Structural Properties Evaluation of Semisolid Extruded Al–Cu–Mg Powder Metallurgy Alloys

Abstract

Structural properties evaluation of semisolid extruded Al–4Cu–xMg alloy preforms have been performed in the present investigation. Pressureless sintering of Al–4 wt% Cu with varying Mg (0, 0.25, 0.5, 0.75 and 1 wt%) powder mixture was performed in an inert atmosphere. The sintering behavior and mechanical properties of all alloys were investigated at different temperatures and compositions, respectively. The maximum density and hardness (647 MPa) were found in the Al–4Cu–0.5 Mg composition sintered at 550 °C. Semisolid extrusion was carried out on sintered Al–4Cu–0.5 Mg alloys having an Initial Relative Density of 80% and 90% to find the structure–property correlation due to deformation. Extrusion was carried out in between solidus (542.7 °C) and liquidus (662.8 °C) temperatures with different solid fractions, which were derived from the TG/DTA analysis. All experiments were performed with low extrusion ratio of 1.44, strain rate of 0.1 s−1 and die approach angle of 30°. Structure–property correlation study of extruded rod was performed at front end, middle part and rear end to understand the temperature and metal flow profiles during deformation process. There were no visible defects found in the demarcated samples. The presence of Al2Cu precipitate in the extruded alloy was identified by X-Ray diffractometer and scanning electron microscope with energy dispersive spectroscopy analysis. The microstructural evolution was observed in all the extruded bars by optical microscope. Micro-hardness of extruded samples was found to be 1001 MPa, which was almost two times of sintered sample.