Kinetics of granulation of discontinuous phase in eutectic structures

Effect of Zr Addition and Aging Treatment on the Tensile Properties of Al-Si-Cu-Mg Cast Alloys

“…Figure 3 shows the macrostructure revealing the grain size for alloy A, about 200 μm. A complete modification of the silicon particles in the microstructure of alloy A in the as-cast condition can be seen in Figure 4 Zhu and Liu [22] proposed a model of the granulation of unmodified eutectic Si composed of three major stages during heat treatment: (i) the mass transport of solute, (ii) a discontinuous phase fragmentation, and lastly (iii) spheroidization. During heat treatment, the silicon atoms in the matrix at the Si particle tips diffuse to locations on the curved surfaces of the particles, leading to the dissolution of eutectic silicon at the tips.…”

“…As a consequence of solution heat treatment, there may also be observed a reduction in the number of silicon particles and a reduction in the density of the silicon phase, due to the diffusion of silicon into the aluminum matrix. The white arrows in Figure4(a) show the rounded shape of the dendrites with grain refining [21], whereas Figure 4(b) reveals the dissolution of the Al 2 Cu phase observed in Figure 4(a)-circled.Zhu and Liu[22] proposed a model of the granulation of unmodified eutectic Si composed of three major stages during heat treatment: (i) the mass transport of solute, (ii) a discontinuous phase fragmentation, and lastly (iii) spheroidization. During heat treatment, the silicon atoms in the matrix at the Si particle tips diffuse to locations on the curved surfaces of the particles, leading to the dissolution of eutectic silicon at the tips.…”

Effet des additifs sur la microstructure et les propriétés mécaniques des alliages d'aluminium-silicium /

“…A number of researchers have proposed 223 ' 227 ' 228 ' 229 that the spheroidization process of silicon through solution heat-treatment takes places in two stages: dissolution/separation of the eutectic branches and spheroidization of the separated branches, hi the first stage, the Si particles are separated into segments at the corners of thin growth steps, but retain their flake-like morphology. In the second stage, the broken segments spheroidize and the aspect ratio decreases.…”

“…The dissolution stage has the greatest effect on the time required to complete spheroidization and is strongly affected by the morphology of the Si particles; the smaller the flake length, the greater the spheroidization. 223 ' 227 Any process which promotes eutectic branching, whether modification or higher cooling rate, will speed up the progress of separation and spheroidization. Modification by addition of impurities tends to refine the eutectic Si greatly, to promote twin branching, to raise the energy state with its inhomogeneity, and consequently to promote the kinetics of the granulation of eutectic silicon.…”

Effect [sic] des paramètres métallurgiques sur le comportement d'usinage des alliages 356 et 319 (étude de forage et de taraudage) /

“…Strontium modification changes the silicon morphology from acicular to fibrous, resulting in a significant decrease in the size of the Si particles, and a corresponding increase in the particle count per unit area. Zhu et al 31 ' 32 have proposed that changes in Si morphology occur in two stages: in the first stage, the Si particles separate into segments at corners or thin growth steps, but they retain their flake morphology. In the second stage, the broken segments spheroidize and the aspect ratio decreases.…”