Manufacturing method of titanium alloy with high-strength and high-formability and its titanium alloy

1. A method of manufacturing a titanium alloy, the method comprising:

preparing a titanium alloy material and equipment for manufacturing a titanium alloy;

manufacturing the titanium alloy having a lamellar structure by cooling the prepared titanium alloy material with water after performing heat treatment at the beta transformation temperature or more; and

rolling that makes ultrafine grains by finishing forming of the titanium alloy at a plastic instability temperature by gradually decreasing the forming temperature in accordance with an increase of a strain after starting the forming at the plastic instability temperature or more, under a condition of a low strain in which the strain is 2.5 or less, after the manufacturing of a titanium alloy having a lamellar structure.

2. The method of claim 1 , wherein, in the rolling, the initial forming start temperature for starting the forming is the plastic instability temperature or more of an initial lamellar structure, the final forming temperature for finishing the forming is the plastic instability temperature or less of an initial lamellar structure, and the process is finished while maintaining the plastic instability temperature or less of the initial lamellar structure when the strain reaches 2.5 while decreasing the temperature along a predetermined drop curve in accordance with an increase in the strain after starting the forming at a forming temperature of the plastic instability temperature or more at the initial stage.