The Influence of the Al-Ti-B/Al-Sr Modification on the Microstructure and Properties of the Hypereutectic Al-Si Alloy in Automotive Piston

Abstract

By using some types of means such as Optical Microscope (OM), Scanning Electron Microscopy(SEM), the testing of tensile mechanical properties and the testing of friction and wear, the impacts of the Al-5Ti-1B and Al-20Sr modification on the Al-16Si-4Cu-0.5Mg-0.2Mn alloy microstructure, mechanical properties and friction properties are researched. The results turn out that the modification can significantly refine the primary silicon and the eutectic silicon in the alloy, the Al-5Ti-1B mainly refined the primary silicon in the alloy, the Al-20Sr refined the eutectic silicon; the alloy’s effect of refinement after compound modification is better than that in separate metamorphism. Modification can improve the tensile strength and elongation of the alloy: the tensile strength of the alloy has been increased by 65MPa after its compound modification; also the elongation by 0.4%. Modification can improve wear-resisting property of the alloy and also its effect of compound modification is better than that of separate metamorphism. The modification mechanism of Al-5Ti-1B is that Al3Ti and TiB2 belongs to heterogeneous nucleation; while the modification mechanism of Al-20Sr is that the strontium changes the growth pattern of Si phase.

Microstructure and Mechanical Properties of TiB₂/Al-Si Composites Fabricated by Electron Beam Rapid Manufacture

“…Under the action of stress, the cracks will further expand, reducing the strength and plasticity of the material. If the second phase is uniformly distributed with small and well-rounded shape in the α-Al matrix, the effect of dispersion strengthening can be generated, so that the strength and toughness of samples can be improved [25,26].…”

Microstructure and Mechanical Properties of TiB₂/ Al-Si Composites Fabricated by TIG Wire and Arc Additive Manufacturing

“…Under the action of stress, the cracks will further expand and reduce the strength and plasticity of the material. If the second phase is uniformly distributed with small and well-rounded shape on the α-Al matrix, the effect of dispersion strengthening can be generated, so that the strength and toughness of samples can be improved [28,29]. Si phase was fully diffused and dissolved after solid solution, the roundness of which was improved.…”

Experimental research on machinability characteristics of Al-9Si alloy: Effect of Sr and Mg additives

“…positively affect hardness and strength properties of Al-Si alloys. 5–13 Cu, Mn, Mg, and Zn additions cause the improvement of mechanical properties due to the solid solution hardening mechanism and/or secondary phase precipitation, Sr, B, Na, Ti, and V grain refinement mechanism. In a recent study, 14 it was revealed that the hardness and mechanical properties of binary Al-9Si alloy produced with permanent mold casting method can be improved even more with 0.1wt.% Sr and/or 0.1wt.% Sr + 0.6wt.% Mg additions, and presented new ternary Al-9Si-0.1Sr and quaternary Al-9Si-0.1Sr-0.6Mg alloys produced with this casting method.…”