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赵瑞峰,周欢,张铁邦,寇宏超,李金山.高Nb-TiAl热变形过程中的晶界特征和显微组织演化[J].稀有金属材料与工程(英文),2018,47(10):2927~2935.[Ruifeng Zhao§,Huan Zhou§,Tiebang Zhang,Hongchao Kou and Jinshan Li.Grain boundary character and microstructural evolution during hot deformation of a high Nb containing TiAl alloy[J].Rare Metal Materials and Engineering,2018,47(10):2927~2935.]
Grain boundary character and microstructural evolution during hot deformation of a high Nb containing TiAl alloy
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Received:March 27, 2017  Revised:May 27, 2017
DOI:
Key words: TiAl  Grain character  Microstructural evolution  Microsegregation  Hot deformation
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Author NameAffiliation
Ruifeng Zhao§,Huan Zhou§,Tiebang Zhang,Hongchao Kou and Jinshan Li  
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Abstract:
      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) have been investigated in this work. The plasma arc-melted alloy exhibits nearly lamellar microstructures with β/B2 phase precipitating along colony boundaries. The retained β/B2 phase rich in Ti, Nb and W and poor in Al is believed to be formed by the β → α transformation during nonequilibrium solidification. This β/B2 precipitation is caused by the relative high cooling rate, low atom diffusion rate of β stabilizers and different partition coefficient of the elements. B and Y elements exist mainly as borides and Y2O3, respectively. The morphology, size, composition and stability of β/B2 phase are determined by hot deformation. The high temperature and press enhance the elements diffusion, thus the variation of the composition of β/B2 phase in deformed samples is obviously observed. When the samples are deformed in (α + γ) phase region, the transformation β/B2 → α2 takes place. Considering the different crystal structures between β/B2 and α2 phases, there is a tendency for β/B2 phase to transform to an increased close packed structure of α2 during deformation. The β/B2 → α2 transformation is promoted by the hot deformation.