Influence of phosphorus on the mechanical properties and γ" phase of aged DA 718 alloy

The growth behavior has been investigated for the gamma '' phase in DA 718 alloy aged at 680 degrees C for 3000 h and the effect of phosphorus on the coarsening behavior has been revealed as well. Results show that the gamma '' phase grows linearly along the radius direction and by a parabolic curve along the thick direction. Addition of phosphorus impedes the growth of gamma '' phase, maybe due to the decrease of diffusion coefficient of the niobium in the matrix. In the mean time, the effect of phosphorus,on the mechanical properties of the aged DA 718 alloys has been investigated. Results show that the phosphorus slightly influences the room temperature hardness and tensile properties, but markedly improves the creep property.