Effects of Mo and Al on the thermal expansion coefficients of Ni-base alloys

The effects of Mo and Al on the mean linear thermal expansion coefficients from room temperature to 10500C were determined for two types of nickel-base alloys. The Solid Solution Alloys were cast and homogenized Ni--Co--Cr--Mo alloys with 0, 31/2, and 61/2 nominal wt percent Mo concentrations. The Gamma Prime Alloys were wrought and heat-treated Ni--Cr--Mo--Al(Ti) alloys with 0, 2, 5, and 8 nominal wt percent Mo in each of four Al plus Ti levels (3 percent Al, 41/2 percent Al, 6 percent Al, or 1 percent Al + 31/2 percent Ti nominal wt percent). Thermal expansion coefficients were determined on at least two specimens from each alloy. It was found that Mo lowers the thermal expansion coefficients of both the cast Ni--Co--Cr solid solutions and the wrought Ni--Cr--Al(Ti) two-phase alloys. Both aluminum and titanium were also observed todecrease expansion coefficients in the two-phase, γ + γ', alloys. Results are discussed in terms of relative melting point effects between solute and solvent elements, and in terms of the volume fraction of the γ' phase present. (U.S.)