Variation of long-period stacking order structures in rapidly solidified Mg97Zn1Y2 alloy

The long-period stacking order (LPSO) structures in rapidly solidified Mg97Zn1Y2 alloy have been studied by conventional and high-resolution transmission electron microscopes (HRTEMs). There are four kinds of stacking sequences in the LPSO structures, i.e., 18R of ABABABCACACABCBCBC, 14H of ACBCBABABABCBC, 10H of ABACBCBCAB and 24R of ABABABABCACACACABCBCBCBC. The 18R structure is dominantly observed in the present study. The rest three are occasionally observed in places. The 10H and 24R structures are recently discovered. The lattice constants of 18R( 1   1 ¯   1   1 ¯   2 )3, 14H( 2 ¯   1   2 ¯   1   1 ¯   1   1 ¯   2   1 ¯   2 ), 10H( 1   3 ¯   1   1 ¯   3   1 ¯ ) and 24R( 1   1 ¯   1   1 ¯   1   1 ¯   2 )3 structures are estimated to be a = 0.320 nm and c = 4.678 nm, a = 0.325 nm and c = 3.694 nm, a = 0.325 nm and c = 2.603 nm, a = 0.322 nm and c = 6.181 nm for the hexagonal structure, respectively.