Porosity in Aluminum Alloy Castings

The inclusions and impurities (such as oxides, carbide, defect, and so on) are formed mostly during the casting process. These inclusions and impurities reduce material properties because an increase in porosity has a tendency to form failure and corrosion of aluminum alloys. The effect of porosity on the fatigue life of AlSi9Cu3 cast alloy was studied, examining the effect of porosity size, distribution, and morphology on the fatigue behavior changes, using image analysis software. A comparison of the fatigue properties was made between material casted into a metallic mold and the material casted into a sand mold under the same conditions of gravity die casting. The fatigue properties were studied on equipment Vibrophores Amsler 50–250 HFP 5100 for material casted into a metallic mold and on Rotoflex for materials casted into a sand molds. The results show that porosity has the greatest detrimental effect on fatigue life. It was found that fatigue life decreases with increasing size of the pores surface. The experimental material casted into the metallic mold had about 98.78% smaller porosity size in comparison to the material casted into the sand mold; therefore, it showed better fatigue and mechanical properties.

Effect of Aluminum Addition on the Microstructure, Tensile Properties, and Fractography of Cast Mg-Based Alloys

The present study was performed on Mg-based alloys containing Zn and Mn. The alloys were cast in a permanent metallic mold preheated to 200°C and with a protective atmosphere of dry air, CO2, and SF6. Two main phases are observed in the as-cast condition: Mg-Al-Zn and Mn-Al intermetallics. The size and morphology of the Mg-Al-Zn phase are significantly affected by the concentration of Al. Tensile properties, using standard ASTM B-108 samples, are directly related to the size, morphology, and density of the existing phase particles. The alloy ductility is reduced with increase in the Al concentration, whereas the ultimate tensile strength and the yield strength are more or less stable. The fracture surface of the tested tensile bars is mostly ductile for low Al-containing alloys and tends to be brittle with the increase in Al content as evidenced by an increase in the density of cleavage ruptured areas.

Optimal Pouring System Design for Investment Casting of Cladding Thin-Plate Heater Using Metallic Mold Flow Analyses

To improve the pouring process efficiently, mold flow analysis and experimental design are adopted to provide feedbacks from defect prediction and thermodynamics evolutions by considering thermal radiation effect between shell molds and the molten metal. Processing parameter, gate and runner layout were regulated to prevent the formation of casting defects, so as to promote pouring yields and reduce the costs and product development cycle effectively.

Grain Refinement Performance of Al Cast Using Machining Chips

In this study, grain refinement performance of as-cast Al using machining chip of Al instead of the grain refiner is investigated. At first, the machining chips of pure Al are placed in metallic mold. Then, pure Al melt is inserted into the mold with the machining chips. From the microstructure of the as-cast Al using the machining chips, it is found that this machining chip in mold can induce grain refinement of as-cast Al. The increment of the Al chips enhances the grain refinement of the as-cast Al. Moreover, it is shown that preheating the mold can reduce the pore inside as-cast Al using the machining chips. This grain-refinement effect by the machining chips would come from the enhancement of cooling rate and the role of the nucleation site. Therefore, it is concluded that the machining chips of Al can enhance the grain refinement of as-cast Al.