Mg-(2-8)wt.%Sn合金經等通道擠型製程後腐蝕性質之研究及改善

Abstract

本實驗室已於96、99年的計畫中分別進行新型合金Mg-Zn-Al系以及Mg-Sn系高溫鎂合金機械性質之研究。深入探討此兩種合金的高溫拉伸、高溫潛變、超塑性…等性質，發現其可經等通道擠型製程獲得較Mg-Al系合金更佳的高溫機械性質。 但是其他性質卻尚未被完整的研究，這可能會限制該材料的應用。以汽車工業上的應用為例，鎂合金應用於汽車零件上最具挑戰的問題即為高溫環境，先前計畫所研究的高溫機械性雖已達到目標，但是對鎂合金而言腐蝕也是一個很大的問題，尤其是在高温油氣環境下(通常含有硫成份)。從文獻回顧中我們可以得知鎂合金極易產生腐蝕現象，Mg-Al系統的抗腐蝕現象相對於其他鎂合金較佳，但是其高溫機械性質卻是一大問題。因此本計劃希望針對先前計畫中具有較佳高溫機械性質的Mg-Sn系合金的抗腐蝕性質進行研究，對於不同環境條件下的腐蝕性質作一個有系统的研究，並提出改善方案。 本計劃分成三年期，第一年研究鎂-錫合金經ECAE製程對其抗腐蝕性之影響，並做化成處理表面改質及分析其抗腐蝕性質，同時以polyimide披覆來改善其抗腐蝕性。第二年深入研究導入ECAE製程後對對應力腐蝕之影響。第三年將模擬特殊環境腐蝕如熱水管、汽車排氣…等高溫環境對經表面改質的鎂合金進腐蝕能力測試。最後我們將建立鎂-錫合金各種環境之腐蝕資料庫及找到最佳改善方法。

Our labortary has studied the new Mg-Zn-Al and Mg-Sn alloys used at elevated temperatures in 2007 and 2010, respectively. From the results of high temperature mechanical properties of these two alloys such as creep and superplasticity etc., we can find out that these two alloys have much better high temperature mechanical properties than that of Mg-Al system. Unfortunately, other properties of these two alloys have not been fully studied; this can result in the reduction of lifetime. For example, the bigger problems for Mg alloys application in auto industry are the high temperature mechanical properties and corrosion resistance. The high temperatures mechanical properties have been resolved. However, the corrosion resistance is also an important problem for Mg alloys, especially in oil gas environment (usually include Sulphur). As we know that Mg-Al alloys have better corrosion resistance than other Mg alloys but they have poor high temperature mechanical properties. Therefore we try to study the corrosion resistance of Mg-Sn alloys which have good high temperature properties in different conditions. Also, we will propose how to improve the corrosion resistance. This study is a three- years project. First year, it plans to study the influence of ECAE on corrosion resistance and improvements of corrosion resistance by surface modification and coating polyimide film. Second year, it plans to study the effect of ECAE process on stress corrosion resistance. Third year, it plans to study corrosion resistance after the improvement of surface modification in special condition such as hot water pipes and exhaust pipes . Finally, we try to establish a complete data base of corrosion properties for Mg-Sn and find up the solution of improvement.