Experimental study on the influence of cryogenic treatment process on machining-induced residual stress and distortion of aluminum alloy

Machining-induced residual stress(MIRS) after milling of thin-walled monolithic aerospace aluminum alloy components cannot be ignored, which could result in torsional distortion. As a result, distortion would lead to high costs because of remanufacturing or even part rejection. To control and reduce MIRS under certain process conditions, cryogenic treatment process on aluminum alloy before conducting milling experiments was proposed in this study. In the meanwhile, the distortion of 25 mm by 25 mm by 1 mm cube sample containing MIRS was measured to evaluate processes. A theory model based on strain energy was developed to explain the connection between MIRS and distortion. The experiments indicate that MIRS of samples after cryogenic treatment process before milling decreases greatly when feed per tooth f z > 0.10, and the maximum normal stress and shear stress decrease by 55.7 % and 71.2 % respectively. The maximum distortion of samples decreases by 30.8 %, and the maximum strain energy decreases by 73.5 % and standard deviation decreases by 82.6 % after cryogenic treatment process before milling. Results show that cryogenic treatment process on aluminum alloy before milling could reduce and homogenize MIRS.