Eiichiro Sato

Effect of minor elements on grain size of Mg-9%Al alloy

The Influence of minor elements, such as Be. Zr, Fe and Mn. on grain size and grain-refining effect of Mg-9%Al alloy was investigated by use of high-purity Mg-9%Al alloy (high-purity alloy). This high-purity alloy was prepared from distilled pure magnesium and 99.99% commercial aluminum. Given amounts of Be. Zr, Fe and Mn were then added Microscopic examination clarified that these elements have grain coarsening action for natural fine-grained high-purity alloys, and the grain refinement by superheating was possible as long as the alloy grain was coarsened by Fe or Mn addition EPMA analysis revealed the existence of some species of aluminum carbide in high-purity alloy Fe-Al-C-O and Mn-Al-C-O compounds were also obscrved in allovs coarsc-grained by Fe or Mn addition Existence of aluminum carbide and its change were probably associated with the grain size of the Mg-9%Al alloy.

Clarification of Grain Refining Mechanisms of Superheat-Treated Mg-Al-Zn Alloy Castings

We performed two experiments to clarify the grain-refining mechanisms of Mg-Al system alloys by superheat treatment of molten alloys. Numerous Al 4 C 3 nucleants were formed in the molten commercial-purity alloy of AZ91 by superheat treatment. The high-purity alloy was made of 99.99% Mg and 99.999% Al. Grain refinement occurred without superheat treatment. A small amount of impurity carbon included in the pure Mg and Al reacted with Al to form Al 4 C 3 compounds. Carbon is an important element for grain refining of commercial-purity AZ91 alloy. Pure carbon powder with an argon gas carrier was therefore blown into the molten AZ91 alloy instead of harmful C 2 Cl 6 . Numerous Al 4 C 3 nucleants were formed in the molten alloy.