Difficult-to-cut　materials　are　widely　used　in　aerospace　and　other　industries.　Titanium　alloys　are　the　most　popular　ones　among　them　due　to　their　high　strength-to-weight　ratio　and　high　temperature　resistance.　However,　in　high-speed　machining,　the　alloys　are　prone　to　produce　serrated　chips,　which　have　a　serious　influence　on　surface　integrity.　In　this　study,　a　coupled　Eulerian-Lagrangian　method　is　used　to　simulate　the　orthogonal　cutting　of　Ti6Al4V　due　to　its　advantages　of　avoiding　element　distortion　and　improving　the　data　extraction　efficiency.　The　internal　relationship　between　serrated　chip　formation　and　periodic　profile　of　machined　surfaces　is　analyzed　by　the　simulation　results　and　experimental　data　which　are　obtained　by　optical　microscope　and　white　light　interferometer.　Furthermore,　thermal-mechanical　loads　on　machined　surfaces　are　reconstructed　based　on　the　simulation　results,　and　a　coupled　finite　element　and　cellular　automata　approach　is　used　to　describe　the　dynamic　recrystallization　process　within　the　area　of　the　machined　surface　during　the　formation　of　a　single　serration.　According　to　the　results,　the　periodic　fluctuation　of　cutting　forces　is　attributed　to　the　serrated　chip　formation　phenomenon,　which　then　leads　to　the　periodic　profile　of　machined　surfaces.　The　period　is　about　60-70　µm,　and　its　amplitude　decreases　with　the　increase　of　cutting　speeds.　Moreover,　the　loads　on　machined　surfaces　also　show　the　same　period　due　to　serrated　chip　formation.　As　a　result,　the　grain　refinement　layer　thickness　(about　2　∼　5　µm)　in　machined　surfaces　is　related　to　the　surface　temperature　and　exhibits　the　same　periodic　characteristics　along　the　cutting　direction.　Copyright　©　2021　by　ASME