High-entropy alloys (HEAs) with an atomic arrangement of a hexagonal closepacked (hcp) structure were found in YGdTbDyLu and GdTbDyTmLu alloys as a nearly single hcp phase. The equi-atomic alloy design for HEAs assisted by binary phase diagrams started with selecting constituent elements with the hcp structure at room temperature by permitting allotropic transformation at a high temperature. The binary phase diagrams comprising the elements thus selected were carefully examined for the characteristics of miscibility in both liquid and solid phases as well as in both solids due to allotropic transformation. The miscibility in interest was considerably narrow enough to prevent segregation from taking place during casting around the equi-atomic composition. The alloy design eventually gave candidates of quinary equi-atomic alloys comprising heavy lanthanides principally. The XRD analysis revealed that YGdTbDyLu and GdTbDyTmLu alloys thus designed are formed into the hcp structure in a nearly single phase. It was found that these YGdTbDyLu and GdTbDyTmLu HEAs with an hcp structure have delta parameter (d) values of 1.4 and 1.6, respectively, and mixing enthalpy (DH mix ) = 0 kJ/mol for both alloys. These alloys were consistently plotted in zone S for disordered HEAs in a d-DH mix diagram reported by Zhang et al. (Adv Eng Mater 10:534, 2008). The value of valence electron concentration of the alloys was evaluated to be 3 as the first report for HEAs with an hcp structure. The finding of HEAs with the hcp structure is significant in that HEAs have been extended to covering all three simple metallic crystalline structures ultimately followed by the body-and facecentered cubic (bcc and fcc) phases and to all four simple solid solutions that contain the glassy phase from high-entropy bulk metallic glasses.

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New bulk glassy alloys were formed in the Ca-Mg-Cu system by the copper mold casting method. The maximum rod diameter (d max ) for the formation of a glassy phase was 2 mm for Ca 67 Mg 19 Cu 14 and above 4 mm for Ca 57 Mg 19 Cu 24 . The glass transition temperature (T g ), crystallization temperature (T x ), supercooled liquid region (∆T x = T x − T g ) and reduced glass transition temperature (T g /T m ) are 387 K, 407 K, 20 K and 0.60, respectively, for the former alloy and 404 K, 440 K, 36 K and 0.64, respectively, for the latter alloy. There is a tendency for d max to increase with increasing ∆T x and T g /T m . Young's modulus (E) and compressive fracture strength are 38 GPa and 545 MPa, respectively, for the Ca 57 Mg 19 Cu 24 alloy rod with a diameter of 2 mm. The success of synthesizing bulk glassy alloys in the simple metal (Ca) base system makes it important as a basic alloy system for examining fundamental chemical and physical properties of bulk glassy alloys.

Ti-based glassy alloy rods with diameters up to 5 mm were prepared for Ti 41:5 Zr 2:5 Hf 5 Cu 42:5 Ni 7:5 Si 1 in a mutli-component system of (Ti, Zr, Hf)-(Cu, Ni)-Si by conventional copper mold casting. The new multi-component glassy alloy exhibits moderate thermal stability with a supercooled liquid region (ÁT x ) above 50 K. The glass transition temperature (T g ), crystallization temperature (T x ), melting temperature (T m ), liquidus temperature (T l ), and the reduced glass transition temperature (T g =T l ) are 680 K, 730 K, 1143 K, 1199 K and 0.57, respectively. The cast glassy alloy exhibits compressive strength of 2080 MPa, tensile strength of 2040 MPa and Young's modulus of 100 GPa. The reason for the high glass-forming ability (GFA) of the Ti-based multi-component alloy is discussed on the basis of knowledge available for bulk glass formation.