Two-phase intermetallic alloy Ni-3(Al, Si): microstructure and mechanical properties

Yield stress in compression (0.2% flow stress) from ambient temperature up to 800 degreesC has been studied on Ni-3(Al, Si) alloy with the atomic comp osition Ni78Al11Si11. When annealed at 1000 degreesC, the alloy has a pure L1(2) (gamma') ordered structure. After subsequent annealing at 750 degrees C, the disordered solid solution of Al and Si in Ni (face centred cubic, ga mma) precipitates in fine coherent particles. Calorimetry helps to describe the various phase transformations necessary to obtain the last microstuctu re. Solute addition of Si, which replaces A1 atoms, increases the 0.2% flow stress of Ni3Al in the fully gamma' microstructure. The gamma precipitatio n shifts the peak stress towards higher temperatures and stresses. (C) 2001 Elsevier Science Ltd. All rights reserved.