The Effect Of Machining Cooling Strategies On The Corrosion Fatigue Performances Of the AZ31 Magnesium Alloy

Magnesium alloys are very attractive biomaterials thanks to their biocompatibility, nontoxicity, and biodegradability. However, they have not been used extensively until nowadays because of their susceptibility to corrosion especially when in synergy to mechanical loads. In this framework, the present work deals with the analysis of the influence that different machining strategies may have on the corrosion fatigue performances of the AZ31 magnesium alloy. To this aim, cryogenic and dry machining operations were carried out, and the machined samples were then subjected to corrosion fatigue tests in a physiological environment at different imposed stresses, namely 100 MPa, 110 MPa and 120 MPa. The obtained results show that the samples processed with the liquid nitrogen adduction had a higher fatigue life than the corresponding dry samples, regardless of the imposed level of stress. After corrosion fatigue testing, both the types of samples showed similar failure characteristics. However, the microstructures of the cryogenic machined samples were characterized by a lower amount of deformation twins thanks to the grain refinement induced by cryogenic cooling close to the machined surface. Both the grain refinement and the reduced amount of deformation twins were used to explain the enhance corrosion fatigue characteristics of the cryogenic machined samples. These results indicate that cryogenic machining can represent a promising approach to enhance the poor corrosion fatigue behavior of the AZ31 magnesium alloy.