Shian Jia

Experimental and Numerical Analysis of the 6061-Based Nanocomposites Fabricated via Ultrasonic Processing

There is strong evidence showing that microstructure and mechanical properties of a cast component can be considerably improved if nanoparticles are used as a reinforcement to form a metal-matrix nanocomposite. In this paper, 6061 nanocomposite castings were fabricated using the ultrasonic stirring technology (UST). The 6061 alloy and Al2O3/SiC nanoparticles were used as the matrix alloy and the reinforcement, respectively. Nanoparticles were injected into the molten metal and dispersed by ultrasonic cavitation and acoustic streaming. The applied UST parameters in the current experiments were used to validate a recently developed multiphase computational fluid dynamics (CFD) model, which was used to model the nanoparticle dispersion during UST processing. The CFD model accounts for turbulent fluid flow, heat transfer, and the complex interaction between the molten alloy and nanoparticles using the ANSYS’s fluent dense discrete phase model (DDPM). The modeling study includes the effects of ultrasonic probe location and the initial location where the nanoparticles are injected into the molten alloy. The microstructure, mechanical behavior, and mechanical properties of the cast nanocomposites have been also investigated in detail. The current experimental results showed that the tensile strength of the as-cast-reinforced 6061 alloy with Al2O3 or SiC nanoparticles increased slightly while the elongation increased significantly. The addition of the Al2O3 or SiC nanoparticles in 6061 alloy matrix changed the fracture mechanism from brittle dominated to ductile dominated.

Ultrasonic Cavitation-Assisted Molten Metal Processing of Cast A356-Nanocomposites

There is strong evidence that the mechanical properties of a cast component can be considerably improved if nanoparticles are used as a reinforcement to form a metal-matrix-nano-composite (MMNC).In this paper, Al2O3 and SiC nanoparticles reinforced A356 matrix composite castings were fabricated by using ultrasonic technology (UST). The A356 alloy and Al2O3/SiC nanoparticles were used as the matrix alloy and the reinforcement, respectively. Nanoparticles were inserted into the molten metal and dispersed by ultrasonic cavitation and acoustic streaming to avoid agglomeration. The microstructures and mechanical properties of the cast nano-composites were investigated in detail. The results showed that microstructures were greatly refined and with the addition of nanoparticles, tensile strength, yield strength and elongation increased significantly. Since the ultrasonic energy was concentrated in a small region under the ultrasonic probe, it is difficult to ensure proper cavitation and acoustic streaming for efficient dispersion of the nanoparticles without determining the suitable ultrasonic parameters via modeling and simulation. Accordingly, another objective of this paper was to develop well-controlled UST experiments that will be used in the development and validation of an UST dispersion modeling and simulation tool.

Numerical modeling of the gas evolution in furan binder-silica sand mold castings

Modelling of gas evolution during sand-mould castings is one of the most important technical and environmental issues facing the metal casting industry. The current effort focused on developing the capability of numerically predicting the gas evolution for the furan binder-silica sand system. Specifically, the decomposition of furan was experimentally analyzed and then predicted based upon the work developed in the current project. This methodology can be easily implemented into existing commercial casting codes. A parametric study was also performed for steel 4340 and aluminium A356 cylinders (D100 × H200 m) and bars (H50 mm × W50 mm × L250 mm) cast into silica sand moulds (furan binder) of 50-mm mould wall thickness to investigate the effects of superheat and heating/cooling conditions of the mould on the gas evolution. Such information would enable more technically and environmentally friendly decisions to be made concerning the process design used to make a given casting.

Ultrasonic Processing of 6061-Based Nanocomposites for High Performance Applications

Previously studies show that microstructure and mechanical properties of a cast component can be considerably improved when ceramic nanoparticles are used as a reinforcement to form a metal-matrix-nano-composite material.

Microstructure, mechanical properties and fracture behavior of 6061 aluminium alloy-based nanocomposite castings fabricated by ultrasonic processing

It has been revealed that microstructure and mechanical properties of aluminium castings can be significantly improved by adding nanoparticles as reinforcement to fabricate aluminium-based metal matrix nanocomposites (MMNCs). One of the common problems in fabricating MMNCs is the agglomeration of reinforcement nanoparticles. In the present study, ultrasonic stirring technology (UST) is deployed to assist 6061 nanocomposite casting process by promoting the dispersion and deagglomeration. Al2O3/SiC nanoparticles are used as reinforcement materials. Nanoparticles are added into the molten alloy and dispersed by ultrasonic cavitation and acoustic streaming caused by UST. The microstructure, fracture behaviour and mechanical properties of 6061-based MMNC samples have been investigated. Tensile strength and yield strength of MMNC samples remain at the same level while the elongation increases significantly compared to reference samples.

A Numerical Model for Predicting the Gas Evolution in Silica Sand (Furan Binder) Mold Castings

Modeling of gas evolution during sand-mold castings is one of the most important technical and environmental issues facing the metal casting industry. The current effort funded by ExOne focused on developing the capability of numerically predicting the gas evolution for the furan binder-silica sand system. Specifically, the decomposition of furan was experimentally analyzed and then predicted based upon the work developed in the current project. This methodology can be easily implemented into existing commercial casting codes. A parametric experimental and theoretical study was also performed for A356 cylinders (D100xH200m) and bars (H50mmxW50mmxL250mm) cast into silica sand molds (furan binder) of 50 mm mold wall thickness to investigate the effects of superheat and heating/cooling conditions of the mold on the gas evolution. Such information would enable more technically and environmentally friendly decisions to be made concerning the process design used to make a given casting.

Recent Advances on the Solidification Processing of Cast Energetic Materials

This paper investigates the solidification of highly viscous energetic materials cast into a projectile. Active cooling and heating (ACH) control solidification technology as well as mechanical vibration (MV) are applied to achieve unidirectional solidification and to reduce cracks, gas pores, and shrinkage defects and to decrease the detrimental gap size between the projectile and the solidified energetic material. A comprehensive numerical model was developed to simulate the solidification processes during casting of energetic materials, as well as the resulting induced thermal stresses. The optimized design parameters of the proposed technologies are developed based on numerical modeling and experiment work.