Comparison of effects of master alloys containing titanium and/or boron on the grain size and dendrite arm spacing of DIN226S aluminium alloy

摘要

Master alloys containing titanium and/or boron are widely-used inoculants in the aluminium casting industry to improve mechanical properties, surface finish, soundness and anodizing properties and to increase casting speed. Much work has been done on the effects of these alloys on the grain refinement of aluminium castings. Aluminium casting alloys containing higher levels of Si are known to be difficult for grain refinement. Most of the experimental work done so far has been concentrated on the influence and mechanisms of Ti and/or B on refinement of the grain size [1-6]. The effects of Ti and/or B on the dendrite arm spacing (DAS) during grain refinement has not been established in the literature, while the DAS refinement can further homogenize the micro-structure of the castings. Thus, a comparative study was done to investigate the effects of additions of master alloys containing Ti and/or B on DAS when being used as a grain size refiner in permanent mould casting of a higher Si-containing aluminium alloy. The Ti addition levels evaluated in the study were 0.11, 0.13, 0.15 and 0.17 wt %. The Ti: B ratios studied were 1 : 6, 1 :4, 1:2, 1: 1, 2: 1, 4: 1 and 6 : 1 at a selected Ti addition level.