Powder metallurgy technology of NiTi shape memory alloy

Jan M. Dutkiewicz 1Wojciech Maziarz 1Tomasz Czeppe 1Wojciech K. Nowacki 2Stefan P. Gadaj 2Jerzy Luckner 2Elzbieta A. Pieczyska 2Lidia Lityńska-Dobrzyńska 1

1. Polish Academy of Sciences, Institute of Metallurgy and Materials Sciences (IMIM PAN), Reymonta 25, Kraków 30-059, Poland
2. Polish Academy of Sciences, Institute of Fundamental Technological Research (IPPT PAN), Świętokrzyska 21, Warszawa 00-049, Poland

Abstract

Nickel-titanium alloys shaping and casting technology is difficult due to a high reactivity of titanium and brittleness in the as cast state. Therefore, powder metallurgy technology offering new technological possibilities and in addition controlled porosity was applied. Shape memory alloy was compacted from the prealloyed powder delivered by Memry SA showing Ms = 10oC and As = -34oC as results from DSC measurements. The hot compaction in the as delivered spherical particle’s statewas performed in a specially constructed vacuum press, at temperature of 680oC and pressure of 400 MPa. The alloy powder was encapsulated in copper capsules prior to hot pressing to avoid oxidation or carbides formation. The alloy after vacuum high pressure and temperature of 680oC compaction (i.e. above the NiTi stability range) has shown similar transformation range as the powder. The porosity of samples compacted in the as delivered state was only 1%. TEM studies shown  presence of small amount of B19' martensite and Ni4Ti3 particles at room temperature. The samples tested in compression up to ε = 0.06 have shown partial superplastic effect and returned back to ε = 0.01 after unloading. They have shown also high ultimate compression strength of 1600 MPa. Measurements of the samples temperature change during deformation allowed to detect temperature increase up to 2 degrees during loading and similar decrease during unloading.

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium E, by Jan M. Dutkiewicz
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 16:43
Revised:   2009-06-07 00:44
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