Studi pengaruh kombinasi komposisi 0,02 wt. % Sr dan 0,063, 0,083 dan 0,108 wt. % Ti terhadap karakteristik paduan aluminium AC4B hasil proses low pressure die casting ( LPDC) = Effect of combination of composition of 0.02 wt. % Sr and 0.063, 0.083 and 0.108 wt. % Ti in aluminium AC4B alloy produced by low pressure die casting (LPDC)