高强韧TWIP铸铁的形变组织与力学性能

Deformed Microstructure and Mechanical Properties of High-Strength and High-Toughness TWIP Cast Iron

采用熔炼法制备出新型Fe-15Ni-12Mn-3.5C-2.5Si高强韧合金铸铁,该合金铸铁经高温固溶碳原子后,表现出高的塑性变形能力,连续冷轧变形量可达50%。拉伸试验结果表明,轧制后的试样经再高温固溶处理,合金的抗拉强度为730.81 MPa,伸长率高达20%,是同类型QT700-2球墨铸铁的伸长率的10倍,并具有较高的加工硬化特性。研究表明,该合金铸铁经固溶处理后组织由奥氏体、球状石墨及少量碳化物组成,良好的塑性是通过奥氏体基体密集孪生切变实现的,其高塑性源于TWIP效应;提高固溶处理温度,铸铁的抗拉强度略有降低而塑性大幅度提高。这种高强韧球墨铸铁合金对于制备减振降噪、安全性高的发动机曲轴、主轴等结构件具有重要的应用前景。

The new Fe-15Ni-12Mn-3.5C-2.5Si alloy cast irons with high strength and toughness were prepared.The alloys have an excellent capacity of plastic deformation after resolution treatment with carbon atoms at high temperature,which was up to 50% continuous cold rolling reduction.The results of tensile test testified that the rolled sample after solution treatment at high temperature exhibited high tensile strength of 730.81 MPa and extreme elongation of 20%.The elongation has been 10 times more than that of the same type of QT700-2 ductile cast iron and it presented higher work-hardening characteristic of plastic deformation.The studies have shown that the soluted matrix microstructure is composed of austenitic and spherical graphite as well as a small amount of carbide.Their high plasticity that resulted from TWIP effect was achieved through intensive twin shear displacement on austenitic matrix.Simultaneously,tensile strength of the cast iron decreased slightly and elongation improved greatly with the increase of solution treatment temperature.This kind of high strength and toughness ductile cast iron alloy would have important application prospects for the preparation of the engine crankshaft,main shaft and other components with the characteristics of vibration,noise reduction and high security.