A Review on the Analysis of Thermal and Thermodynamic Aspects of Grain Refinement of Aluminum-Silicon-Based Alloys

Abstract

The present analysis addresses the solidification and thermodynamic parameters involved during the solidification of aluminum (Al)-based alloys as presented in the literature using different systems viz., binary aluminum-boron (Al-B) and aluminum-titanium (Al-Ti) systems, ternary aluminum-titanium-boron (Al-Ti-B) and aluminum-titanium-carbon (Al-Ti-C) systems, as well as taking into consideration the silicon-titanium-aluminide (Si-TiAl3) interaction in Al-based alloys containing Si. The analysis is supported by recent metallographic evidence obtained by the authors on A356.2 alloys. The sections on thermodynamic aspects cover the different models proposed concerning nucleation and growth on a newly formed Al grain. The value of the recalescence parameter reduces gradually with the increase in the Ti added. At a level of 0.20 wt%, this parameter becomes zero. If the concentration of grain refiner exceeds a certain amount, the grain size becomes minimal. Another parameter to be considered is the interaction between the grain refiner and traces of other metals in the base alloy. For example, Al-4%B can react with traces of Ti that may exist in the base alloy, leading to the reaction between boron and titanium to form titanium diboride (TiB2). Grain refinement is achieved primarily with TiB2 rather than aluminum diboride (AlB2), or both, depending on the Ti content in the given alloy.

Planning Mechanical Behavior of A356 Alloy Wheels by Using Distinct Heat Treatments

“…Moreover, the literature also discusses solution treating, quenching, and artificial aging of the microstructure and on mechanical behavior [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. These articles were probably written because Al-Si-based alloys exhibit excellent castability and affordability and have a low coefficient of thermal expansion and attractive mechanical properties, making them suitable for manufacturing wheels by casting [4][5][6].…”

“…It has also been reported that the microstructural characteristics are influenced by the presence of α-Al dendrites and lamellar eutectic Si [7]. It is widely recognized that a typical as-cast microstructural array affects the resulting properties [6][7][8][9][10][11][12][13][14][15]. When coarse Al and interdendritic Si particles are constituted, the reached ductility is considerably decreased [6][7][8][9][10][11][15][16][17][18][19][20][21][22][23].…”

“…It is widely recognized that a typical as-cast microstructural array affects the resulting properties [6][7][8][9][10][11][12][13][14][15]. When coarse Al and interdendritic Si particles are constituted, the reached ductility is considerably decreased [6][7][8][9][10][11][15][16][17][18][19][20][21][22][23]. This is associated with a plate-like eutectic Si morphology formation [6][7][8].…”

Effect of Aging Treatment on the Strength and Microstructure of 7075-Based Alloys Containing 2% Li and/or 0.12% Sc

“…showed that 7075 alloy, 7075 alloy + Zr, or 7075 alloy + Sc + Zr alloys offer better mechanical properties caused by the precipitation of Al 3 (Sc, Zr) dispersoids [15][16][17][18].…”

The Influence of the Proportions of Titanium and Boron in the Al and AlSi7-Based Master Alloy on the Microstructure and Mechanical Properties of Hypoeutectic Silumin, AlSi7Mg

“…They are the reason for the low mechanical properties of alloys. For many years, a number of technological procedures have been known to refine the microstructure and, at the same time, increase the mechanical properties resulting from the microstructure [12][13][14][15][16][17][18][19][20][21][22]. Hypoeutectic silumins are one of the few alloys in which, as a result of changes in the microstructure, it is possible to increase all mechanical properties, e.g., tensile strength and elongation, at the same time.…”