Fatigue and fracture behavior of bulk metallic glass

Abstract

Tensile, compressive, cyclic tension-tension, and cyclic compression-compression tests at room temperature were systematically applied to a Zr 52.5 Cu 17.9 Al 10 Ni 14.6 Ti 5 bulk metallic glass for comprehensive understanding of its damage and fracture mechanisms. Under tensile loading, the metallic glass only displays elastic deformation followed by brittle shear fracture. Under compressive loading, after elastic deformation, obvious plasticity (0.5 to 0.8 pct) can be observed before the final shear fracture. The fracture strength under compression is slightly higher than that under tension. The shear fracture under compression and tension does not occur along the maximum shear stress plane. This indicates that the fracture behavior of the metallic glass does not follow the Tresca criterion. The fracture surfaces show remarkably different features, i.e., a uniform vein structure (compressive fracture) and round cores coexisting with the radiating veins (tensile fracture). Under cyclic tension-tension loading, fatigue cracks are first initiated along localized shear bands on the specimen surface, then propagated along a plane basically perpendicular to the stress axis. A surface damage layer exists under cyclic compression-compression loading. However, the final failure also exhibits a pure shear fracture feature as under uniaxial compression. The cyclic compression-compression fatigue life of the metallic glass is about a factor of 10 higher than the cyclic tensiontension fatigue life at the same stress ratio. Based on these results, the damage and fracture mechanisms of the metallic glass induced by uniaxial and cyclic loading are elucidated.

Compression-Compression Fatigue and Fracture Behaviors of Zr<SUB>50</SUB>Al<SUB>10</SUB>Cu<SUB>37</SUB>Pd<SUB>3</SUB> Bulk-Metallic Glass

“…Generally, the fatigue-endurance limit is affected by the strength, and the fatigue life is dominated by the crack-propagation region for bulk-metallic glass. 10,12,16) can also be understood. The compression strength is usually higher than the tension strength.…”

“…[7][8][9][10] However, few compression-compression fatigue studies were performed. 11,12) The stress state of the compression-compression fatigue is significantly different from threepoint-bend, four-point-bend, and tension-tension fatigue. Are the fatigue life and fatigue-endurance limit different for fatigue tests under various loading conditions?…”

Structural Relaxation and Crystallization of a Zr<SUB>44</SUB>Ti<SUB>11</SUB>Cu<SUB>9.8</SUB>Ni<SUB>10.2</SUB>Be<SUB>25</SUB> Bulk Metallic Glass

“…1,2) Among them, Zrbased bulk metallic glasses have especially attracted great interest due to their excellent mechanical properties in terms of strength, hardness, elastic response and fatigue at room temperature. [3][4][5][6] In addition, these alloys also exhibit enhanced ductility and good formability during homogeneous viscous flow within the supercooled liquid state, enabling near-net-shape fabrication by conventional mold casting followed by warm deformation and possibly promising various applications as structural materials. [7][8][9][10][11][12][13] These Zrbased metallic glasses show, however, an easy tendency to crystallize when annealed or deformed for considerable time in the supercooled liquid region even below the crystallization temperature, which affects many different physical properties of the material.…”

Properties of Bulk Metallic Glasses

“…Это свидетельствует о высокой чувствительности ОМС к микроскопи-ческим дефектам и концентраторам напряжений. В то же время усталостные характеристики сплавов ОМС на основе циркония сопоставимы со свой-ствами высокопрочных кристаллических спла-вов [55,56].…”

“…1, a показывает изменение значений С р сплава Zr 55 Cu 30 Al 10 Ni 5 в зависимости от темпера-туры при постоянной скорости нагрева в диффе-ренциальном сканирующем калориметре (ДСК) ν = 0,67 К/с (40 K/мин). Начальная величина те-плоемкости сплава в стеклообразном состоянии несколько ниже 25 Дж/(моль·K) и возрастает более или менее монотонно с температурой.…”