Twins In Ti Research Articles

Neutron Irradiation Effect on Twinning Deformation of Titanium

The effects brought by irradiation on the formation of twins in Ti deformed at 77 K were studied on unirradiated and irradiated specimens. Optical microscopic observation revealed different modes of deformation according to the amount of strain; the data also served to determine thevolume fraction and the density of twins as function of strain. Thevolume fraction of twins proved to be larger in irradiated than in unirradiated specimens. Detailed examination showed that irradiation promotes the growth of deformation twins. Transmission electron microscopy indicated that the twins generated in the course of low temperature deformation belonged mostly to the system.

Presentation and computing of ultrasonic data: Krautkramer, H.Applied Materials Research, 4, No. 4, 223 (1965)

The {112¯2}<1123¯> compression twin can accommodate a considerable amount of strain under c-axis compression in Ti. However, unlike the tensile {101¯2}〈1¯011〉 twin, the structure of {112¯2}<1123¯> compression twins has not been completely characterized. Here, we apply a combined technique of HR-TEM characterization, topological analysis, and atomistic simulations to explore the facets that bound the {112¯2}<1123¯> twin in Ti. In addition to the currently known facets (CTB and B-Py), six new facets are observed and categorized for the first time from atomic-scale TEM observations along five crystallographic directions. The six new facets are (112¯0)//(112¯6), PrPr1, PyPy1, (211¯1)//(1¯21¯1), (11¯04)//(011¯1¯), and (011¯0)//(211¯4). Results from the topological and computational analysis are in reasonable agreement with and support the HRTEM observations. Specifically, (1) the observed facets align with low-index interfaces in both twin and matrix domains, (2) the facets with lower surface energies are found to form extended interfaces, and (3) high-surface-energy facets are found at the twin tip region and explained by the fact that the energy of the combined facet and facet junction configuration is energetically preferred in the twin tip region. These results not only provide a comprehensive understanding of the 3D structure of {112¯2}<1123¯> compression twins in Ti, but also validate the MD procedure and the Ti interatomic potential employed. This is extremely important for future study of {112¯2} twin mobility and interactions with other defects, both features that remain extremely challenging to capture in experiments.

The Crystallographic Aspect of the Mechanical Twinning in Ti and α-U

A crystallographic study on the mechanical twinning in Ti and α-U is made by a method similar to that in a previous paper, allowing more kinds of atom movements, and the twin elements, K 1 , K 2 , η 1 and η 2 , are determined. It is found that {11\bar22} and {11\bar24} twins in Ti are reciprocal to each other and that the elements of {11\bar21} twin are in agreement with Hall's result. It is also found that a general result that a plane having the smallest shear S is liable to twin in order nearly holds in Ti and α-U.