Self accomodating shear strain


16-Oct-2020 02:40

On the other hand, we explore the possibility of developing an effective elastic model independently of the Rule, in those cases in which the Rule itself does not work.Our results are based on a close study of the implications of the phenomenon of mechanical twinning with regard to the symmetry properties of the energy function of an elastic crystal.Ti-Nb-based Gum Metals exhibit extraordinary superelasticity with ultralow elastic modulus, superior strength and ductility, and a peculiar dislocation-free deformation behavior, most of which challenge existing theories of crystal strength.Additionally, this kind of alloys actually displays even more anomalous mechanical properties, such as the non-linear superelastic behavior, accompanied by a pronounced tension-to-compression asymmetry, and large ductility with a low Poisson's ratio.Here we use synchrotron-based high-energy X-ray diffuse scattering (HE-XRDS), in combination with computer simulations, to explore in-situ the deformation behavior of a gum-type Ti-24Nb-4Zr-8Sn-0.10O (in weight percent) alloy (abbreviated as Ti2448 from its chemical composition).Besides the high penetration, low absorption, great access to the reciprocal space, and high reciprocal resolution, the HE-XRDS technique can trace in-situ small changes in crystal structure, size, and elastic strain state even for nanocrystalline domains with a small volume fraction during deformation and phase transformation in bulk samples.Under tension the stress-induced phase transformation from B2 nanoclusters to α" is evidenced by the obvious increase in the (021) diffuse scattering signals) and, instead, ω phase starts to form at a compressive stress of ~500 MPa (as indicated by the HE-XRDS pattern displayed in the inset of Fig. After the applied compressive stress is removed, the ω phase remains (as indicated by the HE-XRDS patterns provided in the Supplementary Fig. The crystal structure of α" is determined by using high-energy X-ray diffraction (HE-XRD) by rotating the sample around [110].It is a C222 orthorhombic structure (space group No.

Specifically, we address here a twofold problem: On one hand, we pose the question of the validity of the socalled “Born Rule”, a fundamental hypothesis due to , by means of which continuum theories of crystal mechanics are formulated.The nano-scale martensites consist of frustrated nanodomains of individual martensitic variants, which are distinctively different from the normal self-accomodating polytwinned martensitic plates.