A356.2 alloy is an aluminum alloy material widely used in the production of low-pressure casting wheels. It has good casting properties, mechanical properties and processing properties. However, this alloy cannot be directly remelted and used, and it needs to be refined and refined to meet the performance requirements of cast wheels. A1.10Sr and A1.5Ti-B master alloys are currently the most commonly used and effective modifiers and refiners [¡¤]. Sr modification can change the morphology of eutectic silicon, increase the spheroidization speed of silicon during heat treatment, and reduce the coarsening speed of silicon during heat treatment, which can significantly increase the yield strength and elongation of A356.2 alloy; A1-5Ti. B master alloy can refine 0c. A1 matrix improves the compactness of the alloy, improves the shrinkage ability of the alloy itself, helps eliminate shrinkage porosity, shrinkage cavity, and prevents casting defects such as cold partition [2-3]. Due to the different production processes of Al-10Sr and Al-5Ti-B master alloys, there are certain differences in their internal quality, such as the size of crystal grains and the degree of phase aggregation. These differences affect the modification and refinement effect of A356.2 alloy, and ultimately affect the mechanical properties of cast aluminum wheels. In this paper, under the factory production conditions, A1-10Sr and AI-5Ti-B master alloys from different manufacturers were added to refine the deteriorating A356.2 aluminum liquid, and the influence on the structure and performance of the wheel hub was compared and analyzed. The quality of the wheel hub has certain reference value. 1 Test process: Refining and slagging the molten aluminum in the smelting furnace in accordance with the process instructions, and let it stand for 30-40 minutes until the temperature of the molten aluminum is stable, and then the aluminum will be tapped, and then add the A1-10Sr and A1-5Ti- of manufacturers A and B respectively. The B master alloy starts to degas, and the chemical composition and hydrogen value are qualified, and then transferred to the holding furnace of the die casting machine for testing. The wheels produced by the two corresponding die-casting machines are numbered wheel hub 1 and wheel hub 2, and the follow-up processes (such as heat treatment, machining, painting) are the same. Received date: 2014-12-10 Author profile: Xie Liguang (1979-), male, engineer, mainly engaged in the research of aluminum alloy wheel materials.

1 Test process: Refining and slagging the molten aluminum in the smelting furnace in accordance with the process instructions, and let it stand for 30-40 minutes until the temperature of the molten aluminum is stable, and then the aluminum will be tapped, and then add the A1-10Sr and A1-5Ti- of manufacturers A and B respectively. The B master alloy starts to degas, and the chemical composition and hydrogen value are qualified, and then transferred to the holding furnace of the die casting machine for testing. The wheels produced by the two corresponding die-casting machines are respectively numbered wheel hub 1 and wheel hub 2, and the subsequent processes (such as heat treatment, machining, painting) are the same.

Currently about AI-10Sr, A1.5Ti. The modification and refinement of B master alloys mainly include heterogeneous induced twin theory, boride theory, etc., but a unified theory has not yet been formed. A1. The shape, size and distribution of AlSr particles in the 10Sr master alloy are the key factors that determine the effect of its modification. Studies have shown that modifying Al-Si alloys with fine-structured Al-10Sr master alloys can make eutectic silicon dendrites finer/ix[4_5]. A1. The A1Ti3 and TiB2 particles in the 5Ti-B master alloy are effective refining phases. In addition to the size, the degree of aggregation of TiB particles is an important index to evaluate the refining ability of the A1-5Ti-B master alloy [5_]. The more uniform the distribution of TiB particles and the smaller the aggregation area, the stronger the refinement ability. The A1Sr and TiB particles in the Al-10Sr and A1.5Ti-B master alloy produced by manufacturer A are abundant and more evenly distributed, so the modification and refinement effect of A356.2 aluminum alloy liquid is the best. Correspondingly, die-cast aluminum alloy wheels The tensile strength is also the highest. 3 Conclusion 1) The quality of the A1.10Sr and AI-5Ti-B master alloy produced by manufacturer A is better than that of manufacturer B. After adding A356.2 aluminum alloy liquid,. The A1 matrix crystal grains are obviously refined, the size is more uniform, and the uniform distribution of eutectic silicon is also better. 2) The average size of the macro grains of the hub 1 is smaller, and the inner rim is only 0.49mm; the average tensile strength of the rim is ~tJ279MPa, which is 4.5% higher than that of the hub 2.