Effect of Compound Modification on Structure of Hypereutectic Al-Si Alloy

Abstract

Double compound modification was carried out for hypereutectic Al-24Si alloy. The experiment showed that double modification with phosphorus and rare earth can fine the structure of alloy. The complex modifications of phosphorus and rare earth make the coarse block primary silicon obviously refined and the large needle eutectic silicon modified to the fine fibrous or lamella ones. Phosphorus mainly refines the primary silicon. Rare earth can well refine the primary and eutectic silicon, but its modification effect on the eutectic silicon is more obvious. The alloys with the additions of 0.10% phosphorus and 0.9% rare earth have the optimal microstructure. Compared with the unmodified alloy, the primary silicon of alloys can be refined from 93.5 μm to 24.1 μm and the eutectic silicon can be refined from 8.5 μm to 5.3 μm. Mechanism of double compound modification with phosphorus and rare earth is discussed as well.

Hypereutectic Al-Si Alloy with Completely Nodular Eutectic Silicon: Microstructure and Process

“…Among these, P-addition significantly causes a reduction in the size of primary Si particles, increasing the number evenly distributed through the eutectic matrix. The combination of Si+P [13], RE+P [14], B+P [15] or Al-Ti-C [16] strongly enhances the refinement effect on primary Si induced by P-addition with modified eutectic Si. Recently it was found that adding a small amount of γ-Al 2 O 3 nanoparticles simultaneously refined and modified the Si particles, and reduced the porosity in cast Al-20Si-4.5Cu, resulting in unusual ductility enhancement [17,18].…”

Effect of Compound Modification on Microstructure and Properties of High Silicon Aluminum Alloy

“…AlP and Si are both diamond cubic with very similar lattice parameters [9]. When P is added into the melt of hypereutectic Al-Si alloys, the reaction Al+P→AlP takes place in the modification.…”

“…It has been documented that rare earth(RE) metal can modify the eutectic silicon in the hypereutectic Al-Si alloys [6,7]. The refinement of primary silicon crystals was also found with addition of rare earth elements [8,9]. If combining with P and RE to complexly alloy the hypereutectic Al-Si alloys, both the primary and eutectic silicon in alloys may be modified and the mechanical properties may be improved.…”

Effect of Non-Uniform Concentration Field on TiN Growth in Two-Phase Region with Electropulsing

“…After adding Ti's carbonitride to low carbon microalloyed steel, the mechanical properties of the steel material such as toughness and strength can be improved, but Ti microalloyed steel precipitate at high temperatures TiN has a tendency to aggregate and grow up and will form TiN particles of larger sizes in the steel, which not only fails to refine the grain but also becomes a source of fatigue cracks, which seriously affects the quality of the casting billet [1]. It has been found [2][3][4][5][6][7][8][9] that methods such as applying electric current (electric pulse), magnetic field, and ultrasonic waves during the solidification process of metals can control and improve the solidification organization of metals. Among them, pulsed current is the most widely used, which has the advantages of environmental protection, small cost, simple operation, and good treatment effect, and has become an important research direction in the process of preparing materials [10].…”