The past tense is "malleableized".
Malleability is a property-noun (also not a verb)[2]
These words do not have "past-tenses"
[1] http://www.oxforddictionaries.com/us/definition/american_eng...
Malleate \Mal"le*ate\, v. t. [imp. & p. p. {Malleated}; p. pr. & vb. n. {Malleating}.] [L. malleatus hammered, fr. malleus a hammer. See {Mall}, v. t.] To hammer; to beat into a plate or leaf. [1913 Webster]