Continuous gamma ' precipitation in directionally solidified IN738 LC alloy

A microstructural characterisation of continuously precipitated gamma' part icles in IN738 LC alloy directionally solidified at various cooling rates h as been carried out. With decreasing cooling rate there is a trend for the gamma' morphology to vary from rounded particles to irregular cuboids and, finally, a clusterlike formation. In the interdendritic regions, microsegre gation lends to an increase in the gamma' solvus temperature, and gamma' pr ecipitation begins at higher temperatures than in the dendrite cores, resul ting in differences in particle size and morphology. Observations on the ef fects of solution treatment and aging on the development of gamma' dispersi ons are also reported. MST/4236.