Effect of high pressure rheocasting on mechanical properties of hypereutectic Al Si alloy

The room temperature tensile strength and elongation of A1 and A2 alloys under different processes are shown in Fig. 1. It can be seen from Fig. 1 that for the alloy with the same composition, under the same extrusion pressure, the tensile strength and elongation of the ultrasonic rheological squeeze casting alloy sample are higher than those of the sample without ultrasonic treatment, and the improvement range of the tensile strength of A2 alloy (2% Fe) is higher than that of A1 alloy (1% Fe). Secondly, the tensile strength and elongation of the alloy increase with the increase of extrusion pressure whether or not ultrasonic treatment. For the alloy without ultrasonic treatment, when the extrusion pressure is not applied, the iron rich phase in the alloy is mainly in the form of coarse needle or plate strip. With the increase of extrusion force, the size of lath like δ phase and long acicular β phase decreases, and the strength and elongation of the alloy are increased; after ultrasonic treatment, the iron rich phase in the alloy is refined obviously without extrusion pressure, and with the increase of extrusion pressure, massive δ phase appears The results show that the mechanical properties of the alloy after ultrasonic treatment are higher than that of the alloy with the same extrusion pressure.

It can also be seen from Figure 1 that when the forming process is the same, the room temperature tensile strength and elongation of A1 alloy (1% Fe) are higher than that of A2 alloy (2% Fe). The results show that the tensile strength of A1 alloy is 16.3% – 19.0% higher than that of A2 alloy in the range of extrusion pressure. The reason is that the needle like iron rich in A2 alloy is coarser than that in A1 alloy, and the splitting effect on matrix is more serious. However, the tensile strength of A2 alloy is slightly lower than that of A1 alloy, which is due to the fact that the iron rich phase in A2 alloy is mainly short strip δ phase, and the acicular β phase is less Although there is a part of massive δ phase in A1 alloy, the main iron rich phase is acicular β phase, so the strength values of the two alloys are relatively close.

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