MECHANICAL PROPERTIES OF Ti-(Al3Ti+Al) AND Ti-Al3Ti LAMINATED COMPOSITES

Laminated Ti-(Al3Ti+Al) and Ti-Al3Ti composites have been synthesised with controlled temperature and treating time using 50, 100 and 150 mu m thick titanium and 50 mu m thick aluminium foils. Microstructural examinations showed that Al3Ti was the only phase formed during the reaction between Ti and Al. After 20 minutes of treating at 650 degrees C, not all the aluminium was consumed and the composites consisted of alternating layers of Ti, Al and Al3Ti. After 60 minutes, the aluminium layers were completely consumed, resulting in microstructures with Ti residual layers alternating with the Al3Ti layers. Tensile strength, flexural strength and impact toughness measurements were performed on the materials with different microstructures to establish the properties and fracture behaviour. After 60 minutes of treating, all the composites had a higher yield strength, higher ultimate tensile strength and higher flexural strength than those composites after 20 minutes of treating produced with the same thickness of starting Ti foil. On the other hand, the strain at fracture and impact toughness of the composites behaved conversely. The results of the investigations indicated that the mechanical properties of the composites strongly depend on the thickness of the individual Ti layers and the presence of residual Al layers at the intermetallic centrelines.