New technique for preparing A356 alloy semisolid slurry and its rheo-diecast microstructure and properties

A new technique for preparing semisolid slurry,namely,distributary-confluence runner(DCR),was combined with die-casting(DC)to conduct rheological die-casting(R-DC)of A356 alloy.The mechanism of DCR for semisolid slurry preparation was determined via numerical simulations and experiments.The microstructure and mechanical properties of A356 alloys prepared via DC and R-DC were studied.High-quality slurry containing numerous primary α-Al(α1-Al)with an average size of 49μm and a shape factor of 0.81 could be prepared via DCR.Simulation results indicated that the unique flow state and physical field changes during slurry preparation were conducive to accelerating the uniformity of melt temperature and composition fields,nucleation exfoliation,and spherical growth.Compared with the alloy prepared via DC,the tensile strength,yield strength,and elongation of A356 alloy prepared via R-DC increased by 19%,15%,and 107%,respectively.

Microstructure and properties of rheo-HPDC Al-8Si alloy prepared by air-cooled stirring rod process

A new and effective semisolid slurry preparation process with air-cooled stirring rod(ACSR)is reported,in which the compressed air is constantly injected into the inner cavity of a stirring rod to cool the melt.The slurry of a newly developed high thermal conductivity Al?8Si alloy was prepared,and thin-wall heat dissipation shells were produced by the ACSR process combined with a HPDC machine.The effects of the air flow on the morphology ofα1-Al particles,mechanical properties and thermal conductivity of rheo-HPDC samples were studied.The results show that the excellent slurry of the alloy could be obtained with the air flow exceeding3L/s.Rheo-HPDC samples that were produced with the air flow of5L/s had the maximum UTS,YS,elongation,hardness and thermal conductivity of261MPa,124MPa,4.9%,HV99and153W/(m·K),respectively.Rheo-HPDC samples show improved properties compared to those formed by HPDC,and the increasing rates of UTS,YS,elongation,hardness and thermal conductivity were20%,15%,88%,13%and10%,respectively.