Wire　feeding　speeds　of　3.5,　4.5,　and　5.5　m/min　are　operated　to　arc-braze　TC4　titanium　alloy　to　304　L　stainless　steel　with　the　cold　metal　transfer　method　and　CuNi　filler　wire.　The　microstructure　and　fracture　behavior　of　TC4-304Ldissimilar　joints　were　characterized　by　transition　electron　microscopy　(TEM),　selected　area　electron　diffraction　(SAED)　patterns　and　X-ray　microscope　(XRM).　The　results　show　that　the　TC4/seam　transition　zone　consists　of　an　inner　Ti-rich　layer　and　an　outer　Ti-poor　layer　based　on　the　line　scanning　result,　which　contains　complex　eutectic　microstructures　such　as　(Cu,　Ni)Ti3,　CuNiTi2,　CuNiTi,　(CuxNi1-x)　Ti,　and　(Cu)　solid　solutions.　The　microstructure　of　the　304　L/seam　interface　consists　of　CuNi2Ti,　(Cu,　Ni)　and　(Fe,　Ni)　solid　solutions.　With　increasing　heat　input,　the　thickness　of　the　TC4/seam　transition　zone　and　the　size　of　(Fe,　Ni)　dendrite　grains　increase,　the　ultimate　tensile　strength　decreases　from　350.8　to　230.5　MPa,　and　all　samples　fracture　near　TC4　side　based　on　tensile　samples　and　XRM　results.　The　crack　propagation　is　due　to　both　the　thickness　of　TC4/seam　transition　zone　and　a　large　amount　of　brittle　CuNiTi　equiaxial　dendrite　grains　with　a　high　hardness　of　10.4　GPa.　(c)　2021　The　Authors.　Published　by　Elsevier　B.V.　This　is　an　open　access　article　under　the　CC　BY-NC-ND　license　(http://creativecommons.org/licenses/by-nc-nd/4.0/).