Creep characteristics and internal stress in γ-TiAl

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• 作者：Takahashi ; Osamu ; Terada ; Yoshihiro ; Takeyama ; Masao ; Matsuo ; Takashi
• 关键词：Activation energy ; Stress exponent ; Internal stress ; Elastic modulus ; Effective stress ; Dislocation substructure ; Minimum creep-rate ; Critical stress ; Strain dip test
• 刊名：Materials Science and Engineering: A
• 出版年：2002
• 出版时间：June, 2002
• 年：2002
• 卷：329-331
• 期：Complete
• 页码：835-839
• 全文大小：230 K

文摘

The creep deformation of γ-TiAl single phase alloy with ordered L1₀ structure has been characterized in terms of activation energy for creep Q_c, stress exponent n and internal stress σ_i. The stress exponent of minimum creep rate n becomes 3 at stresses below 70 MPa in the temperatures between 1123 and 1223 K, whereas it increases to 8 above 150 MPa. The activation energy for creep Q_c obtained at 68.6 MPa increases from 250 to 700 kJ mol⁻¹ with increasing the temperature. The large variation of Q_c is attributed to the temperature dependence of dislocation substructure. The internal stress σ_i measured by strain dip tests decreases with increasing temperature. Based on these findings, it is found that the activation energy Q*_c obtained at a constant effective stress σ_e (=σ_a−σ_i) becomes 245 kJ mol⁻¹, independent of the temperature.