Structure-Property Correlation of Gravity Die-Cast and Rheocast Al-Mg-Sc-Zr in situ Nano-TiB2 Composite

Abstract

The present study investigates the structure-property relationship of gravity die-cast and rheocast in situ processed 1wt%TiB2/Al-3.5Mg-0.15Sc-0.075Zr composites. The reinforcement was synthesized via the reaction of fluoride salts (K2TiF6 and KBF4) in the melt at 750 degrees C for an hour. The cooling slope technique was used for rheocasting, wherein the melt (pouring temperature of 700 degrees C) was allowed to flow over the cooling slope at an angle of 60 degrees. Thereafter, all samples (gravity die-cast and rheocast) were aged at 300 degrees C for 5 h. Microstructural characterization, hardness measurements, tensile tests, and fractography were necessary supplements to this investigation. The results obtained from this investigation infer: (a) The presence of nano-TiB2 particles increases the ductility (15%) of the gravity die-cast specimens; (b) rheocasting increases the strength of the specimen due to transformation from dendritic to equiaxed dendritic morphology and uniform particle distribution (reduced agglomeration). (c) Rheocast and aged specimens show maximum strength and adequate ductility due to the combined effects of structure refinement, reduced agglomeration, and the formation of fine precipitates.