Improvement of Microstructure, Mechanical Property and Corrosion Resistance of Mg–9Li–3Al–1Ca Alloy Through Centrifugal Casting

Abstract

The microstructure, mechanical property and corrosion behavior of gravity casting and centrifugal casting Mg–9Li–3Al–1Ca alloy were investigated. The results indicate that the Mg–9Li–3Al–1Ca alloy is mainly composed of α-Mg phases, β-Li phases and Al2Ca phases. After centrifugal casting, the blocky and elongated α-Mg phases of the gravity casting alloy can be refined and spheroidized. Meanwhile, the amount of α-Mg and AlLi phases increases, however, the number of Al2Ca phases decreases. Besides, a strong texture of β-Li phase on the (200) plane can be formed. The microstructure refinement and the decrease of Al2Ca phases lead to the improvement of comprehensive property. The property of centrifugal alloys has gradient along radius direction because the strength of centrifugal force varies with the centrifugal radius. The centrifugal casting Mg–9Li–3Al–1Ca alloy at outside exhibits excellent comprehensive properties. The ultimate tensile strength and elongation of centrifugal casting alloy achieve the value of 198.3 MPa and 6.0%, corresponding to 83.6% and 300.0% increments compared with gravity casting ones, respectively. The corrosion current also decreases to 89.4 μA/cm2, which attributes to the weakening of galvanic corrosion attributing to the decrease of number of Al2Ca phases and the transformation of corrosion pattern caused by grain refinement.