Effect of Al–5Ti–C Master Alloy on the Microstructure and Mechanical Properties of Hypereutectic Al–20%Si Alloy

Abstract

Al–5Ti–C master alloy was prepared and used to modify hypereutectic Al–20%Si alloy. The microstructure evolution and mechanical properties of hypereutectic Al–20%Si alloy with Al–5Ti–C master alloy additions (0, 0.4, 0.6, 1.0, 1.6 and 2.0 wt%) were investigated. The results show that, Al–5Ti–C master alloy (0.6 wt%, 10 min) can significantly refine both eutectic and primary Si of hypereutectic Al–20%Si alloy. The morphology of the primary Si crystals was significantly refined from a coarse polygonal and star-like shape to a fine polyhedral shape and the grain size of the primary Si was refined from roughly 90–120 μm to 20–50 μm. The eutectic Si phases were modified from a coarse platelet-like/needle-like structure to a fine fibrous structure with discrete particles. The Al–5Ti–C master alloy (0.6 wt%, 30 min) still has a good refinement effect. The ultimate tensile strength (UTS), elongation (El) and Brinell hardness (HB) of Al–20%Si alloy modified by the Al–5Ti–C master alloy (0.6 wt%, 10 min) increased by roughly 65%, 70% and 51%, respectively, due to decreasing the size and changing the morphology on the primary and eutectic Si crystals. The change in mechanical properties corresponds to evolution of the microstructure.

Mechanical Properties of Refined A356 Alloy in Response to Continuous Rheological Extruded Al-5Ti-0.6C-1.0Ce Alloy Prepared at Different Temperatures

“…In the solidification process, the Ce element can enrich the solid-liquid interface front and inhibit the growth of the grain. Simultaneously, the Ce element is enriched in the interstices of the dendrites, causing subcooling of the composition and further broken dendrite, which refines the grains [29][30][31][32]. Moreover, the Ce element is the surface active substance that improves the wettability of the aluminum melt to the second phase [33].…”

Effect of CeO2 on Microstructure and Synthesis Mechanism of Al-Ti-C Alloy

“…As compared to Al-Ti-B refiner, Al-Ti-C refiner is considered as the most promising grain refiners for aluminum and its alloy due to the small size of TiC particles, low aggregation tendency in aluminum melt, and difficulty in poisoning with element such as Zr and Cr [3,4,5,6,7]. Unfortunately, the key issue in the production of Al-Ti-C alloy is that the wet-ability between carbon and Al melt is poor, which makes the formation of TiC difficult [8,9,10]. It has been reported that the rare earth metals have certain refining ability and catalytic effect [11,12], which play an important role in promoting the synthesis of fine TiC particles in the preparation of Al-Ti-C alloy, and thus, Al-Ti-C-RE alloys with better refining efficiency than Al-Ti-C have been developed [13,14,15,16].…”

Archives of Metallurgy and Materials

“…The studies have revealed the potential of Ca to modify the eutectic silicon, altering the morphology of the Fe-rich intermetallic to less harmful shapes and improving the fracture toughness and impact properties of high iron containing Al-Si, Al-Si-Cu, and Al-Si-Mg casting alloys [21]. P is the most effective modifier of primary Si in hypereutectic Al-Si alloy and has no modification effect on the eutectic Si, the eutectic Si can still keep the large plate-like (needle) shape [22]. P reacts with Na and probably with Sr and Ca to form phosphides that nullify the intended modification additions.…”