Nano-sized precipitate stability and its controlling factors in a NiAl-strengthened ferritic alloy

Abstract

Coherent B2-ordered NiAl-type precipitates have been used to reinforce solid-solution body-centered-cubic iron for high-temperature application in fossil-energy power plants. In this study, we investigate the stability of nano-sized precipitates in a NiAl-strengthened ferritic alloy at 700–950 °C using ultra-small angle X-ray scattering and electron microscopies. Here we show that the coarsening kinetics of NiAl-type precipitates is in excellent agreement with the ripening model in multicomponent alloys. We further demonstrate that the interfacial energy between the matrix and NiAl-type precipitates is strongly dependent on differences in the matrix/precipitate compositions. Our results profile the ripening process in multicomponent alloys by illustrating controlling factors of interfacial energy, diffusivities, and element partitioning. The study provides guidelines to design and develop high-temperature alloys with stable microstructures for long-term service.

Effect of titanium additions upon microstructure and properties of precipitation-strengthened Fe-Ni-Al-Cr ferritic alloys

“…These submicron, intragranular precipitates were previously identified as B2-NiAl with Fe-inclusions [18,21,22]. Their average radii of 579 nm is in agreement with the previously reported value of 62-65 nm for the same alloy composition exposed to the same heat treatment times and temperatures used here [21,23,24]. Fig 2a shows the FBB8-2Ti alloy, with millimeter-size grains, which was aged at 700°C for 100 h and then subjected to creep for 410 h at 700 ºC while accumulating 4% stain.…”

Strengthening of nanoprecipitations in an annealed Al0.5CoCrFeNi high entropy alloy

“…4(a) shows the SAED pattern of BCC [1 ̅ 11] zone axis and Fig. 4 [23][24], the B2 type brittle but hard intermetallic compound can be effectively used as a strengthening second phase which will provide the same strengthening effect in Al 0.5 CoCrFeNi HEA. In addition, large numbers of nano-sized precipitates (18nm) are dispersed in the dendrite matrix ( Fig.…”

High Temperature Deformation Mechanism in Hierarchical and Single Precipitate Strengthened Ferritic Alloys by In Situ Neutron Diffraction Studies

“…Coherent precipitate-strengthened alloys in Fe-Cr-Ni-Al system have received attentions as a candidate for high-temperatures applications, such as fossil-power plants, due to their promising mechanical properties, corrosion/oxidation resistance, and cost efficiency123456. These materials consist of the primary B2-NiAl precipitate homogeneously distributed in the body-centered cubic (bcc) Fe matrix.…”