Microstructures and mechanical properties of high strength Ti-XAl-2Fe-3Cu alloys fabricated by powder compact extrusion

Ti-XAl-2Fe-3Cu (X = 2.7, 4 wt%) alloys with a high tensile yield strength of up to 1150 MPa were synthesized using powder compact extrusion from blended TiH2 and elemental powders. The microstructures and mechanical properties of the extruded rods without and with a homogenization heat treatment at 1000 °C for 1 h followed by furnace cooling were investigated. It was found that the Al content and heat treatment had significant effects on the microstructures and mechanical properties. With increasing the Al content from 2.7 to 4 wt%, the average lamellar colony size and lamellar thickness of the as-extruded Ti-XAl-2Fe-3Cu alloy decreased from 442.4 to 224.1 µm and 6.7–5.2 µm respectively. The heat treatment increased the lamellar thickness as well as the level of partitioning of Fe and Cu between α and β phases. As a result of the microstructural changes, increasing Al from 2.7 to 4 wt% caused a slight increase in the strength of Ti-XAl-2Fe-3Cu alloys without changing the ductility, while the heat treatment slightly reduced the strength of the alloys, but clearly increased their tensile ductility. The correlation between microstructures and mechanical properties is discussed.