材料期刊网

通过拉伸和撕裂试验及SEM、断口和EBSD晶粒观察,研究了不同回火温度对22MnB5钢力学性能、显微组织、断口形貌及晶粒尺寸的影响.结果表明:在420 ～720℃范围内,淬火试样随回火温度升高,强度降低,韧性增加,吸能性能提升;单位面积裂纹形核功与回火温度线性无关.淬火试样420℃回火后,部分马氏体开始回复,析出碳化物;温度升高至620℃时,马氏体消失,形成铁素体,碳化物长大.原始试样断口韧窝大且深,淬火试样断口出现大量解理面;420℃回火后断口形貌为韧窝和解理面,620℃回火后断口形貌为细小均匀的韧窝.原始试样淬火后晶粒变小,最大值从10.246 μm减小至2.934 μm,回火后尺寸峰值向右移动,晶粒长大,出现少量直径小于1μm的晶粒.

Effects of tempering temperature on mechanical property,microstructure,fracture morphology and grain size of 22MnB5 steel were analyzed by means of uniaxial tensile test,tear test,SEM and EBSD technique.The results show that in the range of 420-720 ℃,with increasing tempering temperature,the tensile strength of the steel decreases,and the elongation and energy absorption ability can be improved.There is no linear relationship between the unit area crack nucleation energy and tempering temperature.Martensite recovery and carbides precipitation are found during tempering at 420 ℃,martensite disappears and carbides begin to grow when tempering at 620 ℃.Fracture morphology of the as-received steel is typical ductile fracture with large and deep dimples,and brittle fracture with a large number of cleavage planes is found in the quenched steel.Mixed-rupture characteristics of cleavage and dimples is found in the steel tempered at 420 ℃,small and uniform dimples is found in the steel tempered at 620 ℃.The grain size of the steel are refined after quenching,and the average grain size reduces from 10.246 μm to 2.934 μm,the grain size increases with increasing tempering temperature and a small amount of grains with a diameter of less than 1 μm are observed.