分流擠型和微量Sc對Al-5.6Mg-0.7Mn合金微結構及熱加工性之影響

Effects of cross-channel extrusion process and scandium on microstructure and mechanical properties of the Al-5.6Mg-0.7Mn alloys

陳建瑋(Chien-wei Chen)

指導教授 ： 李勝隆

國立中央大學/工學院/機械工程學系/碩士(2008年)

摘要

分流擠型(cross-channel extrusion process，CCEP)為本實驗室自行開發之等截面劇烈加工製程，本製程除保有等通道轉角擠型(equal channel angular extrusion，ECAE)等截面加工之特色外，亦能連續加工至指定道次再將材料取出，具有累積應變均勻散佈第二相之效果，因而製造極細晶粒(ultra-fine grain，UFG)材料。
本研究擬於Al-5.6Mg-0.7Mn合金中添加微量(0.3wt.%)Sc元素，鑄造時即能形成細小且均勻散佈之Al3Sc相，期望藉由自行開發之分流擠型來產生細晶且具高溫穩定之微結構，並於高溫下測試其超塑性以評估含Sc之Al-5.6Mg-0.7Mn之熱加工性。
結果顯示合金經分流擠型於300℃下擠製六道次，能獲得晶粒尺寸為1~2μm之細晶微結構，且大幅提升機械性質。含0.3wt.%Sc合金中會產生L12結構之Al3Sc相，能有效抑制再結晶並提高合金之熱穩定性，於500℃下退火一小時仍維持等軸細小之再結晶晶粒，且經分流擠型擠製六道次，於450℃、應變速率為1x10-1s-1下進行高溫拉伸能獲得最大伸長量為873%。

關鍵字

分流擠型 ； 鋁鎂合金 ； 超塑性

並列摘要

Cross-channel extrusion (CCE) is a new method which is designed to improve the process of manufacturing a bulk fine-grained material. The material can be deformed in the cross-shaped channel repeatedly without removing during extrusion time. The CCE process is potentially appropriate for industry application because of its continuing working ability.
The purpose of this study is to investigate the effects of CCE process and scandium on microstructure and mechanical properties of the Al-5.6Mg-0.7Mn alloys.
The result indicate that Al-5.6Mg-0.7Mn alloys with and without 0.3wt.% Sc after extrusion 6 passes at 300 ℃, fine-grained structures were observed with grain sizes of 1~2 μm and improvement of mechanical properties. Addition of Sc to Al-5.6Mg-0.7Mn alloys resulted in a uniform distribution of fine coherent Al3Sc precipitates which effectively pinned grain boundary to obtained equiaxed and fine grain after annealing 1hr at 500 ℃. The maximum elongation to failure of 873% was achieved at 450 ℃ and initial strain rate of 1x10-1 s-1 in an Al-5.6Mg-0.7Mn-0.3Sc alloy extruded by CCEP 6 passes at 300 ℃.

並列關鍵字

cross-channel extrusion process ； Al-Mg alloy ； superplasticity

參考文獻

〔1〕 R. Verma, et al., “Grain refinement and superplasticity in 5083 Al”, Materials Science and Engineering A, pp.143-150, 1995.

〔2〕 D.Y. Maeng, et al., “The effect of transition elements on the superplastic behavior of Al-Mg alloys”, Materials Science and Engineering A, pp.188-195, 2003.

〔3〕 M. Furukawa, et al., “Influrnce of magnesium on grain refinement and ductility in a dilute Al-Sc alloy”, Acta Materialia, Vol.49, pp.3829-3838, 2001.

〔4〕 F. Musin, et al., “High strain rate superplasticity in a commercial Al-Mg-Sc Alloy”, Scripta Materialia, 50, pp.511-516, 2004.

〔5〕 S. Lee, et al., “Influence of scandium and zirconium on grain stability and superplastic ductilities in ultrafine-grained Al-Mg alloys”, Acta Materialia, 50, pp.553-564, 2002.