Yes, TITANIUMS is a Scrabble word!

Letter values in Scrabble US: T 1, I 1, T 1, A 1, N 1, I 1, U 1, M 3, S 1.

Is it a valid word?

TITANIUMS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a light strong grey lustrous corrosion-resistant metallic element used in strong lightweight alloys (as for airplane parts); the main sources are rutile and ilmenite

Also: atomic number 22.