Mediating coherent L12 phase precipitation via two-step aging in Si-modified A-286 alloy

Abstract

Developing an L1₂-strengthened Si-modified A-286 alloy is challenging. Here, we propose a novel strategy to induce L1₂ phase precipitation in Si-modified A-286 alloys through a two-step aging process. It was found that the addition of Si into the A-286 alloy leads to the formation of nanoscale Ni₁₆Ti₆Si₇ G-phase during one-step aging, enhancing the strength of alloy. Subsequently, the growth of the G-phase results in a decrease in Si content in the matrix, thereby increasing the driving force for the L1₂ phase. Consequently, L1₂-type Ni₃(Al, Ti) nanoparticles precipitate and further improve the strength after two-step aging. The L1₂-strengthened Si-modified A-286 alloy offers a promising alternative for fastener applications in lead-cooled fast reactors.