Martensitic transformation and shape memory effect in B2 intermetallic compounds of titanium

2014 Crystallographic and kinetic characteristics of martensitic transformations and parameters of shape memory effect in B2 compounds of titanium Ti50Ni50-xXx (X = Fe, Co, Pd, Pt, Au, Cu) and Ti50Pd50-xYx (Y = Fe, Co, Cu), where 0 ~ x ~ 50 are investigated. Temperature, hysteresis, value of reversible deformation and stress of martensitic shear for martensitic transformations and shape memory effect are defined. Compositions of alloys with optimum conditions for shape memory effect were determined. Revue Phys. Appl. 24 (1989) 733-739 JUILLET 1989, Classification Physics Abstracts 81.30K Titanium exists in BCC and HCP modifications (T03B1~03B2 = 1115 K) and forms binary and multicomponent B2 compounds with Ni, Fe, Co, Pd, Pt, Au, Cu and other metals, many of them being unstable and undergoing various martensitic transformations (MT) at different temperatures [1-4]. The most famous among them are TiNi and alloys on its base where monoclinic martensitic phase B19’ is formed either directly by B2 ~ B19’ or by rhombohedral R structure B2 ~ R B19’ [5]. Shape memory effect (SME) is vividly expressed in these alloys. At present new B2 compounds of titanium of the type Ti(Ni, Cu), Ti(Ni, Pd), Ti(Ni, Pt), Ti(Ni, Au), Ti(Pd, Fe) with different MT and SME characteristics are intensively investigated [2-4, 6, 7]. Some of the alloys have rare and SME characteristics observed neither in TiNi, nor in other SME alloys. However the results of the researches are not well known. The present paper sums the results of the author’s latest publications and presents new data on MT and SME in a series of triple compounds Ti50Ni50-xXx (X = Fe, Co, Pd, Pt, Au, Cu) and TisoPdso-xYx (Y = Fe, Co), where 0 x 50. The present alloys cover the main compounds of titanium with unstable B2 lattice. The methods of making alloys and specimens as well as methods of structure and SME -studies are described in [2-4]. Martensitic transformations. 1. SYSTEMS Ti5oNi5O-,Fe, AND Ti5oNi5O-,CO,MT in Ti50Ni50 xFex (0 x 3) are studied in detail in [5, 8]. However a total (0 x 50) MT diagram with cooling up to 4.2 K is designed only in [9]. At the same time genetically related alloys system Ti5oNi5o _ xCox was studied much less. Figure 1 presents the resultant MT diagram which agrees qualitatively with MT diagram in Ti50Ni50 xFex. In the both systems B2 -+ R -+ B19’ is the basic MT accurately fixed against the temperature dependence of resistivity (Fig. la). The parameters of B19’ martensitic phase (a = 0.288 nm, b = 0.412 nm, c = 0.465 nm, f3 = 97.6° for TisoNi4C07) vary slightly with the change of alloy composition and they are close to the parameters of B19’ martensite in TiNi (a = 0.289 nm, b = 0.412 nm, c = 0.464 nm, f3 = 97.3°). With the increasing of Co(Fe) content at first MT R B19’ and then MT B2 ~ R are under suppression. The stabilization of initial B2 structure in its Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/rphysap:01989002407073300