擠壓鑄造法製作鋁基(2024)/Al2O3複合材料時效硬化之研究

Abstract

以擠壓鑄造法製作氧化鋁纖維強化2024鋁合金複合材料，可藉由熱處理的 析出硬化，改善機械性質。但因含氧化鋁纖維時效行為與基材不同，不能 直接選用基地材料之熱處理條件。本實驗利用DSC、微硬度，並配合 TEM 的觀察及確認析出相以了解2024鋁基複合材料和2024鋁合金析出硬化過程 的差異。結果顯示纖維和基地間的界面提供淬火時空孔消失的位置，而抑 制GP zones的析出，使複合材料的淬火敏感性提高。2024鋁合金的強化相 為GP zone+S'相，而複合材料的強化相只有S'相，且複合材料S'相的析出 量小於2024鋁合金，並S'相的析出量隨氧化鋁纖維的增加而減少。故複合 材料之最大硬度值比2024鋁合金低許多。 Precipitation hardening can influence the mechanical properties of the alumina-reinforced aluminum alloy(2024) composites fabricated by squeeze casting method. Owing to the presence of alumina fibers, the aging behavior of alumina reinforced aluminum alloy is different from aluminum alloy(2024) . Therefore, the condition of heat treatment for aluminum alloy (2024) is not satisfied to alumina-reinforced aluminum alloy (2024) composites. In the present study, we performed investigitions of DSC, microhardness, and observations of TEM to realize the difference of precipitation hardening processing of the two materials. It was found that the aging hardenign response of the matrix alloy in metal matrix composites caused suppression of GP zones forming. The reason is that the fiber- matrix interface can be treated as sinks of quench-in vacancies. In addition, the precipitates of aluminum alloy(2024) are GP zones and S', and that of alumina-reinfoced aluminum alloy(2024) composites is only S'. The precipitation of S' in alumima reinforced aluminum alloy(2024) composites is less than that of aluminum alloy(2024). The precipitation of S' is decreaed with increasing volume fraction of alumina fibers. Therefore, the peak hardness of the matrix of alumina- reinforced aluminum alloy (2024) composites is lower than that of aluminum alloy(2024).