Materials World Network: Structures and Mechanical Behavior of Amorphous Solids Peter K. Liaw, University of Tennessee Knoxville, DMR 0909037 Findings : (1)The high-energy synchrotron diffraction analysis with the pair distribution function (PDF) technique shows that the average atomic distances from load and normal directions (LD and ND) are different during uniaxial compression, indicating an anisotropic deformation behavior for amorphous selenium, as shown in Figure 1. This anisotropic fracture is the result from the anelastisity, and is highly dependent on temperatures and strain rates. (2)Two Zr-based BMGs (Zr 50 Cu 40 Al 10 and Zr 50 Cu 30 Al 10 Ni 10 in atomic percent) are used to study their fatigue behavior at different sample sizes (3x3x25 mm and 2x2x25 mm) using four-point- bend fatigue loading in Figure 2. The stress vs. cycles to failure (S-N) curves demonstrate that BMGs with a large dimension showed longer fatigue lifetime and greater fatigue endurance limits Goals and Objectives : (1)The deformation mechanism of amorphous solids is still not clear. People tend to believe in an isotropic deformation mechanism for amorphous solids due to the lack of ordered lattice structures. However, atoms do not always behave isotropically during deformation. To simplify the amorphous solid system, the one-element amorphous selenium was studied in the present work. (2)Significant bend ductility can be obtained when the sample size of bulk metallic glasses (BMGs) is decreased to a critical value. However, the sample size influence on the fatigue behavior of BMGs is still not clear. Figure 1: Stress relaxation curves at 25% engineering strain at 32 °C. Inserted figures are manipulated diffraction patterns at a certain time. The diffraction ring patterns are obtained at different time: (a) 150 s, (b) 0 500 1000 1500 2000 2500 10 20 30 40 50 60 T ru e S tre s s (M Pa) H old ing T im e (s) A m orphous S e C reep atC onstantE ng ine erin g S tra in 2 5 LD ND a b c e d % Anisotropic visible differences from LD and ND Isotropic Identical LD and ND Figure 2: The applied maximum stress vs. cycles to failure curves for two BMGs with different-size samples under four-point-bend loading.