The influence of isothermal annealing on the molybdenum fibers of a directed solid gamma/gamma prime - alpha alloy

The mechanical characteristics of the directed solid eutectic Ni-Al-Mo (gamma/gamma prime)-alpha alloy at high temperatures make it useful in the blades of gas turbines. Structural changes are observed for the alloy under isothermal annealing, particularly the formation of molybdenum plates at the grain boundary and an increase of the gamma phase in relation to the gamma prime phase. Molybdenum lamellas appear at the grain boundary above 1100 C which can have a negative influence on the mechanical properties. The change in the structure near the grain boundary with the increase in temperature is illustrated through a sequence of pictures.