7075铝合金不同表面强化工艺的对比试验研究

Contrast test of different surface strengthening processes on 7075 Al alloy

对7075高强铝合金试样进行传统的机械喷丸强化与新的激光冲击强化工艺试验,对比它们产生的表面粗糙度、表层显微硬度与残余应力场的分布特性与演变规律,分析喷丸强化工艺对试样在低应力幅下的疲劳寿命改善作用。结果表明,表层残余压应力场分布合理性及其应力松弛趋势是提高试样疲劳寿命的主要因素,机械喷丸同时引起可观的应力集中,需要制定合理的组合式喷丸工艺,以缩小与激光冲击强化间的差距。激光冲击强化可显著改善疲劳性能的最主要因素是具有高的表面残余压应力值,以及持续保持应力影响深度的能力。而机械喷丸主要是高的残余压应力峰值及其向材料内层转移的能力。

Traditional mechanical shot-peening and new laser shock peening treatments were introduced to 7075 high-strength A1 alloy specimens, and the distribution features and evolutions of initial surface roughness, micro-hardness and residual stress field were com- pared to evaluate fatigue life enhancement under low stress amplitude. The results show that fatigue life improvement is attributed to the compressive residual stress field and its relaxation trend in the surface layers. However, stress concentration exerted by SP is obvious, reasona- ble peening combination processes are necessary to bridge the gap between SP and LSP. Mo- reover, the main factors in enhancing fatigue life for LSP are the large surface compressive residual stress and a continuously deep stress-effect-depth, while the main factors in enhan- cing fatigue life for SP are the large compressive peak-residual-stress and its ability of moving inside.