Orthorhombic precipitate variant selection in a Ti2AlNb based alloy
Orthorhombic precipitate variant selection in a Ti2AlNb based alloy
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DOI：
10.1016/j.matdes.2018.08.011
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发表时间：
2018-11
影响因子：
8.4
通讯作者：
Youping Zheng;W. Zeng;Dong Li;Jianwei Xu;Xiong Ma;Xiaobo Liang;Jianwei Zhang
中科院分区：
文献类型：
--
作者：
Youping Zheng;W. Zeng;Dong Li;Jianwei Xu;Xiong Ma;Xiaobo Liang;Jianwei Zhang
研究了Ti-22Al-25Nb合金中晶内和晶间正交析出相的不同选择。结果表明，在含有大量形变引入位错的显微组织中析出晶内正交相(O相)时，会出现较强的变异性选择。所选择的变种生长成平行的O相片层，并发展成团簇结构。在低位错强度的显微组织中，可以观察到所有12个可选择的变种。计算了相变应变与位错应力场之间的相互作用能。结果表明，位错确实可以促进晶内O相的不同选择。高角度晶界的晶间O相通常选择与相邻的两个B2中的一个具有特定取向关系的变体：{0 0 1}O//{110}B2和⟨1 1‘0⟩O//⟨1’11⟩B2(下称一带一路)。在相邻的B2颗粒共享共同的{110}B2平面的特殊情况下，其{001}O平行于共同的{110}B2的两个变体都将被选择。这两个变体使一带一路分别与两个B2颗粒保持在一起，形成了所谓的复晶孪晶结构。此外，当GBO向与之夹持一带一路的相邻B2晶粒内部生长时，将形成O相群体结构。
Variant selections of intragranular and intergranular orthorhombic precipitates in Ti-22Al-25Nb alloy are studied. It was found that strong variant selections occurred when intragranular orthorhombic phases (O phases) precipitated in microstructures with abundant deformation-introduced dislocations. The selected variants grew into parallel O phase lamellae and developed into cluster structures. In the microstructures with low dislocation intensities, all 12 can-be-selected variants could be observed. The interaction energy between the transformation strain and the stress field of prior dislocations were calculated. The results suggested that dislocations could indeed promote variant selections of intragranular O phases. Intergranular O phases (GBO) at high angle boundaries usually select the variants holding the specific orientation relations {001} O//{110} B2 and⟨ 1 1¯ 0⟩ O//⟨ 1¯ 11⟩ B2 (OBOR here after) with one of the two adjacent B2 grains. In a special case where the adjacent B2 grains share a common {110} B2 plane, the two variants that have their {001} O parallel to the common {110} B2 would be both selected. The two variants keep OBOR with the two B2 grains respectively and form so-called ploy-twins structures. Moreover, O phase colony structures would be formed when a GBO grew inward the adjacent B2 grain that holds OBOR with it.