Coherency of ordered γ′ precipitates and thermoelastic martensitic transformation in FeNiCoAlTaB alloys

The martensitic transformation characteristics and coherency of ordered γ′ precipitates are investigated by electrical resistivity tests and HAADF-STEM observation in the aged FeNiCoAlTaB alloys. The results reveal that the precipitate grows up in the Ostwald ripening mode at the initial aging stage. As aging time increasing, the coarsening behavior of precipitates deviates from the Ostwald ripening and the martensitic transformation changes from the thermoelastic type to the non-thermoelastic one. The thermoelastic to non-thermoelastic transition with increasing precipitates size results from coherency loss between precipitates and matrix during martensitic transformation.