Study of the Re-nucleated Phase of Cu-Al-Be Shape Memory Alloy
Date Issued
2006
Date
2006
Author(s)
Lin, Chien-Chou
DOI
zh-TW
Abstract
In this thesis, three kinds of Cu-Al-Be shape memory alloys (SMAs) with Al content near the eutectoid composition were melted down and homogenized in evacuated quartz capsules. The effects of Be content on eutectoid temperature and on order-disorder transition temperature were be discussed. And proceed salt-bath quenching from the solution treatment temperature to the order-disorder transition range and short time aging, to analyze the crystal structure and microstructure of the re-nucleated parent phase. Finally, observing the shape memory recovery change after aging and thermal cycling to evaluate the Cu-Al-Be SMA within fine martensite workability.
The results show that Be addition can effectively lower the eutectoid temperature of the hypoeutectoid Cu-Al alloy, but has no effect for the order-disorder transition. The re-nucleated parent phase can be observed by TEM after heat treatment. The martensite, which doesn’t reversely transform to parent phase, at the re-nucleated phase site has the 18R crystal structure; but the parent phase at the re-nucleated phase site has the D03 crystal structure. However, the chemical composition of re-nucleated phase is slightly different from D03 phase which can be observed by SEM back scattering electron image. Short time aging at order-disorder transition temperature will precipitate α phase, which isn’t favored to shape memory effect (SME). After 250 thermal cycles, the shape recovery of Cu-Al-Be SMA within fine martensite is deteriorative gradually which implies that it cannot be applied practically.
Subjects
鈹含量
共析溫度
序化結構轉變
再成核相
熱循環
形狀回復率
Be concentration
eutectoid temperature
order-disorder transition
re-nucleated phase
thermal cycling
shape recovery
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-95-R94527008-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):5215d73dddcdf7fa728e4c8c7c300d3e