Research On Microstructures And Properties Of Nb Wires Reinforced Ti-48Al-2Cr Composites Made By Melting-casting Process

In this paper, Nb wires reinforced Ti-48Al-2Cr matrix composites were madeby water-cooled copper crucible induction melting furnace and graphite mold. Themicrostructure morphology, the interface morphology, the micro Vickers hardness,the impact toughness and fracture toughness of the composites were studied.Results show that the compositions between Nb wires and the interfaces of thecomposites, which were made by melting-casting technology, were fine. The matrixalloy is composed of lamellar layers of2/γ phases and γ phases, and phaseinterface has serious segregation of Cr elements. Different annealing holding timehas hardly influence on the solidification, size and growth direction of matrix alloy.The interface layer is composed of three kinds of phases with different shapes:2/γ phase close to the matrix alloy with unclear layers and low Nb content, stripphases in the middle of the interface containing Nb content, and tiny paticle pahsesnear Nb wires with high Nb content. The closer the interface to the Nb wire, thehigher is interface’s hardness. With the increase of the time of the annealingtreatment, the interface’ thickness is higher. The number of layer tissues in themiddle of interface layer is decreased, while the volume is increased. With theincrease of the time of annealing heat treatment, the interface’s Vickers is increased.The impact toughness is greatly improved by Nb wires reinforced Ti-48Al-2Crmatrix composites, and the fracture toughness is only increased a little. The impacttoughness of the Ti-48Al-2Cr matrix alloy can be greatly increased by annealingtreatment, while the fracture toughness is decreased. The impact toughness andfracture toughness are weakened after annealing treatment.According to the analysis of the compression fracture of the as-cast andannealed composites, the interface near the Nb wire is of the highest brittleness,which can easily be the priority part for the extension of crack. After annealingtreatment, the adhesive strength between Nb wire and interface layer is increased.