Abstract
The main goal of this work was to examine the effect of aging process on the precipitation behavior including phase morphology, chemical composition and degree of coherence in Fe–28Ni–17Co-11.5Al-2.5Ta single crystals. The nano-sized and coherent γ′ precipitates were used for strengthening process. The particles were investigated with transmission and scanning electron microscopies along with high energy X-ray diffraction. The single crystalline material of [100] (001) orientation was subjected to three different heat treatments: slowly cooled, quenched and then annealed with various aging conditions. Aging at 973 K for short times results in coherent 2-6 nm-sized γ′ precipitates and fully reversible superelastic strains while annealing at 973 K for 5 h and longer times leads to the precipitation of larger γ’ particles formed together with β phase which significantly reduces the transformed martensite volume fraction.
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