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Micro TiB and nano La₂O₃ particles hybrid reinforced difficult-to-deformation Ti-6Al-4V TMCs were processed by severe plastic deformation of equal-channel angular pressing (ECAP). The effect of ECAP temperature on microstructure, formation mechanism of ultrafine grains and mechanical properties was studies by SEM, TEM and room temperature tensile in detail. The results show that ultrafine-grained (UFG) structure has formed in ECAPed matrix, and ECAP temperature have significant impact on the formation mechanism. Plenty of dislocation pile-ups and tangling contribute to cell structures of hundreds of nanometers in matrix at lower ECAP temperature, while dynamic recrystallization occurs at higher ECAP temperature, which promotes the formation of a large number of new ultrafine grains (100~500 nm). The ultimate tensile strength of ECAPed TMCs at 800℃ is up to 1128.01MPa, which is 18% higher than unECAPed ones. In addition, micro-nano reinforcements induce continuous dynamic recrystallization in the interface microdomain, resulting in further refined grains. However, the average aspect ratio of ECAPed TiB whiskers decreases with the increase of ECAP temperature, which makes TiB tend to debond with matrix and be disabled to play a load-bearing role. It results in the inapparent effect of ECAP temperature on ultimate tensile strength. And the voids in matrix formed by debonding induce stress concentration, cause crack easily and reduce ductility of TMCs.