Luo Shou-jing

Development of the technique of extrusion directly following infiltration for the manufacturing of metal-matrix composites

Abstract Metal-matrix composites (MMCs) are now attracting increasing interest because they exhibit improved physical and mechanical properties as compared with the matrix alloys. Although the properties of MMCs are determined primarily by the individual properties of the matrix alloy and the reinforcing material, yet the former are also influenced largely by the manufacturing technique. To obtain MMCs with optimum properties, the manufacturing technique has to assure uniform distribution of the reinforcing material in the matrix and the formation of a good bond between the matrix and the reinforcing phase. Voids must be eliminated also, as well as direct contact bridging or bunching of the reinforcing phases. For this reason, a new technique, extrusion directly following infiltration (EDFI), is proposed. The new technique is developed on the basis of melt infiltration, squeeze casting, and semi-solid extrusion techniques and is particularly suitable for the manufacturing of bars, pipes, plates, and other long shapes of discontinuous fiber, whisker, or particulate reinforced MMCs. This paper presents a detailed description of the technique in principle and a discussion of the experimental results obtained from technical experiment with short alumina fiber and Al-1.5%Mg aluminum alloy.

The optimum selection of technological parameters for liquid forging of pumic — aluminum composite materials

Abstract On the basis of analyzing the technological characteristics of liquid forging of pumice-aluminum composite materials, the main technologic parameters that influence the properties of pumice-aluminum composite materials, i.e. the pressure, the pouring temperature, the particle size of the pumice and the volume ratio of the pumice, were determined. The authors defined the primary and secondary relationships of all of the main factors affecting the properties of the composite materials (tensile strength, compressive strength, impact toughness and density), and ascertained a more suitable range of every factor with orthogonal testing, providing reliable data for applying the liquid forging of pumice-aluminum composite materials in production.

The stress states of a workpiece in the process of liquid-metal forging

Abstract In this paper the authors analyze the stress states of a workpiece in the process of liquid-metal forging, on the basis of numerous experiments. Schematic diagrams of the stress state in every stage for two conditions (i.e., insufficient pressure and sufficient pressure) are given, which reveal that the stress state in a workpiece changes continuously in order that plastic deformation can continue. The results of the analysis have been examined by carrying out engineering calculations, which has indicated that the results are practical and correct for engineering purposes.

Eliminating defects of ZnAl alloy by squeeze casting or liquid extrusion

Abstract In the paper, the two effective methods to eliminate the casting defects of ZnAl alloy, the squeeze casting process and the liquid extrusion process, have been expounded. By using ZA27 alloy as the experimental objective, the microstructures and the properties and the formability by permanent mould casting, squeeze casting and liquid extrusion have been compared. The results show that both the two kinds of processes can not only eliminate the casting defects, but also raise the properties and improve the microstructure of the ZA27 alloy. The effect of the liquid extrusion process is especially good.

Structural characteristics of hot cracks in liquid-forged steel flat flanges

Abstract The Shape, appearance and structural characteristics of hot cracks in liquid-forged steel flat flanges have been experimentally examined and theoretically explained. It is revealed that once a crack occurs in a workpiece it usually grows through four stages, each of which corresponds to a peculiar structural zone. Based on the experimental examinations and theoretical explanations, a structural model for typical hot cracks has been proposed.