High temperature behaviour of a Ti-6Al-4V/TiC sub p composite processed by BE-CIP-HIP method

• Published in: Journal of materials science Vol. 35; no. 15; pp. 3903 - 3912
• Main Authors: Badini, C.,-, Ubertalli, G, Puppo, D, Fino, P
• Format: Journal Article
• Language: English
• Published: 01.08.2000
• ISSN: 0022-2461

The high temperature behavior of a Ti-6Al-4V/TiC sub p composite (10% Vol. of TiC) was investigated. A composite produced by Dynamet Technology according to the blended-elemental-cold-hot isostatic pressing (BE-CHIP) method was used. The stress-strain properties of the material were tested at 25, 200, 400, 500, 600 and 800 deg C. Composite specimens were aged in air at 500 and 700 deg C or under vacuum at 500, 700 and 1050 deg C, for periods ranging between 100-500 h. The thermal stability of the matrix /ceramic interfaces was studied by using scanning electron microscope, electron probe microanalysis and x-ray diffraction. Carbon diffusion from the ceramic particles towards the composite matrix occurred (very likely already during the composite fabrication) because the metal matrix of all the composite samples (either in the as received or thermally treated conditions) showed a high content of carbon ( > 1% at.). However, the thermal treatments carried out at both 500 and 700 deg C under vacuum did not result in a ceramic-metal reaction. In spite of this, the formation of an ordered phase of formula Ti sub 2 C can be inferred. Long period aging under vacuum at 700 deg C (500 h) did not lower the composite tensile strength. On the other hand, > 500 deg C in air the titanum matrix rapidly underwent oxidation, which gave rise to the formation of a thick surface reaction layer; this confirms that the composite material cannot be used above this temperature. Furthermore, the thermal treatment performed at 1050 deg C (under vacuum) resulted in a strong composite microstructure modification: the formation of new mixed carbides of Al and Ti was observed.