Anisotropy in the room-temperature deformation of α-β colonies in titanium alloys:: role of the α-β interface
Anisotropy in the room-temperature deformation of α-β colonies in titanium alloys:: role of the α-β interface
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DOI：
10.1080/1478643032000158305
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发表时间：
2004-04-11
影响因子：
1.6
通讯作者：
Mills, MJ
中科院分区：
文献类型：
--
作者：
Savage, MF;Tatalovich, J;Mills, MJ
在用于激活单个基底滑移系的商业α-β钛合金（Ti-6Al-2Sn-4 Zr-2 Mo-0.1Si（其中成分以重量百分比表示））的单个α（hcp）-β（bcc）菌落中研究了室温临界分辨剪切应力（CRSS）的各向异性。详细的透射电子显微镜（TEM）研究的滑移传输机制，通过α-β接口已被执行，以阐明这些接口在确定屈服和应变硬化行为的作用。显著的各向异性在室温CRSS为三个独特的基底滑移系统的测量，并归因于由于所观察到的近伯格斯取向关系的滑动传输机制活跃。透射电镜结果表明，α-β界面对滑移系的滑移几乎没有阻碍作用，两相位错间的取向差最小。对于第二滑移系，一次位错之间存在11度的取向差，以及β相内交叉滑移的倾向增加，导致更高的CRSS和应变硬化速率增加。在这种情况下，在“出口”α-β界面处的β板条内观察到扩展的位错堆积，以及残余基质位错的形成。对于第三取向，其中B相中没有（a/2）（111）位错紧密对齐以便于与a相中的活性（a/3）[（11）越过棒20]位错的滑移传递，在入口α-β界面处的a相中观察到大的位错堆积。在这些堆积的正前方，在β相中发生向B=a[010]位错的直接传输。B=a[010]位错容易分解成移动的（a/2）（111）位错，其在β相内形成复杂的三维网络。该过程导致中等CRSS和最高应变硬化率。三个殖民地晶体取向的相对属性进行了讨论，根据这些意见。
The anisotropy in room-temperature critical resolved shear stress (CRSS) has been investigated in single alpha(hcp)-beta(bcc) colonies of a commercial alpha-beta titanium alloy (Ti-6Al-2Sn-4Zr-2Mo-0.1Si ( where the composition is in weight per cent)) oriented for activation of individual basal slip systems. Detailed transmission electron microscopy (TEM) studies of the slip transmission mechanisms through the alpha-beta interfaces have been performed to elucidate the role of these interfaces in determining yield and strain-hardening behaviour. Significant anisotropy in the room-temperature CRSS for the three unique basal slip systems is measured and is attributed to the slip transmission mechanisms active owing to the observed near-Burgers orientation relationship. TEM results indicate that the alpha-beta interface provides little hindrance to slip for the slip system with the smallest misorientation between dislocations in the two phases. For the second slip system, an 11degrees misorientation exists between the primary dislocations, as well as an increased propensity for cross-slip within the beta phase, resulting in a much higher CRSS and increased rate of strain hardening. Extended dislocation pile-ups are observed within the beta laths at the 'exit' alpha-beta interface for this case, together with the formation of residual matrix dislocations. For the third orientation, for which none of the (a/2) (111) dislocations in the b phase are closely aligned for easy slip transmission with the active (a/3)[(11) over bar 20] dislocations in the a phase, large dislocation pile- ups are observed within the a phase at the entrance alpha-beta interfaces. Directly ahead of these pile-ups, direct transmission to b=a[010] dislocations within the beta phase occurs. The b=a[010] dislocations readily decompose into mobile (a/2) (111) dislocations which form complex three-dimensional networks within the beta phase. This process results in an intermediate CRSS and the highest rate of strain hardening. The relative properties for the three colony crystal orientations are discussed in the light of these observations.