固溶温度对Mn-N型双相不锈钢拉伸变形行为的影响

  • 金淼 李文权 郝硕 梅瑞雪 李娜 陈雷
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  • 1. 燕山大学机械工程学院  秦皇岛  066004
    2. 国家冷轧板带装备及工艺工程技术研究中心  秦皇岛  066004

收稿日期: 2018-06-27

  修回日期: 2018-07-29

  网络出版日期: 2018-10-24

基金资助

国家自然科学基金项目;河北省自然科学基金;中国博士后科学基金;中国博士后科学基金

Effect of Solution Temperature on Tensile Deformation Behavior of Mn-N Bearing Duplex Stainless Steel

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  • 1 College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004,China 2 National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Qinhuangdao 066004, China

Received date: 2018-06-27

  Revised date: 2018-07-29

  Online published: 2018-10-24

Supported by

National Natural Science Foundation of China;Natural Science Foundation of Hebei province, China;Project funded by China Post Doctoral Science Foundation;Project funded by China Post Doctoral Science Foundation

摘要

在Gleeble-3800试验机上进行了一种新型Mn-N合金化双相不锈钢的拉伸变形试验,获得了不同固溶温度下(1000-1200℃)试验钢的力学性能指标及加工硬化规律。利用光学显微镜(OM),扫描电镜(SEM)和电子背散射衍射技术(EBSD)研究了固溶温度对试验钢的形变亚结构及断裂特征的影响,探讨了固溶温度影响加工硬化的机理。结果表明,随着固溶温度的升高,试验钢屈服强度与抗拉强度均逐渐降低,而延伸率(均匀延伸率和断裂延伸率)则先升高后降低。其中,1100℃固溶时试验钢的塑性最佳,均匀延伸率可达46.7%,且综合力学性能优异,强塑积达44.6GPa·%。不同固溶温度下,试验钢的加工硬化率随应变的增加均表现为开始迅速下降,经再次升高后再下降的“三阶段”特征,但随着固溶温度升高,加工硬化率升高的趋势减弱。经EBSD分析发现,试验钢中奥氏体相发生了形变诱导马氏体相变,且相变表现为γ→ε→α′和γ→α′两种演化机制,从而形成TRIP效应使得加工硬化率升高、塑性增加,但较高的固溶温度会使马氏体转变受到抑制。断口结果表明,不同固溶温度下铁素体与形变诱导马氏体均表现出解理断裂特征,而残余奥氏体则主要为韧性断裂。经计算,随着固溶温度增加(1000-1200℃),奥氏体相的Md30值从81℃降到38℃,即奥氏体稳定性增加,减弱了TRIP效应,进而导致试验钢加工硬化和增塑效果降低。

本文引用格式

金淼 李文权 郝硕 梅瑞雪 李娜 陈雷 . 固溶温度对Mn-N型双相不锈钢拉伸变形行为的影响[J]. 金属学报, 0 : 0 -0 . DOI: 10.119000412.1961.2018.00276

Abstract

Advanced duplex stainless steels (DSSs) in which Ni is mostly or completely replaced by Mn and N have newly been developed in recent years. Such Mn-N bearing DSSs can readily achieve exceptional room-temperature tensile properties through the transformation-induced plasticity (TRIP) effect of metastable austenite. During the processing of DSSs, solution treatment is a critical step that tailors the phase fraction and the overall properties. In particular, the phase chemistry can change due to different element partitioning between the two constituents, resulting in a different TRIP kinetics, when DSS is annealed at different temperature. In this work, the effect of solution temperature on tensile deformation behavior of a new Mn-N bearing DSS is studied. Tensile deformation tests were carried out on a Gleeble-3800 testing machine. The mechanical properties and work-hardening characteristic of the steels annealed at different solution temperature (1000-1200℃) were obtained. The effects of solution temperature on the deformation substructure and fracture characteristics were investigated by optical microscope (OM), scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD). The results show that as the solution temperature increases, the yield strength and tensile strength of the steels decrease, while the elongation (uniform elongation and total elongation) increases firstly and then decreases. The steel annealed at 1100℃ shows the optimum uniform elongation with 46.7%, and a better combination of ultimate tensile strength and ductility with approximately 44.6 GPa·%. The work-hardening rate of the steel shows a three-stage characteristic, namely it declines firstly and then increases and subsequently declines again as the strain increases. However, the increasing extent of the work-hardening rate decreases as the solution temperature increases. The EBSD analysis shows that the strain-induced martensitic transformation (SIMT) of metastable austenite which causes the transformation induced plasticity (TRIP) have two evolution mechanisms of γ→ε→α' and γ→α'. But SIMT can be suppressed when the solution temperature increases. The fracture surfaces of specimens annealed at different temperature show a quasi-cleavage mode, in which both ferrite and strain-induced martensite exhibit cleavage fracture while the residual austenite displays a dimple-mode fracture. Furthermore, the Md30 which can characterize the stability of metastable austenite was calculated. It decreases from 81℃ to 38℃ as the solution temperature increases from 1000℃ to 1200℃. This indicates that the TRIP effect gets weakening at a higher solution temperature, the work-hardening and plasticity therefore decrease.
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