Hypereutectic Aluminum Research Articles

Wear Behavior of CVD-Diamond Tools

Diamond cutting tools are often the only choice for the machining of high-strength and highly abrasive non-ferrous alloys. During machining, a complex interaction of different wear mechanisms takes place on the tools. This interaction considerably hinders a purposeful detection of specific wear mechanisms. Therefore, the objective is to systematically analyze the wear processes that occur when machining a hypereutectic aluminum silicon alloy with CVD-diamond tools. The main wear mechanisms are identified and the limits for the use of various CVD-diamond tools are indicated. The findings gained will serve in the further development of these high-performance cutting materials.

Wear behavior of HFCVD-diamond coated carbide and ceramic tools

This paper describes the wear patterns on hot filament HFCVD-diamond coated carbide and ceramic tools during the cutting process, as well as the origins of these patterns. Knowledge of these phenomena is essential for a process-oriented application and for a full exhaustion of the tool's potential. A focal point is put on the processes turning, milling, and drilling. Fiber reinforced materials, a hypereutectic aluminum–silicon alloy, and a copper–aluminum alloy are used. Closest attention is paid to the abrasive and adhesive wear on the coated tools and similarly on the uncoated substrate carbide. The results show that CVD diamond coated carbide and ceramic tools enlarge the existing range of cutting materials. The wear protective diamond layer suggests an application of the tools in the high-speed range (HSC). Given the demands for an environmentally acceptable production, these tools can be applied in dry machining.

Hypereutectic aluminium alloy tubes with graded distribution of Mg 2Si particles prepared by centrifugal casting

Hypereutectic Al-Mg 2Si alloy tubes were produced by a centrifugal casting process. Primary Mg 2Si particles were formed in the tube periphery with graded distribution. Influence of the rotation speed and cooling rate on formation and graded distribution of Mg 2Si particles was discussed. It is found that in the outer periphery the particle distribution profile at different rotation speeds is quite different from each other, while it is similar in the inner periphery. Extremely higher cooling rates during centrifugal casting resulted in a better particle distribution gradient and a much finer microstructure in the outer periphery of the tube.

軽金属材料の表面処理技術 レーザ照射により表面再溶融処理した過共晶Ａｌ‐Ｓｉ合金の組織および機械的性質

CO2 laser irradiation has been applied to modify the surface of hypereutectic aluminum (Al–23 mass%Si, Al–30 mass%Si) cast alloys. Laser beam, 3 mm in diameter, was irradiated on the alloy surface by moving them with constant velocity (5 mm/s) with beam oscillation of 5 mm in width and 100 Hz in frequency perpendicular to travel direction at 2.3 kW laser power. A part of alloy surface was partially remelted by laser irradiation. After laser beam passed, it was naturally quenched because stored heat was absorbed in specimen. The microstructure of the surface remelted layer consists of primary Si particle, primary α phase and α–Si eutectic phase. These all were very fine. The mean diameter of primary Si was about 12 μm at Al–30 mass%Si. The tensile strength of the surface remelted layer was 254–264 MPa, which was improved to about 1.8 times as that of as-cast material. In dry sliding wear against a steel counter surface, the wear resistance of the surface remelted layer was improved to 1.5–3.0 times as that of as-cast material.

Growth morphology of primary silicon in cast Al–Si alloys and the mechanism of concentric growth

Faceted growth of primary silicon crystals in cast hypereutectic aluminium–silicon alloys is studied by measurement of spacings between successive growth traces observed in microsections. A general equation, derived to specify conditions for stable growth of silicon crystal, is supported by spacing measurements. Some examples of departures from stable silicon growth are studied. Three stages in the development of faceted crystal growth are recognized, changing from spheroidal to faceted to unstable with increasing crystal diameter.

Processing, microstructure and fracture behaviour of a spray atomized and deposited aluminium-silicon alloy

In this study a hypereutectic aluminium–silicon alloy was synthesized by spray atomization and deposition technique. Microstructure characterization studies were performed to provide an understanding of the influence of spray processing on microstructure of the hypereutectic alloy. Ambient and elevated temperature tensile tests reveal the spray-processed alloy to have better strength and ductility than a conventional ingot metallurgy processed alloy having the same chemical composition. The quasi-static fracture characteristics of the spray-processed alloy is presented and discussed in light of processing and intrinsic microstructural effects.

Production of Hypereutectic Al-Si Alloys by P/M Route

In this work hypereutectic aluminium silicon alloys with high silicon content that are difficult to produce by casting, are produced by powder metallurgy (P/M) route. Different alloys are produced with varying silicon content. Aluminium silicon alloys are produced by both hot pressing and sintering of aluminium and silicon powder mixtures for the comparison. The production of hypereutectic Al-Si alloys by sintering of powder compacts is found to be unfeasible in terms of obtaining high density. The hardness and the density values of the alloys containing same amount of silicon, are higher in the alloy produced by hot pressing than the sintered alloys. The increase in hardness of the alloys is observed by increasing the silicon content. 100% theoretical density and 422 kg mm{sup -2} MHV hardness values are reached for the Al-67%Si composite which is hot pressed under 500 MPa and at 600 C. (orig.)

A study of erosion in die casting dies by a multiple pin accelerated erosion test

An accelerated erosion test was developed to evaluate the erosion resistance of die materials and coatings for die casting application. An acceleration in wear was achieved by selecting pyramid-shaped core pins, hypereutectic aluminum silicon casting alloy, high melt temperatures and high gate velocities. Multiple pin design was selected to enable multiple test sites for comparative evaluation. Apilot run was conducted on a 300 ton commercial die casting machine at various sites (pins) to verify the thermal and flow similarities. Subsequently, campaigns were run on two different 300 ton commercial die casting machines to evaluate H13 die material and different coatings for erosive resistance. Coatings and surface treatments evaluated included surface micropeening, titanium nitride, boron carbide, vanadium carbide, and metallic coatings—tungsten, molybdenum, and platinum. Recent campaigns with different melt temperatures have indicated a possible link between soldering phenomena and erosive wear. This paper presents the details of the test set up and the results of the pilot and evaluation tests.

Wear mechanisms in a hypereutectic aluminium silicon alloy sliding against steel

Wear mechanisms in a hypereutectic aluminium silicon alloy sliding against steel

Developments in Pressure Diecasting

The range of diecasting machines has increased, in size and locking force, making possible the production of engine cylinder blocks, transmission housings, and other large and complex components, especially in aluminium alloys. Instrumentation has been developed to measure and control the speed and pressure of metal injection, temperature control of the dies, measurement of machine locking force, and oscillographic monitoring of the diecasting process, sometimes with a computer built into the equipment. Large diecasting plants can now receive molten aluminium alloy consignments direct from the secondary metal smelter. In molten-metal handling in the diecasting plant, further developments are being made in furnace design, both for bulk metal melting of scrap, runners, and ingots and in the bale-out furnaces adjacent to the diecasting machines. Several producers of zinc alloy diecastings are now making their own alloy, under carefully controlled conditions. During the past ten years most diecasting companies have been successful in mechanizing at least part of their production. Most zinc alloy diecastings are now produced automatically and considerable development in the much more difficult automation of aluminium diecasting has been. achieved. Methods of automatic ladling, lubrication, and trimming and machining processes linked with automatic diecasting production are discussed. New deburring processes and specialpurpose machines and robots used in handling all stages of the manufacturing processes are described. The positioning and the correct dimensioning of runners and gates has received much attention during the past ten years. Die designers are obtaining valuable help from the mathematical formulae and monographs which have been developed. While the major production of zinc, aluminium, and magnesium alloy diecastings involves standard alloys that were well known ten years ago, some new alloys have been developed. The hypereutectic aluminium–silicon alloys used in the production of some cylinder blocks are described. The development of new die materials, including those based on molybdenum, has helped to make possible the diecasting of high melting point alloys, including stainless steel. Some new diecasting techniques are discussed, including the possibilities of the oxygen-purging or pore-free diecasting process, developed in Japan, but so far little explored in the West. Improved finishing processes for the electroplating of zinc alloy diecastings are described.

Study on wear of casting aluminium alloys

In the first report, the wear characteristics of aluminium alloys against the same alloys and against carbon steel ware described. In the case of aluminium alloys against carbon steel, the wear loss of each of the materials is vrey small irrespective of the sliding speed and the contact pressure. When aluminium alloys excepting hyper-eutectic aluminium-silicon alloy are combiend against the same alloys, partial welding phenomena (scuffing) can easily occur on the frictional surface as the sliding speed is increased.In this report, frictional characteristics such as the frinctional coefficient, the surface appearance and the surface roughness. The results obtained from this experiment are summerized as under:1. It has been thought that there are not always definite relationships between the frictional coefficient and the wear. However, in this experiment it is made clear that there exist intimate corelations between the two. In the case of aluminium alloys against the same alloys, the frictional coefficient increases along with the increasing of wear loss, especially where scuffing occurs, the frictional coefficient as well as the wear loss show a rapid increase. However, in the case of hyper-eutectic aluminium-silicon alloys against the same alloys and of aluminium alloys against carbon steel, the frictional coefficient decreases in conformity with the deminution of wear loss as the sliding speed is increased.2. In the case of aluminium alloys excepting hyper-eutectic aluminium-silicon alloy against the same alloys, scuffing can easily occur under a high sliding speed and at high contact pressure, and surface roughness in creases. The hyper-eutectic aluminium alloys sach withhard spots coming about on the frictional surface thereon, does not generate scuffing, for the hard spots on the either alloy come into touch with each other. While in the case of aluminium alloys against carbon steel, not only the wear losse but also the frictional coefficient are very small since the frictional surface is protected by an oxidized layer.3. Though unstable at the initial stage of wear, the surface roughness may get to the constant value when wear reaches astationary stage, and the value may be controlled according to the experiment conditions.

Determination of Phosphorus in Hypereutectic Aluminum-Silicon Alloys by a Neutron Activation Method.

A method to determine small amounts of phosphorus in hypereutectic aluminum- silicon alloys is described. The method consists of the thermal neutron activation of the alloy followed by its complete dissolution in 1 to 3 hydrofluoric-nitric acid mixture. The phosphoric acid so formed is converted to the molybdophosphoric acid complex which is extracted into isobutyl alcohol. The isotope P/sup 32/ is then determined by a BETA -counting technique using a liquid counter. Extraction of phosphorus is highly efiicient and selective, and the loss of phosphine on dissoiution in the acid mixture used is negligible. (auth)