【摘要】 通过扫描电镜（SEM）、X射线衍射仪（XRD）和万能力学试验机等方法，系统研究了预变形4%的QP980钢经200～600℃回火处理后的微观组织演变以及力学性能。结果表明，预变形4%的QP980钢的显微组织仍为铁素体、马氏体和少量残留奥氏体。随着回火温度升高，马氏体与残留奥氏体逐渐分解，并伴随析出细小弥散的过渡η-Fe₂C碳化物，最终在600℃转变为稳定的θ-Fe₃C,形成回火索氏体。在此过程中，试样的强度与硬度随回火温度升高呈先增后降的趋势，在300℃回火时显微硬度达到峰值（340 HV0.5）,断后伸长率则先略降后回升。经300℃×20 min回火后，试样可获得较理想的强塑性匹配（抗拉强度1267 MPa,断后伸长率17.2%）,这主要归因于残留奥氏体的TRIP效应及过渡碳化物的弥散强化。拉伸断口分析显示，所有试样均存在明显韧窝，表现为典型韧性断裂，其中300～400℃回火断口较光滑，500～600℃回火时“颈缩”程度更为显著。更多还原

【Abstract】 Microstructure evolution and mechanical properties of QP980 steel with pre-deformation of 4% after tempering at 200-600 ℃ were systematically investigated by means of scanning electron microscope（SEM）, X-ray diffractometer（XRD） and universal mechanical testing machine. The results show that the microstructure of the 4% pre-deformed QP980 steel still consists of ferrite, martensite, and a small amount of retained austenite. As the tempering temperature increases, both the martensite and retained austenite gradually decompose, accompanied by the precipitation of finely dispersed transitional η-Fe₂C carbides. These carbides eventually transform into stable θ-Fe₃C at 600 ℃, leading to the formation of a typical tempered martensite. During this process, the strength and hardness of the specimen first increase and then decrease with rising tempering temperature, reaching a peak microhardness of 340 HV0.5 at 300 ℃, while the elongation after fracture first slightly drops and then recovers. After tempering at 300 ℃ for 20 min, the specimen achieves an optimal strength-ductility balance（tensile strength of 1267 MPa, elongation of 17.2%）, which is primarily attributed to the TRIP effect of the retained austenite and the dispersion strengthening of the transitional carbides. Tensile fracture analysis reveals that all specimens exhibit obvious dimples, characteristic of typical ductile fracture. Among them, the fracture of the specimens tempered at 300-400 ℃ is relatively smooth, while those tempered at 500-600 ℃ show more pronounced necking.更多还原