RESUMO
The dataset presented here shows the microstructure and mechanical properties of secondary (recycled) cast aluminum-silicon (Al-Si) piston alloys processed through severe plastic deformation technique, known as high-pressure torsion (HPT). The HPT processing was undertaken for 1/4, 1/2, 1 and 10 turns of the lower anvil (rotating at constant speed of 1rpm) while the upper anvil maintained at a normal pressure of 3.0 GPa. The data on microstructural evolution obtained at the central region and edge of the circular (disk) HPT sample were obtained using optical and scanning electron microscopy and these data are presented here. The data on the analysis of the particle shape, sizes and distribution from the micrographs using ImageJ software are also presented. Data on mechanical properties characterized using Vickers microhardness measurement across the surface of HPT sample are also shown. Pictures depicting the microhardness measurement scheme, high-pressure torsion facility and sample nomenclature are presented.
RESUMO
Modelling of crack tip behaviour was carried out for a nickel-based superalloy subjected to high temperature fatigue in a vacuum and air. In a vacuum, crack growth was entirely due to mechanical deformation and thus it was sufficient to use accumulated plastic strain as a criterion. To study the strong effect of oxidation in air, a diffusion-based approach was applied to investigate the full interaction between fatigue and oxygen penetration at a crack tip. Penetration of oxygen into the crack tip induced a local compressive stress due to dilatation effect. An increase in stress intensity factor range or dwell times imposed at peak loads resulted in enhanced accumulation of oxygen at the crack tip. A crack growth criterion based on accumulated levels of oxygen and plastic strain at the crack tip was subsequently developed to predict the crack growth rate under fatigue-oxidation conditions. The predicted crack-growth behaviour compared well with experimental results.