本研究使用鑄造法於 AZ91 中分別添加 1.0 wt.% Nd 以及 2.0 wt.% La 形成 AZ91-1Nd、AZ91-2La、AZ91-1Nd-2La 的合金鑄錠，將四塊金屬錠分別進行固溶處理(420°C，16 小時)以及人工時效(190°C，16小時)。探討添加不同添加物以及熱處理對合金之影響，同時對顯微結構、成分和機械性質來進行分析比較。
研究表明，與 AZ91 相比，添加稀土元素具有晶粒細化之效果，由 178 μm 下降至 160 μm 及 168 μm，且同時添加 Nd 及 La 之 AZ91-1Nd-2La 具有更小之晶粒尺寸(157 μm)。透過固溶處理及人工時效製程之試片，AZ91-1Nd-2La 之晶粒大小仍為最低值。由於 Al11RE3為穩定強化相，當 AZ91 添加稀土元素後能有效地提升其硬度值，由原先HV0.1 62.7 上升 HV0.1 72.2，AZ91-1Nd-2La 則提升至 HV0.1 77.3。透過時效處理後，AZ91-1Nd-2La 仍維持為最高值 HV0.187.3。拉伸試驗結果表明，極限抗拉強度由 140.6 MPa 上升至 205.3 MPa；延伸率由 0.85%上升至 2.61 %。由破斷面分析結果得知，AZ91 中含有河流狀及韌窩狀組織，當加入稀土元素後，斷口呈現些微杯錐破裂的形貌。綜合以上結果，同時添加 Nd 及 La 之 AZ91-1Nd-2La 具有最佳之機械性質。

In this study, 1.0 wt.% Nd and 2.0 wt.% La were added to AZ91 by casting method to form alloy ingots of AZ91-1Nd, AZ91-2La, AZ91-1Nd-2La, and the four metal ingots were respectively solution-treated(420 °C, 16 hours) and artificial aging (190 °C, 16 hours). The effect of adding different additives and heat treatment on the alloy is discussed, and the microstructure, composition and mechanical properties are analyzed and compared.
Studies have shown that compared with AZ91, the addition of rare earth elements has the effect of grain refinement, which is reduced from 178 μm to 160 μm and 168 μm, and AZ91-1Nd-2La added with Nd and La has a smaller grain size (157 μm). The grain size of AZ91-1Nd-2La is still the lowest value of the test piece through solution treatment and artificial aging process. Since Al11RE3 is a stable strengthening phase, when AZ91 is added with rare earth elements, its hardness value can be effectively improved, from HV0.1 62.7 to HV0.1 72.2, and AZ91-1Nd-2La to HV0.1 77.3. After aging treatment, AZ91-1Nd-2La still maintains the highest value of HV0.1 87.3. The tensile test results show that the ultimate tensile strength increases from 140.6 MPa to 205.3 MPa; the elongation increases from 0.85 % to 3.65 %. According to the analysis results of the fractured surface, AZ91 contains river-like and dimple structures. When rare earth elements are added, the fractured surface becomes smoother. Based on the above results, AZ91-1Nd-2La with both Nd and La added has the best mechanical properties.

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