Microstructure and Deformation Behaviour of Austenitic Low-Density Steels: The Defining Role of B2 Intermetallic Phase

B. Mishra, R. Sarkar, Vajinder Singh, A. Mukhopadhyay, Rohit T. Mathew, V. Madhu, M. Prasad
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引用次数: 9

Abstract

Abstract The feasibility of significant weight reduction in conjunction with the superior strength-ductility combination makes Fe-Mn-Al-C-based steels the candidate material for automotive and structural applications. The alloy chemistry and processing conditions influence the microstructure in low-density steels (LDS); however, their role in deformation behaviour is not fully understood. In the present study, three different austenitic LDS grades viz. Fe-28Mn-9Al-0.9C, Fe-28Mn-9Al-5Ni-0.9C and Fe-15Mn-9Al-5Ni-0.9C alloys in hot-rolled conditions were used for evaluating the role of secondary phases, especially B2 ordered Fe(Ni)Al phase on deformation characteristics. Ni-free LDS microstructure consisted of the γ-matrix with fine κ-carbides, whereas Ni containing low Mn alloy possessed coarser κ-carbides along with B2 in both bamboo-like stringer and polygonal particle morphology in the γ-matrix. The B2 containing alloy exhibited higher strength with reduced tensile ductility than the B2-free alloy. Hardness of the γ-matrix and B2 phase were similar with B2 grains exhibiting distinct pop-in events in the nanoindentation curves indicating incipient plasticity. The γ-matrix and B2 co-deform near yield, and a favourable orientation relationship (OR) between the γ-matrix and B2 facilitated easy slip transfer, while the non-favourable OR controlled ductility by strain accumulation and B2-cracking. The differences in the strain hardening behaviour of B2-free and B2 containing alloys were elucidated based on the changes in dislocation substructure evolution examined by an automated crystal orientation mapping in electron microscopy.
奥氏体低密度钢的组织和变形行为:B2金属间相的决定性作用
fe - mn - al - c基钢显著减轻重量的可行性,加上其优越的强度-延展性组合,使其成为汽车和结构应用的候选材料。合金化学成分和加工条件对低密度钢组织的影响然而,它们在变形行为中的作用尚不完全清楚。本研究采用Fe- 28mn - 9al -0.9 c、Fe- 28mn - 9al - 5ni -0.9 c和Fe- 15mn - 9al - 5ni -0.9 c三种不同奥氏体LDS合金热轧条件下,评价了二次相,特别是B2有序Fe(Ni)Al相对变形特性的影响。无Ni合金的LDS组织由γ-基体中含有细小的κ-碳化物组成,而含Ni合金的低Mn合金在γ-基体中含有较粗的κ-碳化物和B2,呈竹状弦状,呈多边形颗粒形态。与不含B2的合金相比,含B2的合金具有更高的强度,但拉伸延展性降低。γ-基体和B2相的硬度与B2晶粒相似,在纳米压痕曲线上表现出明显的弹出事件,表明塑性初期。γ-基体与B2在屈服附近共变形,γ-基体与B2之间良好的取向关系(OR)有利于滑移传递,而不利的取向关系通过应变积累和B2开裂控制塑性。利用电子显微镜的自动晶体取向图分析了位错亚结构演变的变化,阐明了无B2合金和含B2合金应变硬化行为的差异。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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