Effect Of Ultrasonic Field On Solidification Process Of Al-Si Piston Alloy

With the development of the times,the internal combustion engine gradually to high-power,high heat efficiency,low emission direction,the piston's work load is more and more high,the requirements of the piston material are increasingly harsh,the traditional process of aluminum alloy piston material has been difficult to meet these requirements.As an effective field treatment technique,ultrasonic fields have a remarkable effect on the refinement of metal microstructure and the improvement of its properties.In this paper,the effect of ultrasonic field on the solidification characteristics,microstructure and precipitation mechanism of the eutectic poly-Al-Si alloy was studied by using Al-11.5Si-4Cu-2.6Ni-1Mg-0.45Fe near Eutectic Al-Si piston alloy modified by P-salt.The main non-equilibrium microstructures include?-Al,primary silicon,eutectic silicon,and intermetallic phases.By means of metallographic microscope?OM?,Scanning electron microscope?SEM?and X-ray diffraction?XRD?,the effect mechanism of ultrasonic field on the solidification process of piston aluminum alloy was analyzed,and the best ultrasonic technology was determined.The main findings are as follows:?1?Melt ultrasonic treatment can improve the precipitation temperature of primary silicon,shortening the eutectic time,at the same time,with the increase of ultrasonic power,the increase of ultrasonic temperature,the prolongation of the time of ultrasonic application of primary silicon,eutectic silicon and alloy heat-resistant phase gradually refinement,?-Al phase from dendrite gradually into isometric,when melt temperature is 720?,Applying 3000W power ultrasound 120s,The temperature of primary silicon precipitation is 588.4?,the minimum eutectic time is 14.5s,the crystallization temperature of the primary silicon is increased by 3.5%and the eutectic time is shortened by 64%when the ultrasonic field is not applied,at this time,the tissue thinning effect is the best,the diameter of the primary silicon is reduced from 21.6?m to 15.4?m,and the eutectic silicon length decreases from 19.6?m to8.45?m The width is increased from 0.92?m to 1.91?m,and the heat-resisting phase of the alloy is connected to each other to form many closed or semi-closed eutectic groups distributed in the alloy matrix.?2?The solidification characteristics and microstructure of piston alloy were significantly influenced by the ultrasonic field of different power?0³000W?at different stages during solidification.When ultrasonic field is processed in the whole solidification process,with the increase of ultrasonic power,the temperature and eutectic temperature of the primary silicon decrease,the eutectic time is shortened,and when the ultrasonic power is 3000W,the temperature of the primary silicon is 560?,The minimum eutectic time was 9.7s,and the temperature decreased by 2.5%when the primary silicon precipitation was not applied to the ultrasonic field.The eutectic time was shortened by 73%,besides,the diameter of the primary silicon was reduced from 25.85?m to 16.7?m,and the eutectic time was significantly influenced by the Eutectic ultrasonic field,and with the increase of ultrasonic power,the eutectic time was shortened and the ultrasonic power was 3000W when eutectic The shortest distance between 13.5s,compared to not applied ultrasonic field shortened by 63%,at the same time,the diameter of the primary silicon 25.85?m reduced to 18.6?m.?3?The solidification process of the alloy was simulated by liquid quenching technology,and it was found that the 600?⁵90?alloy liquid produced and grew into the primary silicon when the ultrasonic field was not applied,and the eutectic silicon and?-al were grown up in the565?⁵41?,and the needle-rich rare earth phase was precipitated in the 552?precipitation T-Al₉Fe Ni phase 541?precipitates?-Al₃CuNi phase and 536?precipitates?-Al₂Cu phase and Q-Al₅Cu₂Mg₈Si₆ phase.The application of ultrasonic field can improve the primary silicon,eutectic silicon and T-Al₉FeNi phase precipitation temperature,reduce the size of primary silicon,so that long needle-like eutectic silicon into a short rod,prompting the T-Al₉FeNi phase from the block into a mesh,the needle-rich rare earth phase in the 600?began to precipitate,with the alloy liquid temperature,The needle-rich rare earth phase was transformed into?-Al₃CuNi phase by peritectic reaction,and the?-Al₃CuNi phase,?-Al₂Cu phase and Q-Al₅Cu₂Mg₈Si₆ phase were precipitated at 520?in ultrasonic field.