It is found that by a thermo-mechanical treatment under severe undercooling, an ultra-fine and gradient grain structure can be obtained.

• 同时采用具有自主知识产权的深过冷热机械处理获得梯度细晶显微组织,认为通过轧制形变前的深过冷进一步降低形变温度是获得超细晶粒的关键。