The formation of intermetallic compounds (IMCs) during the friction stir welding (FSW) of aluminum and steel is problematic because these IMCs can reduce weld strength. In this study, the mechanism behind the observed rapid growth of IMCs during the dissimilar FSW of aluminum and steel was investigated. The temperature during welding was measured using K -type thermocouples, and the microstructures of cross sections of the welded materials were examined via scanning electron microscopy. Microstructural observations indicated that the growth of IMCs was not constant, but occurred in two rapid growth steps. The first phase of rapid IMC growth was observed immediately after the probe contacted the steel, while the second began in the region subjected to the large downward pressure of the tool shoulder on the steel plate. The measurements showed that the temperature underneath the tool shoulder was higher than that at the tool probe. Additionally, it was found that the two IMC growth steps and the growth rate could be expressed by an equation based on metallic diffusion and the measured temperatures. As the IMCs grew rapidly via contact between the steel plate and the tool probe or shoulder, it is necessary to control such contacts to inhibit IMC growth. This strategy and the proposed formula for predicting IMC growth rates could help improve the strength of welds during the fabrication of lightweight materials in the automotive and aerospace industries.

中文翻译：

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铝钢异种搅拌摩擦焊过程中金属间化合物的形成机理

在铝和钢的搅拌摩擦焊 (FSW) 期间形成金属间化合物 (IMC) 是有问题的，因为这些 IMC 会降低焊接强度。在这项研究中，研究了在铝和钢的不同 FSW 期间观察到的 IMC 快速生长背后的机制。采用K型热电偶测量焊接过程中的温度，并通过扫描电子显微镜检查焊接材料横截面的微观结构。微观结构观察表明 IMC 的生长不是恒定的，而是发生在两个快速生长步骤中。在探针接触钢后立即观察到快速 IMC 生长的第一阶段，而第二阶段开始于受到工具肩部对钢板的巨大向下压力的区域。测量结果表明，工具肩部下方的温度高于工具探针处的温度。此外，发现两个 IMC 生长步骤和生长速率可以由基于金属扩散和测量温度的方程表示。由于 IMC 通过钢板与刀具探针或肩部之间的接触快速生长，因此有必要控制这种接触以抑制 IMC 生长。这种策略和用于预测 IMC 增长率的建议公式可以帮助提高汽车和航空航天工业轻质材料制造过程中的焊缝强度。发现两个 IMC 生长步骤和生长速率可以由基于金属扩散和测量温度的方程表示。由于 IMC 通过钢板与刀具探针或肩部之间的接触快速生长，因此有必要控制这种接触以抑制 IMC 生长。这种策略和用于预测 IMC 增长率的建议公式可以帮助提高汽车和航空航天工业轻质材料制造过程中的焊缝强度。发现两个 IMC 生长步骤和生长速率可以由基于金属扩散和测量温度的方程表示。由于 IMC 通过钢板与刀具探针或肩部之间的接触快速生长，因此有必要控制这种接触以抑制 IMC 生长。这种策略和用于预测 IMC 增长率的建议公式可以帮助提高汽车和航空航天工业轻质材料制造过程中的焊缝强度。