H.R.3074 - Common Cents Act (passed by House) - contains the following provisions regarding changing the composition of the nickel.
(1) IN GENERAL.—The 5-cent coin may be a coin with an inner layer of zinc and an outer layer of nickel.
(2) COMPOSITION.—The Secretary may prescribe the composition of zinc and nickel in the 5-cent coin, subject to testing and evaluation that such composition—
(A) reduces the cost incurred to produce such coin; and
(B) to the greatest extent practicable, has a minimal adverse impact on machines designed to accept coins.;