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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 microstructures and strengthening and toughening mechanism of 65Mn steel wire subjected to pre-cooling deformation and rapid heating at low temperature were studied. Work shows that in order to obtain ultrafine grained grains, the original structure should be pseudo- pseudo- and pro-eutectoid ferrite will produce coarse subgrains. When the heating rate exceeds 12 ℃ / s, rapid cooling of pre-cooled deformed steel will only appear multilateral, and no recrystallization process. Rapid heating slightly higher than the A_c3 temperature, the quenched steel will appear a number of non-lath martensite lamellar dislocation, which contains high-density dislocations and uniform precipitation of ε carbides. Tissue characteristics after hot deformation quenching are dislocation cells and sub-crystals evenly distributed on the matrix, the main body of martensite and deformation-induced transformation of bainite and carbides. Carbide mainly along grain boundaries, slip band interface precipitated into a fir-like. Steel wire after ultrafine grained heat treatment can get good overall performance and surface quality, grain size of 11 to 13. Finally, the toughening mechanism of this process is discussed.