Intermetallic/Ceramic Composites Synthesized from Al–Ni–Ti Combustion with B4C Addition

Chih-Yao Ke,Chun-Liang Yeh

doi:10.3390/met10070873

Abstract

The fabrication of intermetallic/ceramic composites by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) was investigated in the Al–Ni–Ti system with the addition of B4C. Two reaction systems were employed: one was used to produce the composites of xNiAl–2TiB2–TiC with x = 2–7, and the other was used to synthesize yNi3Al–2TiB2–TiC with y = 2–7. The reaction mechanism of the Al–Ni–Ti system was strongly influenced by the presence of B4C. The reaction of B4C with Ti was highly exothermic, so the reaction temperature and combustion velocity decreased due to increasing levels of Ni and Al in the reactant mixture. The activation energies of Ea = 110.6 and 172.1 kJ/mol were obtained for the fabrication of NiAl- and Ni3Al-based composites, respectively, by the SHS reaction. The XRD (X-ray diffraction) analysis showed an in situ formation of intermetallic (NiAl and Ni3Al) and ceramic phases (TiB2 and TiC) and confirmed no reactions taking place between Ti and Al or Ni. The microstructure of the product revealed large NiAl and Ni3Al grains and small TiB2 and TiC particles. With the addition of TiB2 and TiC, the hardness of NiAl and Ni3Al was considerably increased and the toughness was also improved.

Highlights

Intermetallic compounds in the Al–Ni–Ti system, such as NiAl, Ni3 Al, TiAl, and NiTi, possess attractive mechanical and physical properties and are recognized as promising high-temperature materials for usage in automotive, aerospace, and turbomachinery applications [1,2,3]
The composition compared to that of Figure 1a. This might imply that combustion exothermicity is reduced by of synthesized products was analyzed by an X-ray diffractometer (Bruker D2, Billerica, MA, US) using increasing the content of Ni and Al
This might imply that combustion exothermicity is reduced by increasing the content of Ni and Al

Summary

Introduction

Intermetallic compounds in the Al–Ni–Ti system, such as NiAl, Ni3 Al, TiAl, and NiTi, possess attractive mechanical and physical properties and are recognized as promising high-temperature materials for usage in automotive, aerospace, and turbomachinery applications [1,2,3]. NiTi alloys demonstrate excellent shape-memory effect, superelasticity, and biocompatibility [3,4]. Both poor ductility and low fracture toughness hinder the extensive industrial use of Niand Ti-aluminides [5,6,7]. An effective way to improve their mechanical properties is to fabricate intermetallic-based composites, where reinforcing ceramic phases such as carbide, boride, nitride, and oxide are added [8,9,10,11]. The SHS technique represents an in situ fabrication route for the preparation of intermetallic/ceramic composites.

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