Microstructure and room temperature mechanical properties of directionally solidified Mg-2.35Gd magnesium alloy

Directional solidification of Mg-2.35Gd (mass fraction, %) magnesium alloy was carried out to investigate the effects of the solidification parameters (growth rate v and temperature gradient G) on microstructure and room temperature mechanical properties under the controlled solidification conditions. The specimens were solidified under steady state conditions with different temperature gradients (G=20, 25 and 30 K/mm) in a wide range of growth rates (v=10-200 μm/s) by using a Bridgman-type directional solidification furnace with liquid metal cooling (LMC) technology. The cellular microstructures are observed. The cellular spacing λ decreases with increasing v for constant G or with increasing G for constant v. By using a linear regression analysis the relationships can be expressed as λ=136.216v−0.2440 (G=30 K/mm) and λ=626.5630G −0.5625 (v=10 μm/s), which are in a good agreement with Trivedi model. An improved tensile strength and a corresponding decreased elongation are achieved in the directionally solidified experimental alloy with increasing growth rate and tempertaure gradient. Furthermore, the directionally solidified experimental alloy exhibits higher room temperature tensile strength than the non-directionally solidified alloy.