Performance Comparison of Al–Ti Master Alloys with Different Microstructures in Grain Refinement of Commercial Purity Aluminum
Three types of Al–5Ti master alloys were synthesized by a method of thermal explosion reaction in pure molten aluminum. Performance comparison of Al–5Ti master alloy in grain refinement of commercial purity Al with different additions (0.6%, 1.0%, 1.6%, 2.0%, and 3.0%) and holding time (10, 30, 60 and 120 min) were investigated. The results show that Al–5Ti master alloy with blocky TiAl3 particles clearly has better refining efficiency than the master alloy with mixed TiAl3 particles and the master alloy with needle-like TiAl3 particles. The structures of master alloys, differing by sizes, morphologies and quantities of TiAl3 crystals, were found to affect the pattern of the grain refining properties with the holding time. The grain refinement effect was revealed to reduce markedly for master alloys with needle–like TiAl3 crystals and to show the further significant improvement at a longer holding time for the master alloy containing both larger needle–like and blocky TiAl3 particles. For the master alloy with finer blocky particles, the grain refining effect did not obviously decrease during the whole studied range of the holding time.
Effects of processing parameters on the performance of Al grain refinement master alloys AlTi and AlB in small ingots
Abstract The effects of the Ti B ratio, the melt holding temperature and the melt mechanical agitation on the performance of aluminum grain refinement master alloys were investigated using small ingot castings. The results confirm that the presence of dissolved Ti in the melt is the key factor for effective grain refinement. Homogenizing the distributionof heterogeneous nuclei in the melt by mechanical agitation can further enhance the performance of TiB based master alloy. When the amount of dissolved Ti in the melt is less than the peritectic point, the columnar-equiaxed transition in master alloy treated melt is more sensitive to heat transfer variation rather than to the number of TiB2 particles retained in the melt. Slow cooling is recommended to avoid columnar growth. As the holding temperature increases, inoculation fade occurs.
Rotating dialysis cell as in vitro release method for oily parenteral depot solutions.
The purpose of the study was to investigate an in vitro release method based on a rotating dialysis cell for parenteral oil depot formulations using different model conditions and test formulations. The total amount of drug released from the rotating dialysis cell was in accordance with the theoretical values calculated from the partition coefficients. The release rates were shown to depend on the total amount of drug available for the release process and to follow first order kinetics. The rotating dialysis cell has a potential as in vitro release method for characterization of oily depot formulations for parenteral administration.