Microstructure and mechanical behaviour of Al–Si–Mg alloys reinforced with Ti–Al intermetallics

Abstract

MMCs of aluminium alloy matrix reinforced with Ti–Al intermetallics were prepared in the laboratory by following a powder metallurgy route and hot extrusion or forging were used as consolidation processes. Different studies were carried out in the composites developed. In order to evaluate possible reaction products and interphases between the matrix and reinforcement, isothermal heat treatments regarding time were carried out at a fixed temperature of 530 °C and at different times of 1, 6, 12 and 24 h. In this study, optical and scanning electron microscopy with X-ray microanalysis, were used to determine the growth of the reaction layer. The influence of production process was also estimated. Ultimate strength and strain to failure were studied. There were performed tests at room temperature of the material in different precipitation state and at high temperature of the material in extrusion state. The type of damage was analysed by scanning electron microscopy. Ultimate strength trends to grow with reinforcement addition in both T1 and T6 conditions for low temperature. Strain to failure remains the lowest on T6 state. The reinforcement addition affect decrease for high temperature testing and matrix influence was demonstrated. Tribological properties were analysed in conditions of dry friction and lubrication. It was studied the evolution of the coefficient of friction in front of the speed of sliding, applied pressure, regime of lubrication and content of reinforcement in the composites. The matrix has shown a great plasticity, whereas the reinforcement has a hardening effect also showing a certain plasticisation.