent properties of the alloy. During T916 process, the precipitation of Guinier Preston (GP) zone is finer and denser during the interrupted ageing, thus resulting in well precipitated strengthening phase.
基金Project(51675465)supported by the National Natural Science Foundation of ChinaProject(E2019203075)supported by the Natural Science Foundation of Hebei Province,China+1 种基金Project(BJ2019001)supported by the Top Young Talents Project of the Education Department of Hebei Province,ChinaProject(Kfkt2017-07)supported by the State Key Laboratory Program of High Performance Complex Manufacturing,China。
文摘The microstructure evolution of 7A85 aluminum alloy at the conditions of strain rate(0.001−1 s^(−1))and deformation temperature(250−450°C)was studied by optical microscopy(OM)and electron back scattering diffraction(EBSD).Based on the K-M dislocation density model,a two-stage K-M dislocation density model of 7A85 aluminum alloy was established.The results reveal that dynamic recovery(DRV)and dynamic recrystallization(DRX)are the main mechanisms of microstructure evolution during thermal deformation of 7A85 aluminum alloy.350−400°C is the transformation zone from dynamic recovery to dynamic recrystallization.At low temperature(≤350°C),DRV is the main mechanism,while DRX mostly occurs at high temperature(≥400°C).At this point,the sensitivity of microstructure evolution to temperature is relatively high.As the temperature increased,the average misorientation angle(θˉ_(c))increased significantly,ranging from 0.93°to 7.13°.Meanwhile,the f_(LAGBs) decreased with the highest decrease of 24%.
基金Project supported by the Research Council of Norway,Hydro and Sapa Technology Under the Project MOREAL
文摘Al-Mn alloys containing similar amounts of solutes but various dispersoid densities were cold rolled. The grain subdivision and micro-texture were examined by electron backscatter diffraction and orientation imaging microscopy. Macro-texture was measured by X-ray diffraction. It is found that a high density of fine dispersoids enhances the development of the copper and S textures at large strains (~3), and also induces a higher fraction of high-angle grain boundaries. At smaller strains, the texture and high-angle grain boundaries are not evidently influenced by the density of dispersoids. It is suggested that the texture evolution, which is enhanced by dispersoid pinning effect, contributes to the grain subdivision and the formation of high-angle grain boundaries.
文摘Hot compression of 7050 aluminum alloy was performed on Gleeble 1500D thermo-mechanical simulator at 350 ℃ and 450 ℃ with a constant strain rate of 0.1 s-1 to different nominal strains of 0.1, 0.3 and 0.7. Microstructures of 7050 alloy under various compression conditions were observed by TEM to investigate the microstructure evolution process of the alloy deformed at various temperatures. The microstructure evolves from dislocation tangles to cell structure and subgrain structure when being deformed at 350 ℃, of which dynamic recovery is the softening mechanism. However, continuous dynamic recrystallization (DRX) occurs during hot deformation at 450 ℃, in which the main nucleation mechanisms of DRX are subgrain growth and subgrain coalescence rather than particle-simulated nucleation (PSN).
文摘Deformation behavior and microstructure of AlMg6Mn alloy subjected to shear spinning were studied by means of mechanical characterization, optical and SEM+EDS microscopy. Specimens were shear spun on an industrial spinning machine using different mandrels, providing reductions of wall thickness of 30%, 50% and 68%. The grain structure developed during shear spinning refines gradually. The grains elongate in axial direction with increase of reduction, and also stretches along circumferencial direction. Optimal combination of strength and elongation is observed. This is attributed to grain refinement and dislocation reactions with particles and atoms of Mg and Mn in solid solution.
基金Project(2017YFB0306300)supported by the National Key R&D Program of ChinaProjects(51601060,51675538)supported by the National Natural Science Foundation of China。
文摘The effect of temperature in range of 155-175 ℃ on the creep behavior, microstructural evolution, and precipitation of an Al-Cu-Li alloy was experimentally investigated during creep ageing deformation under 180 MPa for 20 h. Increasing temperature resulted in a noteworthy change in creep ageing behaviour, including a variation in creep curves, an improvement in creep rate during early creep ageing, and an increased creep strain. Tensile tests indicate that the specimen aged at higher temperature reached peak strength within a shorter time. Transmission electron microscopy(TEM) was employed to explore the effect of temperature on the microstructural evolution of the AA2198 during creep ageing deformation. Many larger dislocations and even tangled dislocation structures were observed in the sample aged at higher temperature. The number of T1 precipitates increased at higher ageing temperature at the same ageing time. Based on the analysed results, a new mechanism, considering the combined effects of the formation of larger dislocation structures induced by higher temperature and diffusion of solute atoms towards these larger or tangled dislocations, was proposed to explain the effect of temperature on microstructural evolution and creep behaviour.
基金Project(2013CB73300)supported by the National Basic Research Program of ChinaProjects(51531005,51434008,51571174)supported by the National Natural Science Foundation of China
文摘The deformation behavior and microstructure of the Zr50Ti50 alloy in β phase field were investigated by isothermal compression tests at temperatures ranging from 700 to 850 °C and strain rates ranging from 0.001 to 1 s?1. The flow curves exhibited typical flow softening. The initial discontinuous yielding behavior was observed at higher strain rates, which was not found in other traditional Zr alloys. The apparent deformation activation energy was calculated to be 103 kJ/mol and constitutive equationdescribing the flow stress as a function of the strain rate and deformation temperature was proposed. The analysis indicated that the hot deformation mechanism was mainly dominated by dynamic recovery. However, dynamic recrystallization was delayed by dynamic recovery. Thereafter, the processing map was calculated to evaluate the efficiency of the forging process at the temperatures and strain rates investigated and to optimize processing parameters of hot deformation. The optimum processing parameters were found to be 830?850 °C and 0.56?1 s?1 for hot the deformation of Zr50Ti50 alloy in the β phase region.