Microstructure and Mechanical Properties of Directionally Solidified Al-7wt.% Ni Alloy

單向凝固A1－7wt.％Ni合金的顯微結構與機械性能

洪銘盤(Ming-Pan Hung) ； 陳信章(Hsin-Chang Chen)

《鑛冶：中國鑛冶工程學會會刊》 27卷1期 (1983/03) Pp. 51-63

https://doi.org/10.30069/MM.198303_27(1).0007

摘要

Al-7wt.%Ni alloys were directionally solidified at various growth rates (R) and temperature gradients (G_L) and the relations between growth parameters, microstructure and mechanical properties were investigated. Experimental results show that aligned rodlike structure is obtained for G_L/R≥10 hr. °C/cm^2, however, cellular structure is obtained for G_L/R＜10 hr. °C/cm^2. The directionally solidified (DS) alloy has a higher value of UTS (24.6 kg/mm^2) than the permanent mold (PM) cast alloy (15.5 kg/mm^2). UTS of the DS alloy falls off drastically to its half value if the angle between loading direction and fiber axis exceeds 15°, and it levels off when the angle falls within the range of 30° to 90°. The stress rupture time of the DS alloy at 250°C is 80 times as much as the PM alloy. Better creep property is obtained for the higher value of G_L because of the well-aligned rodlike structure.

並列摘要

本研究以Al-7wt.%Ni為材料，經過不同單方向凝固處理（不同凝固速度及溫度梯度）後觀察金相組織，並探討各種單方向凝固條件、機械性能與凝固組織間的關係。實驗結果顯示在GL/R≥10hr.°C/cm^2之條件下，所得凝固組織為整齊而朝單一方向排列之棒狀組織，反之則出現細胞狀組織。單方向凝固後抗拉強度可達24.6kg/mm^2，較金屬模鑄件之抗拉強度15.5kg/mm^2高出約60%。外力偏離凝固方向15°以上時強度降低一半以上，而且偏離角度在30-90°間時強度幾乎相同。由250°C的應力破裂試驗得知：經單方凝固處理者，其破裂時間為未處理者的80倍，主要原因是G_L值較大者其棒狀組織排列整齊。