Microstructure And Property Of Liquid Forging On Hypereutectic Al-Si Alloy

Hypereutectic Al-Si alloy with excellent castability, and the low linear expansion coefficient, high wear resistance, is widely used in automotive piston, cylinder and other parts. But the ordinary method of casting shrinkage has porosity and other defects, conventional cast aluminum forming technology is difficult to make a greater deformation rate, especially for parts of complex shape. The use of cast aluminum alloy is limited because of ordinary casting process forming often beyond the reach of operating requirement. Liquid forging is an advanced processing technology, which makes the metal forming under pressure, to avoid shrinkage and internal castings appear loose, and can refine the grain, to improve the microstructure and mechanical properties of the casting; makes the casting shape more accurate size, lower surface roughness, can no longer be processed on the local, can reduce the manufacturing cost of parts, especially parts of complex shape, at the same time the forming of precision castings have features of high-efficiency and high-precision .Therefore, in this paper, the liquid forging was used to prepare three different components of the hypereutectic Al-Si alloy type, and the effects of the alloy properties of heat treatment process was studied.Studies have shown that: by liquid forging molding, Al-13%Si alloy has smallerα-Al phase size, and the share ofα-Al eutectic phase ratio of greater than under the cast, that is the number of eutecticβ-Si phases was reduced, also found that some primary silicon phases appeared; the eutecticα-Al phase ratio of the eutectic of Al-14.5%Si alloy and Al-16%Si alloy were greater than under the cast,βthe number ratio of a primaryβ-Si phase decreased ,and the size of primaryβ-Si phase was smaller; after heat treatment, the coarse dendrite size of the alloy organization become smaller, the distribution become more uniform, eutecticβ-Si phase tends to become spherical from a long strip, and the corner of primaryβ-Si phase become a passivation, round-based shape. Formed by liquid forging, the tensile strength of hypereutectic of Al-13% Si alloy was up to 276.11MPa from 233.92MPa by the cast, and after heat treatment ,tensile strength achieved 365.52MPa, increased 56.3% than the casting; tensile strength of hypereutectic Al-14.5% Si alloy was up to 236.32MPa from 201.5MPa by the cast, after heat treatment tensile strength achieved 287.30MP, increased 42.6% than the cast alloy, tensile strength of hypereutectic Al-16% Si alloy was up to 199.45MPa from 165.21MPa by the cast, after heat treatment tensile strength achieved 247.66MPa, increased 24.2% than the cast alloy.