Influence of pressure solidification on AZ91D magnesium alloy feeding in lost foam casting process

Abstract

Feeding capacity of AZ91D magnesium alloy is enhanced by using pressure solidification in lost foam casting. The pressure-adding time and the surface depression of the casting were calculated and analysed. The results showed that the pressure-adding began at above 590uC, and ended at above 514uC. Compared the castings with the temperature field simulation of the samples, it was found that the surface depression of the castings generated easily at the hot spot where solidified last. The mathematical model of the depression showed that the surface depression is directly proportional to wall thickness. To prevent the depression of the casting surface, the gating system needs to be modified and a riser should be added. After this modification, the directional solidification could be achieved. Thus, the surface depression was transformed to the riser and the last solidified part of the gating system.

Influence of mechanical activation of a cordierite -based filler on sedimentation stability of lost foam refractory coatings

“…The grain size of the cordierite samples were: C 1 (100% -24 x10 -6 m); C 2 (100% -20 x10 -6 m); C 3 (100% -12 x10 -6 m). Refractory coatings and their production processes were designed according to the works [3,8,22], our works [24,26] and domestic norms [43,44]. Based on the analysis of the mechanical activation influence on the filler grain size and shape [27,[28][29][30][31][32][33] as well as of the filler grain size influence on coating suspension sedimentation stability [3,7], cordierite-based, mechanically activated fillers were chosen: first filler C 2 (100% -20 x10 -6 m) and the second combination of fillers C 2 (100% -20x 10 -6 m) and C 3 (100% -12 x10 -6 m).…”

“…These products are a frequent cause for castings' defects [1][2][3][4][5]. To obtain quality castings, it is necessary to apply highly permeable Lost Foam refractory coatings [1,[6][7][8].…”

“…to form an even and uniform, a thinner film of the coat. It is of particular importance when the coat is applied for the Lost Foam casting process, because particles with different (grain and metric) composition are a better match; the filler particles get "stacked" among themselves to form thin, highly permeable layers of coat on the pattern concerned [3,8,16]. According to:…”

The microstructure and the mechanical property of AZ91D solidified under GPa-grade high-pressure

“…The AZ91D alloy is one of the most widely used commercial magnesium alloy in Mg-Al alloy series. It has been reported [1][2][3] that, in the conventionally casted (Sand cast, metal cast or die cast) AZ91D alloys, a coarse microstructure is always obtained and the networked β-Mg 17 Al 12 phase exists among the α-Mg dendrites. This typical structure weakens the strengthening ability of β-Mg 17 Al 12 phases and the tensile elongation of the AZ91D alloy.…”

Effect of vibration frequency on primary phase and properties of grey cast iron fabricated by lost foam casting

“…microstructure and improve casting properties, many researchers have done a lot of investigations in recent years, and proposed many effective methods for refining grains, such as adding a modifier [7] , applying mechanical vibration [8][9][10][11][12][13] , heat treatment [14] , and so on. Compared with other methods for refining grains, applying mechanical vibration during the LFC process can refine casting microstructure through a physical method without contamination of the alloy.…”