Microstructure, microhardness, tensile, electrical, and thermal properties of the Al-Mn-xSi ternary alloys

The effect of Si content (0.5, 1.5, and 5 wt.%) and growth velocity on the microstructure, microhardness, ultimate tensile strength, electrical resistivity, enthalpy, and specific heat properties of the directionally solidified Al-Mn eutectic alloy have been investigated. Al-1.94Mn-xSi (x = 0.5, 1.5, 5 wt.%) samples were prepared from pure metals (99.99 % purity) under the vacuum. These alloys were directionally solidified under constant temperature gradient G (4.9 K mm(-1)) and different growth velocities V (from 8.3 to 978 mu m s(-1)) in a Bridgman-type growth apparatus. Measurements of primary dendrite arm spacing (lambda), microhardness (HV), ultimate tensile strength (UTS) and electrical resistivity (rho) of the samples were carried out and then expressed as functions of growth velocity and Si content (C-o). Additionally, the enthalpy of fusion (Delta H) and specific heat capacity (C-p) for the same alloys were determined by a differential scanning calorimeter (DSC) from the heating curves. It has been found that the values of HV, UTS, and rho increase with increasing values of V and C-o. On the contrary, the values of lambda decrease with increasing V. The increasing Si content in Al-Mn leads to a decrease of Delta H and C-p.