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Semi-Solid Processing of Aluminum Alloys

Semi-Solid Processing of Aluminum AlloysThe advantageous aspects of semi-solid-state metal (SSM) processing were initially discovered by MIT researchers in the early 1970s. The two pertinent processes are rheocasting and thixocasting routes. The temperature of the melt is crucial in determining the optimum point between liquid- and solid-state. SSM processing is most efficient when done at a certain point within the solidification range (depending on the process parameters). Advancements within the process are proving more widespread usage and, at often times, are even resulting in it being preferred over traditional casting and forging methods. As SSM processing becomes more and more prominent throughout worldwide markets, the unique ideas of industry experts are yielding significant advancements throughout all stages of the various applications.

Semi-Solid Processing of Aluminum Alloys — co-authored by Shahrooz Nafisi and Reza Ghomashchi and recently published (1st edition) in 2016 by Springer Nature, a subsidiary of Springer International Publishing AG Switzerland — examines the unique fundamentals and describes in great detail the semi-solid processing of aluminum alloys. This book is a must-read. The principles and techniques taught within are mandatory know-how for process optimization for aluminum researchers, technologists, and educators of aluminum.

The book is comprised of eight chapters pertinent to the processing of aluminum alloys in semi-solid states. Chapter 1 provides an overview of the current-state aluminum industry, as well as the associated impact that aluminum has had on worldwide economies in both qualitative and quantitative terms. Near Net-Shaped Casting (N2SC), a brilliant engineering development which exploits the advantages of utilizing various SSM processing to expedite aluminum part production, is being revolutionized by the various engineering-software producers. Technological advancements within semi-solid metal (SSM) processing are comprehensively explained in Chapter 2.

Chapter 3 predominately explains the solidification, stirring, and alloy distribution of silicon-based aluminum alloys (A356 alloy), which has an average 7%Si 0.35%Mg. Subsequently, Nafisi and Ghomashchi the techniques used to characterize SSM billets which include metallographic and flow behavior, i.e., rheological characteristics, in Chapter 4.

A process that is gaining popularity, called “rheocasting,” is depicted in Chapter 5; it explains how rheocast billets — produced by low pouring temperature, electromagnetic stirring, EMS, and Swirled Enthalpy Equilibration Device (SEED) processes — have been revohas an average 7%Si 0.35%Mg. lutionized via extensive practical and theoretical research.

On the contrary, Chapter 6 provides information on the various melt treatments being utilized within SSM billet casting. The covered general topics pertaining to melt treatment in semi-solid casting are “Effects of Grain Refining on Semi-Solid Structures” and “Effects of Modification on Semi-Solid Structures.” Afterwards, Nafisi and Ghomashchi explain “SEED Technology,” grain refining, and modification in Al7%Si and A356 alloy. In retrospect, the context goes into detail about the various processes and breakthroughs within the control of elements which, in turn, maximizes both the efficiency and quality of any cast aluminum product. There have been several recent breakthroughs within the associated processes including filtering, fluxing, grain refining, and degassing.

Chapter 7 hits on recent discoveries within production processes for thixocast billets. As for the final chapter, Nafisi and Ghomashchi summarize their meeting with the widely recognized Dr. Steve Midson of Midson group – Colorado School of Mines. Dr. Midson researched and pinpointed quality improvements that are seen when switching from conventional production methods to SSM in industrial scale. In summary, Semi-Solid Processing of Aluminum Alloys is a compulsory read for those in the research and manufacturing of SSM to stay ahead of the curve and up to speed with the ever evolving aluminum industry.

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