温度对T91铁素体/马氏体钢拉伸性能的影响

Influence of temperature on tensile properties of T91 ferritic/martensitic steel

在-30～600℃之间进行了ADS嬗变系统候选结构材料T91铁素体/马氏体钢的拉伸试验研究,分析了温度对拉伸曲线、强塑性、瞬时加工硬化率曲线的影响,通过SEM与TEM观察了样品在不同温度拉伸后的断口形貌和显微组织。结果表明,3种不同的机制分别控制着不同温度区间的变形。在-30～100℃之间,变形机制与螺位错热激活滑移和其它热激活过程有关;在150～375℃之间,材料发生动态应变时效,导致塑性出现低谷,强度下降速率减缓,加工硬化能力增强;在400～600℃之间,动态应变时效消失,动态回复过程控制着材料的变形行为,材料强度迅速下降,塑性快速上升,加工硬化能力减弱。

The effect of temperature on the tensile properties of one of the promising candidate materials for ADS, T91 ferritic/martensitic steel, was investigated in the temperature interval - 30-600 ℃ The evolution of tensile flow curves, strength, ductility and instantaneous work hardening rate curves with temperature were analyzed. SEM observation of the fracture surface and TEM observation of the microstrueture of samples deformed at different temperatures were carried out. The results show that three different deformation mechanisms are operative on three different temperature periods respectively. Between - 30 ℃ and 100 ℃, the deformation mechanism is linked to thermally activated gliding of screw dislocations and other thermal activation processes. Between 150 ℃ and 375 ℃ , DSA （ dynamic strain ageing） takes place, which results in a trough of ductility, drop of the rate of strength decreasing and increase of work hardening ability. Between 400 ℃ and 600 ℃ , dynamic recovery controlls the deformation behavior, leading to dramatic decrease of strength, fast increase of ductility and decrease of work hardening ability.