Isothermal coarsening of cooling slope processed semi-solid A380 Al alloy slurry

ABSTRACTPresent study depicts the effect of isothermal holding on microstructural morphology of the cooling slope processed slurry of A380 Al alloy. Along with the primary and eutectic phase morphology, significant effect of isothermal slurry coarsening on Iron (Fe)-rich intermetallic formation is evidenced here. The study also reports the effect of adding refining (0.15 wt% Al-5Ti-1B master alloy) and modifying (0.1 wt% Al-10Sr master alloy) agents within the melt on formation sequence and percentage of Fe- and Mn-rich intermetallics within the slurry matrix. Furthermore, modified Lifshitz-Slyozov-Wagner equation is proposed here to quantify the relative influence of Ostwald ripening and coalescence, towards determining slurry microstructure, during isothermal slurry holding stage. Optimum slurry morphology, i.e. minimum size and maximum sphericity of constituent primary Al grains as well as uniform distribution of Fe, Manganese (Mn) and Copper (Cu)-rich intermetallics, is achieved for the refiner+modifier added slurry, after 7 minutes of isothermal holding.KEYWORDS: Semi-solid slurryA380 alloyisothermal coarseningcoalescenceOstwald ripening AcknowledgmentsThe author also like to thank the personnel of the erstwhile NNMT group, CSIR-CMERI for their cooperation and cordial help towards successful completion of this research work. The author also like to thank Dr. Supriya Bera, NIT Durgapur for his help to carry out XRD studies, presented in this paper. Finally, the author would like to express his gratitude to Director, IISc for his encouragements.Disclosure statementNo potential conflict of interest was reported by the author.Additional informationFundingThe author would like to thank SERB, DST, Government of India and CSIR, Government of India for their financial support to this work vide grant no. SB/EMEQ-449/2014 and OLP121212, respectively.