Abstract
Gadolinium (Gd) (up to 10 wt.%) was added to Mg-7Li dual-phase alloys, and the Gd-containing alloys were heat-treated for 3 h at 698 -748 K. The microstructure and mechanical properties of the as-cast and heat-treated alloys were then examined. The results indicated that the addition of Gd introduced the Mg3Gd phase into the duplex Mg-7Li alloy, containing a-Mg and b-Li phases. Gd also refined the grains, and the addition of 8 wt.% Gd resulted in the highest grain refining effect. The Gd atoms in the a-Mg phase, as well as precipitates in b-Li matrixes and at the surface of the a-Mg phase, strengthened the alloys. The highest strength alloy was obtained after the addition of 6 wt.% Gd, with tensile and compressive yield strengths of 143- 147 MPa, about twice as those of the Mg-7Li alloy. Heat treatment, which was found to be optimum at 723 K for 3 h, can decrease both the amount of precipitate and the hardness of the alloy, but not the amount of the Mg3Gd phase.
Investigation of the microstructure and mechanical properties of squeeze cast Al-11%Si alloy heat treated
