Small-angle x-ray scattering study of the formation and growth of δ' in binary Al－7.87at% Li alloy

The formation and growth of δ' particles in an alloy of Al－7.87at% Li have been investigated using the small angle x-ray scattering technique. It has been shown that a transition zone, which exists between the δ' phase and the matrix after ageing for 16 h, disappears after ageing for 32 h. The existence of a transition zone indicates that the δ' phase is precipitated in the process of spinodal decomposition. This result also indicates that the growth of δ' particles should be divided into two stages. During the first stage, the δ' phase increases eating up the transition zone before ageing for 32 h, and in the second stage it grows by swallowing up each other after ageing for 32 h. In the latter stage, the larger and smaller δ' particles can coexist in the alloy.