Influence of processing on matrix microstructure and properties of titanium matrix composites

Abstract

SiC-fibre reinforced titanium matrix composites are marked by exceptional high specific strength and stiffness at temperatures up to 550C. That is why these materials are considered as promising materials for the compressor section of future aeronautic gas turbines. Different processing routes have been established for the production of titanium matrix composites. <BR>SiC-fibre reinforced titanium alloys with highest quality are obtained by the matrix coated fibre technique. The fibres are coated by the matrix alloy and subsequently consolidated by hot isostatic pressing. To accelerate the materials development modelling techniques are applied. However, there is a mismatch between modelling and experimental results, sometimes. One reason may the altered microstructure of the matrix within the composite resulting in wrong assumptions for the matrix properties. In this approach an important parameter is a study of features of microstructure and phase structure of the matrix, finding-out of the mechanism of occurring transformation and definition of their influence on mechanical properties. To take this into account specimens were produced by the same magnetron sputtering and heat treatment procedure usually used for composite production. Microstructure analysis as well as tensile, creep and fatigue tests were conducted on these specimens. The sputtering process leads to a very fine microstructure while heat treatment coarsens it. In general strength and maximum strain decreases by the applied processing compared to forged material in the as delivered state.