Papers by Keyword: Gas Induced Semi-Solid

Abstract: High Pressure Die Casting (HPDC) is a widely preferred process for the production of non-ferrous metals with low melting temperatures. It is particularly suitable for close-to-finish and high-volume production of relatively complex shaped parts. Aluminum-Silicon-Copper alloys, which are frequently preferred in this method, find themselves in many sectors ranging from automotive to aviation. With the developing technology, the usage of High Pressure Die Casting technology has increased significantly, produced part types and the number of parts produced on an annual basis has reached remarkable amounts with the shortening of cycle times. In this study, a supra-eutectic silicon valued Aluminum-Silicon-Copper alloy was produced by gas-induced semi-solid die casting method using a cold chamber high pressure die casting machine. The study observed that many casting problems, especially shrinkage gaps and gas porosity, were overcome, while the microstructure of the parts on which the gas induced semi-solid die casting method was applied was preserved. In addition, energy saving is achieved by lowering the temperature of the holding pot, and thermal fatigue cracks that will occur in the mold in the long-term depending on the temperature difference will be delayed and the mold life will increase.

Abstract: The purpose of this study was to investigate the tensile properties and plasticity of semi-solid 6061 Al alloy at room and elevated temperatures. The semi-solid 6061 alloy was produced by the Gas Induced Semi-Solid (GISS) technique followed by squeeze casting process. The conventional liquid squeeze cast (CLC) 6061 alloy was also fabricated for comparison. The tensile tests were performed at temperature of 25 °C, 100 °C and 175 °C. The experimental results showed that the UTS, 0.2% yield strength and % elongation at break of the SSM alloy are higher than those of the CLC one at all temperatures. Based on the simple flow law, σt=Kεtn , the strain hardening exponent n and the strength coefficient K of the SSM alloy are lower than those of the CLC. The SSM alloy demonstrates more plasticity than the CLC. The results may be attributed to the more globular structure of the SSM alloy.

Abstract: Creep of rheocast 7075-T6 aluminum alloy produced by the Gas Induced Semi-Solid (GISS) process was investigated at temperature of 300 °C and stress range of 20-70 MPa and compared to that of wrought 7075-T651 aluminum alloy. The rheocast 7075-T6 alloy exhibited lower minimum creep rate and longer rupture time than the wrought 7075-T651 alloy. The total rupture strain of the rheocast alloy was shorter than that of the wrought one. According to the power law creep, the stress exponents, n of the rheocast 7075-T6 and the wrought 7075-T651 alloys were 5.9 and 7.9 respectively. Based on the determined n values, the creep deformation of both alloys was possibly controlled by the dislocation glide and climb-controlled mechanism.

Abstract: A simple and efficient rheocasting process that has recently been invented is being developed for aluminum die casting applications. The process called Gas Induced Semi-Solid (GISS) utilizes the combination of local rapid heat extraction and agitation achieved by the injection of fine gas bubbles through a graphite diffuser to create semi-solid slurry. In the GISS process, the die casting machine and the process cycle remain little changed from those of conventional die casting. The GISS unit creates a low solid fraction of semi-solid slurry in the ladle during the ladle transfer to the shot sleeve. The semi-solid slurry is then poured directly into the shot sleeve. This paper presents the detailed description of the process. The results of the semi-solid die casting experiments with ADC10 alloy using the GISS process are also reported and discussed.