Title: Microstructure and martensitic transformation in sintered NiTiCu alloys

Authors: Tomasz Goryczka, Jan Van Humbeeck

Addresses: Institute of Materials Science, University of Silesia, Bankowa 12, Katowice 40-007, Poland. ' Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, Leuven B-3001, Belgium

Abstract: The main aim of this work was to characterise microstructure and phase transformation, which occurs in Ni (50-X) Ti50CuX shape memory alloys (where X = 2, 3, 5, 10, 15, 20 and 25%) produced by powder technology. The blends were sintered applying various conditions, considering temperature and time: temperature varied from 850°C to 1100°C whereas time from 5 to 50 hr. In order to receive homogeneous alloys, which reveal reversible martensitic transformation, the sintering condition were optimised. It was found, that for alloys containing lower copper addition (less than 10%), the best sintering temperature was 940°C and time 7 hr. For higher Cu content (10–25%) lowering of sintering temperature to 850°C and extension of sintering time up to 20 hr were needed. Depending on copper content, X-ray diffraction studies revealed two different martensitic structures: monoclinic – B19| and orthorhombic – B19. [Received on 31 March 2006; Accepted on 18 February 2007]

Keywords: smart materials; shape memory alloys; powder metallurgy; sintering; nickel titanium copper alloy; microstructure; phase transformation; martensitic structures.

DOI: 10.1504/IJMPT.2008.020585

International Journal of Materials and Product Technology, 2008 Vol.33 No.3, pp.252 - 264

Available online: 01 Oct 2008 *

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