Metal-ceramic composites based on the Ti-B-Cu porosity system
- PDF / 2,680,459 Bytes
- 11 Pages / 613 x 788.28 pts Page_size
- 101 Downloads / 212 Views
I.
INTRODUCTION
C E R A M I C materials have potential uses in challenging engineering application on account of being hard, refractory, and corrosion- and erosion-resistant. The primary drawback of many ceramic materials is their inherent brittleness. They are also prone to thermal shock and fast crack growth. Therefore, ceramics are often not reliable in critical engineering usages. The inherent brittleness is a problem in fabricating components. Most often, the fabrication is undertaken using powder technology, t~,zl As compared to ceramics, metals are tough but commonly cannot withstand high temperatures. It may therefore be expected that metal-ceramic composites will possess good hardness, toughness, strength, and may not be susceptible to undesirable fatigue, thermal shock, and environmental attack. The reinforcement in the composites may be discontinuous t3'4~ or continuous.tS] The goal of this article is to study the mechanical property, microstructure, and processing correlations in metal-ceramic composites made by the combustion synthesis route. Specifically, the study focuses on composites fabricated from a ternary system of Ti(titanium)-B(boron)-Cu(copper). The interest in this system originates from the fact that elemental powders of Ti and B, when processed by powder metallurgy (PM), react to form a ceramic material TiB2 (the equilibrium binary phase diagram of Ti-B is shown in Figure lt61). The process allows for the direct fabrication of parts without a sintering step. I7-~4~ The advantage is that it is a simple process for producing high-temperature mateH.P. LI, Graduate Research Assistant, Department of Materials Science and Engineering, and J.A. SEKHAR, Associate Professor, Department of Materials Science and Engineering, and Director, Center for Micropyretics, are with the University of Cincinnati, Cincinnati, OH 45221-0012. S.B. BHADURI, formerly with the Department of Materials Science and Engineering, University of Cincinnati, is with the University of Idaho, Moscow, ID 83843. Manuscript submitted April l l , 1991. METALLURGICAL TRANSACTIONS A
rials. The disadvantage is that, most often, the product is porous. Therefore, the product is crushed and sintered/ hot pressed to achieve full density. One may, in principle, bypass this difficulty by incorporating a third metal, which would reduce the reactivity of the violent reaction and melt during the exothermic reaction and fill the pores. ~7-~4] By such an approach, the porosity may be reduced to lower than 3 pct I13] while simultaneously increasing the hardness significantly, t~3~ Additionally, the toughness may be increased by the incorporation of a ductile phase in a brittle ceramic, tlS'16j In this article, Cu is tried as a candidate material. This article reports on the microstructure and fracture toughness of the metalceramic composite materials consisting of various ratios of Ti, B, and Cu produced by the combustion synthesis process. Several studies have been reported on ductile phase reinforcement. Typical matrices used were NaC1, Mg
Data Loading...
