Influences of Super-Gravity Field on Aluminum Grain Refining

Abstract

The influence of a super-gravity field on metal grain refining has been mainly investigated using industrial pure aluminum as an example. The relationship between the super-gravity field (gravity coefficient of less than 1000) and the grain size in the equiaxed crystal zone was studied, and the corresponding mechanism for grain refining was discussed in detail. The effect of the super-gravity field on grain refining was remarkable, and the relationship could be well fitted by the second-decreasing-exponential function. For aluminum, the grain size decreased rapidly as the gravity coefficient increased from 1 to 250, and then remained nearly unchanged from 250 to 1000. Under the experimental conditions, the main mechanism was that the fragments of dendritic grains-generated by super-gravity-acted as the nucleation sites and resulted in grain refining. Further, the change of nucleation Gibbs free energy, directly caused by super-gravity, was not remarkable enough to refine the grains, which could be suggested by the stable freezing points under different super-gravity fields.

Effect of Super-gravity Field on Grain Refinement and Tensile Properties of Cu–Sn Alloys

“…Previously, four mechanisms were contributed to the structure refinement of as-cast alloys under super-gravity (centrifugal force) field: the change of nucleation energy mechanism by Chen et al, 18) the dendrite fragments mechanism by Zhao et al, 19) the coexist of free-chill crystals and…”

Selective Separation of Perovskite (CaTiO₃) from Titanium Bearing Slag Melt by Super Gravity

“…Inspired by the successful application of super gravity technology in preparation of functionally gradient materials, 18,19) removing inclusion from alloy melt, 20,21) and ironslag separation at low temperature, 22,23) it is possible to separate perovskite from the titanium bearing slag melt by super gravity. Hence, the precipitation behavior of the titanium bearing molten slag during cooling liquation was first investigated in this study, and the advantageous temperature range for precipitation of perovskite (CaTiO 3 ) was determined according to the variations of diffraction peak intensity and microstructure at different temperatures.…”

Concentrating of Iron, Slag and Apatite Phases from High Phosphorous Iron Ore Gaseous Reduction Product at 1473 K by Super Gravity

“…However, it is impossible to accomplish the separation of slag and iron phases at 1 473-1 573 K under the conventional conditions. Inspired by the successful application of super gravity technology in the preparation of functionally gradient materials 28,29) and removing impurities from alloy melt, 30,31) the super gravity field was applied to the iron-slag separation process at low temperature in this study. In this paper, the experiments on concentrating of iron, slag and apatite phases from high phosphorous iron ore gaseous reduction product at 1 473 K by super gravity were carried out, and the feasibility of this process was verified.…”