Partial　substitution　of　Dy　for　Tb　in　TbFe2　compounds　results　in　improved　magnetostriction　with　high　strains　obtained　at　low　fields.　The　structural　evolutions　of　TbFe2　and　Tb0.4Dy0.6Fe2　compounds　are　studied　in　situ　using　synchrotron-based　high-energy　x-ray　diffraction　under　an　applied　magnetic　field.　It　is　found　that　the　rhombohedral　distortion　in　TbFe2　is　remarkably　reduced　by　substituting　Dy　for　Tb.　When　a　low　magnetic　field　is　applied,　a　preferential　rearrangement　of　rhombohedral　domains　is　directly　evidenced　in　TbFe2　and　Tb0.4Dy0.6Fe2　compounds.　Based　on　the　concept　of　crystallographic　domain-switching,　the　enhancement　in　the　magnetostriction　in　Tb1-xDyxFe2　compounds　is　discussed.　(C)　2015　Elsevier　B.V.　All　rights　reserved.