Microstructure and texture characterisation of linear friction welding of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-6Mo

Guo, Yina (2013). Microstructure and texture characterisation of linear friction welding of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-6Mo. University of Birmingham. Ph.D.

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Abstract

Linear friction welding (LFW) of two α - β titanium alloys, Ti-6Al-4V (Ti64) and Ti-6Al-2Sn-4Zr-6Mo (Ti6246) was studied, focusing on micro-hardness measurement, microstructure and texture characterisation. It has been found that in the as-welded condition Ti6246 has lower micro-hardness values in the weld region than in the base material, while for Ti64 the weld region is harder. The change in hardness is greatly related to the microstructures formed after welding. In cnetre weld zone (CWZ), in the autogenous Ti6246 weld, the microstructure consists of fine β grains with needle shape orthorhombic α″. In the autogenous Ti64 weld, relatively large acicular martensitic α′ phase was found. A very strong texture component, where the basal pole is concentrated in the sample normal direction and one of the {11 20}α poles is concentrated in the oscillation direction, is identified in both the CWZ and thermo-mechanically affected zone. Comparison between the α texture and the β texture suggests that the strong texture component T is the consequence of the deformation β texture developed at high temperature and the preferred variant selection during the β→α transformation. The texture was found to have significant influence on the fracture toughness of the weld region.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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