Magnetostrictive　materials　with　large　magnetostriction,　low　hysteresis　and　wide　working　temperature　range　are　desired　for　applications,　but　rarely　obtained　so　far.　In　this　work,　we　report　a　surprising　finding　in　(1-x)TbFe2-xDyCo(2)　alloys:　the　composition　of　x　=　0.5　exhibits　a　low　hysteretic　magnetostriction,　lambda(parallel　to,max)　similar　to　2066　ppm,　which　is　1.59　times　as　large　as　that　of　the　commercial　giant　magnetostrictive　alloy　of　Terfenol-D,　lambda(parallel　to,max)　similar　to　1298　ppm.　Moreover,　its　temperature　range　for　lambda(parallel　to)　＞　1298　ppm　is　even　larger　than　240　K,　and　another　working　temperature　window　for　lambda(parallel　to)　＞　10　0　0　ppm　is　from　40　K　to　324　K,　which　can　cover　a　large　temperature　fluctuation　in　space　environments　(e.g.　120-290　K　in　Mars).　The　established　phase　diagram　of　(1-x)TbFe2-xDyCo(2)　by　systematic　studies　of　magnetic　susceptibility,　X-ray　diffraction　and　convergent-beam　electron　diffraction　results,　shows　an　emergence　of　morphotropic　phase　boundary　(MPB)　between　rhombohedral　(R)　and　orthorhombic　(O)　ferromagnetic　phases,　which　is　different　from　the　MPB　between　R　and　T　(tetragonal)　phases　in　(1-y)TbFe2-yDyFe(2).　We　reveal　that　the　exceptional　combination　of　giant　magnetostriction,　low　hysteresis　and　wide　working　temperature　range　is　caused　by　this　R-O　MPB.　The　comparison　between　R-O　MPB　and　R-T　MPB　further　shows　the　O　phase　plays　a　vital　role　in　the　property　enhancement　of　R-O　MPB　composition.　Our　work　indicates　the　construction　of　R-O　MPB　may　provide　a　new　way　to　find　high-performance　magnetostrictive　materials.　(C)　2021　Acta　Materialia　Inc.　Published　by　Elsevier　Ltd.　All　rights　reserved.