冷轧中锰钢的超塑性与组织结构演化行为

 为了研究含铝冷轧中锰钢的超塑性能和在超塑性变形下的组织结构演化过程,对冷轧含铝中锰钢在800 ℃进行了高温拉伸试验和不同变形量下的微观组织结构表征。研究结果表明,0.05C5Mn2Al、0.10C5Mn2Al和0.15C5Mn3Al钢伸长率分别达到了740%、850%和350%,都获得了超塑性现象,EBSD表征结果表明0.05C5Mn2Al、0.10C5Mn2Al两种冷轧组织均匀细小,在高温拉伸过程中具有较高的稳定性,拉伸过程中铁素体与原奥氏体均匀长大,且最大晶粒尺寸小于10 μm;但0.15C5Mn3Al冷轧组织存在条带状的铁素体,该组织易于通过吞并细小的铁素体和原奥氏体晶粒而异常长大,高温拉伸后的尺寸达到了20 μm。通过对3种含铝冷轧中锰钢的超塑性行为与微观组织结构演化关系分析,认为初始均匀一致的冷轧组织具有高的组织稳定性而有利于超塑性,而具有粗大条带状的铁素体组织易于发生异常长大而不利于超塑性。

Superplasticity and microstructure evaluation of cold rolled medium manganese steels

In order to study the superplastic properties of aluminum-containing cold-rolled medium-manganese steel and the evolution of its microstructure under superplastic deformation,cold-rolled aluminum-containing medium-manganese steel was subjected to a high-temperature tensile test at 800 ℃ and the microstructure under different deformation. The results show that the elongations of 0.05C5Mn2Al,0.10C5Mn2Al and 0.15C5Mn3Al steels have reached 740%,850% and 350%,respectively,and they have obtained superplasticity. The EBSD characterization results show that the two cold-rolled microstructures of 0.05C5Mn2Al and 0.10C5Mn2Al are uniform and fine. It has high stability during high-temperature tensile process. During the tensile process,ferrite and original austenite grow uniformly,and the maximum grain size is less than 10 μm. However,0.15C5Mn3Al cold rolled microstructure has band-shaped ferrite. This microstructure is easy to grow abnormally by annexing fine ferrite and original austenite grains,and the size reaches 20 μm after high temperature tensile. By analyzing the relationship between the superplastic behavior and microstructure evolution of three cold-rolled medium-manganese steels containing Al,it is considered that the initially uniform cold-rolled microstructure has high stability which is conducive to superplasticity. Band-shaped ferrite is prone to abnormal growth and not conducive to superplasticity.