Hardness. Titanium is a much harder metal than aluminum and approaches the high hardness possessed by some of the heat-treated alloy steels. Iodide purity titanium has a hardness of 90 VHN (Vickers), unalloyed commercial titanium has a hardness of about 160 VHN and when alloyed and heat-treated, titanium can attain hardnesses in the range of 250 to 500 VHN. A typical commercial alloy of 130,000 psi yield strength might be expected to have a hardness of about 320 VHN or 34 Rockwell C.

Impact Resistance. Knowledge of tensile strength and ductility of a metal is insufficient for many engineering applications without the knowledge of toughness. Titanium falls among the few metals capable of possessing good toughness along with high strength and ductility.

Titanium may have impact strengths ranging from more than 100 foot pounds Charpy for the higher purity iodide product and 30 foot pounds for the commercial unalloyed product to 1 or 2 foot pounds for some of the high strength but brittle alloys.

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