Morphologies and characteristics of deformation induced martensite during tensile deformation of 304 LN stainless steel 变形形态和特点变形形态和特点,在拉伸变形诱导马氏体不锈钢在拉伸变形诱导马氏体不锈钢 304;Arpan Dasa, , , S. Sivaprasada, M. Ghosha, P.C. Chakrabortib, S. Tarafdera 世界 Arpan,Sivaprasada . . Ghosha 事务所 Chakrabortib,s . Tarafderaa Materials Science and Technology Division, National Metallurgical Laboratory, Jamshedpur 831007, India 材料科学与技术部门、全国冶金实验室,Jamshedpur 831007,印度b Metallurgical and Material Engineering Department, Jadavpur University, Kolkata 700032, India b 冶金和材料工程部门,Jadavpur 大学,加尔各答 700032,印度Received 12 July 2007. Revised 1 September 2007. Accepted 5 September 2007. Available online 12 September 2007. 2007 年 7 月 12 日收到。2007 年 9 月 1 日修订。接受 5 2007 年 9 月。2007 年 9 月 12 日在 网上。Abstract 文摘The austenite (fcc) matrix of 304 LN stainless steel transforms readily to martensites ? (hcp) and (bcc) on deformation. The formation and nucleation mechanism of deformation induced martensite (DIM) during tensile deformation of 304 LN stainless steel has been studied at various strain rates in room temperature. It is investigated that the enhancement of strain rates during tensile deformation promotes the early formation of DIM, while suppressing its saturation value at fracture. Extensive transmission electron microscopy (TEM) studies showed more than one nucleation site for martensite transformation and the transformation mechanisms were observed to be (fcc) ? (hcp), (fcc) (bcc) and (fcc) ? (hcp) (bcc). (fcc)奥氏体不锈钢 304;矩阵的变换 martensites 很容易吗?(hcp)和 (bcc)对变形。机制 的形成和成核诱导马氏体变形(暗)在拉伸变形的 304 不锈钢进行了研究;在不同应变率在室 温。考察了材料的应变率,提高拉伸变形过程中促进最初形成昏暗的,同时抑制饱和值的骨折。 广泛的透射电子显微镜(TEM)研究表明超过一个网站,为马氏体相变,成核转化机制被观察到 被 (fcc)吗?(hcp),(fcc)(bcc)和 (fcc)吗?(hcp)(bcc)。Keywords 关键词Deformation induced martensite; Martensitic transformation; 304 LN stainless steel; Strain rate effect 变形诱导马氏体;马氏体转变;304;不锈钢;应变率效应1. Introduction 1。介绍It is well known that austenitic stainless steels are unstable upon deformation and transforms in to martensite. Such martensitic transformation during plastic deformation imparts a good combination of strength and toughness to austenitic stainless steels. Generally, the martensitic transformation is believed to be triggered when the austenitic stainless steel is deformed at temperatures below Md, a temperature below which the transformation to martensite readily takes place 1 and 2. Over and above the Md temperature, several other factors are thought to influence the martensitic transformation. In fact, a number of investigations 3, 4, 5 and 6 have been carried out to understand the martensitic transformation in metastable systems and a review of these investigations brings out the fact that the extent of such phase transformation is controlled by the chemistry of the material, rate of deformation, strain, stress state and temperature of deformation 3, 5, 7 and 8. In other words, for a better understanding of the plastic deformation behaviour of austenitic stainless steels, it is a priori to have the knowledge on the martensitic transformation characteristics. Although considerable knowledge base is available on this topic for austenitic stainless steels in general, the understanding developed for a particular alloy system under certain deformation conditions cannot be generalised to other metastable systems. Investigations are therefore necessary to understand to the deformation induced phase transformation in specific cases. 众所周知,在奥氏体不锈钢不稳定变形和改造在马氏体。这样的马氏体转变的塑性变形过程 中给予的完美结合的强度和韧性,奥氏体不锈钢。一般地,被认为是马氏体转变时触发奥氏体 不锈钢变形温度低于 Md、转变温度以下,容易发生马氏体1和2。温度超过 Md,其它一些 因素被认为影响马氏体转变。事实上,许多调查3,4和5和6进行了马氏体转变理解在亚 系统和审核这些调查凸显出了事实相变的范围内控制的化学材料,变形速率、应变、应力状 态和变形温度3,5,78。换句话说,为了更好地了解塑性变形奥氏体不锈钢的行为,这是 一个先验的知识转化的马氏体特征。虽然相当知识库可以在主题为奥氏体不锈钢一般来说, 理解为一个特定的合金体系的发展在一定的变形条件不能应用到其他的亚系统。因此有必 要调查了解到变形诱导相变在特定情况下。Accordingly, this investigation presents the evolution of DIM during tensile deformation of 304 LN stainless steel at various strain rates. The morphologies and characterisation of DIM have been studied using optical-image analysis and transmission electron microscope. The influence of strain rate on DIM and its evolution mechanisms in 304 LN stainless steel have been reported. 因此,这项调查了在拉伸变形演化昏暗的 304 不锈钢在不同;应变率。昏暗的特征性的形貌和 研究使用 optical-image 分析和透射电镜观察。应变速率的影响及其演进机制在昏暗;不锈钢 在 304 年曾被报告过。2. Experimental 2。实验AISI Grade 304 LN stainless steel was available in the form of 320 mm outer diameter and 25 mm wall thickness pipe. Chemical compositions (in wt%) of the material are C 0.03, Mn 1.78, Si 0.65, S 0.02, P 0.034, Ni 8.17, Cr 18.73, Mo 0.26, Cu 0.29, N 0.08 and the balance Fe. The Md30 temperature of the present material at which 50% of the austenite transforms to martensite at a true strain of 0.30 calculated from the equation of Angel 9 is found to be 2.756 C. Microstructure of the as-received material is given in Fig. 1. Room temperature tensile tests were carried out on 6