NiTiHf-based shape memory alloys

Abstract

NiTiHf-based shape memory alloys have been receiving considerable attention for high temperature, high strength and two-way shape memory applications since they could have transformation temperatures above 100°C, shape memory effect under high stress (above 500 MPa) and superelasticity above 100°C. Moreover, their shape memory properties can be tailored by microstructural engineering. However, NiTiHf-based alloys have some drawbacks such as low ductility and high slope in stress induced martensite transformation region. In order to overcome these limitations, studies have been focused on microstructural engineering by aging, alloying and processing. It has been revealed that microstructural control is crucial to govern the shape memory properties (e.g. transformation temperatures, matrix strength, shape recovery strain, twinning type, etc.) of NiTiHf-based alloys. A summary of the most recent improvements on selected NiTiHf-based systems is presented to point out their significant shape memory properties, effects of alloying, aging and microstructure of transforming phases and precipitates.

The effects of substituting B for Cu on the magnetic and shape memory properties of CuAlMnB alloys

“…8b. Their ability to show superelasticity at temperatures near or above 100°C makes them promising high-temperature shape memory alloys and alternatives to NiTiHf alloys [29,33]. Thermal experiments revealed that transformation temperatures are highly dependent on B content in CuAlMnB alloys.…”

“…1b. It should be noted that B3 and B4 alloys can be considered as hightemperature shape memory alloys since they have transformation temperatures near or above 100°C [29]. Hardness measurements were taken at room temperature when all the alloys were martensite and were found to increase with the addition of B.…”

Three-dimensional constitutive model for structural and functional fatigue of shape memory alloy actuators

“…They can operate at high stress levels without the development of significant plastic strains (Karaca et al, 2014). From the analysis of NiTiHf actuator fatigue tests, we see that the number of cycles to failure increases with decreasing cyclic actuation work.…”

Havacilik Ve Uzay Uygulamalarinda Şeki̇l Hafizali Alaşimlar

“…), NiTi ve NiTi-bazlı alaşımlar, dayanım, birim şekil değişim miktarı, korozyon dayanımı, tribolojik özellikleri, biyouyumluluk gibi etkileyici özelliklerinden dolayı üzerinde oldukça fazla çalışılan ve diğer alaşım sistemlerinin (NiTiHf, NiTiPd, NiTiCu, NiTiHfPd, NiTiHfCu vb.) üretiminde temel olarak kullanılan alaşımlardır [10][11][12][13][14]. Bundan dolayı, pratik uygulamalarda en çok kullanılan ve kullanılma potansiyeli olan alaşım sistemleri de NiTi ve NiTi-bazlı alaşım sistemleridir.…”