温度对U-5.7Nb合金动态压缩力学性能影响研究

Dynamic Compression Behavior of U-5.7Nb Alloy at Elevated Temperatures

利用Hopkinson杆装置开展了–100~400℃较宽温度范围下U-5.7Nb合金的动态压缩变形行为研究,结果表明:U-5.7Nb合金的压缩性能对温度和应变率较为敏感。随实验温度升高,屈服应力迅速下降,下降速率约为2 MPa/℃,而加工硬化行为基本不变,当温度升高至200℃以上时,静动态应力~应变曲线形态由"双屈服"转变为"单屈服";随应变率提高,屈服应力及去孪生引起的硬化模量均明显增大。最后,结合金相分析结果讨论了400℃时静动态力学曲线分歧的来源。

High strain rate compression experiments of U-5.7Nb alloy were conducted at temperatures from -100 to 400 ℃ with split Hopkinson pressure bar apparatus. Results show that the compressive stress-strain response depends sensitively on the applied strain rate and test temperature. The yield stress of U-5.7Nb alloy is found to decrease rapidly with the increasing temperature at a rate of about 2 MPa/℃, while the work hardening rate is relatively constant. At temperatures higher than 200 ℃, the shape of the stress-strain curves changes from duplex yield character to elastic-plastic character for both quasi-static and dynamic compression experiments. The hardening modulus caused by detwinning and the yield stress increase obviously with the increasing strain rates. Finally, the divergency of the low- and high-rate deformation curves at temperature of 400 ℃ was discussed based on the optical micrography