EFFECTS OF THREE DIMENSIONAL DIRECTION OF SECOND DENDRITE ON COMPETITIVE GRAIN GROWTH IN DD8SUPERALLOY

来源期刊：中国有色金属学报(英文版)1996年第2期

论文作者：Liu Zhiyi Wei Pengyi Fu Hengzhi

文章页码：111 - 116

Key words：second dendrite;　nickel base superalloy;　three dimensional direction;　competitive grain growth

Abstract: Effects of three dimensional direction of DD8 nickel base single crystal superalloy on its competitive grain growth were investigated by seed crystal method.Experimental results showed that〈100〉×〈100〉(the first direction parallel to temperature gradient direction, the second direction perpendicular to temperature gradient direction and the contact plane of two half column seed crystal) grain competed with〈110〉×〈110〉grain for growth under the conditions ofG=250 K/cm,V=47.6μm/s, and the former eliminated the later; however at the same experimental conditions,〈100〉× 〈110〉grain competed with〈110〉×〈100〉grain for growth, and the later eliminated the former. Metallographic observations of cross sections of specimens showed that the migration velocity at various locations of grain boundaries was different in the process of competitive grain growth. It is indicated that the three dimensional direction of second dendrite is a key factor in the competitive grain growth, and the nonequilibrium grain boundary migration in the competitive grain growth is associated with the stagger between the grain dendrites.