不同镍含量奥氏体基低密度热轧钢的组织与力学性能

研究了3种Fe-18Mn-10Al-1C-(0, 3, 5)Ni-0.08V-0.03Nb(wt%)奥氏体基低密度双相钢在热轧后的组织和力学性能。结果表明,热轧后,试验钢的组织由拉长的奥氏体、条带状B2相及沿再结晶奥氏体晶粒晶界处的块状B2颗粒组成。此外,在奥氏体晶粒和B2颗粒中分别形成了纳米级κ-碳化物和DO₃相。5Ni钢屈服强度高达1352 MPa,这主要是由于奥氏体晶界存在大量纳米级别的B2颗粒以及VC相产生析出强化效果。随着Ni含量的增加,钢的强度与硬度均增加,5Ni钢屈服强度比0Ni钢高116 MPa,归因于5Ni钢中更多的B2相含量(16.9%)。但含Ni钢在强度增加的同时,极大损失了塑性,导致钢的伸长率极低,分析其原因为条带状B2相主要分布在奥氏体晶界处,试样在变形过程中裂纹更易沿晶界断裂,断口有分层现象。

Microstructure and mechanical properties of low density austenitic matrix hot rolling steel with different Ni contents

The microstructure and mechanical properties of three kinds of Fe-18Mn-10Al-1C-(0, 3, 5)Ni-0.08V-0.03Nb (wt%) austenitic matrix low density dual phase steels after hot rolling were studied. The results show that the microstructure of the steel after hot rolling is composed of elongated austenite, band B2 and massive B2 particles along the grain boundaries of recrystallized austenite grains. In addition, nano-sized κ-carbide and DO₃ phase are formed in austenite grains and B2 grains, respectively. The yield strength of the tested 5Ni steel reaches 1352 MPa, which is mainly due to the precipitation strengthening effect of a large number of nano-sized B2 particles and VC phase in the austenite grain boundary. With the increase of Ni content, the strength and hardness of the steel increase, and the yield strength of 5Ni steel is 116 MPa higher than that of 0Ni steel, which is attributed to more B2 phase content (16.9%) in the 5Ni steel. However, while the strength of the Ni-containing steel increases, the plasticity of the steel is greatly lost, resulting in a very low elongation. The reason is that the banded B2 phase is mainly distributed at the austenite grain boundary, and the crack is easier to break along the grain boundary in the process of deformation. In the meantime, delamination can be observed on the fracture surface.