Control of the Lamellar Structure and Analysis of Tensile Properties of TiC/Ti-6Al-3Sn-9Zr-1.5Mo Composite Produced by In Situ Casting Technique

Abstract

In the present paper, new heat treatment was performed on 10 vol.% TiC/Ti-6Al-3Sn-9Zr-1.5Mo composite fabricated by an in situ casting technique. The aim is to obtain fully lamellar structure in matrix, control the lamellar structure quantitatively and understand the variation of the tensile properties of as-cast and heat-treated composites. For as-cast composite, matrix exhibited fully lamellar structure with some extent of basket-weave characteristics, and reinforcement was mainly in fine rod and strip shape. After β heat treatment, matrix microstructure was refined visibly. As the new cooling method was employed, wider α lath in matrix was obtained. The composite with very fine lamellar structure showed better yield strength (YS) in comparison with that with coarse lamellar microstructure below 650 °C. At 700 °C, fine grain strengthening cannot exert effective influence on tensile strength. It is proved that the enhanced YS is mainly ascribed to the refinement of α lath at ambient temperature. The heat-treated composites with wider α lath displayed excellent ductility at ambient temperature. Above 600 °C, the effect of α phase size on tensile elongation was negligible in the heat-treated composites, since matrix was softened.

Keywords

• titanium matrix composite
• lamellar microstructure
• tensile properties
• heat treatment
• TiC