Study on hot extrusion process and semi-solid forming of magnesium alloys

• Main Authors: Kuo,Jer Liang, 郭哲良
• Other Authors: Hsiang, su-hai
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/18588775354046212790

博士 === 國立臺灣科技大學 === 機械工程系 === 93 === This study mainly investigated the hot extrusion processes of magnesium alloy and the characteristics of this alloy under semi-solid state. Taguchi’s method, ANOVA analysis and Artificial Neural networks (ANNs) are applied to estalsish the analytical model for analyzing the experimental results. The main topics discussed in this study are the fllowing five items. 1. Taguchi’s experimental method is used to carry out the experiments of AZ31 and AZ61 magnesium alloys on the hot extrusion, extrusion ratios of the die are 35.89 and 55.85. From the results of experiment we try to find out the optimal hot extrusion process of magnesium alloy sheet, furthermore, by the factor effect response analysis and ANOVA analysis, the relation between process parameters and products can be derived. 2. According to the process developed on hot extrusion of magnesium alloy sheet. We try to predict the timing of adjusting extrusion speed during extrusion of converging die (die angle is 60°). Moreover, ANNs analysis is applied to the developed multi-speed method, to predict the timing of adjustment of the initial speed of extrusion in the different billet temperatures. 3. For the prupose of establiship a database of hot extrusion process of magnesium alloy, process parameters considered in this study are material types, extrusion ratios, product types, initial extrusion speeds, billet heting temperatures, lubricants, and hold time at specified temperature. Moreover, the mechanical properties of magnesium alloy rod can be predicted. 4. Applying the ANNs analylical model to predict tensile strength of extruded rectangular tube, and to find the relationship between the billet temperatures and tensile strengths. Furthermore, the microstructures of products under different forming temperature were observed. 5. Some experiments are carried out to find the semi-solid temperature range of AZ61 magnesium alloy, and the changes of microstructures of AZ61 magnesium alloy from normal temperature to 400℃, in a hot chamber within the semi-solid state, and under the condition of semi-solid compression and extrusion. In this study a called multi-speed method is developed in the extrusion of magnesium alloy sheet. The parameters that influence the mechanical properties of extruded parts are analyzed syematically, then the database of magnesium alloy extrusion in established. Applying ANNs analytical model, the optimal condition of acquring sound extruded products can be obtained. Finally, the semi-solid temperature range and the characteristics of semi-solid forming of AZ61 magnesium alloy are investigated. We hope the results derived from this study can be a useful reference to the industry of magnesium alloy forming, and researches who engage in the related metal forming field.