Titanium composite material and hot working the titanium material for

A first surface portion 2, and the inner layer portion 4, a titanium composite material 1 and a second surface portion 3, the first surface portion 2 and the second surface portion 3 is made of titanium alloy, the inner layer portion 4, consists commercially pure titanium having voids, at least one of the chemical composition of the first surface portion 2 and the second surface portion 3, [8.0 titanium composite 1 ratio is 2-20%, the volume ratio in a cross section perpendicular to the thickness direction of the gap is 30% or less than 0% titanium composite.