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

doi:10.13251/j.issn.0254-6051.2021.12.006

Abstract

Abstract: 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.

Key words: austenite matrix, low density steel, Ni content, B2 phase, hot rolling, mechanical properties

CLC Number:

TG142.1

Wang Fengquan, Sun Ting, Wang Maoqiu, Yu Wenchao, Zhou Xiaolong. Microstructure and mechanical properties of low density austenitic matrix hot rolling steel with different Ni contents[J]. Heat Treatment of Metals, 2021, 46(12): 31-39.

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