Deformation mechanisms of bulk metallic glass matrix composites

摘要: Bulk metallic glasses (BMGs) possess a unique set of mechanical properties that make them attractive structural materials: yield strength > 2 GPa, fracture toughness ~20 MPa.m1/2 and elastic strain limit ~2%. BMGs can also be cast into intricate shapes which retain their dimensional integrity require no further machining. Unfortunately, monolithic fail catastrophically under unconstrained loading by forming shear bands. To overcome this problem, BMG matrix composites with fiber dendritic reinforcements were proposed. The former type includes fibers Ta, Mo stainless steel. latter develop precipitates during casting are thus called in-situ composites. Here, the form an interpenetrating structure enhance ductility composite. This study investigated deformation behavior these two types Loading measurements performed neutron or high-energy X-ray diffraction to determine lattice strains in crystalline reinforcements. data then combined finite element self-consistent modeling deduce amorphous matrix, as well understand effective mechanisms composite. The wire was studied using integrated (FE) approach. FE model yielded reasonable version stress-strain plots for both matrix. It found first started transferring load remained throughout whole experiment. seen strengths lower than forms, likely due annealing processing. After optimizing material fit experimental data, developed reasonably successful describing macroscopic composite evolution reinforcements. In case composites, detailed high energy conducted model. compressive second phase (in its form) investigated. shown ductile yields upon followed multiple band formation process enhances composite. discovered reinforcements, indirectly composite, highly variable quite sensitive processing conditions. This resulted from unstable nature BCC beta tend transform ordered leading significant stiffening, but loss ductility. An additional heat treatment confirmed evolution. The overall conclusion is induce bands turn latter’s point, need stiff. These best optimized via judicious combination microstructure control treatment.