Cu-P-Cr-Ni-Mo耐候钢双相区多道次轧制模拟的组织演变

 为了实现Cu-P-Cr-Ni-Mo耐候钢的铁素体晶粒细化从而充分提高其强塑性，通过热模拟压缩试验，利用金相、SEM、EBSD等微观组织分析方法研究了其在双相区的多道次压缩变形过程中的组织演变。结果表明，试验钢在变形过程中，第二相（马氏体、贝氏体）呈条带状分布于铁素体基体上，随着道次增加，铁素体晶粒逐步细化，第5道次变形后得到1.8 μm左右的超细晶铁素体。前期铁素体晶粒细化的主要机制是形变强化铁素体相变，即多道次的累积大变形使组织内畸变能增大，铁素体形核点增多，促进铁素体快速析出，形成细小铁素体晶粒；后面几道次变形中，随着应变量继续增大，在铁素体晶粒内形成大量亚晶界，且亚晶界逐步累积扭转成大角度晶界，分割原来的粗大晶粒，发生铁素体连续动态再结晶细化。

Microstructure Evolution of Cu-P-Cr-Ni-Mo Weathering Steel by Multi-Pass Rolling Simulating in the Intercritical Region

The microstructure refinement supplies an alternative approach to improve the strength of low carbon steel without loss of room temperature ductility. The microstructure evolution of weathering steel Cu-P-Cr-Ni-Mo in multi-pass hot deformation in the intercritical region was investigated by means of hot compression simulation. The results indicated that the fine ferrite grains of 1.8 μm can be achieved under the conditions of general large strain through multi-pass deformation in the intercritical region. The banded second phase distributed on the ferrite matrix and turned thinner with the passes increasing. Microstructural analysis shown that at the forehead passes deformation, the strain was large enough to lead strain enhanced ferrite transformation and promoted large number of ferrite nucleation, precipitation and refinement. While the continuously dynamic recrystallization of ferrite was responsible for the ferrite grains refinement at the latter passes deformation. A lot of subgrains appeared and the misorientation angle between subgtrains continuous increasing led to forming high angle grain boundaries (HAGBs) and the coarse grains were segmentated.