Scanning 3DXRD Measurement of Grain Growth, Stress, and Formation of Cu6Sn5 around a Tin Whisker during Heat Treatment
Scanning 3DXRD Measurement of Grain Growth, Stress, and Formation of Cu6Sn5 around a Tin Whisker during Heat Treatment
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DOI：
10.3390/ma12030446
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发表时间：
2019-02-01
期刊：
影响因子：
3.4
通讯作者：
Wright, Jonathan P.
中科院分区：
文献类型：
--
作者：
Hektor, Johan;Hall, Stephen A.;Wright, Jonathan P.
利用扫描3DXRD研究了锡晶须周围的三维微观结构及其在热处理过程中的演变。使用滤波反投影算法重建样品中每个颗粒的形状。然后可以使用衍射数据的正向建模来细化局部晶格参数和晶粒取向，空间分辨率为250。结果发现，锡涂层具有纹理，其中晶粒被定向为使得它们的c轴主要平行于样品表面。具有其他取向的晶粒在热处理期间被晶粒生长消耗。发现大多数晶界的取向差大于15，并且发现了许多重合晶格（CSL）或其他类型的低能晶界。具有CSL晶界的晶粒没有一个被晶粒生长消耗。在热处理过程中，发生了预先存在的Cu 6Sn 5的生长;这些晶粒被标记为六方相，通常记录为仅在超过186的温度下稳定。这表明该相可以长时间以亚稳态存在。锡涂层被发现是在压缩静水应力下，从晶须的根部向外延伸的静水应力的负梯度。负应力梯度通常被认为在为材料向晶须根部的扩散提供驱动力方面起重要作用。
The 3D microstructure around a tin whisker, and its evolution during heat treatment were studied using scanning 3DXRD. The shape of each grain in the sample was reconstructed using a filtered-back-projection algorithm. The local lattice parameters and grain orientations could then be refined, using forward modelling of the diffraction data, with a spatial resolution of 250 . It was found that the tin coating had a texture where grains were oriented such that their c-axes were predominantly parallel to the sample surface. Grains with other orientations were consumed by grain growth during the heat treatment. Most of the grain boundaries were found to have misorientations larger than 15, and many coincidence site lattice (CSL) or other types of low-energy grain boundaries were identified. None of the grains with CSL grain boundaries were consumed by grain growth. During the heat treatment, growth of preexisting Cu6Sn5 occurred; these grains were indexed as a hexagonal phase, which is usually documented to be stable only at temperatures exceeding 186 . This indicates that the phase can exist in a metastable state for long periods. The tin coating was found to be under compressive hydrostatic stress, with a negative gradient in hydrostatic stress extending outwards from the root of the whisker. Negative stress gradients are generally believed to play an essential role in providing the driving force for diffusion of material to the whisker root.