Effect of cooling speed and ultrasonic vibration on solidification structure and mechanical properties of 7085 aluminum alloy

Abstract

Three different cooling methods of furnace cooling, air cooling and water cooling were adopted, and ultrasonic outfield assisted technology was applied to study the effects of cooling speed and ultrasonic outfield on the solidification structure and properties of 7085 aluminum alloy. Metallographic microscope, scanning electron microscope and electronic universal mechanics testing machine were used to characterize the matrix structure, second phase, tensile strength and elongation of the samples, and the solidification mechanism was analyzed. The results show that under the above three cooling methods of furnace cooling,air cooling and water cooling, after ultrasonic field the microstructure refinement rate of α-Al in each group is 40.2%, 14.6%, and 21.6%, respectively. The fitting relationship between grain size and cooling speed is as follows: LW=154.4+25.33/v,LS=148.1+15.3/v, the second phase of the area fraction are relatively reduced by 32.1%, 16.9% and 18.5%, the average length and width of the second phase are also relatively less, the tensile strength of 7085 aluminum alloy, which is increased by 21.7%, 21.7% and 3.6%, respectively, after the introduction of ultrasonic outfield auxiliary technology, compared to the group without ultrasound. Elongation of 7085 aluminum alloy is further enhanced by 31.3%, 15.7% and 41.4% respectively. Under the synergistic effect of ultrasonic field and water cooling, the microstructure and mechanical properties of 7085 aluminum alloy are better.

Keywords

• cooling speed
• ultrasonic field
• microstructure
• second phase
• fitting relationship