178 research outputs found
Near Surface Modification Affected by Hydrogen Interaction: Global Supplemented by Local Approach
The current study is centered on elastic-plastic solid interaction with hydrogen. Here, the environment isfree hydrogen, from either external or internal origins providing as such aggressive effects. In this context, near surface displacement occurred, beside microcracking onset or growth, significant interfacial weakening, as critical forms of mechanical degradation. Metastable austenitic stainless 316L steel was selected, in order to provide a comprehensive study on bulk surfaces. Globalfindings on hydrogen effects were supplemented by nanoscale information. Only for the nanosection, Ti/Cu thinfilms were also included, namely an additional small-volume case. Samples have been charged with hydrogen under lowfugacity conditions and the outcoming effects have been sorted out by mechanical response tracking assisted by contact mechanics methodology. Nanoindentation and continuous scratch tests were utilized supplemented by Scanning Probe Microscopy (SPM) visualization. Local resolution provided remarkable input to the globalfindings, in terms of dislocation nucleation aspects, near surface modification, plastic localization and microfracture onset. In thin layers, the effective work of the adhesion was reduced indicating significant degradation that could be expressed quantitatively. Global/local benefits of the stainless steel system under study made it possible to apply multiscale models describing complex microΒmechanical processes.Π Π°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°Π΅ΡΡΡ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΠ΅ ΡΠΏΡΡΠ³ΠΎΒ-ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠ²Π΅ΡΠ΄ΠΎΠ³ΠΎ Π²Π΅ΡΠ΅ΡΡΠ²Π° Ρ Π²ΠΎΠ΄ΠΎΡΠΎΒΠ΄ΠΎΠΌ. Π‘ΡΠ΅Π΄ΠΎΠΉ ΡΠ»ΡΠΆΠΈΡ ΡΠ²ΠΎΠ±ΠΎΠ΄Π½ΡΠΉ Π²ΠΎΠ΄ΠΎΡΠΎΠ΄ ΠΎΡ Π²Π½Π΅ΡΠ½Π΅Π³ΠΎ ΠΈΠ»ΠΈ Π²Π½ΡΡΡΠ΅Π½Π½Π΅Π³ΠΎ ΠΈΡΡΠΎΡΠ½ΠΈΠΊΠ°, ΡΡΠΎ ΡΠΎΠ·Π΄Π°Π΅Ρ Π°Π³ΡΠ΅ΡΡΠΈΠ²Π½ΡΠΉ ΡΡΡΠ΅ΠΊΡ. Π ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠ΅ ΠΏΡΠΎΠΈΡΡ
ΠΎΠ΄ΠΈΠ»ΠΎ ΠΏΡΠΈΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠ½ΠΎΠ΅ ΡΠΌΠ΅ΡΠ΅Π½ΠΈΠ΅, ΠΊΡΠΎΠΌΠ΅ Π½Π°ΡΠ°Π»Π° ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΡ ΠΌΠΈΠΊΡΠΎΡΡΠ΅ΡΠΈΠ½ ΠΈΠ»ΠΈ ΠΈΡ
ΡΠΎΡΡΠ° ΠΈ Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠ³ΠΎ ΠΌΠ΅ΠΆΡΠ°Π·Π½ΠΎΠ³ΠΎ ΡΠ°Π·ΒΡΠΏΡΠΎΡΠ½Π΅Π½ΠΈΡ, ΡΡΠΎ ΡΠ²Π»ΡΠ΅ΡΡΡ ΠΎΡΠ½ΠΎΠ²Π½ΡΠΌΠΈ ΠΏΡΠΈΡΠΈΒΠ½Π°ΠΌΠΈ ΠΏΠΎΡΠ΅ΡΠΈ ΠΌΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΏΡΠΎΡΠ½ΠΎΡΡΠΈ. ΠΠ»Ρ Π²ΡΠ΅ΡΡΠΎΡΠΎΠ½Π½Π΅Π³ΠΎ ΠΈΠ·ΡΡΠ΅Π½ΠΈΡ Π²Π½ΡΡΡΠ΅Π½Π½Π΅ΠΉ ΡΡΡΡΠΊΒΡΡΡΡ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ Π±ΡΠ»Π° Π²ΡΠ±ΡΠ°Π½Π° ΠΌΠ΅ΡΠ°ΡΡΠ°Π±ΠΈΠ»ΡΠ½Π°Ρ Π°ΡΡΡΠ΅Π½ΠΈΡΠ½Π°Ρ Π½Π΅ΡΠΆΠ°Π²Π΅ΡΡΠ°Ρ ΡΡΠ°Π»Ρ 316Π. ΠΠ±ΡΠΈΠ΅ Π΄Π°Π½Π½ΡΠ΅ ΠΎ Π΄Π΅ΠΉΡΡΠ²ΠΈΠΈ Π²ΠΎΠ΄ΠΎΡΠΎΠ΄Π° Π±ΡΠ»ΠΈ Π΄ΠΎΠΏΠΎΠ»Π½Π΅Π½Ρ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΠ΅ΠΉ Π½Π° Π½Π°Π½ΠΎΡΡΠΎΠ²Π½Π΅. ΠΠ»Ρ ΠΏΠΎΠ»ΡΡΠ΅Π½ΠΈΡ Π΄Π°Π½Π½ΡΡ
Π½Π° Π½Π°Π½ΠΎΒΡΡΠΎΠ²Π½Π΅ Π±ΡΠ»ΠΈ ΠΈΠ·ΡΡΠ΅Π½Ρ ΡΠΎΠ½ΠΊΠΈΠ΅ ΠΏΠ»Π΅Π½ΠΊΠΈ Ti/Cu, Ρ.Π΅. ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½Ρ ΠΈΡΠΏΡΡΠ°Π½ΠΈΡ Π½Π° ΠΌΠ°Π»ΠΎΠΌ ΠΎΠ±ΡΠ΅ΠΌΠ΅ ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»Π°. ΠΠ±ΡΠ°Π·ΡΡ ΠΎΠ±ΡΠ°Π±Π°ΡΡΠ²Π°Π»ΠΈ Π²ΠΎΠ΄ΠΎΡΠΎΒΠ΄ΠΎΠΌ Π² ΡΡΠ»ΠΎΠ²ΠΈΡΡ
Π½ΠΈΠ·ΠΊΠΎΠΉ Π»Π΅ΡΡΡΠ΅ΡΡΠΈ, Π° ΡΠ΅ΒΠ·ΡΠ»ΡΡΠ°ΡΡ ΠΊΠ»Π°ΡΡΠΈΡΠΈΡΠΈΡΠΎΠ²Π°Π»ΠΈ ΠΏΠΎ ΠΌΠ΅Ρ
Π°Π½ΠΈΒΡΠ΅ΡΠΊΠΎΠΌΡ ΠΎΡΠΊΠ»ΠΈΠΊΡ ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌ ΠΊΠΎΠ½ΡΠ°ΠΊΡΠ½ΠΎΠΉ ΠΌΠ΅Ρ
Π°ΒΠ½ΠΈΠΊΠΈ. ΠΡΠΈΠΌΠ΅Π½ΡΠ»ΠΈ Π½Π°Π½ΠΎΠΈΠ½Π΄Π΅Π½ΡΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΠΈ Π½Π΅ΠΏΡΠ΅ΡΡΠ²Π½ΠΎΠ΅ ΡΠ°ΡΠ°ΠΏΠ°Π½ΡΠ΅ Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ ΡΠΊΠ°Π½ΠΈΡΡΡΡΠ΅ΠΉ ΠΌΠΈΠΊΡΠΎΡΠΊΠΎΠΏΠΈΠΈ. Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ Π»ΠΎΒΠΊΠ°Π»ΡΠ½ΡΡ
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ ΠΏΠΎΡΠ»ΡΠΆΠΈΠ»ΠΈ Π·Π½Π°ΡΠΈΒΡΠ΅Π»ΡΠ½ΡΠΌ Π²ΠΊΠ»Π°Π΄ΠΎΠΌ Π² ΠΎΠ±ΡΠΈΠ΅ Π²ΡΠ²ΠΎΠ΄Ρ, Π²ΠΊΠ»ΡΡΠ°Ρ Π·Π°ΡΠΎΠΆΠ΄Π΅Π½ΠΈΠ΅ Π΄ΠΈΡΠ»ΠΎΠΊΠ°ΡΠΈΠΉ, ΠΏΡΠΈΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠ½ΡΡ ΠΌΠΎΠ΄ΠΈΡΠΈΠΊΠ°ΡΠΈΡ, Π½Π°ΡΠ°Π»ΠΎ ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠΎΠΉ Π»ΠΎΠΊΠ°Π»ΠΈΒΠ·Π°ΡΠΈΠΈ ΠΈ ΠΌΠΈΠΊΡΠΎΡΠ°Π·ΡΡΡΠ΅Π½ΠΈΡ. ΠΡΡΠ΅ΠΊΡΠΈΠ²Π½Π°Ρ ΡΠ°Π±ΠΎΡΠ° Π°Π΄Π³Π΅Π·ΠΈΠΈ Π² ΡΠΎΠ½ΠΊΠΈΡ
ΡΠ»ΠΎΡΡ
ΡΠΌΠ΅Π½ΡΡΠΈΠ»Π°ΡΡ, ΡΡΠΎ ΡΠ²ΠΈΠ΄Π΅ΡΠ΅Π»ΡΡΡΠ²ΡΠ΅Ρ ΠΎ ΡΡΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎΠΌ ΡΠ½ΠΈΠΆΠ΅ΒΠ½ΠΈΠΈ ΠΌΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠ²ΠΎΠΉΡΡΠ², Π²ΡΡΠ°ΠΆΠ°Π΅ΠΌΠΎΠΌ ΠΊΠΎΒΠ»ΠΈΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎ. ΠΡΠ΅ΠΈΠΌΡΡΠ΅ΡΡΠ²Π° Π³Π»ΠΎΠ±Π°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΈ Π»ΠΎΠΊΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄ΠΎΠ² ΠΏΡΠΈ ΠΈΠ·ΡΡΠ΅Π½ΠΈΠΈ Π½Π΅ΡΠΆΠ°ΒΠ²Π΅ΡΡΠ΅ΠΉ ΡΡΠ°Π»ΠΈ ΠΏΠΎΠ·Π²ΠΎΠ»ΠΈΠ»ΠΈ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°ΡΡ ΠΌΠ½ΠΎΠ³ΠΎΡΡΠΎΠ²Π½Π΅Π²ΡΠ΅ ΠΌΠΎΠ΄Π΅Π»ΠΈ, ΠΎΠΏΠΈΡΡΠ²Π°ΡΡΠΈΠ΅ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ½ΡΠ΅ ΠΌΠΈΠΊΡΠΎΠΌΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΏΡΠΎΡΠ΅ΡΡΡ
Hard amorphous hydrogenated carbon films deposited from an expanding thermal plasma
Diamondlike amorphous hydrogenated carbon is deposited from an expanding thermal argon/acetylene plasma. It is observed that the film quality improves with increasing deposition rate. To obtain the best material quality the admixed acetylene flow has to be of comparable magnitude as the argon ion flow from the plasma source (critical loading). A new method to determine the ion density in an argon/acetylene plasma, by probe measurements, is presented. They reveal that the deposition during critical loading is governed by radicals. It is suggested that acetylene is dissociated once and that the C2H radical is formed dominantly
Scale effects for strength, ductility, and toughness in "brittleβ materials
Decreasing scales effectively increase nearly all important mechanical properties of at least some "brittleβ materials below 100 nm. With an emphasis on silicon nanopillars, nanowires, and nanospheres, it is shown that strength, ductility, and toughness all increase roughly with the inverse radius of the appropriate dimension. This is shown experimentally as well as on a mechanistic basis using a proposed dislocation shielding model. Theoretically, this collects a reasonable array of semiconductors and ceramics onto the same field using fundamental physical parameters. This gives proportionality between fracture toughness and the other mechanical properties. Additionally, this leads to a fundamental concept of work per unit fracture area, which predicts the critical event for brittle fracture. In semibrittle materials such as silicon, this can occur at room temperature when the scale is sufficiently small. When the local stress associated with dislocation nucleation increases to that sufficient to break bonds, an instability occurs resulting in fractur
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Fracture of hard thin films using nanoindentation and nanoscratch techniques: A materials and mechanics approach
Thin films are used in many applications where special properties are needed to insure performance and reliability. Of particular interest are thin tantalum nitride films. They are used extensively in microelectronic applications because of their long term stability and low thermal coefficient of resistance. They are sputter deposited which produces films with a high structural defect content and high compressive residual stresses both of which can alter the physical and mechanical properties of microelectronic thin films. Although these films are strong heat generators, they exhibit no changes in structure or composition of the interface with aluminum oxide substrates that degrade performance or reliability. However, the use of high power density components is driving a move to replace aluminum oxide with aluminum nitride for greater heat transfer. 6 This replacement substrate creates concern as residual stresses and long-term operation could induce detrimental changes along the thin film interface not observed in aluminum oxide devices. As a result, the authors employed nanoindentation and continuous nanoscratch testing to determine the effects of the intrinsic compressive residual stresses on the properties and fracture resistance of the thin tantalum nitride films. These techniques sample small volumes of material while preserving the production configuration of a free surface. Although nanoscratch tests lack a rigorous derivation of stress distributions and strain energy release rates, good approximations for strain energy release rates can be obtained using mechanics-based models for blister formation where residual stresses dominate interfacial fracture behavior. When combined with scanning and transmission electron microscopy, the results define structure-property relationships and resistance to fracture of these hard films
Effect of deformation schedule on the microstructure and mechanical properties of a thermomechanically processed C-Mn-Si transformation-induced plasticity steel
Thermomechanical processing simulations were performed using a hot-torsion machine, in order to develop a comprehensive understanding of the effect of severe deformation in the recrystallized and nonrecrystallized austenite regions on the microstructural evolution and mechanical properties of the 0.2 wt pct C-1.55 wt pct Mn-1.5 wt pct Si transformation-induced plasticity (TRIP) steel. The deformation schedule affected all constituents (polygonal ferrite, bainite in different morphologies, retained austenite, and martensite) of the multiphased TRIP steel microstructure. The complex relationships between the volume fraction of the retained austenite, the morphology and distribution of all phases present in the microstructure, and the mechanical properties of TRIP steel were revealed. The bainite morphology had a more pronounced effect on the mechanical behavior than the refinement of the microstructure. The improvement of the mechanical properties of TRIP steel was achieved by variation of the volume fraction of the retained austenite rather than the overall refinement of the microstructure. <br /
Effect of microstructure on the stability of retained austenite in transformation-induced-plasticity steels
Two Fe-0.2C-1.55Mn-1.5Si (in wt pet) steels, with and without the addition of 0.039Nb (in wt pet), were studied using laboratory rolling-mill simulations of controlled thermomechanical processing. The microstructures of all samples were characterized by optical metallography, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The microstructural behavior of phases under applied strain was studied using a heat-tinting technique. Despite the similarity in the microstructures of the two steels (equal amounts of polygonal ferrite, carbide-free bainite, and retained austenite), the mechanical properties were different. The mechanical properties of these transformation-induced-plasticity (TRIP) steels depended not only on the individual behavior of all these phases, but also on the interaction between the phases during deformation. The polygonal ferrite and bainite of the C-Mn-Si steel contributed to the elongation more than these phases in the C-Mn-Si-Nb-steel. The stability of retained austenite depends on its location within the microstructure, the morphology of the bainite, and its interaction with other phases during straining. Granular bainite was the bainite morphology that provided the optimum stability of the retained austenite.<br /
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METASTABLE AUSTENITIC STEELS WITH ULTRA-HIGH STRENGTH AND TOUGHNESS
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Micromechanisms of brittle fracture: Acoustic emissions and electron channeling analyses
The objectives of this work are to: (i) Evaluate the initial stages of cleavage nucleation in single and polycrystalline samples; (ii) Determine the controlling event(s) which lead(s) to unstable cleavage (is it an unstable cluster'' of microcracks or a crack-tip opening displacement criterion for an array of ligaments surrounding these microcracks ); (iii) Determine how the process zone, which depends upon microstructure and processing history, affects the controlling event(s); (iv) Use selected area channeling patterns (SACP's) to assist in an independent measure of the cleavage fracture stress of grains cleaved at or just outside the elastic-plastic boundary; also, use it to evaluate static and dynamic strain distributions; and (v) Evaluate the effects of dislocation shielding and overload using combined methods of computational mechanics with discretized dislocation arrays and direct observations of dislocations using channeling, etch pit and birefringence methods. Accomplishments are discussed. 15 refs., 3 figs
Microstructural approach to fatigue crack processes in polycrystalline bcc materials. Annual technical progress report I
Two commercial low-alloy high-strength steels, four Fe-base alloys, and Ti-30 Mo were evaluated. Dislocation dynamics, strain-rate sensitivity and fatigue and fracture characterization were studied. (FS
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THE MECHANICAL NATURE OP STRESS-CORROSION CRACKING IN Al-Zn-Mg ALLOYS
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