The grain of gear blanks need to be ultra-refined for realizing superplastic precision forming of gears.The grain of samples was refined from 30~40μm

to 4～5μm after three passes of treatment repeated heating and cooling.Then the samples were put into a designed high pressure torsion apparatus, which was fixed on the torsion press of 2000kN. The sample was twisted for half rotation,under the steady pressure of 100kN,which further enhanced the grain ultra-refinement by deformation.

The results reveal that the grain is refined clearly and equiaxed,The size of grain

 reaches 1μm. The samples have characteristics of the coupled performances after treatment of coupled transformation with deformation.

为实现齿轮零件的超塑性精密成形,需要对齿坯材料晶粒进行超细化。试样经过3个道次的循环加热和冷却处理后,晶粒尺寸由初始的30～40μm细化到4～5μm,再将试样置于设计好的高压扭转装置内,利用2000kN的扭转压力机,在100kN保压状态下,使试样扭转0.5圈,通过形变进一步促进晶粒的超细化。结果表明：经过相变和形变耦合处理后,试样具备性能耦合的特征,晶粒得到了明显的细化和等轴化,晶粒尺寸达到了1μm。