预变形和双级时效对Fe-30Mn-11Al-1.2C奥氏体低密度钢显微组织和力学性能的影响  

Effects of Pre-Strain and Two-Step Aging on Microstructure and Mechanical Properties of Fe-30Mn-11Al-1.2C Austenitic Low-Density Steel

作　　者：任平 陈兴品[1] 王存宇[2] 俞峰[2] 曹文全[2] REN Ping;CHEN Xingpin;WANG Cunyu;YU Feng;CAO Wenquan(College of Materials Science and Engineering,Chongqing University,Chongqing 400044,China;Special Steel Institute,Central Iron and Steel Research Institute,Beijing 100081,China)

机构地区：[1]重庆大学材料科学与工程学院,重庆400044 [2]钢铁研究总院特殊钢研究所,北京100081

出　　处：《金属学报》2022年第6期771-780,共10页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目Nos.51871062;52171105;中央高校基本科研业务费项目No.2020CDJDPT001。

摘　　要：采用EBSD、TEM和万能试验机等研究了冷轧预变形和双级时效对Fe-30Mn-11Al-1.2C (质量分数,%)奥氏体低密度钢微观组织演变和力学性能的影响。结果表明,双级时效可以显著地提高材料的屈服强度,从固溶时的580 MPa到1120 MPa,但同时使得均匀延伸率急剧降低至几乎为0;而经过轧制预变形+双级时效处理后的样品,材料的屈服强度进一步提高,达到1220 MPa,同时材料的均匀延伸率大幅提高至18.2%,钢的综合力学性能得到明显提升。微观组织分析表明,双级时效后材料屈服强度的提升归因于κ′碳化物的有序化强化;预变形可以在奥氏体基体中引入有效的异质形核点,诱导晶内析出;该析出相(析出强化)结合预变形引入位错(形变强化)进一步提高材料的屈服强度,同时提高了材料的应变硬化能力,这是材料高塑性的根本原因。该工艺为奥氏体低密度钢的性能改善提供了新思路。Lightweight Fe-Mn-Al-C steels are promising candidates for automobile structural materials and have gained increased scientific and commercial interest owing to their outstanding mechanical properties and low density.To date,several studies have been conducted to illustrate the mechanism of phase transformation,strengthening,and strain hardening under solution and aging state.Moreover,prestrain before aging as a low-cost and simple method to tailor precipitates and control properties has been widely reported;however,it has been barely investigated in the Fe-Mn-Al-C alloy system.Therefore,in this study,the effects of pre-cold rolling and two-step aging on the microstructure and mechanical properties of Fe-30Mn-11Al-1.2C(mass fraction,%) austenitic low-density steel are investigated using EBSD,TEM,and universal testing machine.Results showed that the yield strength(YS) significantly increased via the two-step aging from 580 MPa(at solution state) to 1120 MPa,but the uniform elongation(UE)sharply decreased to approximately 0.However,after the pre-cold rolling and two-step aging,the YS of the material further improved to 1220 MPa,and the UE significantly increased to 18.2%,which implies an improvement in the comprehensive mechanical properties of the material.According to the microstructure analysis,the increase in YS after the two-step aging was caused by the ordering strengthening effect of κ’carbide.Further,the pre-cold rolling could introduce heterogeneous nucleation sites,inducing intragranular precipitation.The combination of the precipitation strengthening of the precipitates and deformation strengthening induced via the pre-cold rolling further increased the YS of the material.Moreover,these intragranular precipitates could improve the work hardening capability,which is the root cause of the high plasticity of materials.This process provides a novel idea for improving the performance of austenitic lowdensity steels.

关 键 词：Fe-Mn-Al-C钢 低密度钢 轧制预变形 加工硬化 双级时效 

分 类 号：TG142.1[一般工业技术—材料科学与工程]