温度梯度下Ni-Al合金γ’相沉淀过程研究

Precipitation of γ’ in a Ni-Al Alloy under Temperature Gradient

镍基高温合金航空发动机涡轮叶片等高温部件,材料经受高温下的温度梯度和应力作用。合金强化相Ni3Al在温度梯度下的沉淀及微观组织演变动力学决定着其空间形貌和分布,从而影响高温合金的性能。采用相场动力学模型,将温度增量耦合到自由能函数中,研究温度梯度下Ni-Al合金γ＇（Ni3Al）相的微观形貌、尺寸、颗粒数密度以及成分演化规律。随着温度梯度的增加,高温区γ＇相的数量减少,方块状形貌更加明显,γ＇相的体积分数达到平衡值的时间延长,平衡体积分数逐渐减小。在长大及粗化阶段,γ＇相颗粒半径随着温度梯度的增加而增加,γ＇相颗粒数密度逐渐减小。温度梯度下γ＇相的演变动力学规律对非均匀温度下的合金微观组织演变和性能分析有一定的参考价值。

Nickel-based superalloys are used for the turbine blades of aeroengine and they endure the temperature gradient and stress of high temperature. The precipitation of γ＇ phase in Ni-Al alloys under temperature gradient determines the microstructure evolution and spatial distribution,which affects the properties of the alloys. By using phase field model and free energy function coupled with the temperature gradient,the microstructure,the average particle radius,the particle number density and the temporal of Al composition ofγ＇ phase were studied in the Ni-Al alloys. As the temperature gradient increased,the number of γ＇ particles decreased and the cubic shape of γ＇ phases were more obvious. The time for reaching the stable volume fraction of γ＇ particles increased,while the value of volume fraction decreased with the temperature gradient increasing. At the growth and coarsening stage,the average particle radius of γ＇phase increased and the number density of γ＇ phase decreased with the elevated temperature gradient increasing. The results of morphology evolution and dynamic of γ＇ phase under temperature gradient were helpful for the analysis of microstructure and properties of alloy under inhomogeneous heating.