Al3Ni　nanowires　were　fabricated　via　the　selective　etching　of　directionally　solidified　Al–Ni　eutectic　alloys.　The　effects　of　different　growth　rates　from　2　to　1000　μm/s　on　the　microstructure　and　morphology　of　eutectic　alloys　under　a　temperature　gradient　of　10　K/cm　were　investigated.　The　mechanism　of　the　cross-sectional　morphology　transformation　of　Al3Ni　nanofibers　was　investigated　using　the　dynamic　undercooling　degree　ΔTk.　Then,　the　morphologies　of　the　Al3Ni　nanowires　at　different　growth　rates　and　corrosion　time　were　studied　using　the　constant　potential　corrosion　method.　Increasing　the　growth　rate　increased　the　roundness　of　the　section　and　decreased　the　fiber　phase　spacing　and　diameter.　At　a　growth　rate　of　2　μm/s,　both　Al　and　Al3Ni　exhibited　kinetic　undercooling　(ΔTk,Al3Ni　and　ΔTk,Al),　with　values　below　the　critical　kinetic　undercooling　(ΔTk,Al3Nic　and　ΔTk,Alc).　The　Al3Ni　fibers　underwent　faceted　growth　and　developed　a　thin　ribbon　structure.　At　5　μm/s,　the　kinetic　undercooling　of　Al3Ni　and　Al　exceeded　ΔTk,Al3Nic　and　ΔTk,Alc,　respectively,　leading　to　nonfaceted　growth　and　elliptically　shaped　Al3Ni　fibers.　With　prolonged　corrosion　time,　the　length　of　the　Al3Ni　nanowires　increased.　©　The　Minerals,　Metals　&　Materials　Society　and　ASM　International　2024.