Fracture Behavior and Delamination Toughening of Molybdenum in Charpy Impact Tests

Abstract

This study combines advanced characterization techniques with conventional Charpy impact tests to relate the mechanical properties to the microstructure of technically pure molybdenum, especially regarding its toughness. V-notched samples with different orientations were prepared from a rolled molybdenum plate in stress-relieved and recrystallized condition. The ductile-tobrittle transition-temperature was analyzed in terms of the delamination behavior influenced by the microstructure. A pronounced increase of toughness was found for specific oriented samples, which can be explained by macroscopic delamination. Elongated grains led to enhanced delamination in Charpy impact tests with variations for different orientations. In general, delamination occurs as a result of brittle fracture; however, an increase in toughness in the Charpy impact test can be provoked. This mechanism is called thin sheet toughening or delamination toughening. Electron backscatter diffraction measurements were performed to get a deeper knowledge about crack propagation and delamination behavior in the rolled plate. Recrystallization shifts the transition region to significantly higher temperatures, which is explained by the globular grain shape as well as grain boundary segregation. The occurrence of delamination is discussed, taking texture, grain shape and segregation effects into account.

Thermally activated dislocation mechanism in Mo studied by indentation, compression and impact testing

“…2d). A similar fracture behavior was observed by Babinsky et al [27]. Dislocation slip becomes easier with an increase in temperature due to a reduction in the flow strength of Mo.…”

“…There are several publications dealing with the BDT or the temperature-dependent mechanical properties of Mo and its alloys [18,[20][21][22][23][24][25][26][27]. In the most studies, tensile or impact tests were carried out.…”

“…It is unclear how the thermally activated dislocation mobility changes in this high dislocation density region. In addition, different strengthening mechanisms, like grain boundaries or dislocation hardening, will influence the underlying mechanism and change the BDT behavior [6,9,26,27].…”

Brittle fracture resistance and damping properties of layered metal-polymer composites

“…Давление прессования составило 7. [15,16,17]. При знакопеременном циклическом нагружении образцов слоистых композитов по «мягкой» схеме (с контролем по нагрузке) при максимальной нагрузке в полуцикле растяжения и сжатия 12 кН и величине напряжения 80 МПа, отнесенного к сечению всего композита и не превышающего его предварительно определенный статический предел упругости, в течение всех 100 циклов нагружения были зафиксированы выраженные петли механического гистерезиса в координатах «напряжение-деформация».…”

Microstructure and brittle fracture resistance of layered steel composites produced by explosion welding and pack rolling followed by heat treatment

“…At first, the layered structure and, in particular, the appearances of delaminations at the dissimilar steel joints of the studied materials inhibit the development of the main crack and contribute to the crack initiation in each layer [18 -19]. Such mechanical behavior of layered materials at dynamic loading gives a rise of impact strength characteristics due to the realization of the "delamination toughening" effect [20]. At second, the transition of the triaxial stress state in each layer into a biaxial (flat) layer, which is less dangerous for the fracture process, leads to the crack growth retardation [21].…”