The Effect of Mn Addition and Heat Treatment on the Microstructure, Mechanical, and Thermophysical Properties of Al-Si-Mg Eutectic Alloy

Abstract

The study added Mn at different rates to the Al-Si-Mg eutectic alloy and heat-treated the quaternary alloy. Therefore, the microstructure morphology of the Al-Si-Mg eutectic alloy was examined after Mn addition and heat treatment. Also determined were the hardness, tensile strength, fracture surface analysis, and thermoelectric characteristics of the newly produced Al-12.95%Si-4.96%Mg-X%Mn [X=0.5, 1.0, and 1.5 (wt.)] alloys. Along with the predicted Si and Mg2Si phases in the Al matrix phase, this investigation found a randomly distributed Mn-rich Al15Mn3Si2 intermetallic phase and a Mg-rich Al5Si3Mg2 phase. Mn-doped samples without heat treatment were somewhat softer than the parent alloy. After heat treatment, the hardness more than doubled for the Al-Si-Mg eutectic system and Mn-doped samples. After heat treatment, the alloy with 1.5% Mn added had the maximum hardness value of 94.3 +/- 5.0 HV. Heat treatment improved tensile strength by up to 80%, and the alloy with 0.5% Mn had 144.7 MPa. Melting temperatures (T-m) (K), fusion enthalpy (Delta H) (J/g), and specific heat C-pl (J/gK) were determined for non-heat-treated materials. The 0.5, 1.0, and 1.5 Mn-added samples had T-m of 566.30, 568.96, and 566.40 degrees C, respectively. The Delta H value of samples with 0.5%, 1.0% and 1.5% Mn addition is 662.29, 657.93 and 639.11, respectively. C-pl was 0.788, 0.781, and 0.761 J/g.K. for 0.5%, 1.0%, and 1.5% Mn-added samples. In both heat-treated and non-heat-treated samples, Mn enhanced electrical resistance.