Abstract:

USP forming on AA2024-T351 sheet was studied. Improvement of the surface integrity of treated AA2024-T351 and the relations among several parameters (micro hardness, residual stress distribution, surface topography, surface roughness and full width half maximum(FWHM)) and different USP process parameters were analyzed. The research shows that micro hardness of treated material is improved obviously(about 20%) with influenced area of 300μm depth down. Residual compressive stress is introduced, which is higher and gradient distribution, depth of residual compressive stress field is about 500~650μm, and the maximum point is located at the 200μm layer below the surface. There are many furrows on the surface of workpices at the sametime, the roughness of surface increases slightly, the half-width of X-ray diffraction of sample is increased, the 125μm layer below the surface, which shows the cold work hardening is occurred and crystal dislocation density is considerably increased. The experiments show that the improvement of micro hardness and induced residual compressive stress by ultrasonic shot peening forming make great positive influence on
the fatigue life, wear resistance and corrosion resistance of AA2024-T351.

Key words: ultrasonic shot peening(USP), surface integrity, residual stress, micro hardness

摘要：

采用试验方法对AA2024-T351进行数控超声波喷丸成形,研究了超声波喷丸成形制件的显微硬度、残余应力场、表面形貌、表面粗糙度及半高宽等随超声波喷丸过程参数变化的规律,定性地探讨了AA2024-T351超声波喷丸后表面完整性的改善状况。结果表明:超声波喷丸后,制件的显微硬度得到了明显提高（最大增幅为20%）,同时在材料表面产生了一定厚度的硬化层（深度约为300μm）;制件内部引入数值较高、分布呈现梯度形式的残余压应力场,残余压应力场的临界深度在500~650μm之间,在距表面200μm处产生了最大残余压应力;制件表面形成一道道犁沟,表面喷丸区域的粗糙度Ra有一定程度的增大;制件表面层的半高宽值变大,深度在125μm左右,半高宽的增大表明材料冷作硬化程度加大、晶体内部位错密度有一定程度的增大。显微硬度的提高、残余压应力场的引入及表面层组织的细化有助于喷丸成形制件疲劳寿命、抗磨损和抗腐蚀性能的提高。

关键词: 超声波喷丸, 表面完整性, 残余应力, 显微硬度