As-Casting Structure and Homogenization Behavior of Ta-Containing GH4151 Ni-Based Superalloy

Area of Science:

• Materials Science
• Metallurgy
• Physical Chemistry

Background:

• GH4151 alloy is a high-performance material used in demanding applications.
• Understanding the effects of alloying elements like tantalum (Ta) is crucial for optimizing its properties.
• Microstructural evolution and deformation behavior significantly influence alloy performance.

Purpose of the Study:

• To investigate the impact of tantalum (Ta) addition on the microstructure, phase dissolution, and hot deformation behavior of GH4151 alloy (Ta-GH4151).
• To determine the optimal hot deformation parameters for Ta-GH4151 alloy.
• To elucidate the role of Ta in element segregation and diffusion kinetics.

Main Methods:

• Optical microscopy (OM), Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA), Differential Scanning Calorimetry (DSC).
• Mechanical testing and simulation (MTS), Electron Backscattering Diffraction (EBSD).
• Analysis of as-cast microstructure, microsegregation, secondary precipitation kinetics, and thermal deformation behavior.

Main Results:

• Ta addition influences the distribution of elements, with Ti, Ta, Nb, and Mo showing negative segregation and Cr, W showing positive segregation.
• Initial dissolution temperatures for Laves phase, eutectic (γ + γ'), and η phase are elevated by Ta.
• Optimal hot deformation conditions for homogenized Ta-GH4151 alloy are identified as 1160-1170 °C at a strain rate of 0.3-1 s⁻¹.

Conclusions:

• Tantalum (Ta) addition enhances the redissolution temperatures of key phases and increases the segregation of Nb, Ta, and W in GH4151 alloy.
• The study provides critical data on diffusion activation energies and hot deformation energy.
• Findings offer insights for the modification and accelerated application of GH4151 alloy.