高锰奥氏体钢动态压缩性能及绝热剪切行为

Dynamic Compression Properties and Adiabatic Shear Behavior of NPR Steel

摘要:

采用微型霍普金森压杆系统，研究了一种高锰奥氏体钢（NPR钢）在超高应变速率下的动态压缩性能和剧烈塑性变形微观结构。NPR钢在超高冲击下表现出卓越的抗冲击性和应变硬化能力，屈服强度约为550 MPa，极限抗压强度约为1 500 MPa，断裂应变为0.7。通过分析准静态和动态条件下的应变速率敏感性系数λ，发现NPR钢具有2个不同的应变速率敏感区。在应变速率为1×10⁴ s^-1时，NPR钢未发生断裂，沿冲击截面晶界处产生大量聚集型微孔洞，孔洞的形成方向与冲击方向呈65°。随着应变率增加到2×10⁴ s^-1，NPR钢发生断裂，冲击截面出现由大量微孔洞聚集长大形成的绝热剪切带，绝热剪切带的生长方向与冲击方向呈70°。此外，沿冲击方向形成大量的异质结构，包括扭折带、形变孪晶以及孪晶相互作用区域产生的旋转纳米晶，表明在超高应变率下，NPR钢结构具有复杂的损伤机制。

Abstract:

Using a miniature split Hopkinson pressure bar （m-SHPB） system， the dynamic compression properties and severe plastic deformation microstructure of a high-manganese austenitic steel （NPR） were investigated under ultra-high strain rates. The NPR steel demonstrated excellent impact resistance and strain-hardening capability under ultra-high impact loading， with a yield strength of approximately 550 MPa， an ultimate compressive strength of approximately 1 500 MPa， and a fracture strain of 0.7. Analysis of the strain-rate sensitivity coefficient （λ） under quasi-static and dynamic conditions revealed two distinct strain-rate-sensitive regions for NPR steel. At a strain rate of 1×10⁴ s^-1， NPR steel did not fracture， but a significant number of aggregated microvoids formed along grain boundaries on the impact cross section， with the pore initiation direction oriented at an angle of 65° relative to the impact direction. As the strain rate increased to 2×10⁴ s^-1， NPR steel fractured， with adiabatic shear bands forming on the impact cross section due to the coalescence and growth of these microvoids， oriented at an angle of 70° to the impact direction. Additionally， a large number of heterogeneous structures was formed along the impact direction， including kink bands， deformation twins， and rotational nanocrystals generated in twin-twin interaction regions， indicating that NPR steel exhibits complex damage mechanisms under ultra-high strain rates.