After four ECAP deformation passes, the sizes of subgrains change little, but the subgrain boundary becomes straight and thinner, the increment of hardness is insignificant.

• 经过4道次连续ECAP变形后, 亚晶并未进一步细化, 但亚晶界趋于平直、清晰, 且亚晶内部基本未见位错组织, 材料硬度提高也不显著；