Authors: Hasan Kotan Kris A Darling Mostafa Saber Ronald O Scattergood Carl C Koch
Publish Date: 2013/08/14
Volume: 48, Issue: 24, Pages: 8402-8411
Abstract
The thermal stability of nanostructured Fe100−x−y Ni x Zr y alloys with Zr additions up to 4 at was investigated This expands upon our previous results for Fe–Ni base alloys that were limited to 1 at Zr addition Emphasis was placed on understanding the effects of composition and microstructural evolution on grain growth and mechanical properties after annealing at temperatures near and above the bcctofcc transformation Results reveal that microstructural stability can be lost due to the bcctofcc transformation occurring at 700 °C by the sudden appearance of abnormally grown fcc grains However it was determined that grain growth can be suppressed kinetically at higher temperatures for high Zr content alloys due to the precipitation of intermetallic compounds Eventually at higher temperatures and regardless of composition the retention of nanocrystallinity was lost leaving behind fine micron grains filled with nanoscale intermetallic precipitates Despite the increase in grain size the in situ formed precipitates were found to induce an Orowan hardening effect rivaling that predicted by Hall–Petch hardening for the smallest grain sizes The transition from grain size strengthening to precipitation strengthening is reported for these alloys The large grain size and high precipitation hardening result in a material that exhibits high strength and significant plastic straining capacity
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