While the deformation behavior of rare-earth magnesium alloys at high temperatures has been extensively studied,the deformation mechanisms under moderate-to-low temperatures and high strain rates remain insufficiently...While the deformation behavior of rare-earth magnesium alloys at high temperatures has been extensively studied,the deformation mechanisms under moderate-to-low temperatures and high strain rates remain insufficiently understood.To address this gap,hot compression tests were conducted on a Mg-11Gd-3Y-0.5Zr(wt.%)alloy over a temperature range of 150℃–450℃under strain rates of 10^(-3) s^(-1)(low strain rate(LSR))and 10 s^(-1)(high strain rate(HSR))to explore the strain rate-temperature coupling effects during hot deformation.The results revealed an anomalous increase in peak stress at 150℃–250℃as the strain rate decreased,attributed to the combined effects of nano-precipitates,dislocation cell structures,and serrated flow induced by dynamic strain aging.At higher temperatures,strain rate influences softening pathways:under HSR at 450℃,the effect of twinning shifts from strengthening to facilitating dynamic recrystallization(DRX),resulting in substantial grain refinement(-4 μm,81%area fraction at a strain of 0.6).In contrast,at LSR,softening is dominated by dynamic recovery at 350℃,with limited DRX(-4 μm grains,10%area fraction at a strain of 0.6)occurs at 400℃.These findings clarify the dual role of twinning and its interaction with rate-temperature conditions,providing valuable insights into optimizing the hot processing of rare-earth magnesium alloys.展开更多
The dynamic tensile behaviors of a newly developed Ti-6 Al-2 Sn-2 Zr-3 Mo-1 Cr-2 Nb-Si alloy（referred as TC21 in China） over a wide range of strain rates from quasi-static to dynamic regimes(0.001-1 200 s-1) at diff...The dynamic tensile behaviors of a newly developed Ti-6 Al-2 Sn-2 Zr-3 Mo-1 Cr-2 Nb-Si alloy（referred as TC21 in China） over a wide range of strain rates from quasi-static to dynamic regimes(0.001-1 200 s-1) at different temperatures were experimentally investigated. A split Hopkinson tension bar apparatus and a static material testing system were utilized to study the stress-strain responses under uniaxial tension loading condition. The experimental results indicate that the tensile behavior of TC21 titanium alloy is dependent on the strain rate and temperature. The values of initial yield stress increase with increasing strain rate and decreasing temperature. The effects of strain rate and temperature on the initial yield behavior are estimated by introducing two sensitivity parameters. The phenomenological-based constitutive model, Johnson-Cook model, is suitably modified to describe the rate-temperature dependent constitutive behavior of TC21 titanium alloy. It is observed that the modified model is in good agreement with the experimental data subjected to the investigated range of strain rates and temperatures.展开更多
基金financially supported by the National Natural Science Foundation of China (grants 52301146 and 52275308)the Fundamental Research Funds for the Central Universities (grant 2023JG007)China Postdoctoral Science Foundation (grant 8206300226)。
文摘While the deformation behavior of rare-earth magnesium alloys at high temperatures has been extensively studied,the deformation mechanisms under moderate-to-low temperatures and high strain rates remain insufficiently understood.To address this gap,hot compression tests were conducted on a Mg-11Gd-3Y-0.5Zr(wt.%)alloy over a temperature range of 150℃–450℃under strain rates of 10^(-3) s^(-1)(low strain rate(LSR))and 10 s^(-1)(high strain rate(HSR))to explore the strain rate-temperature coupling effects during hot deformation.The results revealed an anomalous increase in peak stress at 150℃–250℃as the strain rate decreased,attributed to the combined effects of nano-precipitates,dislocation cell structures,and serrated flow induced by dynamic strain aging.At higher temperatures,strain rate influences softening pathways:under HSR at 450℃,the effect of twinning shifts from strengthening to facilitating dynamic recrystallization(DRX),resulting in substantial grain refinement(-4 μm,81%area fraction at a strain of 0.6).In contrast,at LSR,softening is dominated by dynamic recovery at 350℃,with limited DRX(-4 μm grains,10%area fraction at a strain of 0.6)occurs at 400℃.These findings clarify the dual role of twinning and its interaction with rate-temperature conditions,providing valuable insights into optimizing the hot processing of rare-earth magnesium alloys.
基金Funded by the National Natural Science Foundation of China Academy of Engineering Physics and Jointly Set up “NSAF” Joint Fund(No.U1430119)
文摘The dynamic tensile behaviors of a newly developed Ti-6 Al-2 Sn-2 Zr-3 Mo-1 Cr-2 Nb-Si alloy（referred as TC21 in China） over a wide range of strain rates from quasi-static to dynamic regimes(0.001-1 200 s-1) at different temperatures were experimentally investigated. A split Hopkinson tension bar apparatus and a static material testing system were utilized to study the stress-strain responses under uniaxial tension loading condition. The experimental results indicate that the tensile behavior of TC21 titanium alloy is dependent on the strain rate and temperature. The values of initial yield stress increase with increasing strain rate and decreasing temperature. The effects of strain rate and temperature on the initial yield behavior are estimated by introducing two sensitivity parameters. The phenomenological-based constitutive model, Johnson-Cook model, is suitably modified to describe the rate-temperature dependent constitutive behavior of TC21 titanium alloy. It is observed that the modified model is in good agreement with the experimental data subjected to the investigated range of strain rates and temperatures.
