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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.46  No.7 (2005)  >  pp.1604-1609

MATERIALS TRANSACTIONS
<<Previous article Vol.46  No.7 (2005)   pp.1604 - 1609 Next article>>

The Influence of Aluminum Content on Shape Memory Effect of Ti–7Cr–Al Alloys Fabricated Using Low Grade Sponge Titanium

Masahiko Ikeda1), Daisuke Sugano1), Shingo Masuda1) and Michiharu Ogawa2)
1) Department of Materials Science and Engineering, Faculty of Engineering, Kansai University
2) Research and Development Laboratory, Daido Steel Co., Ltd.


In this study, the influence of aluminum content on shape memory effect of Ti–7Cr–Al alloys fabricated using low-grade sponge titanium was investigated by measurement of electrical resistivity and Vickers hardness, along with shape-recovery testing. The results obtained are as follows.
In the STQed state, the phase constitution of non-Al added alloy, Ti–7Cr–0Al alloy, was found to consist of retained β phase and athermal ω, whereas those of Al added alloys, Ti–7Cr–1.5Al, 3.0Al and 4.5Al alloys, were found to consist of orthorhombic martensite, α″, and retained β phase. Resistivity (ρ) at liquid nitrogen (LN) and room temperature (RT) increased monotonously with Al content. Resistivity ratio (ρLN⁄ρRT) increased drastically at 3Al, exceeding unity.
Shape recovery was exhibited in the 1.5Al, 3.0Al, and 4.5Al alloys having been fabricated using low-grade sponge titanium as raw material. In the 3.0Al and 4.5Al alloys, shape recovery ratio was about 90% at temperatures above 523 K and recovery surface strain was at least 0.03. The resistivity change indicates that stress-induced orthorhombic martensite was produced during bending of the 4.5Al alloy.


Keyword:
shape memory effect, low grade sponge titanium, orthorhombic martensite, metastable beta phase, electrical resistivity, reverse transformation

Received: January 24, 2005
Accepted: June 06, 2005 , Published online: October 18, 2005
Copyright (c) 2005 The Japan Institute of Metals

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