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提出采用孔挤压方法来提高7A85铝合金直耳片的高周疲劳性能。孔挤压后耳片孔壁的显微组织、显微硬度和残余应力的测试结果表明孔挤压后孔壁处形成了大约150μm的塑性变形层。塑性变形层内,显微硬度较高,存在残余压应力,且晶粒在平行于挤压棒运动方向上被拉长,垂直于挤压棒运动方向上被压缩。高周疲劳测试结果表明,孔挤压后的耳片疲劳寿命和疲劳强度均得到了较大的提高。通过对比孔挤压与未孔挤压耳片的疲劳源区和裂纹扩展形貌,分析了孔挤压提高7A85铝合金耳片疲劳性能的内在机理。
Proposed using hole extrusion method to improve the high cycle fatigue properties of 7A85 aluminum straight prongs. Test results of the microstructure, microhardness and residual stress of the hole wall of the ear hole after the extrusion of the hole revealed that a plastic deformation layer of about 150 μm was formed at the hole wall after the hole extrusion. In the plastic deformation layer, the microhardness is high, residual compressive stress exists, and the grains are elongated in the direction parallel to the moving direction of the extruding rod and compressed perpendicularly to the moving direction of the extruding rod. High-cycle fatigue test results show that the fatigue life and fatigue strength of the extruded ears have been greatly improved. By comparing the fatigue source region and the crack growth morphology of extruded and non-porous extruded ears, the inherent mechanism of hole extrusion to improve the fatigue properties of 7A85 aluminum alloy ear was analyzed.