鋁合金雙層複合材料A356及6063之半固態鍛造成形探討

The Development of Semi-solid Forging for A356 and 6063 Alloy Double Layer Composite Material

黃書偉(Shu -Wei Huang)

指導教授 ： 鄭芳松

國立虎尾科技大學/工程學院/機械與電腦輔助工程系碩士班/碩士(2013年)

摘要

鋁具有質輕、高比強度、及易回收再利用之優異特性，對於追求輕、薄、短、小及環境友善之科技產品而言，將是跨世紀最熱門之金屬材料之一。傳統對於3C產品的殼件，會以鍛型或壓鑄製程做為加工方式，藉此降低成本，但由於板材的鍛型相當困難，只能做簡單之特徵型狀，再者壓鑄之強度及表面質感仍不足；目前主要的3C產品殼件是以鋁合金板材，採NC加工為主要的成形，但此加工方式，加工時間上過為冗長，加工成本也相對的提升許多；近期業界也開始往鋁合金之半固態成形方向發展，但因為加熱方式採用高週波或電熱爐方式使整副模具加熱，除了持溫時間太長之外，也因為持溫時間過長造成內部組織的改變，然而加熱過後之模具，因須拿至沖壓機進行沖壓，溫度在此段時間會急速下降，造成沖壓時溫度不足而破壞內部結構之外，更容易造成充填性不足之現象。有鑑於此，本研究藉由電阻式加熱機進行沖頭的局部加熱，經熱傳導效應使鋁合金快速加熱，使材料處於半固態下進行沖鍛成形；因此可以快速成形複雜特徵之鋁合金之板材，也可以使鋁合金之板材因為鍛造之特性所造成的晶粒細化現象與高強度之特性，藉由田口方法之運用，來探討製程參數組合使之最佳化，已達到最低限制條件下使鋁合金晶粒細化之效果。
　　利用田口方法尋找出影響品質之特性之成形參數，故控制溫度、壓力等相關之條件下，尋找出成形之最佳條件；球化鋁合金之板材，其球化之晶粒目前分布於200μm左右，但經由傳統之製程使球化過後之鋁合金成形，晶粒會變為粗大與組織分布不均勻之缺陷，所以利用電阻式加熱機使鋁合金之板材瞬間加熱，材料於半固態狀態下沖鍛成形，因晶粒細化有高強度之特性，以便觀察鋁合金之流動特性與晶粒分布之現象。
　　球化鋁合金之細晶成形，先行利用模擬軟體進行基本的實驗參數探討，如溫度與壓力之相互的配合下，套用至實驗參數之下，一方面可與理論值做比對，一方面可以減低實驗之設置條件；雙層複合材之鋁合金，是藉由最後研磨成形後球化鋁合金，藉由金相組織來探討製程參數對於鋁合金之細晶效果之研究。

關鍵字

鋁合金 ； 球化晶粒 ； 田口方法 ； ECAE

並列摘要

Aluminum is characterized with light weight, high toughness and easy recycling. To technological products pursuant to lightness, thinness, shortness and smallness, as well as eco-friendliness, the aluminum material will be the hottest metal material across the century. Traditionally, the cases and chassis of 3C products are made by forging or molding to reduce the costs. However, since it is very difficult to forge the sheet materials, only simply featured shapes can be made. Furthermore, the strength and texture touch from forging are not very ideal. So far, cases and chassis for 3C products are mainly made of aluminum alloy with NC process which is time consuming and costly. Recently, the industry has turned its attention to aluminum alloy's semi-solid forming. However, this heating approach adopts high frequency or electric heating to heat up the entire mold, which makes too long the temperature retention time, thus brings in changes of the internal tissues; even more concerned is when the heated mold is taken to the press for stamping, its temperature will rapidly drop in the midst, resulting in insufficient stamping temperature that can impair the internal tissue structure and easily cause inadequate filling. In view of this, this research takes a resistive heater to partially heat the stamping head and, by way of the heat conduction effect, rapidly heat up the aluminum alloy, to forge stamping and shape the material under a semi-solid state, thus making it possible to quickly shape up complex patterns of aluminum alloy sheet materials. With the Taguchi method, the refined granularity and high strength features of the forged aluminum alloy sheets can be referenced for setting optimal production parameters in order to reach a fine granularity with minimal constraints.
　　With the Taguchi method, the forming parameters that affect the quality can be identified, and the temperature and pressure can be better controlled for setting an optimal conditions for the sheet formation. The aluminum alloy sheet in sphericity has grains distributed within the range of about 200μm, but the formation of aluminum alloy through a traditional process can make the grains coarsened and unevenly distributed. Therefore, using a resistive heater to instantly heat up the aluminum alloy sheet in a semi-solid state for the forging stamping formation, the high toughness of the grain refinement allows observation of the flow characteristics and grain distribution of the aluminum alloy.
　　For the formation of the refined grains of a aluminum alloy in sphericity, a simulation software is used to identify experimental parameters, such as temperature and pressure, and their interaction is set into the experimental models to compare the results with theoretical values and reduce the experimental installation requirement as well. A dual-layer composite aluminum alloy is formed into sphericity by abrading in the final stage, and the metallographic texture is used to explore the effect the production parameters make on the aluminum alloy granularity.

並列關鍵字

Al alloy ； Crystal ball ； Taguchi method ； ECAE

參考文獻

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