喷丸成形压力对7B50-T7751铝合金力学性能的影响

Effects of Shot Peening Forming Pressure on Mechanical Properties of 7B50-T7751 Aluminum Alloy

目的 研究7B50-T7751铝合金在不同喷丸成形压力下力学性能的变化规律,探究喷丸成形压力对材料表面形貌、疲劳寿命及静力性能的影响。方法 在不同的喷丸成形压力(0.42、0.50 MPa)下对7B50-T7751铝合金进行处理,分析材料的表面形貌。在此基础上,通过细节额定疲劳基准值和截止值进行计算,并进行压缩试验,结合铝合金材料在喷丸前后应变层的位错密度和形态,分析喷丸成形压力对合金材料疲劳寿命和静力性能的影响。结果 与未喷丸试件相比,在0.42 MPa的成形压力下,合金材料的疲劳寿命和静力性能均有所提高。喷丸成形之后,材料表层引入了一定深度的残余压应力层,形成位错密度较大的加工硬化组织,阻碍裂纹扩展,宏观上提高了材料的强度。在0.50 MPa的成形压力下,材料表面更加粗糙,裂纹易在晶粒连接薄弱处萌生,导致合金材料的疲劳寿命有所降低。结论 随着喷丸成形压力的增大,合金材料的疲劳寿命先增大后减小,抗压强度有所增大。在0.50 MPa的成形压力下,部分裂纹易于在弹坑边缘萌生,在一定程度上会降低合金材料的疲劳强度。

The work aims tostudy the change law of mechanical properties of 7B50-T7751 aluminum alloy under different shot peening forming pressure,investigate and the effects of shot peening forming pressure on the surface morphology,fatigue life,and static properties of the material.The 7B50-T7751 aluminum alloy was treated under different shot peening forming pressure(0.42,0.50 MPa),and the surface morphology of the material was analyzed.Based on this,the effects of shot peening forming pressure on the fatigue life and static properties of the material were analyzed through base and cutoff values calculated through the detailed fatigue rating(DFR)method,as well as compression tests,combined with the dislocation density and morphology of the strain layer before and after shot peening.Compared with the unpeened specimens,the fatigue life and static properties of the alloy were improved under forming pressure of 0.42 MPa.After shot peening,a residual compressive stress layer of certain depth was introduced into the surface layer of the material,forming a work-hardened structure with high dislocation density,hindering crack growth,and improving the strength of the material macroscopically.Under forming pressure of 0.50 MPa,the surface of the material became rougher,and cracks were prone to initiate at weak grain connections,resulting in a decrease in the fatigue life of the alloy material.With the increase of the shot peening forming pressure,the fatigue life of the alloy material increases first and then decreases,and the compressive strength increases to some extent.Under forming pressure of 0.50 MPa,some cracks are prone to initiate at the edge of the crater,which to some extent reduces the fatigue strength of the alloy material.