The　over　tenfold　magnetostriction　enhancement　by　soluting　nonmagnetic　Ga　into　body　centered　cubic　(BCC)　Fe　has　been　ascribed　to　crystal　lattice　softening,　which　indicates　that　the　Fe-Ga　solid　solution　lies　in　the　crossover　of　martensitic　transformation.　Identifying　the　martensitic　phase　then　becomes　essential.　Herewe　report　the　stress-induced　local　six-layer　modulated　monoclinic　(6　M)　martensites　in　a　Fe79Ga21　alloy　solution-treated　at　1373　K.　Although　X-ray　diffraction　(XRD)　and　magnetic　measurements　reveal　that　the　bulk　sample　exhibits　BCC　average　structure,　the　transmission　electronic　microscopy　(TEM)　characterizations　however　show　that　the　mechanically　grinded　foil　sample　contains　local　6　M　phase.　First　principal　calculations　suggest　that　low　formation　energy　barrier　between　the　ordered　D0(3)　and　the　6　M　phases　are　responsible　for　the　stress-induced　structural　transformation.　Our　work　provides　evidence　for　the　lattice　softening　of　Fe-Ga　solid　solution,　adding　important　insight　into　understanding　the　origin　of　its　extraordinary　magnetostriction　enhancement.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.