Mechanical Properties of <I>in situ</I> Synthesized Titanium Matrix Composites at Elevated Temperature

Abstract

TiB and TiC reinforced titanium matrix composites were produced by common casting technique utilizing the self-propagation hightemperature synthesis between titanium and B 4 C. The mechanical properties and fracture mechanism of in situ synthesized titanium matrix composites have been investigated by means of uniaxial tension at elevated temperatures. As temperature increases, the ultimate tensile strength decreases and ductility increases. Compared with the matrix alloy, ultimate tensile strength of the composite was improved obviously because the in situ synthesized reinforcements are very stable at elevated temperatures and can strengthen the matrix alloy effectively. The fracture behavior was dependent on temperature. The composites fail at low strain at room temperature due to the fracture of the reinforcements. As temperature increases, voids are likely to initiate and grow at the interface between the reinforcement and the matrix alloy, and their coalescence eventually leads to the fracture of the composites. The debonding between the reinforcements and the matrix alloy becomes the main reason for the composites failure.

Temperature dependence of tensile properties and fracture behavior of as rolled TiB/Ti composite sheet

“…2(b), indicating that the matrix microstructure is significantly refined by rolling compared to that within the as cast composite [11]. The fine a laths are attributed to the various factors such as prior b grain size, deformation degree, cooling rate and the role of TiB whiskers [11][12][13][14][15]. Fine a laths and high density of dislocations near the TiB whisker can be clearly seen in the bright-field TEM image of the composite shown in Fig.…”

“…2(c). Previous studies have revealed that the presence of TiB assists the nucleation of a phase and restricts the grain growth [9][10][11][12][13][14][15][16]. It can be deduced that the a laths within the TiB/Ti composite are finer than those within the matrix alloy.…”

“…As it is known, one main aim to develop the TMCs is to expand the service temperature region. The effort in previous studies on tensile properties of TMCs was mainly concentrated on RT-700 1C temperature range [12][13][14]. However, published researches relative to the tensile properties of TiB/Ti composites above 700 1C are still lacking.…”

Oxidation Behavior of <i>In Situ</i> Synthesized TiB/Ti Composite in Air Environment

“…On the basis of the former papers, [3][4][5][6] the commercial pure titanium and TMCs reinforced with TiB were in situ fabricated by non-consumable vacuum arc remelting. The total volume percentage of reinforcements TiB was 8% and 5%, respectively.…”

“…4) The microstructure and mechanical properties at room temperature and elevated temperature have also been investigated. [5][6][7] The main aim to develop the TMCs is to widen the utilization field at high temperature. In spite of numerous studies on physical and mechanical properties of the in situ synthesized TMCs, an understanding of the oxidation behavior of the TMCs has not yet been fully achieved, which is an important factor for use at high temperature.…”