  The "titanium fire" as produced during high pressure and friction is the
major failure scenario for aero-engines. To alleviate this issue, Ti-V-Cr and
Ti-Cu-Al series burn resistant titanium alloys have been developed. However,
which burn resistant alloy exhibit better property with reasonable cost needs
to be evaluated. This work unveils the burning mechanisms of these alloys and
discusses whether burn resistance of Cr and V can be replaced by Cu, on which
thorough exploration is lacking. Two representative burn resistant alloys are
considered, including Ti14(Ti-13Cu-1Al-0.2Si) and
Ti40(Ti-25V-15Cr-0.2Si)alloys. Compared with the commercial non-burn resistant
titanium alloy, i.e., TC4(Ti-6Al-4V)alloy, it has been found that both Ti14 and
Ti40 alloys form "protective" shields during the burning process. Specifically,
for Ti14 alloy, a clear Cu-rich layer is formed at the interface between
burning product zone and heat affected zone, which consumes oxygen by producing
Cu-O compounds and impedes the reaction with Ti-matrix. This work has
established a fundamental understanding of burning resistant mechanisms for
titanium alloys. Importantly, it is found that Cu could endow titanium alloys
with similar burn resistant capability as that of V or Cr, which opens a
cost-effective avenue to design burn resistant titanium alloys.
