Abstract In this paper, the directional growth behavior of Sn whiskers was found to be associated with the interfacial γ-Ag2Al IMCs at Sn-3.5Ag/Al interface. A 100 μm thick columnar structured Sn-3.5Ag coating consisted of β-Sn phases and γ-Ag2Al phases was fabricated on Al substrate. The as-formed interfacial IMCs between Sn-3.5Ag and Al were confirmed as γ-Ag2Al and μ-Ag3Al. After aging treatment, the growth direction of Sn whiskers was found to be consistent. μ-Ag3Al phases transformed into γ-Ag2Al. The newly formed hexagonal γ-Ag2Al grew out of the IMCs layer and provided the out-of-plane stress for whisker growth. Ag atoms diffused into Sn sub-grain boundaries and formed γ-Ag2Al IMCs leading to the formation of in-plane stress. The c-axis of the β-Sn and γ-Ag2Al is parallel, leading to the similar growth direction of the whiskers. The misorientation between the whisker and the underneath grain was lower than 2°. A transitional area formed between the whisker and underneath grain, which consists of extra half-planes of atoms. A mathematical model was proposed to calculate the heterogeneous distribution of Ag atoms. By comparing the calculated growth rate with the measured growth rate of whisker, the Sn atomic transport mode was pipe diffusion.

中文翻译：

---

金属间化合物诱导铝基体上 Sn-3.5Ag 涂层中 Sn 晶须的定向生长

摘要 在本文中，发现 Sn 晶须的定向生长行为与 Sn-3.5Ag/Al 界面处的界面 γ-Ag2Al IMC 相关。100 μm 厚的柱状结构 Sn-3.5Ag 涂层由 β-Sn 相和 γ-Ag2Al 相组成。Sn-3.5Ag 和 Al 之间形成的界面 IMC 被确认为 γ-Ag2Al 和 μ-Ag3Al。时效处理后，发现锡晶须的生长方向是一致的。μ-Ag3Al 相转变为 γ-Ag2Al。新形成的六边形 γ-Ag2Al 从 IMCs 层中生长出来，为晶须生长提供了面外应力。Ag 原子扩散到 Sn 亚晶界并形成 γ-Ag2Al IMC，导致形成面内应力。β-Sn 和 γ-Ag2Al 的 c 轴平行，导致晶须的生长方向相似。晶须和下面的晶粒之间的错误取向低于 2°。在晶须和下方晶粒之间形成的过渡区域，由额外的原子半平面组成。提出了一种数学模型来计算Ag原子的异质分布。通过将计算的生长速率与实测的晶须生长速率进行比较，Sn 原子传输模式是管扩散。