User blog comment:Fairy Tail Grand Master/What is the hidden blade made of?/@comment-4862210-20120627211714/@comment-4043223-20120627212540

They did not have such advanced metallurgical furnaces that were required for smelting metals such as titanium. At best during that time period he could simply have folded the metal during the smithing process to increase its resistance to breaking. Likely it was made of steel as that was the common metal of the time.