Effects of processing and ternary alloying on the microstructure and fracture toughness of Al2Ti

Previous study on the binary intermetallic alloy Al2Ti showed it has promising mechanical and oxidative properties compared to similarly processed binary Al3Ti and TiAl. It was also found that the mechanical and oxidative properties of binary Al2Ti are strongly dependent on the processing method used. In this study, the effects of processing conditions on the fracture toughness of binary Al2Ti and the effects of alloying on the microstructure, room temperature hardness, and fracture toughness of ternary-alloyed Al2Ti were investigated. Are melting was used to produce ternary-alloyed (Al2Ti)(m)X(1-3m), where 3m approximate to 0.98 and X is one of the following: Si, V, Cr, Mn, Fe, Ni, Cu, Nb, Mo, or W. Each ingot was cut into three sections. One section of each ingot was annealed at 1100 degrees C for 2 hr, and another section was hot forged at 1150 degrees C to 50% reduction in height. As-cast and cast & annealed material conditions were analyzed for each composition, and select compositions in the cast & hot forged material condition were also analyzed. Optical microscopy and SEM/EDS were used to study the microstructure of each composition and processing condition. Fracture toughness was evaluated using the critical load necessary to initiate cracking during microhardness indentation. Cast & thermal mechanically treated and powder processed Al2Ti exhibit 50-80% higher fracture toughness compared to A-C Al2Ti. Most of the ternary alloying elements except Ni improve the fracture toughness compared to binary A-C Al2Ti. Annealing A-C ternary-alloyed Al2Ti improves the fracture toughness by IO - 50% with the exception of Fe, Cr, or Mn-alloyed AI(2)Ti.