Al-Mg合金の羽毛状晶における双晶境界の間隔ならびに傾斜角に及ぼす凝固条件の影響

抄録

The feathery crystal billets in Al-Mg alloys were solidified by using "Graphite Mold Submerging (GMS) process", which is that the graphite mold filled with molten metal is constantly submerged into water directly and the solidifying rate and cooling rate can be controlled by combining descending speed of mold and casting temperature. The changes of the spacing or direction of twin boundaries in each feathery crystal billet were examined microscopically. Features of twin boundaries are as follows: (1) The twin boundary spacing decreases with the increase of solute concentration and solidifying rate and is little affected by the temperature gradient. (2) Immediately after the generation of feathery crystals, the mean spacing of twin boundary λ increases temporarily under any circumstance. (3) In the stable growth state, the angle θ between the twin boundary and the billet axis and λ tends to become lager at the periphery than at the center of the billet.