[en] An ion implantation technique at the elevated temperature was used for designing the surface area of a titanium alloy and for irradiation-enhanced hardening of the surface. The Ti₆Al₄V alloy was treated by nitrogen ion implantation at fluences of 9x10¹⁷ cm^-2 and at ion energy 90 keV. Samples were annealed in the vacuum chamber after the nitrogen ion implantation at the temperatures 300, 400, 500 and 600°C. The continuous measurement mode was used to obtain depth profiles of the indentation hardness of the modified surface area. The annealing temperature limit with highest mechanical properties is 400°C. We have found the limit value of the temperature, in which the mechanical properties of modified surface Ti₆Al₄V alloy decrease. (author)