Cast Microstructure and Fatigue Behavior of a Grain-Refined Magnesium-Zinc-Zirconium Alloy

摘要

Microstructure studies were conducted on grain-refined Mg-5.1 pct Zn-0.6 pct Zr alloy plates, sand-cast and end-chilled. Grains in this alloy are spherical, nondendritic and increase in diameter with distance from the chill. Coring in these grains is spherical. The volume fraction of interspherical nonequilibrium secondary phase decreases with distance from the chill, sheras that of microporosity increases. Fatigue strength of this alloy at room temperature was measured in reversed bending at a stress level of 10,000 psi and was found to decrease with increasing distance from the chill, both in the as-cast and the cast and solutionized conditions. Solutionizing was found to increase fatigue life. (Author)