Properties of a composite made from an ultrafine-grained titanium matrix and continuous boron fiber

Abstract

This paper presents the ultrafine-grained structure of the Ti-Al-V alloy foil. This structure was formed through combined processing, including repeated forging with varying deformation axes of the workpiece under gradual cooling from 800 to 650 °C and subsequent isothermal rolling at 550 °C. On the basis of analysis of the temperature and strain-rate conditions for superplasticity of the Ti-Al-V alloy in the ultrafine-grained state, a multilayer metal-matrix composite was obtained by vacuum pressing at 650 °C. The composite consists of alternating layers of 0.2 mm thick titanium foil and continuous high-strength boron fiber with a diameter of 140 μm. The superplasticity regime during pressing ensured uniform filling of the matrix material between the fibers and high-quality bonding of the foil layers in the resulting composite. The mechanical and dynamic properties of the resulting metal-matrix composite were studied at room temperature under three-point bending. Fractographic analysis of post-test specimen fractures revealed that the achieved increase in strength and impact toughness is due to the formation of a homogeneous ultrafine-grained state in the matrix material and the high strength of the fibers, which redistribute stress and alter the crack trajectory.