ZHANG Ming-ya
,
ZHU Fu-xian
,
ZHENG Dong-sheng
钢铁研究学报(英文版)
Through the comparison of microstructure for polygonal ferrite (PF) matrix transformation induced plasticity (TRIP) seamless steel tube at different positions before and after tensile rupture, the transformation behavior of retained austenite (RA) was studied. The results showed that there were no yield points in tensile process and the splendid elongation and tensile strength were contributed by the uniform ferrite/bainite grains and the transformation of RA. The stability of RA was to some extent in inverse proportion with the ability of transformation induced plasticity. The coarse retained austenite located in ferrite and ferrite/bainite laths were all transformed into martensite during the tensile process.
关键词:
TRIP steel
,
retained austenite
,
austempering
,
heat treatment
JIANG Hai-tao
,
DING Wei
,
TANG Di
,
HUANG Wei
钢铁研究学报(英文版)
Mechanical properties and microstructure in high strength hot dip galvanizing TRIP steel were investigated by optical microscope (OM), transmission electron microscope (TEM), X-ray diffraction (XRD), dilatometry and mechanical testing. On the heat treatment process of different intercritical annealing (IA) temperatures, isothermal bainitic transformation (IBT) temperatures and IBT time, this steel shows excellent mechanical properties with tensile strength over 780 MPa and elongation more than 22%. IBT time is a crucial factor in determining the mechanical properties as it confirms the bainite transformation process, as well as the microstructure of the steel. The microstructure of the hot dip galvanizing TRIP steel consisted of ferrite, bainite, retained austenite and martensite during the short IBT time. The contents of ferrite, bainite, retained austenite and martensite with different IBT time were calculated. The results showed that when IBT time increased from 20 to 60 s, the volume of bainite increased from 14.31% to 16.95% and the volume of retained austenite increased from 13.64% to 16.28%; meanwhile, the volume of martensite decreased from 7.18% to 1.89%. Both the transformation induced plasticity of retained austenite and the hardening of martensite are effective, especially, the latter plays a dominant role in the steel containing 7.18% martensite which shows similar strength characteristics as dual-phase steel, but a better elongation. When martensite volume decreases to 1.89%, the steel shows typical mechanical properties of TRIP, as so small amount of martensite has no obvious effect on the mechanical properties.
关键词:
TRIP steel
,
isothermal bainitic transformation
,
martensite
,
mechanical property
郭延明，王桂新，冯建航，陈翠欣，彭会芬
钢铁研究学报
目前的TRIP钢由于Mn、Si含量较低，室温条件下仅保留约10%的残余奥氏体，结果使变形过程中材料产生的相变诱发塑性量有限，不能满足一些要求产生更大相变诱发塑性场合的需要。研究表明：提高钢中Mn、Si含量并辅以适量其它合金元素(如铬和镍)是提高材料相变诱发塑性的有效途径。研究了Fe-17Mn-5Si-10Cr-4Ni合金在不同应变速率下的变形特性，结果表明：该合金经1100℃×1h正火处理后具有单相奥氏体组织，在1.1×10-4~5.5×10-2 s-1的应变速率内对其进行变形，真应力随真应变的增加而线性增大，且应力的增加与变形速率基本无关。变形速率为1.1×10-2 s-1时，材料的抗拉强度为750MPa，伸长率为49%。该合金在拉伸变形过程中产生如此大变形量的主要原因是发生了奥氏体→ε-M相变，应变速率增加，材料的相变诱发塑性量变化不大，但材料中的ε-M量却逐渐减少。
关键词:
TRIP钢
,
Fe-Mn-Si-based alloy
,
stress-induced martensitic transformation
