Influence of solidification rate and alloying elements on structure, mechanical and electrical properties of Al-Cu-X alloys

Abstract

The present work aims to explore the effects of the alloying elements (Si, Bi, Sb, Ni, and Co) and solidification rates (V) on the microstructural morphology, microhardness, ultimate tensile strength and electrical resistivity of Al-Cu based eutectic alloys by Bridgman-type solidification apparatus, metallographic observation, scanning electron microscopy, microhardness testing, tensile testing and four-point probe testing. Firstly, the Al-33 Cu-2X (wt.%) samples were produced by using metals of high purity (> 99.95 %) in the vacuum and hotfilling furnaces; these alloys were unidirectionally solidified under different solidification rates, V (8.28-167.08 mu m s(-1)) and constant temperature gradient, G (average 8.50 K mm(-1)). Secondly, metallographic examination and measurement processes: lamellar spacings (lambda), microhardness (HV), ultimate tensile strength (UTS) and electrical resistivity (rho) were measured and expressed as functions of V. It has been found that the addition of the alloying elements (AE) content in Al-Cu eutectic as well as increasing of V lead to a decrease of lamellar spacings. On the contrary, the values of HV, UTS, and rho increase with increasing V values and the addition of alloying elements. Relationships between lambda-V, lambda-HV, lambda-UTS (sigma) and lambda-rho were found by regression analysis, and the results found in this research were compared with the previous similar studies.