Glassy alloy rods with diameters up to 1.5 mm exhibiting a large supercooled liquid region before crystallization and high mechanical strength were formed in Cu-Zr and Cu-Hf binary alloy systems by the copper mold casting method. The large supercooled liquid region exceeding 40 K was obtained in the composition range of 30 to 70 at%Zr and 35 to 60 at%Hf. The largest value of the supercooled liquid region defined by the difference between glass transition temperature (T g ) and crystallization temperature (T x ), ÁT x ð¼ T x À T g ), was 58 K for Cu 60 Zr 40 and 59 K for Cu 55 Hf 45 . The reduced glass transition temperature (T g =T l ) of the two alloys was 0.61 and 0.59, respectively. The alloys with large ÁT x above 50 K were formed into a bulk glassy alloy form with diameters up to 1.5 mm by copper mold casting. The Cu 60 Zr 40 , Cu 45 Zr 55 , Cu 60 Hf 40 and Cu 55 Hf 45 glassy alloy rods exhibited high fracture strength of 1920, 1880, 2245 and 2260 MPa, respectively, Young's modulus of 107, 102, 120 and 121 GPa, respectively, a nearly constant elastic elongation of about 1.9% and plastic elongation up to 2.2%. The formation of these binary glassy alloy rods can be interpreted in the framework of the concept of the formation of the unique glassy structure consisting mainly of icosahedral atomic configuration as similar to that for special multi-component alloys with the three component rules.

New Cu-based bulk glassy alloys with large supercooled liquid region and high mechanical strength were found to be formed in Cu-Zr-Al ternary system. The large supercooled liquid region exceeding 70 K was obtained in the composition range of 40 at%Zr at 2.5 at%Al, 37.5%Zr to 47.5%Zr at 5%Al and 42.5%Zr at 7.5%Al. The largest ∆T x was 74 K for Cu 55 Zr 40 Al 5 and Cu 50 Zr 42.5 Al 7.5 alloys and the highest T g /T l was 0.62 for the former alloy. The alloys with large ∆T x values above 70 K were formed into a bulk glassy rod form with diameters up to 3 mm by copper mold casting and the glassy alloy rods exhibit high compressive strength of 1885 to 2210 MPa and Young's modulus of 102 to 115 GPa combined with elastic elongation of 1.60 to 1.95% and plastic elongation of 0 to 0.4%. The addition of 2.5 to 7.5%Al to Cu-Zr alloys was very effective for the increase in glass-forming ability as well as the stabilization of supercooled liquid. The effectiveness can be interpreted on the basis of the concept of the formation of the unique glassy structure in special multi-component alloys with the three empirical component rules.

This microfluidic flow-stretch chip integrates fluid shear stress (FSS) and cyclic stretch (CS), two major mechanical stimulations in cardiovascular systems, for cultured cells. The model chip can deliver FSS and CS simultaneously or independently to vascular cells to mimic the haemodynamic microenvironment of blood vessels in vivo. By imposing FSS-only, CS-only, and FSS+CS stimulation on rat mesenchymal stem cells and human umbilical vein endothelial cells, we found the alignment of the cellular stress fibers varied with cell type and the type of stimulation. The flow-stretch chip is a reliable tool for simulating the haemodynamic microenvironment.

Bulk glassy Ni-based alloys with high fracture strength exceeding 2700 MPa were prepared in Ni 60 Nb 40−x−y Ti x Zr y system by copper mold casting. The glassy alloys with distinct glass transition were obtained in the wide composition range from 0 to 35%Ti and 0 to 30%Zr and the largest supercooled liquid region before crystallization was 76 K for Ni 60 Nb 15 Ti 10 Zr 15 . The maximum diameter was 2 mm for Ni 60 Nb 20 Ti 15 Zr 5 and the glass transition temperature (T g ), crystallization temperature (T x ) and reduced glass transition temperature (T g /T l ) of the bulk glassy alloy were 841 K, 898 K and 0.61, respectively. The Young's modulus (E), compressive fracture strength (σ c,f ) and compressive fracture elongation (ε c,f ) were 156 GPa, 2770 MPa and 2.4%, respectively, for the bulk alloy. There is a tendency for fracture strength to increase with increasing E, T g and liquidus temperature (T l ). It is therefore interpreted that the high strength is due to strong bonding nature among the constituent elements.

No abstract