Cast　Al–Si　alloys　are　widely　used　for　their　excellent　casting　properties,　but　their　applications　are　restricted　in　some　special　fields　because　of　their　low　mechanical　properties.　In　this　paper,　H3BO3　and　TiO2　were　used　as　raw　materials　to　prepare　TiB2/Al–Si　composites　with　different　mass　fractions　by　in　situ　generation.　The　effects　of　TiB2　particle　content　on　microstructure　and　properties　of　the　alloy　were　studied.　The　results　showed　that　the　microstructure　of　the　alloy　was　mainly　composed　of　coarse　primary　α-Al　dendrites　and　long-striped　eutectic　Si　particles.　The　coarse　primary　α-Al　particles　were　obviously　refined　and　the　edge　of　acicular　eutectic　Si　was　rounded　with　the　addition　of　TiB2　particles.　When　the　particle　content　was　low,　the　particle　distribution　was　dispersed,　and　a　large　number　of　particles　were　located　in　the　grain　boundary.　When　the　particle　content　was　high,　the　particles　were　agglomerated　and　gathered　at　the　grain　boundary.　With　the　increase　of　particle　content,　the　mechanical　properties　of　the　material　were　obviously　enhanced.　When　the　content　of　TiB2　particles　was　5%,　the　tensile　strength　and　yield　strength　reached　200　and　160　MPa,　which　were　22.8　and　34%　higher　than　those　of　matrix,　respectively.　©　2019,　Springer　Nature　Singapore　Pte　Ltd.