ZM1镁合金的滚轧形变强化及机理

研究了ＺＭ１铸造镁合金的表面滚压强化特性。结果表明，密排六方结构的ＺＭ１镁合金的表面滚压强化效果相当显著，缺口疲劳极限提高达１５７％～２１２％，并大大超过未滚压的光滑疲劳极限。高的缺口疲劳强度可为构件提供充裕的强度裕度，缺口疲劳极限大于光滑疲劳极限可为构件的等强度设计提供可能性。滚压时该镁合金通过滑移和孪生两种方式进行塑性变形，伴随着位错密度的显著增高和引入高的残余压应力。缺口疲劳极限大幅度地提高主要归因于残余压应力有效地延缓疲劳裂纹的扩展以及显著地降低疲劳缺口敏感性的作用。此即表面形变残余压应力强化的观点。

SURFACE PLASTIC DEFORMATION STRENGTHENINGBEHAVIOURS AND ITS MECHANISM OFMAGNESIUM ALLOY OF ZM1

The surface plastic deformation strengthening behaviours of magnesium alloyof ZM1 are studied.The results show that there is an excellent surface plastic defor-mation strengthening effect for magnesium alloy of ZM1 with hexagonal close-packedstructure, the increments of the notch fatigue limit is about 157%-212% after surfacerolling and is greatly above the smooth fatigue limit of non-rolling. The high notch fati-gue strength can provide extra ample strength for parts, and notch fatigue limitthat exceeded the smooth fatigue limit can also provide a possibility for equel strengthdesign of parts. Duriag surface rolling, the plastic deformation can be carried out in thesurface layer of specimens by way of both slip and twin, with increasing the dislocationdensity and the introducing the high residual compressive stresses. The impro vement ofnotch fatigue limit is mainly attributed to the high residual compressive stresses. Basedon this, a new strengthening viewpoint of residual stress is proposed, which the residualcompressive stresses play a dominant role in the fatigue strength for surface plasticdeformation parts.