Effect of high-pressure torsion on the structure and properties of the natural layered amorphous-crystalline Ti2NiCu composite

The room-temperature high-pressure torsion (HPT) behavior of a natural layered amorphous-crystalline composite with the precursor phases of the same chemical composition, but differing in structure has been studied by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and the measurements of indentation hardness (HIT) and indentation modulus (EIT) over the cross section of the samples. The force deformation parameters (torsion moment) realized upon HPT of the Ti2NiCu samples tested in three initial structural states (amorphous, crystalline, and composite) have been traced in situ with a special facility. Three different regions of amorphous, crystalline, and transitional structures are distinguished in the composite. It is shown that two different deformation mechanisms are simultaneously realized in crystalline and amorphous regions of the composite upon HPT. An attempt was made to identify the role of the transition layer upon deformation of the composite. •Three regions (amorphous, crystalline and transitional) of the layered Ti2NiCu composite.•Two different deformation mechanisms realized in the Ti2NiCu composite upon HPT.•The transitional region of the composite plays a dual role upon HPT.•Upon HPT at n ≥ 4, both parts of the composite become similar in structure.