Sumio Sugiyama

Application of mushy/semi-solid joining—Part 3

Abstract A process to join glass or stone onto base metal alloys is proposed. The process characteristics allow using various kinds of glasses or stones, such as craft glass, beads, tile, amethyst, agate and hematite with different shapes and sizes. The process utilizes excellent and active join ability of mushy or semi-solid alloy’s properties. In this study, the mechanism of the joining was investigated and some applications were showed. The process itself has several useful properties like: (1) easy-to-operate, (2) ability to get good joining condition, and (3) applicability to a continuous production system. Through the study, it is found that the mushy joining is a useful and valuable manufacturing method for developing and manufacturing glass/metal or stone/metal composites. The mushy joining process is different from the existing cloisonne and enameling process.

A New Method to Detect Solid Fractions of Mushy/Semi-Solid Metals and Alloys

Abstract A new method to detect so—called solid fractions of mushy or semi-solid metals and alloys is proposed. Firstly, the relationships between electric resistance (or electric potential difference) and temperature in the range from solid—line to liquid—line are measured with respect to binary alloys and multi—component alloys. Secondly, the relationships between solid fractions of mushy or semi-solid binary alloys and their temperatures are obtained by referring their equilibrium phase diagrams. By combining both results, the unified relationship between normalized electric potential difference and solid fraction is obtained for all of the tested binary alloys. This relationship is used to determine the solid fractions of multi—component alloys from their measured normalized electric potential differences. The assumed values are verified by the rapid solidification method.

Effects of heat treatment on the microstructures and mechanical properties of a new type of nitrogen-containing die steel

Nitrogen can increase the strength of steels without weakening the toughness and improve the corrosion resistance at the same time. Compared with conventional nitrogen-free die steels, a new type of nitrogen-containing die steel was developed with many superior properties, such as high strength, high hardness, and good toughness. This paper focused on the effects of heat treatment on the microstructures and mechanical properties of the new type of nitrogen-containing die steel, which were investigated by the optimized deformation process and heat treatment. Isothermal spheroidal annealing and high-temperature quenching as well as high-temperature tempering were applied in the experiment by means of an orthogonal method after the steel was multiply forged. The mechanical properties of nitrogen-containing die steel forgings are better than the standard of NADCA #207-2003.

Recycling of Minute Metal Scraps by Semisolid Processing: Manufacturing of Design Materials

As a new attempt to recycle minute metal scraps, the possibility of manufacturing design materials by semisolid extrusion processing was shown. A design material with an intended shape, such as a character or petal shape, was manufactured using minute metal scraps. Similarly, a design material with an intended color pattern for each metal, such as red copper in a white aluminum matrix, resembling grainlike wood, was manufactured by mixing two or more types of minute metal scrap. In addition, secondary design materials, which have engraved patterns on the surface of the target metal made by an electric discharge machine using the above primary design material as an electrode, were manufactured.

Mashy-State Rolling of Aluminum Alloys and Cast Irons

Summary Mechanical and metallurgical features of mashy-stare (or mushy-state) rolling processes are investigated. Washy-state rolling of aluminum alloy sheets and cast iron sheets are carried out and effects of rolling conditions, such as solid fraction (weight percentage of solid component) of workpiece and thickness reduction, on flow and deformation characteristics of liquid component and solid component at roll gap, internal structure and mechanical property of rolled sheet are widely investigated. The results are as follows. (1) The rolling force decreases distinctively following to the decrease in solid fraction of workpiece. (2) When the solid fraction of workpiece is low, the solid and liquid components flow separately at roll gap. (3) In that case, the internal structure of rolled sheet differs completely from that obtained by hot rolling. (4) Mechanical properties of aluminum alloys and cast irons may be improved and new type of functional sheets of those metals can be manufactured by the mashy state rolling.

Refining and Recycling of Metal Scraps by Semisolid Processing

In this study, the authors propose a new refining process different from the rheorefining (a screen method) or the melt zone method. This new refining process is based on the gradient of solidification speed of the molten metal poured into a container. The molten metal in the cylindrical container firstly solidifies to columnar crystals from the wall of the container and a liquid phase gradually changes to semisolid state and progresses to the central portion of the container. After an intended semisolid state is achieved, a backward extrusion is carried out to extract the liquid phase component. The liquid component is known to contain a lot of impurity substances. For the refining trials, three aluminium alloys were selected: wrought aluminium alloy A2011, cast aluminium alloy AC4C and aluminium beverage can scraps. Backward extrusion (extraction) was applied twice, and the amount of pure Al increased from 90.59 % in the initial ingot to 96.34 % in the refined material. This new refining process can easily achieve the purification level of the rheorefining or the melt zone method.

Mashy Metal/Alloy Joining a New Process for Manufacturing New Products

Abstract A new process to join metal and ceramics components on to aluminum, copper and magnesium alloys was proposed. The process is based on joinability of mashy (mushy/semi-solid) alloys. This paper shows the obtained results regarding two types of joinings as follows. (1) Multi wire fins (pins) were joined on to base blanks of an aluminum alloy, (ex. Wire fin type heat-sinks were made.) (2) Multi sheet fins were joined on to base blanks of an aluminum alloy (ex. Sheet fin type heat-sinks were made.). The effects of process parameters on the shear strength of interfaces between joined fins and base blanks and their internal structures were investigated. Through the study, it is found that the mashy-state joining makes it possible to join various materials together which can not be joined by other processes such as welding and soldering.

Effects of Post Heat Treatment on Microstructure and Mechanical Properties of RAP-Processed Cr-V-Mo Steel

Owing to the phase segregation occurred during semisolid process, the ferroalloys products manufactured by semisolid process always exhibit inhomogeneous microstructure and poor mechanical properties. In this study, the post heat treatments including quenching treatment and tempering treatment with various processing parameters were carried out to improve the quality of Cr-V-Mo steel (JIS SKD61, AISI H13, DIN 1.2344) which processed by RAP (recrystallization and partial melting) processed. The microstructural characteristics (phase transformation, morphology of carbides, and distribution of alloying elements) and mechanical properties (hardness, tensile strength, elongation, impact toughness, and resistance to high-temperature wear) of specimens processed by RAP and heat treatments under various experimental conditions were investigated experimentally. Being quenched from 1050 °C after isothermal holding for 480 s and then tempered twice at 560 °C for 2 h, the microstructural evolution took placed in both former solid-phase and liquid-phase regions of the RAP-processed Cr-V-Mo steel specimen. During this post heat treatment strategy, the weakening of phase segregation, the redistribution of carbides, and the release of residual stress occurred and resulted in the improvement of microstructure and a good combination of mechanical properties.

Effect of Recrystallization and Partial Melting Method on Microstructural Evolution of SKD61 Tool Steel in Semi-Solid State

The microstructural evolution and basic refinement mechanism of the semi-solid-state SKD61 tool steel fabricated by recrystallization and partial melting (RAP) method were investigated experimentally. The effects of different parameters in RAP processing were systematically clarified to achieve the grain refinement of cast SKD61 steel in the semi-solid state. Results showed that, the microstructure of RAP processed specimen were finer and more globular than the microstructure of starting material. The distribution of finer solid particles in the RAP processed specimen was affected by the distribution of strain during predeformation. Uniform and spherical solid particles inclined to locate in the regions suffered from larger strain. The specimens subjected to a plastic predeformation at a lower temperature have a more uniform and spherical semi-solid microstructure than those specimens undergoing predeformation with the same reduction at higher temperatures. In addition, the grain refinement mechanism of SKD61 tool steel processed by RAP method was discussed.

Semisolid Extrusion of Wrought Magnesium Alloy AZ61 and Its Mechanical Properties

The basic characteristics of extrusion tests on semisolid wrought magnesium alloy AZ61 are investigated. The selected temperature range is from hot extrusion at 300°C up to the semisolid temperature. Other process parameters investigated are extrusion ratio, which was varied from 6.3 to 39, and extrusion speed which was varied from 3 mm/s to 150 mm/s. Results are expressed in terms of forming load and process limit by comparing hot extrusion with semisolid extrusion. Moreover, the microstructure and hardness of the extruded products are investigated and correlated with the mechanical properties.