γ′晶体的蠕变及持久性能

本文报导了对以Ni₃Al为基的r′单晶体所做的蠕变及持久试验的结果。结果表明,r′晶体的稳态蠕变速ε_s遵从 ε_s=Cσ^mexp(-Q_c′/RT) 的关系。指数m仅和温度有关。m(850℃)=3.95,m(950℃)=3.62。对Ni₃Al,Q_c′=88kcal/g-at。合金元素Ti,Nb,W都使Q_c′升高,其中Nb的作用最大,然而W在提高蠕变强度上最有效。晶体取向对ε_s有显著影响。<111>取向的Ni₃Al晶体ε_s最低,持久寿命t_r最长。在1050℃,σ=5kg/mm²时,t_r可≥100小时,Ni₃Al单晶体也同样符合Monkman-Grant关系t_r(ε_s)^p=常数,其中p=0.82。r′晶体蠕变中的滑移系统是{111}<211>。

THE CREEP AND STRESS-RUPTURE PROPERTIES OF γ′ CRYSTALS

In this paper, the results of creep and stress-rupture tests on Ni₃Al base γ′ monocrystals are presented. The results show that the steady state creep rate ε_s conforms to the relationship: ε_s=Cσ^mexp(-Q_c′/RT). The exponent m depends only on temperature. m(850℃)=3.95, m(950℃) = 3.62. The apparent activation energy of creep Q_c′ amounts to 88 k cal/g-at. for Ni₃Al crystals. All of the alloying elements studied Ti, Nb and W raise Q_c′, the effect of Nb being the greatest, while W proves to be most effective in improving the creep strength. The orientation of crystals has a marked influence on ε_s. <111> oriented crystals have the lowest ε_s and the longest stress-rupture life t_r. t_r≥ 100 hr for T= 1050℃ and σ= 5 kg/mm². The Monkman-Grant relation t_r(ε_s)^p=const. holds likewise for Ni₃Al single crystals, with p = 0.82.The glide system of γ′ crystals in creep appears to be {111} <211>.