Pulse Plasma Sintering of NiAl-Al2O3 Composite Powder Produced by Mechanical Alloying with Contribution of Nanometric Al2O3 Powder.

Katarzyna Konopka,Konrad Cymerman,Paulina Piotrkiewicz,Justyna Zygmuntowicz,Marek Krasnowski,Marcin Wachowski

doi:10.3390/ma15020407

Abstract

NiAl-Al2O3 composites, fabricated from the prepared composite powders by mechanical alloying and then consolidated by pulse plasma sintering, were presented. The use of nanometric alumina powder for reinforcement of a synthetized intermetallic matrix was the innovative concept of this work. Moreover, this is the first reported attempt to use the Pulse Plasma Sintering (PPS) method to consolidate composite powder with the contribution of nanometric alumina powder. The composite powders consisting of the intermetallic phase NiAl and Al2O3 were prepared by mechanical alloying from powder mixtures containing Ni-50at.%Al with the contribution of 10 wt.% or 20 wt.% nanometric aluminum oxide. A nanocrystalline NiAl matrix was formed, with uniformly distributed Al2O3 inclusions as reinforcement. The PPS method successfully consolidated NiAl-Al2O3 composite powders with limited grain growth in the NiAl matrix. The appropriate sintering temperature for composite powder was selected based on analysis of the grain growth and hardness of Al2O3 subjected to PPS consolidation at various temperatures. As a result of these tests, sintering of the NiAl-Al2O3 powders was carried out at temperatures of 1200 °C, 1300 °C, and 1400 °C. The microstructure and properties of the initial powders, composite powders, and consolidated bulk composite materials were characterized by SEM, EDS, XRD, density, and hardness measurements. The hardness of the ultrafine-grained NiAl-Al2O3 composites obtained via PPS depends on the Al2O3 content in the composite, as well as the sintering temperature applied. The highest values of the hardness of the composites were obtained after sintering at the lowest temperature (1200 °C), reaching 7.2 ± 0.29 GPa and 8.4 ± 0.07 GPa for 10 wt.% Al2O3 and 20 wt.% Al2O3, respectively, and exceeding the hardness values reported in the literature. From a technological point of view, the possibility to use sintering temperatures as low as 1200 °C is crucial for the production of fully dense, ultrafine-grained composites with high hardness.

Highlights

To the best of our knowledge, this paper represents the first time NiAl-Al2O3 composite powders have been consolidated by the pulse plasma sintering method after mechanical alloying
Final NiAl-Al2 O3 composites were obtained from composite powders that were produced by mechanical alloying of powder blends containing Ni-50at.%Al, with the contribution of 10 wt.% and 20 wt.% nanometric aluminum oxide powder
Al2 O3 powder was used for the reinforcement of synthetized intermetallic matrix powder in mechanical alloying (MA) processes; the presence of ultrafine-grained structures of composites after Pulse Plasma Sintering (PPS) sintering enhanced the hardness

Summary

Introduction

Ceramics are combined with metals and intermetallic materials to produce composites. Various metals are used, such as V, Mo, Cu, Ni, Ti, or Fe [1,2,3,4,5,6,7], along with intermetallics such as NiAl [8,9] or Ni3 Al [10]. Such materials have been developed because of their desirable properties. The presence of nanocrystalline or ultrafine structure in composites may further enhance their desired properties [13,14]

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