Microstructure, mechanical and tribological properties of nickel-aluminium bronze alloys developed via gas-atomization and spark plasma sintering

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2017-11, Vol.707, p.325-336
• Main Authors: Zhai, Wenzheng, Lu, Wenlong, Zhang, Po, Zhou, Mingzhuo, Liu, Xiaojun, Zhou, Liping
• Format: Article
• Language: English
• Subjects: Alloy development; Aluminum bronzes; Atomizing; Characterization; Concentration (composition); Copper alloys; Crack tips; Dislocation density; Gas atomization; Grain boundaries; Grains and interfaces; Intermetallic compounds; Mechanical properties; Microstructure; Modulus of elasticity; Nickel alloys; Nickel aluminides; Nickel base alloys; Nickel compounds; Plasma sintering; Powder methods; Precipitates; Solution strengthening; Spark plasma sintering; Tribology; Twin boundaries; Wear resistance; Yield strength
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2017.09.047

This work investigated the effect of sintering temperatures (600–750°C) on mechanical and tribological behaviors of nickel-aluminium bronze (NAB) alloys developed by gas atomization and spark plasma sintering. Results indicated an increase of the volume fraction of B2-type NiAl precipitates with increasing sintering temperature, leading to an improvement of the yield strength and the wear resistance. Specifically, detailed microstructural analyses of sintered NAB alloys at 750°C showed the presence of ultrafine grains with an average size of 367nm, nanoscale twins with a volume fraction of 11.7% and dislocations with a density of 1.3 ± 0.1 × 1014m−2. A much higher yield strength of 620MPa was obtained in NAB, if compared to that of conventional cast counterparts (280–440MPa). Estimations of strengthening mechanisms suggested the predominant mechanism of grain boundary strengthening (335MPa) for NAB alloys with contributions from precipitate strengthening (54MPa), dislocation strengthening (75MPa), twin boundary strengthening (89MPa) and solid solution strengthening (50MPa). Moreover, dislocations was blocked at twin boundaries to form complex dislocation barriers and networks, further contributing to the high strength. The high wear resistance of NAB could be ascribed to the reduction of the local stress around crack tips due to the high elastic modulus mismatch (ENiAl/ECu), and to the crack extension toughening near the interface of the matrix and the precipitate caused by the high plastic mismatch (σNiAl/σCu).