Q&P热处理工艺对含Cu TRIP钢组织和性能的影响

随着能源的短缺和环境污染的日益严重,汽车轻量化需求日益迫切,如何通过工艺及成分设计革新、获得兼具高强度和高塑性的钢板尤为重要.尝试将Cu作为合金元素加入TRIP钢中,采用淬火配分(QP)工艺对含Cu TRIP钢进行一步法和两步法热处理,通过拉伸试验、X射线衍射分析、扫描电镜、透射电镜等实验手段,对热处理后的组织及性能进行测试和观察,探究了不同热处理工艺对组织和性能的影响.研究结果表明:一步法处理后的显微组织为铁素体、马氏体和残余奥氏体,两步法处理后不仅包含上述3种组织,还含有贝氏体.一步法处理后,抗拉强度达2 200 MPa,拉伸延展率为15%,强塑积为33 GPa·%;两步法处理后综合力学性能优于一步法,在400℃等温5 min后,抗拉强度为1 300 MPa,拉伸延展率为43%,强塑积超过55 GPa·%.实验钢良好的综合力学性能得益于铁素体、马氏体/贝氏体和残余奥氏体的合理配比,变形过程中残余奥氏体的相变诱导塑性效应,以及马氏体位错与Cu粒子的交互作用.

Influence of quenching and partitioning on microstructure and mechanical properties of a Cu-TRIP steel

A Cu-TRIP steel was heat-treated by quenching and partitioning ( Q&P ) processes including one-step (QT=PT, Quenching Temperature, Partitioning Temperature) and two-step(QT≠PT). Microstructures and properties differences were investigated by means of tensile tests, X-Ray diffraction ( XRD ) , scanning electron microscopy ( SEM ) , and transmission electron microscopy ( TEM ) . Results show that microstructure after one-step consists of martensite, ferrite, and retained austenite while that after two-step contains bainite except for the aforementioned three microstructures. Tensile strength and elongation are 2 200 MPa and 15%respectively after one-step, accompanied with a product of strength and elongation of 33 GPa?%. As far as two-step is concerned, a combination of tensile strength of 1 300 MPa and elongation of 43% is obtained at partitioning temperature of 400℃ with the highest product of strength and elongation of ~55 GPa?% which is prior to one-step. The eminent mechanical properties benefit from relative contents of phases, TRIP effect, and interaction between Cu precipitates and dislocation in martensite.