单晶高温合金定向凝固过程中晶体竞争生长观察

本文选用镍基单晶高温合金，用籽晶法控制各晶粒的晶体取向，进行了多晶组合的竞争生长实验，模拟了定向凝固中不同晶体取向晶粒间的生长过程与竞争规律，结果表明：晶粒的竞争生长过程取决于晶粒的相对取向关系及其与热流方向的夹角，择优生长方向与热流方向最接近的晶粒将淘汰其它晶粒并逐渐占据整个试样截面，当两个晶粒的择优生长方向都与热流方向不平行且大发散角方式组合时，两晶粒间可出现第三个晶粒并最最终扩展至整个试样截

OBSERVATION OF COMPETITIVE GROWTH IN A DIRECTIONALLY SOLIDIFIED NICKEL BASE SINGLE CRYSTAL SUPERALLOY

Experiments have been done on bi and tetra-crystal competitive growth in a nickel base single crystal superalloy to imitate the competitive growth during directional solidification. The grain orientations were controlled by seed crystals. Results show that the competitive growth is dependent on the relative orientations of grains and their relation with the direction of maximum temperature gradient. Grains with their preferred growth direction (<001> in nickel base superalloy) nearer to maximum temperature gradient will grow faster than those with their preferred growth direction far away from maximum temperature gradient in the condition of bi-crystal as well as tetra-crystal competitive growth. A third grain may appear and grow as a single crystal if two seed crystals with their preferred growth directions are far away from that of maximum temperature gradient in a divergent way in bicrystal competitive growth.