Alpha Variant Selection Determined from Grain Misorientations in Ti-6Al-7Nb Alloy with a Duplex Microstructure
Abstract
Titanium occurs in two structures; a high temperature body-centered cubic structure which is known as beta phase and an ambient temperature alpha phase which has the hexagonal closed-packed structure. In the present study a biomedical Ti-6Al-7Nb alloy was investigated.
The so-called duplex structure consisting of alpha lamellae and equiaxed primary alpha-grains was prepared by a thermal treatment. The alpha lamellae are created during cooling from a beta-field according to the Burgers relation.
This relation allows the formation of the alpha lamellae with different crystallographic orientations - so-called variants. The preferential misorientation between alpha lamellae was studied by a detailed electron backscattered diffraction analysis.
The misorientation of grains in the duplex structure was modelled by a sum of random Mackenzie distribution and Gaussian peaks related to the preferred misorientations according to the Burgers relation. The preferred misorientations based on the Burgers relationship were identified in the biomedical Ti-6Al-7Nb alloy with duplex structure.
It is confirmed that the variant selection of alpha lamellae is not random.