TEM study of H and Z phases in rapidly solidified Al-Li-Cu-Mg-Zr alloy

The paper reports a special rotation domain in Z phase and a new tetragonal H phase observed in rapidly solidified Al-Li-Cu-Mg-Zr alloy. The detailed analysis to the sequence of SAD patterns displays that H phase belongs to a lattice with parameters a = 2.8nm, c = 2.4nm and c/a = 0.866. From the HREM image, an orientation relationship between H and Z phase can be given by: [100]H [1120]Z, [010]H [0001]Z, and no obvious phase interface between them would be detected. The orientation relationship between two domains in Z phase, [0001]A [1120]B, [1100]A [1100]B, coinciding with the interface on (1100)A (1100)B, was also displayed. This indicate that the length of the c axis should be that of the a axis for the hexagonal Z phase. Energy spectrum quantitative analysis indicate that H phase might be the metastable phase corresponding to Z phase.