Of Ultrasound On The Az31b Magnesium Alloy Casting Temperature Field In The Study

Magnesium alloy is a new structural material which has been widely used in military, automotive, electrical appliances, mobile phones, computers and other electronic equipment products. Conventional continuous roll-casting of magnesium strip, with advantages of lower energy consumption, shorter production cycle, higher yield of finished products and lower processing cost, overcomes the shortcomings of traditional processing methods of magnesium strip. However, the magnesium strips worked out by continuous roll-casting have highly-developed branching of dendrite, uneven microstructure, coarse grains, which affect the mechanical properties intensive processing performance of magnesium strip. Therefore, based on the conventional roll-casting of magnesium strip, the ultrasound has been introduced to realize the ultrasound roll-casting. By taking use of the finite element software ANSYS to establish the three-dimensional finite element models of ultrasound roll-casing of magnesium strip, simulating the temperature field of the roll-casting process, the author preliminarily masters various process parameters of ultrasound roll-casting of magnesium strip by doing plentiful experiments and explores the influence of those parameters on solidification structure and mechanical properties. The main contents of this article are as following.1. Analysisng the fundamental theory of ultrasonic propagation and the impacts of cavitation effects and acoustic streaming effects of ultrasonic on solidification structure of metals.2. Elaborating the basic theory of thermal analysis, establishing the three-dimensional finite element models of ultrasonic roll-casing of magnesium strip with the use of the ANSYS, studying the effects of Ultrasound vibration on heat transfer between melted Magnesium and caster mouth,rolls and air, dealing with the thermal effect of ultrasound with the way of heat conversion, successfully converting the ultrasonic vibration function into corresponding dynamic boundary condition by making use of the Function Editor of the ANSYS, and confirming the other boundary conditions of the process of ultrasound roll-casting according to the certain experimental conditions.3. Simulating the temperature field of ultrasound roll-casting by using the ANSYS to get the regularities of distribution of the temperature field under the conditions of different former case temperature, speed and ultrasonic power. The results of simulation showed that ultrasonic had obvious effects on the temperature field. The reasonable former case temperature was 685℃～695℃and the speed of casting was 2.1m/min～2.5m/min.4. The metallographic comparison made between ultrasound and conventional roll-casting of magnesium strip showing that the conventional roll-casting strip has highly-developed branching of dendrite, uneven microstructure, the average size (diameter) is between 50μm～60μm; whereas, the ultrasound strip has much evener microstructure with refined grains whose mean size (diameter) is between 20μm～30μm.The tests of mechanical properties of the strips verify that the tensile strength, yield strength and elongation of ultrasound strips raise by 22.85%,34.36% and 123.06% respectively compared with those of conventional ones.