【摘要】 用光学显微镜、扫描电子显微镜及X射线衍射仪对20Mn2SiVB钢在贝氏体区不同温度等温不同时间所获得的组织和形态进行了研究。试验表明,20Mn2SiVB钢在贝氏体等温转变时,首先在奥氏体晶界析出贝氏体铁素体,随着等温时间的延长,铁素体板条增多,分割奥氏体晶粒,形成贝氏体铁素体和其板条间的富碳奥氏体岛;在920℃奥氏体化,420℃贝氏体区等温不同时间后空冷所获得组织为:无碳化物贝氏体、粒状贝氏体、残留奥氏体和马氏体,各相的体积分数随着保温时间的不同有所变化。在920℃奥氏体化420℃等温5 min后,试样可获得较好的综合性能,具有一定的TRIP效应,其Rm≈1090 MPa;A≈15.4%。更多还原

【Abstract】 Microstructure and morphologies of 20Mn2 SiVB steel austempered at different temperatures in a salt bath for different time were investigated by means of optical and scanning electron microscopes and X-ray diffractometer. The tests show that bainitic ferrite precipitates at the boundary of the austenite first,and with the prolonging of the isothermal time,the amount of ferrite lath increases. Then the ferrite decollate the austenite grain and lath-shaped bainitic ferrite with little island-shaped austenite formed during the holding time. The results show that carbide-free bainite,granular bainite,retained austenite and martensite can be obtained and the phase portion changes with holding time duration and better comprehensive property can be gained by austenizing at 920 ℃ and isothermal at 420 ℃ holding for 5 min,a certain TRIP effect can be obtained and Rm≈ 1090 MPa,A≈ 15.4%。更多还原