【摘要】 C1023铸造镍基高温合金,在试验温度(800～950℃)范围内时效50小时,有σ相析出,析出数量在900℃出现峰值,其数量多少主要取决于相的长大线速度,低于900℃时,σ相长大线速度主要取决于扩散因素,随温度升高而增加;高于900℃,σ相相变激活能随温度的升高增加,σ相析出数量随温度的升高而降低;本文分析了合金元素对γ相自由能的影响,得出了合金元素对σ相析出作用的规律。更多还原

【Abstract】 Discusses the mechanism of σ-phase formation in high temperature Ni-based cast alloy C1023 and tries to conclude some rules in its phase transformation since although such alloying elements as Al and Ti play the role of forming γ’ phase they forster the formation of the brittle σ-phase which is harmful to both the strength and ductility. In C1023 cast alloy the σ-phase was precipitated by ageing for 50 hr at the range of 800~950℃ and the peak value of precipitation amount emerged at 900℃. The forming amount of σ-phase is mainly dependent upon its linear growth rate which is related to diffusion and increases with its temperature. As the temperature is increasing to be higher than the critical value (900℃) the activation energy in σ--phase transformation increases with temperature as well but the precipitating amount of σ-phase decreases. The σ--phase disappears if the difference of free energy between σ-phase and γ solid solution is greater than zero. Discusses in detail the effects of Al and Ti on σ--phase precipitation.更多还原