高Nb-TiAl热变形过程中的晶界特征和显微组织演化（英文）  

Grain Boundary Character and Microstructural Evolution During Hot Deformation of a High Nb Containing TiAl Alloy

作　　者：赵瑞峰[1] 周欢[1] 张铁邦[1] 寇宏超[1] 李金山[1] Zhao Ruifeng, Zhou Huan, Zhang Tiebang, Kou Hongchao, Li Jinshan(State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi＇an 710072, China)

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072

出　　处：《稀有金属材料与工程》2018年第10期2927-2935,共9页Rare Metal Materials and Engineering

摘　　要：研究了Ti-45Al-8.5Nb-(W,B,Y)合金热变形过程中的晶界特征和显微组织演化规律。采用等离子冷床炉熔炼制备的Ti-45Al-8.5Nb-(W,B,Y)合金具有典型的近片层组织并在晶界有高温β/B2相残留,富Nb、W、Ti等、贫Al的晶界β/B2相主要是冷床炉熔炼过程中因冷速过快、β稳定元素的低扩散系数以及合金中各元素的分配系数差异导致β→α相变不能完全发生。合金中的B和Y等微量元素分别以硼化物和Y_2O_3的形式存在。晶界β/B2相的形态、尺寸、成分和稳定性等受后续热变形影响显著,高温和应力作用会使β相发生破碎,细化并促进合金中的元素扩散会引起晶界β/B2相的成分变化。当合金在(α+γ)两相区进行热压缩变形时,会有部分β相向α相转变(β/B2→α_2),主要通过β相中二次α的析出和β相被相邻α相的蚕食等方式进行,热压缩变形会促进β/B2相向更为密排结构的α_2相转变。Grain boundary character and microstructural evolution during hot deformation of a high Nb-containing TiAl alloy with the composition of Ti-45Al-8.5Nb-（W,B,Y）was investigated.The plasma arc-melted alloy exhibits nearly lamellar microstructures withβ/B2 phase precipitates along colony boundaries.The retainedβ/B2 phase rich in Ti,Nb and W and poor in Al is formed by theβ→αtransformation during nonequilibrium solidification.Thisβ/B2 precipitation is caused by the high cooling rate,low atom diffusion rate ofβstabilizers and different partition coefficients of the elements.B and Y elements exist mainly as borides and Y_2O_3,respectively.The morphology,size,composition and stability ofβ/B2 phase are determined by hot deformation.The high temperature and press enhance the elements diffusion,and thus the variation of the composition ofβ/B2 phase in deformed samples is obviously observed.When the samples are deformed in（α＋γ）phase region,the transformationβ/B2→α_（2 ）takes place.Considering the different crystal structures ofβ/B2 andα_2 phases,there is a tendency forβ/B2 phase to transform to a more closed packed structure ofα_2 during deformation.Theβ/B2→α_2 transformation is promoted by the hot deformation.

关 键 词：TIAL 晶界特征 显微组织演化 微观偏析 热变形 

分 类 号：TG146.23[一般工业技术—材料科学与工程]