Machining introduced microstructure modification in aluminium alloys

In the present study, the impact of machining on the microstructure of AA7150-T651 aluminium alloy is investigated. It is found that a near-surface deformed layer is formed on the alloy due to severe shear strain during machining operation. The near-surface deformed layer of approximately 500 nm thickness distributes uniformly across the machined alloy surface. Ultrafine equiaxed grains with the dimensions of 50-100 nm are formed within the near-surface deformed layer. Further, the strengthening precipitates (MgZn2) that are initially present in the alloy in T651 temper are dissolved into the alloy matrix within the near-surface region. Subsequently, the dissolved alloying elements segregate at the grain boundaries of the newly formed fine grains in the near-surface deformed layer.