Effect of Minor Elements on the Fluidity of Secondary LM25 and LM27-Type Cast Alloys
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In this study, the effect of individual and combined additions of Fe, Mn, Cr, Sr and Al-5Ti-1B grain refiner on the fluidity of secondary LM25 and LM27-type cast alloys was investigated. No change in fluidity was observed when the Fe level was increased from 0.14 to 0.4% in LM25, but it increased by 21% when Fe was raised to the critical content of 0.48%. Furthermore, a decrease of 32% resulted when the Fe level was increased to 0.6%. A combination of 0.3%Mn or 0.6%Cr with 0.6%Fe in LM25, resulted in a fluidity increase of 13 and 8%, respectively compared to the base alloy, but a combination of 0.6%Fe, 0.3%Mn and 0.2%Cr decreased the fluidity by 9%. A 34% increase in fluidity was observed when the Fe content in LM27 was raised from 0.41% to the critical level of 0.6%Fe with further increase when Mn was raised to 0.3%Mn. Increasing the Fe content to 1% in LM27 led to a drop in fluidity of 9%. Addition of 0.015%Sr and 0.02%Sr increased the fluidity of LM25 and LM27 by 9% and 21% respectively. Furthermore, a 0.28% Al-5Ti-1B grain refiner addition decreased the fluidity of LM 25 and LM27 by 2% and 19% respectively while a combined addition of 0.02%Sr and 0.28%Al-5Ti-1B decreased the fluidity of LM27 by 8%. Possible reasons for these observations are discussed.