Mn含量对高强韧TWIP球墨铸铁组织和性能的影响

Effect of Mn Content on Microstructures and Properties of High-Strength and High-Toughness TWIP Ductile Iron

采用熔炼法制备了3种锰含量的Fe-xMn-3.5C-3Si-3Cu-8Ni(x=10、13、16)合金铸铁,铸铁铸态组织为奥氏体基体上分布着球形石墨和碳化物。随着锰含量提高,凝固组织中碳化物数量增多,经1 050℃保温10 h固溶处理后,获得奥氏体与石墨两相组织。经过拉伸变形,奥氏体基体上出现大量形变孪晶,铸铁表现出极高的强度和塑性。研究表明,这种铸铁的高强韧性源于形变过程中的TWIP效应,锰含量越高,形变孪晶越密集,TWIP效应越显著,铸铁的综合力学性能越优异。当锰含量为16%时,抗拉强度达到最大值726.5 MPa,伸长率也高达29.36%,抗弯强度和冲击韧度也分别增加到1 423 MPa和161.5 J.cm-2,综合力学性能远高于其他同类型普通球墨铸铁。

The Fe-xMn-3.5C-3Si-3Cu-8Ni （x=10, 13, 16） alloys with three different contents of manganese were prepared. Their as-cast structures are composed of spherical graphite and carbide, which dispersed in the austenite matrix, and the carbide amount increases with the increase of manganese content. After solution treatment at 1 050 ℃for 10 h, the microstructure of the iron changed into two phases： austenite and graphite. There were a large number of deformation twins in the austenite matrix after tensile deformation, which indicated extremely high strength and plasticity. The research result shows that the high strength and plasticity of the cast irons result from the TWIP effect in the deformation process. The higher the manganese content, the more intensive the deformation twins, and the more obvious the TWIP effect, thereby the better comprehensive mechanical properties. When the manganese content is 16 wt.%, the tensile strength of the ductile iron reaches its maximum value of 726.5 MPa; its elongation also reaches 29.36%, and its bending strength and impact toughness up to 1 423 MPa and 161.5 J ·cm^-1, respectively. It is clear that the cast irons are superior in performance to other ductile irons of the same type.