Machining-induced surface residual stress behavior in Al2O3-SiC nanocomposites

The machining and subsequent annealing behavior of an Al2O3-SiC nanocomposite (Al2O3 + 5 vol% 0.2 mu m SiC particles) was compared to that of single-phase Al2O3. The machining-induced residual line force was determined by measuring the extent of elastic bending in thin disk specimens, and the surface roughness was evaluated by profilometry, The results showed that, when the two materials were subjected to the same grinding conditions, they developed compressive residual stresses and surface roughness values of similar magnitude. The maximum thickness of the residual stress layers was estimated to be similar to 10 mu m for the Al2O3 and similar to 12 mu m for the nanocomposite, A direct linear correlation was observed between the residual force and the surface roughness for different machining treatments, Annealing of the machined samples produced complete relaxation of residual stresses in the single-phase Al2O3, whereas only partial stress relaxation occurred for the nanocomposite.