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Casting and Foundry Work
Published in Sherif D. El Wakil, Processes and Design for Manufacturing, 2019
The ability of the molten metal to flow easily without premature solidification is a major factor in determining the proper filling of the mold cavity. This important property is referred to as castability or, more commonly, fluidity. The higher the fluidity of a molten metal, the easier it is for that molten metal to fill thin grooves in the mold and exactly reproduce the shape of the mold cavity, thereby successfully producing castings with thinner sections. Poor fluidity leads to casting defects such as incomplete filling or misruns, especially in the thinner sections of a casting. Because fluidity is dependent mainly upon the viscosity of the molten metal, it is clear that higher temperatures improve the fluidity of molten metal and alloys, whereas the presence of impurities and nonmetallic inclusions adversely affects it.
Introduction
Published in Namrata Gangil, Arshad Noor Siddiquee, Sachin Maheshwari, Composite Fabrication on Age-Hardened Alloy using Friction Stir Processing, 2020
Namrata Gangil, Arshad Noor Siddiquee, Sachin Maheshwari
Aluminum alloy as base metal (BM) or matrix has attracted material researchers for airframe applications due to their better corrosion resistance, high strength, and good formability. Al-based Metal Matrix Composites (AMMC) possess high specific strength, high thermal conductivity, and superior damage tolerance; which make them promising structural materials for many industries. The utilization of AMMC in the aircraft and aerospace industries increased dramatically due to their superior structural performance over un-reinforced aluminum alloys. The significant increase in the availability of reinforcement infusion processes has ensured the fabrication of bulk and SCs economically. Various liquid- and solid-state practices are investigated by researchers for the fabrication of bulk and surface AMMCs. One of the major conventional practices for fabrication of bulk composites through the liquid processing method is the stir casting process [17]. It involves the incorporation of reinforcement particles into molten aluminum during stirring by rotating impeller and allowing the mixture to solidify. The major advantages of stir casting are its simplicity, low cost, large range of shape, and large size up to 500 kg can be economically produced. Squeeze casting has also been investigated due to rapid solidification advantages but it can fabricate limited shape and size of the components [17, 18]. It is well known that casting/liquid metallurgy practices, if not controlled precisely, are associated with inhomogeneous particle distribution, segregation, clustering of reinforcement, deleterious interfacial reactions, and unavoidable casting defects which lead to poor mechanical properties.
Design and development of quality system for gear case casting
Published in Alka Mahajan, Parul Patel, Priyanka Sharma, Technologies for Sustainable Development, 2020
Vaibhav Suthar, Bimal Kumar Mawandiya, Kaushik Patel, Dhaval Shah
Borowiecki et al. (2011) used the Pareto chart to find out which defect drives the most percentage as compared to others. It was found that the majority of the defect that occurs due to the faulty gating system design. In the process of the gating system, improvement enables proper directional solidification, the velocity of the molten metal, prevents misrun, etc. Shivappa et al. (2012) focused on the analysis of the casting defect and its remedial measure. In this paper, the casting process was observed and found that the four defects i.e. blowhole, mismatch, sand drop and oversized were repetitive at a particular location. To nullify the casting defect, the mould was cleaned properly, six locators were provided to avoid mismatch and modification in the gating system. The given remedial measure was adopted and production was carried out and the reduction in rejection of casting was observed. Jadhav and Jadhav (2013) observed that in each case, the gating system design was not responsible for the casting defect. The casting defect can be reduced by controlling alloy composition and pouring temperature. The seven quality control tools were used to reduce defects which include check sheet, Pareto chart, scatter diagram, flow chart, etc. Siekanski et al. (2003) performed the analysis of foundry defect and remedial measure for the same defect was suggested. Ishikawa diagram was used to find the risk of failure. The cause and effect diagram represent the factors responsible for the defect. The Pareto chart shows some defect which drives the majority of the percentage of the defects like displacement, slag, misrun, shrinkage, etc. Pandey and Jain (2016) used the six sigma methodologies for reducing the defect of the ingot mould in foundry. The quality tools like flow chart, why-why analysis, cause and effect diagram, etc. were used. Using the Taguchi method, the optimum level of parameters that affect the casting process was identified.
Constitutive equation and microstructure analysis of Al0.6CoCrFeNi high entropy alloy during hot deformation
Published in Philosophical Magazine, 2022
Jingyi Wang, Pan Yang, Dan Wang
CoCrFeNi quaternary alloy has a simple face-centered cubic structure and good plasticity, but its strength and hardness are low. To improve its strength, an appropriate amount of Al can usually be added because the radius of Al atom is very different from that of other atoms, which causes strong lattice distortion and improves its strength. Finally, AlxCoCrFeNi high entropy alloy was obtained [11]. AlxCoCrFeNi high entropy alloy is a typical HEA system. The structure and properties will change with the content of Al. When 0 < x < 0.3, the alloy is face-centred cubic structure, when 0.5 < x < 0.7, the alloy is face-centred cubic + body-centered cubic structure, and when 0.9 < x < 1.8, the alloy is body-centred cubic structure [12,13]. As all known, face-centred cubic structure has good plasticity and toughness, and body-centred cubic structure has good strength and hardness [14,15]. Al0.6CoCrFeNi high entropy alloy has FCC + BCC dual-phase structure, so it has high strength and hardness and good plastic toughness. Al0.6CoCrFeNi high entropy alloy has more development potential than a single high entropy alloy. As we all know, casting alloys usually have casting defects such as shrinkage porosity, coarse grain size, and uneven structure. To obtain materials with uniform structure, refined grains, and excellent properties, it is usually carried out thermomechanical processing on cast alloys to obtain ideal properties [16–18].
Coupled level-set and immersed-boundary method for simulation of filling in a complex geometry based mold
Published in Numerical Heat Transfer, Part B: Fundamentals, 2018
Nihar Thakkar, Absar Lakdawala, Atul Sharma, Shyamprasad Karagadde
Various products having intricate shapes and complexity are manufactured with the help of casting process, which should be defect free. Out of various casting defects, some common, and frequent defects observed are shrinkage cavity, shrinkage porosity, misrun, and entrapment of gas. Shrinkage cavities and porosity generally occurs during solidification stage while misrun and entrapment of gas occurs during filling of molten metal into the mold. For the minimization of the filling defects, it is important to design a proper gating system. Design and selection of gating system depends upon the fluid flow behavior of liquid metal during the filling process, that is, splashing of liquid and free surface turbulence, which cannot be predicted with the help of empirical knowledge or intuition. In this context, a proper numerical tool giving insights of fluid flow behavior during mold filling process can be a handy tool.