基于等通道角挤压工艺制备超细晶中碳钢

Ultra-fine grained medium-carbon steel produced by equal-channel angular pressing process

将马氏体相变与强塑性变形工艺相耦合,开发了在马氏体形态下通过等通道角挤压强塑性变形工艺快速制备亚微米级中碳钢。研究表明:马氏体钢快速加热到923K并保温适当时间后进行等通道角挤压,在位错分割、动态再结晶、应变诱导相变的共同作用下,可使过饱和铁素体组织快速细化到0.5μm以内,同时应变诱导使过饱和的碳以碳化物的形式在晶内或晶界以质点的形态弥散析出。通过控制回火温度及时间,可得到最佳铁素体晶粒尺寸以及碳化物分布。试验表明,采用这种工艺制备出的中碳钢超细晶材料具有很高的热稳定性。

Ultrafine grained medium-carbon steel was prepared by heating the steel with martensite microstructure to temperature below Ac1 and then quickly conducting equal-channel angular pressing.The results show that the ultra-fine grained ferrite with mean grain size smaller than 0.5μm is obtained in the steel with martensite microstructure heated to 923K and held for proper time and then ECAPed quickly.The grain refinement is due to the interactions of dislocations,dynamic recrystallization,and strain-induced phase transformation.The fine carbide particles are uniformly precipitated from the supersaturated ferrite inside grains and at grain boundaries during ECAP.The grain size and quantity of ferrite,the size and distribution of carbide particles can be controlled by changing tempering temperature and time.The experiment indicates that the ultra-fine microstructure of the steel exhibits excellent thermal stability.