鎂元素對鋁鋅鎂基複合材料時效行為影響之研究

Abstract

本實驗利用擠壓鑄造法製作鋁基複合材料，基地為鋁鋅鎂合金，強化相為 氧化鋁纖維。製作過程中改變合金中的鎂含量(1.23wt%~2.97 wt%)，以探 討鎂元素對複合材料時效行為的影響。DSC分析結果顯示，氧化鋁纖維會 抑制基地強化相，η'相的析出，使得基地時效硬度降低，並提早析出完 全。複合材料基地中，添加鎂元素可使複合材料基地中，η'相的析出量 增加，並延長其析出完全的時間。複合材料基地的最大微硬度，也隨著鎂 含量的增加而上昇。鋁鋅鎂合金與複合材料的耐磨耗實驗，其結果顯示， 複合材料的耐磨耗性較鋁鋅鎂合金為優。但在磨耗圈數增加時，由於複合 材料的磨屑中，含有硬度較高的氧化鋁纖維，反而造成複合材料的磨耗量 增高。 The effect of adding magnesium on the aging behavior of Al-Zn- Mg alloy reinforced with aluminum (Al2O3) was studied using differential scanning calorimeter(DSC) technique, hardness measurement. The magnesium contents were varied from 1.23wt% to 2.97wt%. The addition of magnesium was found to increase the amount of η'-phase formation in composites. The formation enthalpy of composites was 0.932cal/g and 1.375cal/g for lower magne- sium content(1.23wt%) and higher magnesium content(2.97 wt%) respectively. The time needed for the saturation of precipiat- ing in the composites changed from 12 hr to 48hr as the magne- sium content increased from 1.23wt% to 2.97wt%. The maximum hardness occurred in composites with 2.97wt% Mg that contained a maximum amounts of η'-phase precipitates. The hardness of the composites was always less than that of monoli- thic alloys because of alumina fibers caused suppression of η' formation in composites. Difference of wearability between composites and Al-Zn-Mg alloy was also performed in this study. The weight loss decreased with increasing the volume fraction of alumina and with increasing the magnesium content.