生长速度对定向凝固Ti-50Al-6Nb合金微观组织演变及其硬度的影响  

Effect of Growth Rate on Microstructure Evolution and Hardness in Directionally Solidified Ti-50Al-6Nb Alloy

作　　者：刘国怀[1] 张元[1] 李新中[1] 陈瑞润[1] 苏彦庆[1] 郭景杰[1] 傅恒志[1] 

机构地区：[1]哈尔滨工业大学,黑龙江哈尔滨150001

出　　处：《稀有金属材料与工程》2015年第7期1655-1660,共6页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(51071062;51274077;51271068);华中科技大学磨具技术国家重点实验室开放基金项目(2011-P03);中央高校基本科研业务费项目(HIT.NSRIF.2013002);国家重点基础研究发展计划(2011CB610406)

摘　　要：对Ti-50Al-6Nb(at%)合金进行不同生长速度下的定向凝固实验,研究了生长速度对微观组织演变、相变路径、微观偏析和硬度值的影响。结果表明,在较低的生长速度下(≤10μm/s),凝固过程为完全β相凝固,固液界面随生长速度的增加发生平胞枝转变,最终得到α2/γ层片组织(在10μm/s时为α2/γ+B2相的组织),其中层片结构与生长方向呈45°或0°夹角。在较高速度(≥15μm/s)时,初生相为α相,固液界面为规则枝晶生长。最终组织为α2/γ层片组织,并与生长方向呈90°夹角。该成分合金的硬度值随着生长速度的增加而增加。与其它合金相比,该成分合金的硬度值较小。Bridgman type directional solidification experiments were conducted for Ti-50Al-6Nb alloy at different growth rates.The effect of growth rate on the solidification behavior, phase transition path, microsegregation and the hardness was investigated.Results show that the growth of single β phase is observed at the low growth rates（≤10 μm/s）, during which the planar to cellular, then to dendritic growths occur with the increase of the growth rates, and the final microstructure of a fully α2/γ lamellar structure is obtained except a multiphase microstructure（B2 phase, α2/γ lamellar structure） at 10 μm/s.The lamellar structure is 45° or 0° to the growth direction after the directional solidification.While the regular dendritic growth of primary α phase is observed at the high growth rates（≥15 μm/s）, and the final microstructure is composed of α2/γ lamellar structure, which is always 90° to the growth direction.Additionally, the hardness in this alloy increases with the increase of the growth rates, which is always smaller than those of other Ti Al-based alloys in our studies.

关 键 词：TIAL合金 定向凝固 微观组织 相变路径 硬度 

分 类 号：TG146.23[一般工业技术—材料科学与工程] TG249.9[金属学及工艺—金属材料]