Laser-assisted processing of Ni-Al-Co-Ti under high pressure

ABSTRACT

Laser-assisted processing and in-situ characterization of a Ni_0.7-Al_0.1235-Co_0.15-Ti_0.0265 alloy were carried out under a range of simultaneous hydrostatic high pressures of ∼30 GPa and high temperature conditions ∼2000°C using a laser-assisted heating in diamond anvil cell with synchrotron X-ray micro-diffraction. The characterization of the microstructure and X-ray diffraction analysis at ambient conditions confirmed the formation of the cuboids of ordered γ′ phase in the disordered γ matrix. The isothermal bulk modulus (B₀) and its first-order derivative (B₀’) of the alloy were determined to be B₀ = 123 ± 9 GPa and B₀’ = 5.7 ± 2.8. The in-situ characterization of the alloy at high temperatures under high pressures revealed that the γ′ phase transforms into the tetragonaly distorted D0₂₂-type structure. This transformation is similar to the transformation that occurs in the ordered Ni₃Al, responsible for the improved strength at high temperatures. High pressure was found to increase the onset temperature of the structural distortion. The pressure–temperature phase diagram of the Ni_0.7-Al_0.1235-Co_0.15-Ti_0.0265 up to ∼30 GPa and ∼2000°C was determined and is reported here.

KEYWORDS:

• Microstructure
• modulus
• strength
• structures
• superalloys
• temperature
• thermodynamics
• XRD