臺灣博碩士論文加值系統

本實驗的目地是在探討二元及添加合金元素之鐵鋁基合金
在高溫的機械性質.其所有退火的合金皆為B2晶格結構的介
金屬化合物,二元系列主要為Fe-17Al,Fe-27Al和Fe-35Al (
皆為原子百分比),經過一系列的熱機處理過程後在不同的溫度下
對所有合金進行500-800度高溫拉伸實驗.在機械性質方面,溫
度愈高時,拉伸強度愈低,尤其在600度時,強度有顯著的下降
.但在伸長率方面:低鋁含量(<23%)的合金,溫度伸高時其伸
長率先上升而後卻下降,高鋁含量(>23%)合金的拉伸值隨溫度
的增加其伸長率亦持續增加.所有合金在高溫拉伸時並無氫脆的
現象.二元合金經添加第三元素後,晶粒有明顯的細化,但二元
合金的延性較優於添加第三元素的合金.Fe-27Al在800度時有最
加的超塑性伸長率(180%),Fe-35Al-5Cr-0.1Zr-0.05B則在500度
時有最大的抗拉強度(500MPa),但在著後者的破斷面顯示出劈裂
的穿晶脆性特徵,其它合金在500度以上皆為渦穴或頸縮的延性
破斷面特性,另外,在觀察顯微切面時,有二種不同的形式:
一為拉長的晶粒,另一位動態再結晶所照造成的微細晶粒,並且發現大
部份具高延性的合金又皆有孔洞的存在.
關鍵字:鐵鋁基合金,超塑性,熱機處理,氫脆現象,動態再結晶

Elevated-temperature mechaincal properties of iron-aluminide
base alloys have been studied. Alloys investgated included binary
and ternary with additions of macro- and microalloying
elements (such as Cr,Zr,Si,Nb). Fe-17Al,Fe-27Al and Fe-35Al (in at%)
were selected as binary series. Ordered B2 crystal structure
was obtained for all alloys after annealing. After application of
thermochanical treatment, tensile tests at various temperatures
(500-800) were carried out in air. results showed that
elongation of low Al-content (<23%) alloys decreased with
increasing temperature between 600-800, whereas for high Al-content
(>23%) alloys elongation increased with increasing temperature
between 500-800. Addition of alloying elements
could obviously refine grain structure, but yielded no measurement
improvement in ductility. The strength of all alloys showed
dramatically drops at 600. In this study, Fe-27Al showed the
best elongation (180%) at 800, while Fe-35Al-5Cr-0.1Zr-0.05B
exhibited the maximum tensile strength (500MPa) at
500 among Fe-Al alloys.No hydrogen embrittlement effect was
thus found in the test temperature range. Expect Fe-35Al and Fe-35Al
-5Cr-0.1Zr-0.05B alloys showing a brittle transgranular
cleavage fracture, all other Fe-Al alloys exhibited dimple or
necking ductile fracture features. Sectional microstructureal
observations indicated several types of grain structures: elongated
grains, cavitations as well as small recrystallized grins due to the
dynamic recrystallization during the test.
(Keyword: iron-aluminide base alloys, B2, thermochanical teratment,
hydrogen embrittlement, superplasticity, dynamic recrystallization.)