Outstanding high-temperature strength of novel Fe-Cr-Ni-Al-V ferritic alloys with hierarchical B2-NiAl precipitates

We designed and developed a novel ferritic alloy, which reveals excellent high-temperature yield strength enhanced by coherent hierarchical precipitates. The composition of designed ferritic alloy was tailored via addition of Vanadium into a Fe-Cr-Ni-Al alloy to control the size and volume fractions of coherent B2-NiAl precipitates. The evolutions of microstructures, mechanical properties, and strengthening mechanisms at 973 K were examined by the experimental efforts coupled with theoretical approach, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, compressive mechanical tests at 973 K, and theoretical (strengthening calculations) approach. It was found that the vanadium results in the reduction of the lattice misfit between B2-NiAl precipitate and matrix and decrease of the precipitate size. Furthermore, a hierarchical structure in the precipitate, i.e., nano-scale Fe23Zr6 phase within the B2-NiAl precipitate, was established in V-containing ferritic alloys, which plays a vital role in enhancing the yield strength at 973 K.

Automated summary

We designed and developed a novel ferritic alloy that exhibits excellent high-temperature yield strength enhancement through coherent hierarchical precipitates. The composition of the alloy was tailored by adding Vanadium to a Fe-Cr-Ni-Al alloy to control the size and volume fractions of coherent B2-NiAl precipitates. Experimental and theoretical approaches were used to examine the evolutions of microstructures, mechanical properties, and strengthening mechanisms at 973 K. It was found that the addition of Vanadium reduces the lattice misfit and precipitate size, and a hierarchical structure within the precipitate plays a vital role in enhancing the yield strength at 973 K.