Crystallization of the supercooled liquid Zr41Ti14Cu12.5Ni10Be22.5

The bulk metallic glass Zr41Ti14Cu12.5Ni10Be22.5 has a high glass forming ability and a wide existence range for the supercooled liquid between glass transition and crystallization. In this temperature range remarkable structural changes are observed, even after short annealing periods. We have studied the crystallization at 623 K and 673 K for different times using transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). After heat treatment of the supercooled liquid at 623 K between 5h and 508 h only a negligible fraction of small crystals (fcc, a=1.0045 nm or monoclinic, a=0.585 nm, b=0.934 nm, c=0.414 nm) is observed, while at 673 K for times between 1 h and 19 h in addition to crystallization of two new phases with fee structure (a=0.406 nm) and with hexagonal structure (a=0.382 nm, c=0.324 nm) in agreement with the ZrBe2, structure occurs. Preannealing at 623 K for 15 h slows down significantly the subsequent crystallization at 673 K. The TEM results are compared with results from X-ray diffractometry (XRD) and with results from small angle neutron scattering (SANS) and are discussed with respect to correlations between amorphous decomposition and crystallization.