TEM observations of mechanical twins in a hot-deformed Ti-45Al-10Nb alloy
TEM observations of mechanical twins in a hot-deformed Ti-45Al-10Nb alloy
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DOI：
10.1016/s0921-5093(98)00673-x
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发表时间：
1998-09
期刊：
影响因子：
6.4
通讯作者：
J. G. Wang;L. Zhang;G. Chen;H. Ye
中科院分区：
文献类型：
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作者：
J. G. Wang;L. Zhang;G. Chen;H. Ye
用高分辨透射电镜（HREM）研究了热变形Ti-45 Al-10 Nb合金中的两种{111}]孪晶。P型（（111）[112 <$]）孪晶既可以通过位错机制形成，也可以在晶界处形成。前者可以进一步描述为两种机制。一种是极点机制，另一种是完全位错机制的解离。对于孪晶在晶界处的形成，孪晶可以通过在晶界处从孪晶位错中脱出而成核，并且通过在每个相邻孪晶平面上的孪晶位错的顺序发射而传播。1/3[111]在某些双胞胎的非相干双胞胎边界上的台阶处可以观察到弗兰克部分位错。已经提出了一种机制来说明在非相干孪晶边界上的台阶处有或没有1/3[111]弗兰克分波的孪晶的传播。Q型（（1 <$11）[1 $> 12 <$]）孪晶通常形成于片层界面。这些片层界面上的台阶是Q型孪晶形核的共同场所。片状TiAl合金的形变孪晶被认为是界面位错堆积的应力松弛过程。讨论了在片层界面上产生孪晶位错的可能位错机制。
Two types of {111} 〈112̄] twins in a hot-deformed Ti–45Al–10Nb alloy were investigated by high resolution transmission electron microscopy (HREM). Type P ((111) [112̄]) twins can be formed either through dislocation mechanisms or at grain boundary. The former can be further described by two mechanisms. One is the pole mechanism and the other is the dissociation of a perfect dislocation mechanism. For the formation of twins at the grain boundary, twins can be nucleated by bowing out of twinning dislocations at the grain boundary and propagated by the sequential emission of twinning dislocations on every adjacent twinning plane. 1/3[111] Frank partial dislocations can be observed at steps on the incoherent twin boundary of some twins. A mechanism has been proposed to illustrate the propagation of the twins with or without 1/3[111] Frank partials at the steps on the incoherent twin boundary. Type Q ((1̄11)[1̄12̄]) twins usually formed at the lamellar interfaces. The steps on these lamellar interfaces are the common sites for the nucleation of type Q twins. Deformation twinning in lamellar TiAl alloys was suggested as a stress relaxation process for the pile-up of interfacial dislocations. Possible dislocation mechanisms for the generation of twinning dislocations on the lamellar interface are discussed.