Liquid phase sintering of metal matrix composites

Abstract

Sintering temperature is one of the critical parameters in composite sintering. Generally, sintering of compact can be carried out when the compact is heated to a temperature of over approximately one-half its absolute melting temperature. However, the sintering process can be improved if the compact is sintered in a partial liquid phase. It is found that for sintering of metal matrix composites, because of the existence of reinforcement, the viscosity of the liquid is very low. The volume fraction of liquid phase can be increased in comparison with the sintering of the matrix materials. The amount of extra liquid phase can be assumed by combining two extreme cases: firstly, the particulates are agglomerated together. Since SiC particulates cannot be deformed, the amount of the liquid phase required is equivalent to the amount needed to fill a block of loose particulates. That is, if a volume Vr of particulates is agglomerated, it will occupy a space of volume Vs. The difference between Vs and Vr is the amount of liquid phase needed in LPS. In the second case, the reinforcement particulates are homogeneously distributed, such as phase required. Hence, the amount of liquid phase required for liquid phase sintering is a function of the size and the distribution of the particulates. Several examples of application are also presented in the present paper. The results of the model lead to suggestions for optimal selection of sintering temperature, particle size, and others.