Enhanced superplasticity in a Ti-6Al-4V alloy processed by severe plastic deformation
Enhanced superplasticity in a Ti-6Al-4V alloy processed by severe plastic deformation
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DOI：
10.1016/s1359-6462(00)00496-6
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发表时间：
2000-10
影响因子：
6
通讯作者：
A. Sergueeva;V. Stolyarov;R. Valiev;A. Mukherjee
中科院分区：
文献类型：
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作者：
A. Sergueeva;V. Stolyarov;R. Valiev;A. Mukherjee
结果通过路线1从直径为2μm的区域获得的加工态合金的TEM显微照片和选区电子衍射图案（SAED）如图1a所示。可以看出，在变形状态下，由于存在高密度的不同类型的晶格缺陷，Ti-6Al-4V 合金的显微结构高度应变，具有复杂的不均匀对比度。暗场图像表明结构的单独片段的尺寸在 100-200 nm 范围内。具有沿圆圈排列的许多斑点的衍射图案（插图）表明存在由大角度边界分隔的微晶。衍射斑明显条纹的出现表明存在高内应力和晶格弹性变形。在两种途径处理的样品中都观察到了这种微观结构，但在较高压力下进行 HPT 后，SAED 图案上的斑点条纹及其数量略高（途径 2），表明晶格缺陷密度较高。观察到的衍射图仅对应于 α 相，没有显示任何 β 相的存在，表明其在 SPD 处理过程中溶解。
ResultsTEM micrographs and selected area electron diffraction patterns (SAED), obtained from region with a diameter of 2 μm, of as-processed alloy by routes 1 is shown in Fig. 1a. It is seen that in the as-deformed state the microstructure of the Ti-6Al-4V alloy is highly strained with complicated non-uniform contrast because of the presence high density of different type of lattice defects. The dark field images indicate that the size of separate fragments of structure is within 100–200 nm. The diffraction pattern (inset) with numerous spots arranged along circles indicates the presence of crystallites separated by high angle boundaries. The appearance of significant streaking of diffraction spots indicates the presence of high internal stresses and elastic distortions of crystal lattice. Such microstructure was observed in samples processed by both routes but the streaking of spots and their number on SAED patterns were slightly higher for the alloy after HPT under the higher pressure (route 2), suggesting higher density of lattice defects. Observed diffraction patterns have corresponded only to α-phase and did not reveal any presence of β-phase, indicating its dissolution during SPD-processing.