A good fluidity of high strength Al-alloys is required to cast thin wall castings needed to reduce the weight of cast parts. The fluidity, measured as the length to which to metal flows in a standard channel, is affected by many factors, such as the pouring temperature, solidification type of the alloy, the channel thickness, melt head, mold materials and temperature, coating etc. Therefore the experimentally measured fluidity scatters very much and makes it difficult to estimate the fluidity of a melt with a few measurements.
The effect of Ti content and grain refinement on the fluidity of high strength aluminum alloy was investigated with a test casting with 8 thin flow channels to reduce the scattering of the fluidity results. The fluidity of Al-4.8%Cu-0.6%Mn, Al-6.2%Zn-1.6%Mg-1.0%Cu and well-known commercial alloy, A356 was tested. Initial content of Ti was varied from 0 to 0.2wt% and Al-5Ti-B master alloy was added for grain refining. The flow length varied linearly with superheat. By adding Ti and Al-5Ti-B, the fluidity increased. The grain size decreased by adding grain refiner at the same time. The Fluidity depended on the degree of grain refining. The fluidity of the alloy solidifying in mushy type is improved by grain refining, because grain refining increases the solid fraction at the time of flow stoppage.
The hot tearing behavior was tested by grooved mold. Due to the addition of Al-5Ti-B grain refiner, hot tearing of Al-4.8%Cu-0.6%Mn was prevented. But the hot tearing occurred in Al-6.2%Zn-1.6%Mg-1.0%Cu because the solidification range is larger than that of the Al-4.8%Cu-0.6%Mn.
The feeding property was investigated to eliminate micro-shrinkage porosity. 5mm-thick plates (200mm length, 60mm width) were cast with padding taper of 3%. The porosity volume percentage was calculated by measuring density. Procast® was used to simulate the feeding property and the mapping factor $G/\sqrt{L}$ was calculated in simulation result
