400℃退火对ECAP形变Q235钢的强度和位错强化的影响

将经过淬火预处理和等通道转角挤压加工(ECAP)的Q235钢进行400℃退火.采用拉伸试验、X射线衍射(XRD)分析及描述强度-位错密度关系的Taylor公式,研究400℃退火对ECAP形变低碳钢的强度和位错强化的影响.拉伸试验表明:400℃退火使ECAP形变Q235钢强度降低,屈服强度从825 MPa下降到725 MPa,加工硬化能力和塑性显著提高.基于XRD分析和Taylor公式的定量计算说明,400℃退火对ECAP形变Q235钢的位错强化影响很小,实际强度的降低不是来自于位错强化的降低,而是来自于其他强化机制(晶界、亚晶界等)的降低.

Effect of 400 ℃ annealing on strength and dislocation strengthening of Q235 steel processed by equal-channel angular pressing

Q235 steel was quenched and subjected to equal-channel angular pressing(ECAP) proces-sing.The effect of 400 ℃ annealing on strength and dislocation strengthening of the ECAP-processed Q235 steel was investigated by tensile testing,X-ray diffractometer analysis and Taylor equation of strength-dislocation density relationship.Tensile testing indicates that the yield strength of the ECAPed Q235 steel is decreased from 825 MPa to 725 Mpa by 400 ℃ annealing,while the strain hardening capacity and ductility are obviously improved.The theoretical calculation based on X-ray diffractometer analysis and Taylor equation indicates that 400 ℃ annealing has slight influence on the dislocation strengthening.The decreasing of strength is not due to the dislocation strengthening decrease,but may due to grain boundary or subgrain boundary strengthening.