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Surprises and Pitfalls in the Development of Magnesium Powder Metallurgy Alloys
Published in Leszek A. Dobrzański, George E. Totten, Menachem Bamberger, Magnesium and Its Alloys, 2020
Paul Burke, Yiannis G. Kipouros, William D. Judge, Georges J. Kipouros
Spray forming has been used to produce magnesium alloy billets [36]. Spray forming allows the direct rapid solidification and deposition of high density from a liquid alloy. The process has the benefit that contamination is minimized because powder production, compaction and consolidation are completed in one step. The process is somewhat net-shaped, as the spray can be manipulated as the layers are deposited, so simple two-dimensional parts are possible. However, to realize full strength and density, the parts were first extruded.
Spray Systems
Published in Efstathios E. Michaelides, Clayton T. Crowe, John D. Schwarzkopf, Multiphase Flow Handbook, 2016
e spray forming process combines the atomization and spraying of a metal melt with the consolidation and compaction of the sprayed mass on a substrate. A typical scheme of the spray forming process is illustrated in Figure 19.98. e metallurgically prepared metal melt is distributed from the melting crucible via a tundish into the atomization area. Typically by means of a twin- uid atomizer with external mixing, inert gas jets with high kinetic energy impinge onto the metal stream and cause the melt disintegration. In the resulting spray, the droplets are accelerated toward the substrate and thereby cool down and partly solidify by intensive heat transfer to the cold atomization gas. e mixture of liquid droplets and semisolid or solidi ed particles in the spray impinge onto the substrate consolidating to the desired deposited product. is mixture of droplets in di erent solidi cation stages on impingement is an essential feature of the spray forming process. e overall amount of the superheat (above the liquidus temperature) and of the latent heat (solidi cation) is extracted from the sprayed mass in the spray at high cooling rates (approximately 105 K/s). e solidi cation of the remaining melt in the deposit (typically 10%40% remaining liquid) is started at an already high ( nely distributed) solid content (Annavarapu and Doherty, 1995, Doherty et al., 1997), thereby resulting in extreme ne and equiaxed grain structures. A er consolidation, the remaining metal nally solidi es and cools down further at cooling rates that are just comparable to casting processes.
Influence of various trace metallic additions and reinforcements on A319 and A356 alloys—a review
Published in Cogent Engineering, 2022
D Srinivas, Gowrishankar M C, Pavan Hiremath, Sathyashankara Sharma, Manjunath Shettar, Jayashree P K
Among many alloy preparation techniques, spray forming is treated as a potential and advanced technique to increase ductility. Otani et al. (2019) observed that spray-formed deposits performed by hot swaging resulted in high ductility and hence offer possibilities for various applications. Robles Hernández and Sokolowski (2009) used the electromagnetic treatment on A319 alloy by varying the range of magnetic field (alternating current). They found that Cu phase, dendritic size, and grain size are sensitive for this stirring modification. Positive changes were observed by using this technique, but no significant modification was seen in Al-Si eutectic. Billet casting is also used as one of the techniques to produce matrix alloys (Lombardi et al., 2015). Semi-solid metal processing is gaining importance because it can produce near net-shaped products with better properties compared to conventional methods. Thixoforming is a semi-solid metal processing method where two steps are to be performed viz., preparing a feedstock material and heating to forming temperature (Alhawari et al., 2017). Thixoforming helps in enhancing corrosion properties and getting coarser microstructure of Al alloys (L. Wang et al., 2016).