摘要:
针对高速冲击下传统金属材料能量释放效率低、动态响应不足等瓶颈问题,研究聚焦于Ti-Zr-Nb-V系难熔高熵合金,利用其多组元协同效应开发出一种单相BCC结构高熵合金(Ti2Zr)1.5NbVAl0.5,其晶格常数3.3501Å,平均晶粒尺寸336.7μm。随后开展了准静态/动态力学测试与直接弹道试验,结果表明,合金具有良好的强塑性协同效应,屈服强度885.2MPa,当压缩应变速率由0.001s-1增大至6000s-1时,屈服强度提升123%,并且低温下对应变速率的敏感性显著高于高温。当冲击速度由734m/s增至1375m/s时,弹丸的破碎程度加剧,准密闭容器内温度场不断升高至峰值2124.15K,相应的释能持续时间由5ms延长至12ms。利用FEM-SPH算法复现了高熵合金侵彻温升与破碎行为,验证了拟合的Johnson-Cook本构参数及Grunsien状态方程的可靠性。微观分析揭示了(Ti2Zr)1.5NbVAl0.5高熵合金能量释放源于绝热剪切带内的位错重组,高速冲击下交滑移抑制导致位错达到饱和状态,并引发局部晶格失稳进一步导致整体结构失效,而低速冲击下动态再结晶行为能够有效延缓失效的进程。
Abstract:
To address the bottlenecks of traditional metal materials such as low energy release efficiency and insufficient dynamic response under high-speed impact, this study focuses on Ti-Zr-Nb-V based refractory high-entropy alloys. By utilizing their multi-component synergistic effect, a single-phase BCC structure high-entropy alloy (Ti2Zr)1.5NbVAl0.5 was developed, with a lattice constant of 3.3501Å and an average grain size of 336.7μm. Subsequently, quasi-static/dynamic mechanical tests and direct ballistic experiments were carried out. The results show that the alloy has a good strength-ductility synergy, with a yield strength of 885.2MPa. When the compressive strain rate increases from 0.001s-1 to 6000s-1, the yield strength increases by 123%, and the sensitivity to strain rate at low temperatures is significantly higher than that at high temperatures. When the impact velocity increases from 734m/s to 1375m/s, the fragmentation degree of the projectile intensifies, the temperature field in the quasi-closed container rises continuously to a peak value of 2124.15K, and the corresponding energy release duration extends from 5ms to 12ms. The FEM-SPH algorithm was used to reproduce the penetration temperature rise and fragmentation behavior of the high-entropy alloy, verifying the reliability of the fitted Johnson-Cook constitutive parameters and Grunsien equation of state. Microscopic analysis reveals that the energy release of the (Ti2Zr)1.5NbVAl0.5 high-entropy alloy originates from dislocation recombination in the adiabatic shear band. Under high-speed impact, the suppression of cross-slip leads to dislocation saturation, which triggers local lattice instability and further causes overall structural failure. However, under low-speed impact, dynamic recrystallization can effectively delay the failure process.