Microstructure and dynamic strain aging behavior in oxide dispersion strengthened 91Fe-8Ni-1Zr (at%) alloy

Mechanically alloyed 91Fe-8Ni-1Zr (at%) powders were fabricated through high energy ball milling of elemental powder and subsequently consolidated via equal channel angular extrusion (ECAE) at 800 °C and 1000 °C. The resulting microstructure was fine grain with a nano-dispersion of Zr-oxide within the matrix, which was spherical for the 800 °C. ECAE and plate-like (and volumetrically larger) for the 1000 °C ECAE conditions. Atom probe tomography confirmed trace levels of C, N, and Cr impurities within the alloy making it similar to a low-carbon steel. By performing mechanical testing at a quasi-static strain rate (10⁻³ s⁻¹) and at high strain rate (10³ s⁻¹) at room temperature and 473 K, a load drop was noted after yielding. In general, this load drop became more pronounced with increasing strain rate and temperature and has been shown to be a result of dynamic strain aging in the ODS alloy.