TWIP钢的动态力学性能及变形机制研究

Dynamic Mechanical Properties and Deformation Mechanism of TWIP Steel

利用Zwick/Roell Z100万能材料试验机和Hopkinson拉杆对TWIP钢进行了准静态及动态力学性能的研究。基于力学实验结果,修正了Johnson-Cook动态本构模型中应变硬化项以及应变强化项。采用X射线衍射(XRD)、扫描电镜(SEM)、电子背散射衍射(EBSD)技术对TWIP钢拉伸变形前后的组织进行了观察与分析。结果表明:TWIP钢在准静态加载下表现为负应变率敏感性,动态加载时表现为正应变率敏感性。拉伸过程中,孪生诱发塑性是TWIP钢的主要变形机制,同时滑移也起到重要作用;动态加载下TWIP钢中形变孪晶的起始应变和孪晶体积分数均小于准静态加载过程;形变孪晶的生成以及孪晶相互作用导致的晶粒细化,使TWIP钢兼具高强度、高塑性及高动态吸能性能,在抗冲击、抗爆领域具有广泛的应用前景。

The quasi-static and dynamic mechanical properties of TWIP steel were investigated by Zwick/Roell Z100 universal testing machine and Hopkinson tensile bar.The strain hardening and strain strengthening in Johnson-Cook dynamic constitutive model were modified based on mechanical test results.The microstructure of TWIP steel before and after tensile deformation were analyzed by XRD,SEM and EBSD.The results demonstrate that TWIP steel exhibits negative strain rate sensitivity when it exhibits quasi-static loads,while it exhibits positive strain rate sensitivity when subjected to dynamic loads.Twinning induced plasticity is the primary deformation mechanism of TWIP steel during tensile process,and slip also plays a significant role.The initial strain of twins in TWIP steel under dynamic loading is less than that under quasi-static loading,and the dislocation density is higher than that under quasi-static loading.TWIP steel has exceptional strength and plasticity because deformation twins and the grain refinement brought on by twin contact,implying that it has a broad application in the fields of impact resistance and anti-explosion.