Papers by Keyword: Ceramic Foam Filter

Abstract: As-cast and solution-treated microstructures of AZ91D alloy before and after the purification by MgO ceramic foam filter (CFF) with different thicknesses at the range from 15 mm to 35 mm were investigated by optical microscopy and scanning electron microscopy. Meanwhile, the tensile mechanical property and impact toughness were tested. The results show that the impurities in the alloy melt could be eliminated by the filtration purification effectively. With increasing the thickness of CFF, the tensile mechanical property and impact toughness first increased significantly, and then decreased slightly. The AZ91D alloy purified by the CFF with the thickness of 20 mm and the porosity of 10 ppi exhibited the best comprehensive mechanical property. The tensile strength σ_b, elongation δ and impact toughness α_nK at ambient temperature reached 205 MPa, 8.5% and 16 J/cm², with the improving amplitude of 13%, 31% and 46% comparing with the corresponding unpurified value, respectively. At the same time, σ_b and δ at elevated temperature reached 195 MPa and 31.5%, with the improving amplitude of 9% and 174%, respectively. After the alloy was solution treated, the mechanical property was enhanced further, and the improving amplitude was larger for the alloy by the filtration purification. σ_b reached 260 MPa and 205 MPa at ambient and elevated temperatures, with the improving amplitude of 32% and 5% comparing with the unpurified value, respectively. α_nK reached 27 J/cm², with the improving amplitude of 69%.

Abstract: In the design of runner systems, ceramic foam filters are used for reducing the velocity of liquid metal in order to avoid so called bifilm defect resulting from a high gating velocity (over its critical gating velocity) in aluminum gravity casting. In this study, two types of runner systems incorporated with the ceramic foam filters were designed. In order to observe the flow phenomena in these two runner systems with and without the filters, a water analogy experiment in a transparent plastic mold was utilized. Furthermore, in order to understand the effect of the filters used in these systems, an aluminum sand casting experiment was conducted. The quality of the cast metal in the outlet area of the filter for these systems was investigated. The defect content of this casting sample was measured by the re-melt reduced pressure test (re-melt RPT) and followed by measuring its bulk density. An optimized runner system with the filter was suggested in this study. Keywords: ceramic foam filter, runner system design, gravity casting, critical gating velocity, bifilm defect.

Abstract: The effects of non-flux purification on the mechanical properties, microstructure and fracture pattern of AZ31+xCa magnesium alloys have been studied. The results show that the purification process of ceramic foam filters incorporating gas bubbling process can improve obviously the ultimate tensile strength σb and elongation δ of AZ31 alloy. With 20ppi MgO filter incorporating gas bubbling treatment under Ar flow rate of 2 l/min and temperature of 730°C, the σb and δ of AZ31 can be improved from 144.6MPa and 5.21% to 180.8MPa and 9.06% by 25% and 73.9%, respectively. Addition of 0.13%Ca to magnesium can not only increase the strength but also improve the elongation. With the further increase of more than 0.13% Ca content, the strength and elongation decrease. The experimental results show that under low Ca content, filtration purification process can greatly improve the σb and δ of AZ31+xCa alloy. However, with the increase of Ca content, the filtration effects decrease. The effective sequence of different filters is as follows: 20ppi MgO>20ppi Al2O3>10ppi MgO>10ppi Al2O3.