摘要
通过扫描电镜组织观察并结合Gleeble热模拟试验,对两种化学成分不同的1000 MPa级高强钢在盐浴Q&P处理过程中的组织转变进行分析,进一步结合力学性能与XRD位错密度计算,分析组织转变对力学性能的影响.结果表明,试验高强度钢在盐浴Q&P处理过程中发生两阶段相变,盐浴配分过程对第一阶段相变形成的板条马氏体起到回火效果,形成了存在强度差异的复相回火板条马氏体组织,使得两种试验钢屈强比均不高于0.87.随盐浴淬火温度升高,屈服强度与屈强比降低,随配分温度升高,强度和屈强比变化不大.在450℃盐浴配分时,板条马氏体组织部分分解,位错密度降低,导致强度明显降低.
Abstract
Microstructure transformation of two 1000 MPa grade high strength steels with different chemical compositions during salt bath Q&P treatment was analyzed through microstructure observation by scanning electron microscope and Gleeble thermal simulation test.The effect of microstructure transformation on mechanical properties was further analyzed by combining mechanical properties and XRD dislocation density calculation.The results show that two-stage phase transformation occurs during the salt bath Q&P treatment,where the salt-bath partitioning process has a tempering effect on the lath martensite formed in the first phase transformation stage to form a multi-phase tempered lath martensite with different strengths,making the yield ratio of both the tested steels not higher than 0.87.As the salt bath quenching temperature increases,the yield strength and yield ratio decrease,while as the partitioning temperature increases,the strength and yield ratio do not change much.When salt bath partitioned at 450℃,the lath martensite structure is partially decomposed and the dislocation density decreases,leading to a significant reduction in the strength.
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