Effect of B and Cr on elastic strength and crystal structure of Ni3Al alloys under high pressure

• Published in: Journal of alloys and compounds Vol. 619; no. C; pp. 616 - 620
• Main Authors: Raju, S.V., Oni, A.A., Godwal, B.K., Yan, J., Drozd, V., Srinivasan, S., LeBeau, J.M., Rajan, K., Saxena, S.K.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.01.2015; Elsevier
• Subjects: Elastic properties; High pressure; Nano-indentation; Superalloys; X-ray diffraction; X-ray diffraction; Elastic properties; Superalloys; Nano-indentation; High pressure
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.09.012

•Ni3Al, Ni3Al:B and Ni ̶ Al ̶ Cr alloys were prepared by Bridgman-Stockburger technique.•Crystal structures confirmed by XRD and Electron microscopy studies.•Bulk modulus from XRD studies under pressure and Young’s modulus from nano ̶ indentation were determined.•Combining the above results enabled shear modulus and Poisson’s ratio.•K/G ratio suggests that Ni3Al doped with B (500ppm) has the highest hardness with ductility. Samples of Ni3Al, Ni3Al:B and Ni–Al–Cr super alloys were prepared by directional solidification method and their effect of alloying with ternary elements on the mechanical properties was investigated. In-situ X-ray diffraction studies were carried out on undoped Ni3Al, Ni3Al:B with boron 500ppm and Ni–Al–Cr with 7.5at.% of chromium super alloys at high pressure using diamond anvil cell. The results indicate that micro-alloying with B forms γ′-phase (L12 structure), similar to the pure Ni 3Al, while Ni–Al–Cr alloy consists of γ′ precipitates in a matrix of γ-phase (Ni-FCC structure). The crystal structure of all three alloys was stable up to 20GPa. Micro alloying with boron increases bulk modulus of Ni3Al by 8% whereas alloying with chromium has the opposite effect decreasing the modulus by 11% when compared to undoped alloy. Further, the elastic modulus and hardness of Ni3Al, Ni3Al:B and Ni–Al–Cr alloys were determined using the nano-indentation technique, in combination with compressibility data which enabled the estimation of shear modulus and Poisson’s ratio of these alloys.