No. It is impossible for the action of an angel, or of any creature, to be its own substance because it would be necessary for it to be subsisting (since a subsisting act of intelligence can be but one) and consequently an angel's substance would neither be distinguished from God's substance, which is His very act of understanding subsisting in itself, nor from the substance of another angel.
It is impossible for anything which is not a pure act, but which has some admixture of potentiality, to be its own actuality: because actuality is opposed to potentiality. But God alone is pure act. Hence only in God is His substance the same as His existence and His action.