Effect of Reactive SPS on the Microstructure and Properties of a Dual-Phase Ni-Al Intermetallic Compound and Ni-Al-TiB2 Composite.

Paweł Hyjek,Lucyna Jaworska,Krzysztof Bryła,Piotr Malczewski,Iwona Sulima

doi:10.3390/ma13245668

Paweł Hyjek, Lucyna Jaworska + Show 3 more

Open Access

https://doi.org/10.3390/ma13245668

Copy DOI

Abstract

As part of the tests, a two-phase NiAl/Ni3Al alloy and a composite based on this alloy with 4 vol% addition of TiB2 were produced by the reactive FAST/SPS (Field Assisted Sintering Technology/Spark Plasma Sintering) sintering method. The sintering process was carried out at 1273 K for 30 s under an argon atmosphere. The effect of reactive SPS on the density, microstructure, and mechanical and tribological properties of a dual-phase Ni-Al intermetallic compound and Ni-Al-TiB2 composite was investigated. Products obtained were characterized by a high degree of sintering (over 99% of the theoretical density). The microstructure of sinters was characterized by a large diversity, mainly in regard to the structure of the dual-phase alloy (matrix). Compression tests showed satisfactory plastic properties of the manufactured materials, especially at high temperature (1073 K). For both materials at room temperature, the compressive strength was over 3 GPa. The stress–strain curves were observed to assume a different course for the matrix material and composite material, including differences in the maximum plastic flow stress depending on the test temperature. The brittle-to-ductile transition temperature was determined to be above 873 K. The research has revealed differences in the physical, mechanical and tribological properties of the produced sinters. However, the differences favourable for the composite were mostly the result of the addition of TiB2 ceramic particles uniformly distributed on grain boundaries.

Highlights

Ni-Al alloys are characterized by high melting point, low density, high thermal conductivity, very good corrosion resistance and resistance to wear, and so the properties are extremely interesting for industrial use [1,2]
austenite start (As) a result of the exothermic reaction occurring between Ni and Al, a two-phase NiAl alloy structure was formed (Figure 3)
The results of the studies of the physical, mechanical and tribological properties show that the addition of 4 vol% TiB2 to the composite matrix improves these properties, and despite significant differences, the obtained values of these parameters depend on the particle hardening effect rather than on the difference in matrix microstructure observed during tests

Summary

Introduction

Ni-Al alloys are characterized by high melting point, low density, high thermal conductivity, very good corrosion resistance and resistance to wear, and so the properties are extremely interesting for industrial use [1,2]. In spite of the fact that these materials exhibit satisfactory mechanical properties at elevated temperatures, they tend to be brittle at room temperature [3,4,5,6]. This factor, which limits their use, can be partially solved by reducing the grain size or producing a two-phase (β + γ’) alloy [7,8,9,10]. One of the promising ways of producing fine-grained intermetallics is powder metallurgy and its combustion synthesis (CS) or self-propagating high-temperature synthesis (SHS) [11,12].

Objectives

Methods

Results

Conclusion