Effects of Heat Treatment on the Mechanical Properties of Al-4% Ti Alloy

This paper examines the effects of heat treatment processes on the mechanical properties of as-cast Al-4% Ti alloy for structural applications. Heat treatment processes, namely, annealing, normalizing, quenching, and tempering, are carried out on the alloy samples. The mechanical tests of the heat treated samples are carried out and the results obtained are related to their optical microscopy morphologies. The results show that the heat treatment processes have no significant effect on the tensile strength of the as-cast Al-4% Ti alloy but produce significant effect on the rigidity and strain characteristic of the alloy. With respect to the strain characteristics, significant improvement in the ductility of the samples is recorded in the tempered sample. Thus, for application requiring strength and ductility such as in aerospace industries, this tempered heat treated alloy could be used. In addition, the quenched sample shows significant improvement in hardness. 1. Introduction Aluminium like all pure metals has low strength and cannot be readily used in applications where resistance to deformation and fracture is essential. Therefore, other elements are added to aluminium primarily to improve strength. The low density with high strength has made aluminium alloys attractive in applications where specific strength (strength-to-weight ratio) is a major design consideration. For structural use, the strongest alloy which meets minimum requirements for other properties such as corrosion resistance, ductility, and toughness is usually selected if it is cost effective. Hence, composition is the first consideration for strength [1]. Structural application of aluminium alloy at high or moderate temperature requires a fine, homogeneous, and stable distribution of crystal hardening up to the temperature of use. High melting point intermetallics phases are good candidate for that. Al3Ti is very attractive among all intermetallics, because of its high melting point (1350°C) and relatively low density (3.3？g/cm3) [2]. Recently, aluminium based alloys, especially with titanium, are becoming more useful for high temperature applications due to their excellent properties [3]. Previous researchers have looked mainly at the effect of titanium as a grain refiner in aluminium alloy as grain refinement plays an important role in determining the ultimate properties of aluminium alloy products. It improves tensile intensities and plasticity, increases feeding complex castings, and reduces the tendency of hot tearing and porosity [4]. In reality grain refinement of aluminium by