Titanium Alloys
Titanium alloys are generally classified into four main categories:
Alpha alloys which contain neutral alloying elements and alpha stabilizers only and are not heat-treatable.
Near-alpha alloys contain a small amount of ductile beta-phase.
Alpha-beta alloys are metastable, generally include some combination of alpha and beta stabilizers, and can be heat treated.
Beta and near beta alloys are metastable and contain sufficient beta stabilizers to maintain the beta phase when quenched. They can also be solution-treated and aged to improve strength.
The ASTM International standard on titanium and titanium alloy seamless pipe reference the following alloys, requiring the following treatment:
Grades 1-4 are unalloyed and considered commercially pure. Generally, the tensile and yield strength goes up with the grade number for these “pure” grades. The difference in their physical properties is primarily due to the number of interstitial elements.
Grade 7 contains 0.12 to 0.25% palladium. This grade is similar to Grade 2. The small quantity of palladium added gives it enhanced crevice corrosion resistance at low temperatures and high pH.
Grade 11 contains 0.12 to 0.25% palladium. This grade has enhanced corrosion resistance.
Alpha Alloys:
Commercially Pure – ASTM grades 1, 2, 3 and 4
Ti/Pd Alloys – ASTM grades 7 and 11
Alpha + Compound
Ti-2.5%Cu – IMI 230
Near Alpha Alloys:
Ti-8%Al-1%Mo-1%V
Ti-6%Al-5%Zr-0.5%Mo-0.2%Si – IMI 685
Ti-6%Al—2%Sn-4%Zr-2%Mo-0.08%Si
Ti-5.5%Al-3.5%Sn-3%Zr-1%Nb-0.3%Mo-0.3%Si – IMI 829
Ti-5.8%Al-4%Sn-3.5%Zr-0.7%Nb-0.5%Mo-0.3%Si – IMI 834
Ti-6%Al-3%Sn-4%Zr-0.5%Mo-0.5%Si – Ti 1100
Alpha-Beta Alloys:
Ti-6%Al-4%V
Ti-4%Al-4%Mo-2%Sn-0.5%Si
Ti-4%Al-4%Mo-4%Sn-0.5%Si – IMI 551
Ti-6%Al-6%V-2%Sn
Ti-6%Al-2%Sn-4%Zr-6%Mo
Metastable Beta Alloys:
Ti-3%Al-8%V-6%Cr-4%Zr-4%Mo – Beta C
Ti-15%Mo-3%Nb-3%Al-0.2%Si – Timetal 21 S
Ti-15%V-3%Cr-3%Sn-3%Al
Titanium is used regularly in aviation, military applications, spacecraft, bicycles, medical devices (metal orthopedic joint replacements and bone plate surgeries specifically), jewelry, expensive sports cars, and premium sports equipment.