The Cu/Nb ratio influencing microstructure, mechanical and electrical properties in as-cast Al3CuxNb alloys.

Abstract

Abstract In this work, solidification experiments were performed with Al-3CuxNb alloys (x = 0.5, 3 and 5wt.%). The role of the Cu/Nb ratio was investigated on thermal parameters such as growth and cooling rates (VL and TR), structure, microhardness (HV) and electrical properties such as electrical resistance, resistivity and conductivity (R, ρ, and σ, respectively). A columnar to equiaxed grain transition (CET) was observed for lower Cu/Nb ratios. The typical solidification microstructure was quantified by means of secondary dendritic spacings (λ2). It was observed that the decrease of the Cu/Nb ratio with the increase of the Nb content increased the HV, R, and ρ values, but the σ values decreased. It was deduced that the harder particles of the Al3Nb and Al2Cu intermetallic phases contributed to the increase of HV, while the Al3Nb phase influenced the decrease of electrical conductivity with the increase of Nb content.