摘要
研究了经预冷变形快速加热低温形变复合热处理65Mn 钢丝的显微组织及强韧化机理。工作表明为了获得超细晶粒组织,原始组织应全伪共析化,先共析铁素体的出现将产生粗大的亚晶。当加热速度超过12℃/s,预冷变形钢快速加热时将仅出现多边化,而未见再结晶过程。快速加热稍高于 A_c3温度,淬火后钢中将出现若干呈块状的无板条界位错马氏体,其中含有高密度位错和均匀析出的ε碳化物。热形变淬火后的组织特征是位错胞和亚晶均匀地分布在基体上,主体为马氏体及形变诱发转变下贝氏体和碳化物。碳化物主要沿晶界,滑移带界面析出成杉树状。钢丝经超细晶粒形变热处理后可获得很好的综合性能和表面质量,晶粒号为11～13级。最后讨论了本工艺的强韧化机理。
The microstractural features and streng thening mechanism ofprecold worked high speed heating LTMT processed 65Mn steel wire were studied.It showed that in order to obtain ultra fine grained structure,the orginal structuremust be fully quasi eutectoid and any free ferrite precipitated will produce coarsesubgrain.With heating speed greater than 12℃/s the precold worked steel will notappeared any recrystallization and only shows polygonization structure.Heating upto temperature not far above Ac_3 with high speed,after quenching,the steel willshow some no lath boundary martensite areas which look like an aggreation ofsubgrains.There are high dislocation within the α' crystal,and ε-carbide are uni-formly precipitated.New morphology appeared after hot deformation and quenchingare the matrix with uniformly distributed dislocation cells and subgrains,and themain structures are martensite,deformation induced transformation lower bainite andcarbide.Carbides are mainly precipitated along the grain boundaries and slidingband,which sometimes look like fir tree.Steel wire after ultra fine grained LTMTtreated excellent properties are obtained with good surface quality and the grainsize meets 11-13 grade ASTM specification.The strengthening and tougheningmechanism is discussed in detail.
基金
国家自然科学基金
关键词
超细晶粒
形变热处理
钢丝
强韧化
precold worked
ultra fine grain
low temperature thermomechanieal treatment
no lath boundary dislocated martensite
deformation induced transformation
