耳片孔结构二次冷挤压强化残余应力分析研究

文章对7050铝合金耳片孔进行压合衬套二次冷挤压强化，从残余应力和显微硬度2个方面进行分析。通过X射线衍射仪(X-ray diffractometer,XRD)和显微硬度计对残余应力和显微硬度进行检测，研究压合衬套二次冷挤压强化对耳片孔残余应力和显微硬度的影响。结果表明：压合衬套二次冷挤压使耳片孔沿孔壁径向形成了一定深度的残余压应力层；随着相对挤压量增大，残余压应力峰值和应力层深度随之增大；当相对挤压量为$2.5\%$ 时，最大残余压应力可达 $-400.3\mathrm{MPa}$ ，并形成了约 $14\mathrm{mm}$ 深的残余压应力层；同一相对挤压量下，同向压合衬套二次冷挤压试样挤出端的残余压应力大于挤入端，反向压合衬套二次冷挤压试样2个端面的残余压应力基本一致；当相对挤压量为 $2.5\%$ 时，强化后的试样沿孔壁径向形成了约 $4.5\mathrm{mm}$ 深的组织硬化层，最大硬度提升达到 $19.4\%$ ；压合衬套二次冷挤压强化后孔壁沿径向形成了残余压应力层和组织硬化层，进而提高了耳片孔的表面性能。

Secondary cold extrusion strengthening of press-fit bushing was performed on the 7050 aluminum alloy lug hole, and its residual stress and microhardness were analyzed. The effects of secondary cold extrusion strengthening of press-fit bushing on the residual stress and microhardness of the lug hole were studied through X-ray diffractometer(XRD) and microhardness tester. The results indicate that the secondary cold extrusion of press-fit bushing causes a residual compressive stress layer along the radial direction of the hole wall. As the relative extrusion amount increases, the peak residual compressive stress and the depth of the stress layer also increase. When the relative extrusion amount is$2.5\%$ , the maximum residual compressive stress can reach $-400.3\mathrm{MPa}$ , forming a residual compressive stress layer of about $14\mathrm{mm}$ . Under the same relative extrusion amount, the residual compressive stress at the outlet end of the codirectional secondary cold extrusion sample is bigger than that at the inlet end, while the residual compressive stress at the two ends of the reverse secondary cold extrusion sample is basically the same. When the relative extrusion amount is $2.5\%$ , a microstructure hardening layer of about $4.5\mathrm{mm}$ is formed along the radial direction of the hole wall, with a maximum hardness increase of $19.4\%$ . After the secondary cold extrusion strengthening of press-fit bushing, a residual compressive stress layer and a microstructure hardening layer are formed along the radial direction of the hole wall, thereby improving the surface performance of the lug hole.