1 College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China 2 State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083, China 3 Institute of Light Alloy Research, Central South University, Changsha 410083, China
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.
LI R Q , LI X Q , CHEN P H , et al. Phase transition behavior of ultrasonic cast 7085 aluminum alloy during heat treatment[J]. Jour-nal of Materials Engineering, 2016, 44 (6): 24- 30.
YANG W , YIN H M , SHANG J L , et al. Hetero-nucleation and high temperature grain growth of fast cold magnesium alloys with SiC particles[J]. Chinese Journal of Nonferrous Metals, 2017, 27 (2): 243- 250.
PAN L , TAO J , CHEN Z F , et al. Acoustic effect of high energy ultrasound in particle/metal melt system[J]. Journal of Materials Engineering, 2006, (1): 35- 37.
JUNG J , LEE S , CHO Y , et al. Effect of transition elements on the microstructure and tensile properties of Al-12Si alloy cast under ultrasonic melt treatment[J]. Journal of Alloys and Compounds, 2017, 712 (4): 277- 287.
ZHANG L , JIANG R P , LI X Q , et al. Microstructure modification for 2219 Al alloy through ultrasonic treatment and fast coo-ling[J]. Materials Science and Technology, 2019, 35 (11): 1392- 1400.
LI X Q , JIANG R P , ZHANG L H , et al. Effect of ultrasonic vibration depth and cooling mode on solidified microstructure of pure aluminum[J]. Journal of Beijing Institute of Technology, 2008, 28 (4): 290- 293.
HUANG M Z , LI X Q , JIANG R P , et al. Effect of ultrasonic field on the matrix and phase of 7085 aluminum alloy[J]. Journal of Central South University, 2015, 46 (7): 2439- 2445.
STJOHN D H , QIAN M , EASTON M A , et al. The interdepen-dence theory: the relationship between grain formation and nucleant selection[J]. Acta Materialia, 2011, 59 (12): 4907- 4921.
FAN Y Z , XU X J , RUAN H Y . Effect of enhanced solid solution treatment on microstructure and mechanical properties of Sr 7085 aluminum alloy[J]. Thermal Processing Technology, 2015, 44 (18): 192- 194.
CHEN S Y , CHEN K H , PENG G S , et al. Effect of initial microstructure on thermal processing properties of 7085 aluminum alloy[J]. Chinese Journal of Nonferrous Metals, 2013, 23 (4): 956- 963.
YAO L , HAO H , JI S , et al. Effects of ultrasonic vibration on solidification structure and properties of Mg-8Li-3Al alloy[J]. Transactions of Nonferrous Metals Society of China, 2011, 21 (6): 1241- 1246.