Comparison between Titanium Grade 1, Titanium Grade 2 , Titanium Grade 3 and Titanium Grade 4

Titanium Grade 1, Titanium Grade 2 , Titanium Grade 3 and Titanium Grade 4 are considered commercially pure. Microstructurally, they are all alpha-phase alloys. The difference, however, lies in the amount of interstitial elements added to each grade. The figure below shows the interstitials level of each grade and its corresponding mechanical properties.

Interstitial elements such as O², Fe and N, with oxygen (Oxygen) being the most significant. Titanium Grade 1 contains the least interstitial elements and has the lowest ultimate tensile stress (UTS) i.e. 0.18% wt. O², 0.20% wt. Fe and 240 MPa. Titanium Grade 4, on the other hand, contains the most interstitial elements and has the highest UTS (more than twice that of Titanium Grade 1) i.e. 0.40% wt. O², 0.50% wt. Fe and 550 MPa. Therefore, we can conclude that the higher the interstitials e.g. O² and Fe, the stronger the alloy. It is evident that as UTS increases, elongation decreases, making the alloy less ductile. The strength of commercially pure Titanium thus increases with the Grade number i.e. Titanium Grade 4 is stronger than Titanium Grade 3, Titanium Grade 3 is stronger than Titanium Grade 2 and Titanium Grade 2 is stronger than Titanium Grade 1.

Grade	UTS (MPa)	0.2% (MPa)	%El	O2 %wt	C %wt	N %wt	H %wt	Fe %wt
1	240	138	24	0.18	0.08	0.03	0.015	0.20
2	345	275	20	0.25	0.08	0.03	0.015	0.30
3	450	380	18	0.35	0.08	0.05	0.015	0.30
4	550	483	15	0.40	0.08	0.05	0.015	0.50