Abstract
Nanostructured metals received significant attention due to their high mechanical strength. However, their poor thermal stability hinders their applications at high temperature. Here we show extraordinary thermal stability of FeZr nanocomposites with micron-sized Fe grains well distributed in the nanostructured Fe/Fe2Zr eutectic laminates. The hardness of annealed FeZr nanocomposites remained unchanged up to 700°C. Grain growth at higher annealing temperatures leads to hardness drop. Moreover, in situ annealing inside a transmission electron microscope revealed an unexpected coarsening mechanism of α-Fe grain: thermal stress arising from thermal expansion mismatch between Fe and Fe2Zr led to plastic yielding of large α-Fe grains. Debonding between α-Fe grain and Fe2Zr along phase boundary introduced nanometer thick gaps, which were subsequently filled by Fe from eutectic laminates, manifested as grain coarsening of α-Fe grains.
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