L-J PHASE IN A CU2.2MN0.8AL ALLOY

A new type of precipitate (designated L-J phase) with two variants was observed within the (DO3 + L2(I)) matrix in a Cu2.2Mn0.8Al alloy. Tra nsmission electron microscopy examinations indicated that the L-J phas e has an orthorhombic structure with lattice parameters a = 0.413 nm, b = 0.254 nm and c = 0.728 nm. The orientation relationship between th e L-J phase and the matrix is (100)(L-J)//($($) over bar$$ 011)(m), (0 10)(L-J)//(1 ($) over bar 1 ($) over bar 1)(m) and (001)(L-J)//(211)(m ). The rotation axis and rotation angle between two variants of the L- J phase are [021] and 90 deg. The L-J phase has never been observed in various Cu-Al, Cu-Mn, and Cu-Al-Mn alloy systems before.