将一种低碳结构钢循环加热淬火得到超细晶粒奥氏体,再以20℃/s的速率将其冷却至两相区进行真应变量为2的大变形, 分析了形变后的瞬态组织.结果表明: 用该工艺制备的超细晶奥氏体在两相区的高速大变形的后期, 始终呈现应变硬化特征,并伴随有一定程度的形变诱导相变或铁素体动态再结晶等软化行为; 同时,在较低温度快速大变形容易在试样的个别碳过饱和区导致应变诱导孪晶马氏体组织的生成,且随着形变温度降低孪晶马氏体量增加. 循环加热淬火前的原始组织影响奥氏体内碳浓度分布,在一定程度上影响冷却变形过程的应力应变行为和形变后的瞬态组织.
Ultra-fine austenite was obtained by repetitive treatment of reheating and quenching of a low carbon steel. Large deformation with true strain (ε=2) was applied when the samples was undercooled to relatively lower temperatures in two-phase region with a cooling rate of 20℃/s, and the results showed that: a work-hardening behavior continuously presented during the after-deforming, while an extent of softening mechanisms, such as deformaiton induced tranforamation (DIF) or recrystallizaiton of ferrtie also existed simutaneously; strain-induced twin martensite formed at some separate locations with over-saturated carbon concentration, and the amount of twin martensite increased with decreasing of deformation temperatrue. The stress-strain behaviors and transient microstructure after deformation were more or less affected the distribution of carbon concentration in the ultra-fine grained austeite which was greatly dependent on the starting microstructre.
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