Generally, there are 8 grades of titanium and titanium alloys that are most commonly used in industrial applications in which corrosion resistance is often of primary concern. Among these titanium materials, titanium Grade 1, Grade 2, Grade 3, and Grade 4 are known as unalloyed titanium or commercially pure titanium, while titanium Grade 5, Grade 7, Grade 9, and Grade 12 are known as titanium alloys. The UNS designation, nominal composition, and crystal microstructure (phase types) are listed in below table.

 

ASTM / ASME Grade	UNS Designation	Nominal Composition	Phase Types
Grade 1	R50250	Unalloyed Titanium	α
Grade 2	R50400	Unalloyed Titanium	α
Grade 3	R50550	Unalloyed Titanium	α
Grade 4	R50700	Unalloyed Titanium	α
Grade 5	R56400	Ti-6Al-4V	α+β
Grade 7	R52400	Ti-0.15Pd	α
Grade 9	-	Ti-3Al-2.5V	Near-α
Grade 12	R53400	Ti-0.3Mo-0.8Ni	Near-α

*The nominal composition are in mass fraction, %.
*α refers to single α-phase (hexagonal close-packed crystal structure).
*Near-α refers to the phase containing relatively small amount of β phase(body center cubic crystal structure)in an α matrix.
*α+β refers to compositions that support a mixture of α and β phases and may contain between 10% and 50% β phase at room temperature.