I would suggest that everything else on the knife would break before you would twist or buckle the titanium in a lock bar.
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If I recall correctly Spyderco managed to shear off the notch that receives the lock bar in a 3 mm S30V blade (may have been VG-10) which is hardened to 59 Rc when testing the strength of their backlocks, I have absolutely no doubed that a Ti lockbar which is tough and flexible but not overly hard will easily buckle or twist (not necessarily break, but that isn't needed for a lock to fail) under the same forces on compression. I could see though, that the same Ti lockbar under tension may fair much better.