鉬鈮元素對鐵鋁錳合金高溫機械性質之影響

Abstract

本研究添加單一種合金元素的鉬(2.9%),鈮(0.84)或兩種合金元素2Mo- xNb(x=0.92,0.398,0.239wt%)對鐵鋁錳合金在25℃至550℃間之拉伸機械 性質之影響.以兩種不同的起始溫度熱軋延，一為1200℃,另為1000℃。研 究結果指出，含2Mo-xNb(0.398,0.239) 合金，有利形成大小約3μm、近 圓形的碳化物;它可 減少只添加Mo及只添加Nb所產生的多邊型或立方形碳 化物應力集中的情形. 1000℃的熱軋延製程能增加晶界碳化物析出的成核 點，使得沿晶有非鏈狀的碳 化物分佈,增加鐵鋁錳合金的高溫拉伸強 度(550℃有745MPa的降伏強度，16.5% 的延伸率)。Mo、Nb碳化物析出量 的增加，會降低沃斯田鐵基地內的碳含量，造成K相析出量減少及影響低 溫(250℃)動態應變時效的型態。 Molybdeum addition of 2.9wt%,niobium addition of 0.84 wt% and 2MoNbx (x=(0.92,0.398,0.239wt%) where added to the FeMnAl alloys respectively ,to investigate the effect of mechanical behavior on the FeMnAl alloysfrom 25℃to 550℃.Two hot rolling procedures were used. One operation temperature was started at 1200 ℃and the other at 1000℃. The results indicated that the FeMnAl alloys with 2MoNbx(x=0.395,0.239wt%) preferentially formed the sphereical carbide about 3μm to avoid the formationof polygonal or cubic molybeum carbide and niobium carbide by adding solelyMo or Nb.The hot rolling procedure at 1000℃ increased nucleus site of carbide at grain boundary,and made the discrete carbide distribution along the grain boundary,and made the carbide discrete along the grain boundary .Furthermore,the yield strength and elongation of the FeMnAl alloys were promoted to 745MPaand 16. 5% at 550℃,individually. The molybdeum carbide and niobium carbide would influenced at the carbon content in the austenite matrix, which affected the amount of K-phase and the type of dynamic strain ageing.