The effect of mild-carbon steel and high-temperature alloy GH1131 on the microstructure of HIPed TC4
alloy was studied. The results show that mild-carbon steel die prevents the transfer of the stress for densification of TC4
during the process of HIP, different from the GH1131 die. When the die is designed,the deep cavity structure should
be avoided for the mild-carbon steel. Due to the interdiffusion of elements,the alloy surface is contaminated by both of
the die materials. Although the thickness of the boundary between TC4 and mild-carbon steel is slim,the alloy surface
is coarse with the wave-like morphology. And the thickness of the boundary between TC4 and GH1131 is raised to
more than 100 μm. In order to gain the clean and smooth material surface,the die cavity surface must be treated to
form a protect layer compatible with TC4.