9 research outputs found
Mechanisms and control of macrosegregation in DC casting
Macrosegregation is a severe, unrecoverable defect often occurring in large-scale castings. This paper offers a critical review of mechanisms involved in the formation of macrosegregation during DC casting of aluminum alloys. These mechanisms include thermo-solutal and forced convection, shrinkage-driven flow and transport of solid crystals. It is demonstrated that the impact of melt flow on macrosegregation depends on the flow direction and pattern, and on the extent of the slurry zone in the sump. The shrinkage-induced flow contributes to the negative centerline segregation but this contribution depends on the shape of the macroscopic solidification front and on the permeability of the mushy zone. Accumulation of floating crystals will result in negative segregation but the occurrence of these grains and their composition depends on grain refinement and melt How pattern. It is shown that macrosegregation can be controlled by practical means such as process parameters, structure modification and melt flow management
Analysis of Hydrogen Content in the Main Stages of Low-Alloy Aluminum Alloy Flat Ingot Manufacture
Macrosegregation Behavior of Ti-10V-2Fe-3Al Alloy During Vacuum Consumable Arc Remelting Process
Effect of starting powder properties on the structure and mechanical characteristics of Al–8Cr–1.5Fe alloy for high-temperature applications
Thermal Melt Processing of Metallic Alloys
Using melt superheating as a means to control the structure and properties of metallic alloys has been studied extensively and demonstrated some promising results, though the industrial implementation is limited due to the required high energy for melt heating and holding. The physical mechanisms behind this technology can be divided into two major groups: (1) achieving homogeneous metallic melt with the resultant high undercooling upon solidification and (2) formation of heterogeneous substrates either by formation or transformation of insoluble impurities. In this chapter, we first discuss the structure of melts and its changes with temperature during high-temperature holding. Although mostly of academic interest, these studies demonstrate the complexity of temperature influence on the molten and solidifying melt. Some examples on the effects of the initial melt condition on the solidification microstructures are given as well. After that we consider some practical implications of the changes in insoluble impurities with temperature on the microstructure formed during solidification in some metallic alloys. © 2018, Springer Nature Switzerland AG