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Production of Ni-35Ti-15Hf alloy via the FFC Cambridge process

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Wang, B. X., Bhagat, R. (Rohit), Lan, X. Z. and Dashwood, R. J.. (2011) Production of Ni-35Ti-15Hf alloy via the FFC Cambridge process. Journal of The Electrochemical Society, Vol.158 (No.10). D595-D602. ISSN 0013-4651

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Official URL: http://dx.doi.org/10.1149/1.3615845

Abstract

The NiTiHf system alloy is considered to be one of the most attractive shape memory alloy (SMA) at elevated temperatures. This paper outlines how the FFC Cambridge Process was applied to produce the Ni-35 atom % Ti-15 atom % Hf (henceforth referred to as NiTiHf) alloy from sintered precursors of NiO, TiO(2) and HfO(2). In order to illuminate the reduction pathway, a number of partial reductions were completed at different reduction times. The samples were characterised by SEM, X-EDS and XRD. It was found that the key stages of reduction involved: (1) the reduction of NiTiO(3) and NiO to Ni, (2) the reduction of CaTiO(3) to Ti and the simultaneous formation of Ni(3)Ti, (3) the reaction of Ni(3)Ti with CaTiO(3) to form NiTi, (4) the reduction of HfO(2) and CaHfO(3) to form NiTiHf alloy and finally (5) the deoxidation and the Ti/Hf homogenisation of NiTiHf alloy. The sintered oxides precursors were reduced to metal alloy after 9 h reduction. After twenty-four hours reduction, a homogeneous alloy was formed with an oxygen content of 1600 ppm. DSC analysis shows that the austenite transformation temperature of the produced NiTiHf alloy was close to that seen in literature. An electrochemical predominance diagram for the Hf-Ca-Cl-O system was constructed to help understand the reactions during reduction.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry T Technology > TA Engineering (General). Civil engineering (General) T Technology > TP Chemical technology
Divisions:	Faculty of Science > WMG (Formerly the Warwick Manufacturing Group)
Library of Congress Subject Headings (LCSH):	Shape memory alloys -- Synthesis
Journal or Publication Title:	Journal of The Electrochemical Society
Publisher:	Electrochemical Society, Inc.
ISSN:	0013-4651
Date:	28 July 2011
Volume:	Vol.158
Number:	No.10
Number of Pages:	8
Page Range:	D595-D602
Identification Number:	10.1149/1.3615845
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Warwick Manufacturing Group, China Scholarship Council (CSC)
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URI:	http://wrap.warwick.ac.uk/id/eprint/38524