Physical Properties of Directionally Solidified Al-1.9Mn-5Fe Alloy

Al-1.9Mn-5Fe (wt.%) alloy was prepared by adding 5 wt.% Fe to the eutectic Al-Mn alloy. This alloy undergone controlled solidification under four different growth velocities (V) in Bridgman-type furnace. Eutectic spacings (λ), microhardness (HV), ultimate tensile strength (σ_U) and electrical resistivity (ρ) of these alloys were determined. While the HV and σ_U increased with increasing V values or decreasing λ, the elongation (δ) values decreased. In addition, relationships between these parameters were investigated using linear regression analysis. Microstructure photographs of directionally solidified samples were taken by optical microscope and scanning electron microscope (SEM). The eutectic spacings were measured from these photographs. The relationships among growth velocity (V), eutectic spacing (λ), microhardness (HV), ultimate tensile strength (σ_U) and electrical resistivity (ρ) were measured by suitable method and tests. The ρ measurements were carried out depending on V and temperature (T). While temperature coefficient of resistivity (α_TCR) was calculated from the ρ–T curve, the values of thermal conductivity (K) predicted by Wiedemann–Franz (W–F) and Smith–Palmer (S–P) equations. It was found that the microstructure, microhardness, tensile strength and electrical resistivity were affected by both eutectic spacing and the growth velocity.