Abstract
The probability of Si grain refinement in hypereutectic Al-25 mass% Si alloy is examined by a compression test of cylindrical specimen (φ15xh15) at over eutectic melting point of 577 ℃. The tested condition comprises a combination of temperatures, T, of 580 and 590 ℃, compression rates, ν, of 5, 25, and 125 mm/min, and compression stroke, Oh, of 5, 10, and 12 mm. The viscosity and the shear rate are observed in the range from 0.2 MPa・s to 3 GPa・s and in the range from 2 ms^<-1> to 2 s^<-1>, respectively. The finer Si grain is obtained in cases of lower tested temperature, higher compression rate, and larger compression stroke, i.e., in case of T=580 ℃, ν=125 mm/min, and Δh=12 mm. The relations between Si grain size and shear rate for each tested temperature are summarized in a simple line on a single logarithmic plot. The process of Si grain refinement can be associated mainly with applied shear force.
