In this paper, the 24 karat (99.99 wt.% pure) and 22 karat gold (Au-5.8wt.%Cu-2.5wt.%Ag) were grain refined with Au-6wt.%Ti master alloy and the mechanism of grain refinement was studied. The Au-6wt.%Ti master alloy containing Au 2 Ti and Au 4 Ti intermetallic particles was added into 24 karat and 22 karat gold at various addition levels of Ti (0.1, 0.2 and 0.3 wt.%) for grain refinement. The intermetallic particles undergo peritectic reaction with liquid Au in sequence to nucleate α-Au solid. It is observed that both the 24 karat gold and 22 karat gold showed efficient grain refinement at the lowest addition level of Ti (0.1 wt.%). However, 22 karat showed better grain-refining efficiency than 24 karat at all addition level of Ti studied. The mechanism of grain refinement of gold in this study matches with the “Peritectic theory” and “Solute paradigm” proposed for the grain refinement of aluminium. It is also observed that increasing the master alloy addition level to 0.2 and 0.3 wt.% Ti coarsening in the grain size in both 24 karat and 22 karat, but significant in the case of 24 karat gold due to recalescence effect. The grain-refined 24 karat and 22 karat gold at 0.1 wt.% Ti showed improvement in the hardness in comparison to the un-grain refined one.

中文翻译：

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使用 Au-6wt.%Ti 晶粒细化剂对 24 克拉金（99.99 wt.% 纯度）和 22 克拉金（Au-5.8wt.%Cu-2.5wt.%Ag）进行晶粒细化

本文采用 Au-6wt.%Ti 中间合金对 24 克拉 (99.99 wt.% 纯度) 和 22 克拉金 (Au-5.8wt.%Cu-2.5wt.%Ag) 进行晶粒细化和晶粒机制细化进行了研究。将含有Au 2 Ti 和Au 4 Ti 金属间化合物颗粒的Au-6wt.%Ti 中间合金以不同的Ti 添加水平（0.1、0.2 和0.3 wt.%）添加到24 克拉和22 克拉金中以细化晶粒。金属间化合物颗粒依次与液态金发生包晶反应，使α-金固体成核。据观察，24 克拉金和 22 克拉金在 Ti 的最低添加水平 (0.1 wt.%) 下都显示出有效的晶粒细化。然而，在所研究的所有 Ti 添加水平下，22 克拉比 24 克拉显示出更好的晶粒细化效率。本研究中金的晶粒细化机制与铝晶粒细化所提出的“包晶理论”和“溶质范式”相吻合。还观察到，将母合金添加水平增加到 0.2 和 0.3 重量％的 Ti 会使 24 克拉和 22 克拉的晶粒尺寸变粗，但在 24 克拉金的情况下，由于再辉效应而显着。与未磨粒精炼的金相比，含 0.1 wt.% Ti 的磨粒精制 24 克拉和 22 克拉金的硬度有所提高。