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題名 | 充氫對Ti-6AI-6V-2Sn合金之超塑性成形特性之影響=The Effect of Hydrogenation on the Superplastic Deformation Behavior of Ti-6AI-6V-2Sn Alloy |
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作 者 | 林聖朝; 王文雄; | 書刊名 | 材料科學 |
卷期 | 29:2 1997.06[民86.06] |
頁次 | 頁117-127 |
分類號 | 440.39 |
關鍵詞 | 暫時充氫; 超塑性成形; Temporary alloying of hydrogen; Superplastic forming; |
語文 | 中文(Chinese) |
中文摘要 | 細而且等軸的晶粒、相當的兩相體積分率是鈦合金材料展現現超塑性成形特性的 最基本要求。 在本實驗中以 Ti-6Al-6V-2Sn 合金之細晶材料為對象,評估以充氫的方法來 降低鈦合金之β相變態溫度,以期在較低的溫度下得到相當的α與β相體積分率,進而獲致 降低合金超塑性成形溫度的可能性。 實驗的結果顯示:只要有 0.25% 左右之含氫量就足夠 使 Ti-6Al-2Sn 合金之β相變態溫度由原來之 950 ℃驟降至 800 ℃,其效果十分顯著,然 而由金相顯微組織觀察發現充氫雖然可以促成α相轉換成β相,使得在同一溫度下之β相體 積分率增加,但在α相轉換的過程中其原來等軸的晶粒結構遭到破壞,使得不規則形狀之α 相在晶界殘留,以及在新生成之β相晶粒中夾雜α相晶粒的析出,造成材料在成形時晶粒滑 動的困難,以致超塑性成形特性無法展現,因而成形能力大幅降低。除此之外,充氫處理後 適合成形之兩相共存在區域溫度過低,以及成形時在β相中有氫原子的固溶,兩者都對差排 的擴散或移動能力造成不利的影響,同時降低了材料之變形能力。 |
英文摘要 | Fine and equiaxed grains, and equivalent volume fractions of alpha and beta phases are prerequisites for developing superplasticity of titanium alloys. The potential for temporary charging of hydrogen into fine-structural Ti-6Al-6V-2Sn alloy, in order to reduce the beta transus temperature and then to achieve adequate volume fractions of the alpha and beta phases at lower temperature to reduce the superplastic forming temperature, was evaluated in this study. The test results show that the beta transus temperature was effectively reduced from 950 ℃ to 800 ℃ by 0.25 weight percent charging of hydrogen. Although the alpha phase was effectively activated to transform into the beta phase and more beta phase was obtained by means of hydrogen charging, some irregular alpha grains, instead of the original equiaxed alpha grains, were, meanwhile, retained in the grain boundaries. As a result, the superplastic deformation capability of the alloy was lost. Furthermore, it is believed that the deformation temperature of the hydrogenated alloy, at which near equal volume fractions of alpha and beta phases were achieved, was too low for the superplastic deformation mechanism to operate. |
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