Densification of a rapidly solidified nickel aluminide powder: Part II Characterization of microstructure and mechanical properties

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Abstract

A Ni3Al–X intermetallic compound prepared from a rapidly solidified powder was consolidated with hot isostatic pressing (HIP). Its microstructural development during the process has been examined. It involves a change from an inhomogeneous structure (a mixture of dendritic and equiaxed structures) to a uniformly distributed equiaxed structure and the formation of a disordered γ network phase from a metastably ordered matrix supersaturated with chromium, as a result of non-equilibrium solidification of the powder. The resulting microstructure of the consolidated material is mainly a function of HIP temperature. Mechanical properties of the HIP material at room and elevated temperatures have been determined. The results show that both the hardness and yield strength of the material decrease, while both the ultimate tensile strength and tensile elongation increase with rising HIP temperature up to 1250°C. Scanning electron microscope examination of the fracture surfaces of tested samples reveals a transition from interparticle fracture to transparticle fracture with increasing HIP temperature.

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