Ideal superelasticity in Ni-based Heusler alloys

• The hysteresis that occurs during superelasticity caused by the stress-induced first-order martensite transformation is sometimes detrimental to the properties of superelastic materials. In this paper, first-principles calculations are performed to systematically investigate the effects of the chemical composition and crystal disorder on the superelasticity of Ni50-xCoxM25Ga25 (M = Mn, Fe) Heusler alloys. Calculations of the stress-strain relation in the studied alloys reproduce the recent experimental findings for nonhysteretic superelasticity within an acceptable range of composition and ordering. We evaluate the Bloch spectral function to study the Fermi surface topology in connection with nonhysteretic superelasticity. We propose the Landau-de Gennes model-dependent critical parameter P-c, which can be used to predict the composition range of nonhysteretic superelastic materials. For the ferromagnetic L2(1) Ni50-xCoxMn25Ga25 and B2 Ni50-xCoxFe25Ga25 alloys, the nonhysteretic superelasticity phenomenon theoretically occurs for Co contents over x = 16 at.% and x = 28 at.%, respectively.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

Nyckelord

Heusler alloys

shape memory alloys

martensitic phase transformation

nonhysteretic superelasticity

first-principles calculation

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