贝氏体形态对细晶铁素体/贝氏体双相钢室温力学性能的影响

基于过冷奥氏体动态相变的思想,通过两道次压缩变形结合控制冷却的热模拟轧制工艺,获得不同贝氏体含量及形态的细晶铁素体贝氏体双相钢。通过显微组织观察及力学性能测试,考察了第二相贝氏体特征对双相钢室温拉伸变形行为的影响。研究结果表明,形变后快速冷却可获得无碳板条状贝氏体,较慢的冷速或在贝氏体转变区保温处理可获得粒状贝氏体。贝氏体体积分数大于20%左右的细晶铁素体/贝氏体双相钢具有低的屈服强度,高的抗拉强度,高的伸长率,低屈强比以及连续屈服特性。屈服强度既与铁素体晶粒尺寸相关,也与贝氏体形态和数量相关。板条贝氏体引起的屈服强度提高大于粒状贝氏体,粒状贝氏体具有比板条贝氏体更好的塑性。

Effect of bainite characteristics on room temperature mechanical properties of fine ferrite/bainite dual phase steel

Fine ferrite/bainite dual phase microstructures were achieved by two pass compression process combing with the controlled cooling process on thermal simulation, which was on the basis of dynamic transformation of undercooled austenite. The effects of bainite characteristics on the room temperature mechanical behavior were conducted. The results show that carbon free lath bainites are obtained by fast cooling directly after deformation, and granular bainites are achieved by slow cooling or holding at bainite transformation region. When the volume fraction of bainite exceeds about 20%, the stress strain curve shows continuous yielding, the dual phase steel has low yield strength, high ultimate strength, good plastic elongation and low yield strength ratio. The yield strength is related to not only the ferrite grain size but also bainite morphology and the volume fraction. Lath bainite has greater strengthening effect on the yielding strength than granular bainite. But granular bainite has greater plasticity than lath bainite.