中碳钢在等通道角挤压过程中的组织演化

Processing of Micro-structural Evolution of a Medium-carbon Steel by Equal-channel Angular Pressing

论述了等通道角挤压(ECAP)技术的基本原理和组织演化过程,采用45钢作为试验材料,在室温条件下进行ECAP试验。试验发现:强烈的剪切变形起初主要发生在铁素体内,使铁素体内形成大量位错缠结和位错胞,构成亚晶,同时,珠光体内剪切变形的结果使渗碳体由原来的层片状被剪切断裂而细化,成为颗粒状,其颗粒尺寸逐渐细化到1μm,之后随同铁素体一道参与大的塑性流动,使原先块状铁素体和珠光体两相组织在大的塑性流动下被融合在一起,形成较均匀的亚微米组织。挤压四道次后,由高密度位错构成的位错胞崩塌变成大角度晶粒,其晶粒尺寸约为200nm,并且颗粒状渗碳体较均匀地分布在铁素体基体上。

This paper described the principles of equal channel angular pressing(ECAP)and evo- lution of fine grained microstructure introduced by ECAP.Experiments were conducted on medium carbon steel to investigate the processing of grain refinement during equal-channel angular pressings. The results show that at first two passes ECAP severe shearing plastic deformation produces a large number of dislocation twines and dislocation grains in the regions of ferrites and with the consequent severe shearing plastic deformation are also produced in the regions of pearlites and lamellar pearlites are broken down and converted into even granular pearlites that are 1μm.At he same time developed sub-grain bands in ferrites will be become equiaxed grains.After four passes,the original lumpy fer- rites and pearlites are homogeneously kneaded by severe plastic flow and the homogeneous high angle boundaries ultra-fine grains in ferrites which are about 200nm can be achieved.