High-strength cast Cu alloys often contain substantial quantities of alloying elements that promote the nucleation of heterogeneous particles, particularly at grain boundaries (GBs). In the Cu-6Ni-1.3Si alloy, intermetallic compounds such as Ni2Si form within the matrix and along the GBs following homogenization. Ni2Si particles within the matrix are homogeneously nucleated with diameters of a few tens of nanometers, which enhances matrix strength. However, heterogeneously nucleated Ni2Si particles at GBs, which can be several micrometers in size, negatively impact overall strength. To improve the strength of Cu-6Ni-1.3Si alloy, 2.1 wt% Mn was added. This Mn addition led to the formation of plate- or film-shaped intermetallic compounds, specifically Ni16Si7Mn6 (G-phase), at GBs after homogenization. Despite the Mn addition, Ni2Si precipitates with diameters of a few tens of nanometers still formed within the grains, but these were more densely distributed in the Mn-added alloy compared to the Mn-free alloy. Fatigue tests conducted on round bar specimens of both alloys showed that Mn addition enhanced fatigue strength. This enhancement is attributed to the suppression of both crack initiation and propagation along the GBs and within the matrix.

中文翻译：

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添加Mn形成晶界相对均质Cu-6Ni-1.3Si合金疲劳裂纹起生和扩展的影响


高强度铸造铜合金通常含有大量的合金元素，这些元素会促进异质颗粒的成核，尤其是在晶界 （GB） 处。在 Cu-6Ni-1.3Si 合金中，均质化后在基体内和沿 GB 形成金属间化合物，例如 Ni2Si。基体中的 Ni2Si 颗粒以几十纳米的直径均匀成核，从而提高了基体强度。然而，GB 的异质成核 Ni2Si 颗粒（大小可能为几微米）会对整体强度产生负面影响。为了提高 Cu-6Ni-1.3Si 合金的强度，添加了 2.1 wt% Mn。这种 Mn 添加导致在均质化后在 GB 处形成板状或薄膜状金属间化合物，特别是 Ni16Si7Mn6（G 相）。尽管添加了 Mn，但晶粒内仍然会形成直径为几十纳米的 Ni2Si 析出物，但与不含 Mn 的合金相比，这些析出物在添加 Mn 的合金中分布更密集。对两种合金的圆棒试样进行的疲劳测试表明，Mn 添加提高了疲劳强度。这种增强归因于抑制了沿 GB 和基体内部的裂纹萌生和扩展。