Casting Surface of AZ91 Alloy and Its Reaction with Sand Mold

Abstract

Due to its light weight and abundance as a resource, the utilization of magnesium is increasing. AZ91 alloy is the most common cast magnesium alloy and is widely used as die-casting material. AZ91 is also used for sand mold casting. In sand mold casting, reaction with mold sand is expected because magnesium is a very reactive element. This study investigated the surface condition of AZ91 castings using sand mold.Higher pouring temperature promoted the reaction with silica sand, and the surface of castings became rough. Reacting with mold sand, Mg 2 Si and Mg and Al complex oxides were precipitated near the casting surface.

Erosion Resistance of Heat-Treated Aluminum Cast Iron to Aluminum Alloy Melt

“…3 and 4, the increase in Al content decreased the thickness of the oxides and the decarburized layers would be attributed to the Al 2 O 3 , which was formed on the surface and suppressed the diffusion of oxygen into the decarburized layer. Although Takamori et al 8,9) reported similar tendency of the effects of the heat treatment on the oxidation behavior of the Al cast irons, the chemical composition and heat treatment condition are different from those in this study. Considering the castability and bonding of the oxide layer, the optimal condition in this study was the 3%Al content in the cast iron heat-treated at 1173 K for 10 h.…”

“…The addition of Al to cast iron, which is the popular alloy as the mold material, followed by heat treatment in air to form alumina (Al 2 O 3 ) can be expected to improve the erosion resistance of the cast iron with a low cost. Takamori et al [7][8][9] reported that the addition of Al and heat treatment improved the oxidation resistance at high temperature and wear resistance of the cast iron. However, the erosion resistance of the cast irons in the Al alloy melt have not been reported by them.…”