The　micro-mechanical　behavior　of　lamellar　structured　Ti6Al4V　alloy　to　a　small　compressional　strain　of　4.5%　was　studied.　Strain　and　stress　intends　to　localize　along　grain　boundaries　(GBs),　triple　points　(TPs)　as　well　as　grain　interiors　(GIs).　The　maximum　strain　and　stress　is　found　at　some　GB-TPs　with　soft　and　grain　clustering　mostly　owing　to　their　strong　strain　incompatibility.　Their　heterogeneous　distribution　is　highly　related　to　individual　crystallographic　orientation,　their　size,　shape　and　grain-grain　interactions.　The　local　dislocation　behavior　forms　ledges　along　with　Geometrically　necessary　dislocations　(GNDs)　to　accomodate　strain　incompatibility.　EBSD　and　crystal　plasticity　(CP)　simulation　disclosed　some　long　range　meso-bands　(about　45°　to　loading　direction)　which　crosse　multi-grains　and　some　mini-bands　within　grain　interiors　(GIs)　reflecting　a　concentrated　strain　behavior　and　ductile　nature　of　the　Ti6Al4V　material.　Prismatic　slip　dominates　Ti6Al4V　lattice　(mainly　from　surface　dislocation　activation)　determined　by　its　low　critical　resolved　shear　stress　(CRSS)　which　is　away　from　some　findings　of　literature.　Dislocation　is　found　commenced　from　some　high　angle　GBs　(HAGBs)　and　extened　into　GI　which　can　pass　through　GBs　of　both　low　(LA)　and　high　angles　given　their　slip　plane　coherency.　The　substructures　(α-lamellae)　separated　by　LAGBs　within　α-colonies,　have　no　significant　effect　to　dislocation　movement.　Fatigue　failure　can　be　inferred　from　the　early　stage　micro-mechanical　behavior　through　accumulated　plastic　strain　and　strong　strain　incompatability.　Fractography　reaveals　fatigue　failure　from　surface,　sub-surface,　shearing,　cleavage　and　intergranular　modes　are　presumed　highly　related　to　surface　defects,　compressional　residual　stress　gradient,　easy　prismatic　slip　and　soft　and　hard　GBs.　Multiple　crack　origins　from　such　combinations　are　deemed　for　reduced　fatigue　life　of　shot　peened　samples　regardless　of　the　surface　compressional　residual　stress　being　generated.　©　2023　Elsevier　Ltd