Oxidation behavior of Al3Ti-based L12-type intermetallic alloys

The oxidation kinetics of Ni, Fe and Mn modified Ti--Al alloys was investigated in air at temperatures ranging from 1073-1373K. A Ni-based superalloy (Rene 80) was also tested in the same condition at selected temperatures for comparison. The tested materials had nominal compositions of Al67Ni8Ti25, Al66Fe9Ti25 and Al67Mn8Ti25. Specimens of the alloys were heated to the testing temperatures at a rate of 16 K min exp --1 held for 50 h in air and cooled to room temperature. Total weight gain was automatically recorded using a continuously reading Cahn microbalance. Weight gain/unit surface area was calculated. It was found that the alloys containing Fe and Ni exhibited excellent oxidation resistance in air up to 1373K. The continuous protective Al2O3 scales formed on the surface. The Mn-modified alloy showed poorer oxidation resistance at temperatures > 1273K than the other two. A strong tendency to form transient Ti-rich oxides was found to surpass the formation of the continuous Al2O3 scales.