The invention relates to a heat treatment process for improving obdurability of a near
beta type or metastable
beta type titanium alloy. The process comprises the following steps of: firstly, preserving heat at the temperature of T which is more than or equal to T beta-50 DEG C and less than or equal to T beta-10 DEG C, wherein the heat preservation time T (min) is eta *
delta max, the
delta max is the maximum section thickness of a
forge piece, the unit is mm, the eta is a heating coefficient, and the value of the heating coefficient eta is 0.5 to 1.5min / mm; secondly, discharging the
forge piece out of a furnace and cooling the
forge piece to
room temperature by air or water; thirdly, preserving heat of the cooled forge piece at the temperature of T which is more than or equal to 520 DEGC and less than or equal to 560 DEG C, wherein the heat preservation time T is more than or equal to 20min and less than or equal to 1.5h; fourthly, discharging the forge piece out of the furnace andcooling the forge piece to
room temperature by air; fifthly, slowly heating the cooled forge piece to the temperature of T which is more than or equal to 480 DEG C and less than or equal to 540 DEG Calong with the furnace, wherein the heating rate is controlled to be within 5 DEG C / min, and the heat preservation time T is more than or equal to 6h and less than or equal to 12h; and finally, cooling the forge piece along with the furnace or discharging the forge piece out of the furnace and cooling the forge piece to
room temperature by air. The process is suitable for heat treatment of the near
beta type or metastable beta type
titanium alloy with ultrahigh obdurability so as to obtain a tissue with high comprehensive performance and multi-scale precipitated phases, which has the requiredultrahigh strength (Rm is more than or equal to 1,500 MPa), high
plasticity (A is more than or equal to 5 percent) and high obdurability (KIC is more than or equal to 45 MPa.m < 1 / 2 >), and meet important bearing structural members with ultrahigh obdurability matching required by airplanes.