Processing method of fine-grain superplastic TA15 titanium alloy medium-thickness plate

The invention discloses a processing method of a fine-grain superplastic TA15 titanium alloy medium-thickness plate. The processing method comprises the following steps that 1, vacuum consumable arc melting is carried out to obtain a TA15 titanium alloy cast ingot; 2, after heat preservation, a primary forging stock is obtained through upsetting, drawing, cogging and forging; 3, after heat preservation, a second-stage forging stock is obtained through beta-phase region upsetting and drawing forging; 4, upsetting and drawing forging in an alpha + beta two-phase region is carried out to obtain afourth-stage forging stock; 5, a forge piece is obtained through upsetting, drawing and finish forging; 6, after heat preservation, a first-fire rolled plate blank is obtained through first-fire rolling; 7, after heat preservation, a second-fire rolled plate blank is obtained through second-fire rolling; and 8, the TA15 titanium alloy medium-thickness plate is obtained through annealing treatment. According to the proces