Grain Type post weld in Grade 1 titanium

[lennoc]

Hi Folks,

I have attached an old image of a butt joint laser weld from thin sheet grade 1 titanium . The quality of the image is poor however I am slighty confused as to what the grain structure and type of this sample is post weld. I can see both alpha and beta phases present which should not be considering grade of material - is this correct?

Care to comment?

 

[metengr]

If this is Grade 1 CP titanium, my technical references indicate the resultant microstructure of the butt weld fusion zone should be acicular alpha-phase within large previously formed beta-phase grains. However, the beta-phase will transform back to alpha-phase upon cooling. I see relatively coarse grains in the vicinity of the weld fusion zone but beyond this observation, I cannot delineate phase constituents.
If you are actually seeing beta-phase constituents you have a contaminant (iron) that was introduced.

 

[TVP]

lennoc,

I agree with metengr, the weld should not have any beta phase unless there is contamination, etc. Here is an excellent article by George Vander Voort on metallography of titanium alloys, with some images of CP titanium showing essentially alpha phase only:

http://www.industrialheating.com/Articles/Feature_Article/43bf616b05cad010VgnVCM100000f932a8c0____

 

[lennoc]

hi all, I have another question in relation to weld structures in cp grade 1 weld. I see the coarsening of the grain compared to the base metal, but what are the structures I have highlighted in red. are these pockets of alpha case?