(1) The results show that the Fe rich phase in al-17si-1fe alloy contains only long needle like β phase when the extrusion force is 0, while the al-17si-2fe alloy contains not only acicular β phase but also lath like δ phase. With the increase of extrusion force, the length of iron rich phase in the two alloys decreases gradually.
(2) The results show that the Fe rich phase in al-17si-1fe and al-17si-2fe alloys are mainly composed of acicular β – phase and small-sized δ phase, and the size of Fe rich phase decreases with the increase of extrusion pressure. This is because the cavitation effect and acoustic flow effect of ultrasonic promote the formation of small δ phase in the alloy. After ultrasonic treatment, the solidification of alloy melt under pressure will further refine the iron rich phase.
(3) When the alloy composition is the same, the tensile strength and elongation of the ultrasonic treated alloy are higher than that of the alloy without ultrasonic treatment under the same extrusion pressure, and the mechanical properties of the alloy increase with the increase of extrusion force.
(4) The results show that the tensile strength of al-17si-1fe alloy is 16.3% – 19.0% higher than that of al-17si-2fe alloy in the extrusion pressure range of 0-300mpa without ultrasonic treatment, and the tensile strength of al-17si-2fe alloy is 16.3% – 19.0% higher than that of al-17si-2fe alloy under the same extrusion pressure without ultrasonic treatment It is slightly lower than that of al-17si-1fe alloy.