本研究使用 Mg-5Gd (wt.%) 合金進行內部氫化製程，內部氫化製程之處理溫度為 300 °C 及 325 °C ，吸氫壓力為 0.34 MPa，分別以 36、48 及 60 小時之吸氫時間，1 小時放氫時間來交叉分析，並對成分、金相結構、機械性質進行分析，探討內部氫化製程對於 Mg-5Gd 合金之影響。
研究結果顯示，Mg (Gd) 合金經內部氫化製程後，其相組成由 ?-Mg 轉為 ?-Mg 及 GdH2 氫化物。Mg (Gd) 合金經過內部氫化製程後得到均勻散佈於鎂基底的 GdH2 氫化物，但原本固溶於基底中的 Gd 原子會與氫反應形 GdH2，使基底失去固溶強化效果且長時間熱處理有晶粒成長現象，導致硬度、抗拉強度低於處理前的合金。吸氫 36 小時之內部氫化製程參數下，其氫化物含量少且分佈不均勻，因基底固溶強化效果下降且有晶粒成長現象，導致硬度、抗拉強度下降。除 325-48 試片外，吸氫 48 小時之熱氫製程參數下，氫化物均勻散佈得到散佈強化效果，但失去固溶強化效果又加上晶粒成長現象，導致硬度及抗拉強度下降。本研究中最佳參數，於 325 ℃ 吸氫 48 小時之內部氫化製程參數下，氫化物均勻散佈導致散佈強化，但又失去固溶強化效果，且無晶粒成長現象，故其硬度、降伏強度與原材數值相差無幾。

In this study, internal hydrogenation treatment was performed on Mg-5Gd (wt.%) alloy. Hydrogenation was carried out at 300, and 325 °C under 0.34 MPa of hydrogen for 36, 48, and 60 hours, followed by desorption for 1 hour. The effect of internal hydrogenation on composition, microstructure and mechanical properties of Mg-Gd alloy were studied.
The results show that Mg(Gd) solid solution has transformed to ?-Mg and GdH2 hydride after internal hydrogenation. GdH2 hydride uniformly dispersed in the magnesium matrix is obtained. However, the Gd atoms originally dissolved in the Mg matrix reacts with the hydrogen to form GdH2. As the result, the solid solution strengthening effect is reduced. Moreover, grain growth of Mg after longtime heat treatment is observed. Compared to the alloy before treatment, the reduced solid solution strengthening effect and grain growth lead to lower hardness and tensile strength in the alloy after internal hydrogenation. After hydrogenation for 36 hours, the amount of hydride is low and its distribution is not uniform. Due to the reduction of effect of solid solution strengthening and the phenomenon of grain growth, the hardness and tensile strength decrease. Except the 325-48 specimen, uniformly-dispersed GdH2 hydride is observed and dispersion strengthening is obtained in the samples after hydrogenation for 48 hours. However, the loss of the effect of solid solution strengthening and the grain growth, resulting in a decrease of hardness and tensile strength.
In this study, the optimal temperature and time for internal hydrogenation process are 325 °C and 48 hours, respectively. The effect of dispersion strengthening is canceled by the loss of solid solution strengthening. Plus, no grain growth is observed. Therefore, the hardness and yield strength are almost identical to those of the alloy before treatment.

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