High-pressure and high-temperature sintering of nanostructured bulk NiAl materials

• Published in: Journal of materials research Vol. 24; no. 6; pp. 2089 - 2096
• Main Authors: Wang, Shanmin, He, Duanwei, Zou, Yongtao, Wei, Jianjun, Lei, Li, Li, Yongjun, Wang, Jianghua, Wang, Wendan, Kou, Zili
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01.06.2009; Springer International Publishing
• Subjects: Applied and Technical Physics; Biomaterials; Grain size; Inorganic Chemistry; Materials Engineering; Materials Science; Nanostructure; Nanotechnology; Sintering; Grain size; Sintering; Nanostructure
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/jmr.2009.0227

Nanostructured bulk NiAl materials were prepared at high pressure and temperature (0–5.0 GPa and 600–1500 °C, respectively). The sintered samples were characterized by x-ray diffraction, scanning electron microscope, density, and indentation hardness measurements. The results show that NiAl nanoparticles may have a compressed surface shell, which may be the reason why NiAl nanomaterials were difficult to densify sintering using conventional methods and why high-pressure sintering was an effective approach. We also observed that B2-structured NiAl could undergo a temperature-dependent phase transition and could be transformed into Al0.9Ni4.22 below 1000 °C for the first time. It is interesting to note that Vickers hardness decreased as grain size decreased below ∼30 nm, indicating that the inverse Hall-Petch effect may be observed in nano-polycrystalline NiAl (n-NiAl) samples. Moreover, a tentative interpretation was developed for high-pressure nanosintering, based on the shell-core model of nanoparticles.