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ABSTRACT

In the present study, we investigated the fracture toughness of alumina matrix composite reinforced with nickel at ratios of 1%, 3%, 5% and 7% by weight prepared by powder metallurgy method. Sintering process was performed at 1425 and 1440°C for 1h in graphite powder. The fracture toughness of test materials for 1425°C and 1440°C were 5.1, 5.2, 6.0, 6.7 MPa.m1/2 and 5.4, 5.7, 6.1, 7.1 MPa.m1/2 respectively. It was found that the more Ni content leads the higher fracture toughness because of crack arresting/energy absorbing effect of metallic ductile Ni particles. The distribution of reinforced nickel particles in the matrix was characterized by optical and SEM and the presence of nickel and alumina phases were confirmed with EDS and XRD analysis. XRD analysis showed that it has not been detected any oxidized Ni body in the composite. Optical and SEM studies revealed that the distribution of nickel particles is uniform in the alumina matrix.

Keywords: Fracture toughness, Al2O3-Ni composite, hardness, sintering, powder metallurgy.

1. INTRODUCTION

The limitations imposed on using ceramics as structural components are mostly due to their low toughness. Thus, the toughening of ceramic materials is very necessary, and has been investigated for the years. Enhancing the latter can be done by different ways. The use of ductile phases is one of the most applicable techniques known. The toughness increment achieved in these composites is due to the, "bridging", of ductile phase across the crack so exerting a closure stress behind its tip. Especially in Al2O3 system, the incorporation of a ductile phase has been considered an effective toughening mechanism because its dispersion can lead to a remarkable absorption of the energy of crack propagation due to plastic deformation. The dispersion of a ductile metallic phase (Ni, W, Mo, Cu etc.) in a brittle ceramic matrix is found to be a promising way [1-5]. Besides, the distribution of ductile phase in ceramic is very important for optimizing mechanical and functional properties of composites. The main aim of present study is to investigate the preparation process and resultant fracture toughness properties of alumina/Ni composites manufactured by powder metallurgy method.

2. EXPERIMENTAL DETAILS

2.1 Powder Processing

In this study, Al2(SO4)3 was used as raw material to prepare pure alumina powders with an...

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