Effect of Al, Ti and Ta contents on the microstructure in Ni-base single crystal superalloy during aging

The influence of gamma' formation and strengthening elements (Al, Ti and Ta) on the microstructure during aging for a long term has been studied for a single crystal of nickel superalloy. The results show that the size of gamma' phase increases with the increasing of Al, Ti and Ta after heat treated under the same condition. The morphology of gamma' changes from spherical to cubic then to a irregular shape. During aging at 950 degrees C for a long time, the size of gamma' phase increases and the cubic degree decreases until 1000 h, the gamma' phase did not link and raft. The size of gamma' phase in-creases obviously and the cubic degree decreases. during aging at 1050 degrees C for 500 h: As a result, the gamma' phase rafts in the alloy B,C and D, and keeps the same shape for the alloy A and E. A TCP (mu) phase precipitates in alloy E both in the two aging conditions.