Improvement of Formability by Moderate Temperature Forming and Thermo-mechanical Process and Examination of Fatigue Properties of TRIP-aided Dual-phase Steel Sheets.

trip辅助双相钢（TDP钢）的发展是为了通过减轻车辆重量来提高安全性和燃油效率。本研究的目的是提高TDP钢的拉伸成形性和拉伸法兰性，并对TDP钢的疲劳强度进行检测。在20 ~ 200℃的温度下进行成形，提高了TDP钢的拉伸成形性能和拉伸翻边性。残余奥氏体的Ms温度越低，可成形性越好，最佳成形温度越低。α + γ区域的热机械过程产生了大量的残余奥氏体和细小的组织，但增加了残余奥氏体的Ms温度，特别是对于低锰和低硅钢。由于残余奥氏体的应变诱导转变和基体与第二相强度差异引起的内应力，TDP钢出现了较大的疲劳硬化。随着试验温度的升高，疲劳硬化程度降低。与传统双相钢相比，在100 ~ 200℃的温度下获得了更高的疲劳极限。原因正在调查中。

TRIP-aided dual-phase steels (TDP steels) have been developed to improve safety and fuel efficiency by reducing vehicle weight. The purpose of the present investigation is to improve stretch-formability and stretch-flange-ability and to examine fatigue strength of TDP steels.The stretch-formability and stretch-flangeability of TDP steels were improved by moderate temperature forming at 20ﾟC to 200ﾟC. The lower Ms temperature of the retained austenite, the greater these formability and the lower the optimum forming temperature. Thermo-mechanical process in alpha+gamma region gave a significant amount of retained austenite and fine microstructure, but increased the retained austenite Ms temperature, particularly for low manganese and low sili-con steels.Great fatigue hardening appeared for TDP steels owing to strain induced transformation of the retained austenite and internal stress resulting from a difference of strength between matrix and second phase. The fatigue hardening decreased with increasing testing temperature. Higher fatigue limit compared to that of a conventional dual-phase steel was obtained at 100 to 200ﾟC. The reason is under investigation.