Special Effects in Deformation Mechanism Maps for Austenitic Stainless Steels

2016 ◽  
Vol 869 ◽  
pp. 543-549
Author(s):  
Sergio Neves Monteiro ◽  
Frederico Muylaert Margem ◽  
Lucas Tedesco Bolzan ◽  
George Lobo Nobre Fernandes ◽  
Verônica Scarpini Cândido
Keyword(s):  
Grain Boundary ◽  
Stainless Steels ◽  
Deformation Mechanism ◽  
Austenitic Stainless Steels ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Engineering Systems ◽  
Special Effects ◽  
Operational Life ◽  
Boundary Sliding

The domains of the existence of deformation mechanisms in a map associated with phase transformation and mechanical effects related to aging processes were investigated in austenitic stainless steels. It was also discussed the participation of grain boundary sliding, both as an additional deformation mechanism and a damage accumulation process. A prediction analysis for two typical high temperature engineering systems was attempted based on the map information. This prediction indicates the possibility of grain boundary sliding and creep strain jumps to interfere with the expected operational life of components in these systems operating at high temperatures.

Dislocation Plasticity and Complementary Deformation Mechanisms in Polycrystalline Mg Alloys

2004 ◽  
Vol 449-452 ◽  
pp. 665-668 ◽  
Author(s):  
Junichi Koike
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Deformation Mechanism ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Mg Alloys ◽  
Deformation Mechanisms ◽  
Slip Systems ◽  
Dislocation Plasticity ◽  
Boundary Sliding

Deformation mechanisms of Mg-Al-Zn (AZ31) alloys were investigated by performing tensile test at room temperature. In fine grain Mg alloys deformed at room temperature, nonbasal slip systems were found to be active as well as basal slip systems because of grain-boundary compatibility effect. Slip-induced grain-boundary sliding occurred as a complementary deformation mechanism to give rise to c-axis component of strain. With increasing grain size, the activation of the nonbasal slip systems was limited near grain boundaries. Instead of grain-boundary sliding, twinning occurred as a complementary deformation mechanism in large grained samples. Orientation analysis of twins indicated that twinning is induced by stress concentration due to the pile up of basal dislocations. The grain-size dependence on deformation mechanism was found to affect yielding behavior both microscopically and macroscopically which can influence various mechanical properties such as fatigue and creep.

Research on Micro-Mechanism of Nanocomposite Ceramic in Two-Dimensional Ultrasound Grinding

2007 ◽  
Vol 359-360 ◽  
pp. 344-348 ◽  
Author(s):  
Bo Zhao ◽  
Yan Wu ◽  
Guo Fu Gao ◽  
Feng Jiao
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Deformation Mechanism ◽  
Ground Surface ◽  
Grain Boundary Sliding ◽  
Second Phase ◽  
Two Dimensional ◽  
Composite Ceramics ◽  
Nano Composite ◽  
Boundary Sliding

Surface microstructure of nano-composite ceramics prepared by mixed coherence system and machined by two-dimensional ultrasonic precision grinding was researched using TEM, SEM, XRD detector and other equipments. Structure, formation mechanism and characteristic of metamorphic layer of ground surface of nano-composite ceramics were researched. The experiment shows micro deformation mechanism of ceramic material in two-dimensional ultrasound grinding is twin grain boundary and grain-boundary sliding for Al2O3, and it is crystal dislocation of enhanced phase, matrix grain boundary sliding, coordination deformation of intergranular second phase as well as its deformation mechanism for nano-composite ceramics. The fracture surfaces of nano-composite materials with different microscopic structure were observed using TEM and SEM. Research shows that ZrO2 plays an important influence on the generation and expansion of crack, and enhances the strength of grain boundaries. When grain boundaries is rich in the ZrO2 particles, the crack produced in grinding process will be prevented, and the surface with plastic deformation will be smooth. The results shows nanoparticles dispersed in grain boundary prevents crack propagation and makes materials fracture transgranularly which makes the processed surface fine.

Structure Evolution and Deformation Mechanisms in Ultrafine-Grained Aluminum under Tension at Room Temperature

2010 ◽  
Vol 667-669 ◽  
pp. 915-920
Author(s):  
Konstantin Ivanov ◽  
Evgeny V. Naydenkin
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Structure Evolution ◽  
Dislocation Slip ◽  
Polished Surface ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Boundary Sliding

Deformation mechanisms occurring by tension of ultrafine-grained aluminum processed by equal-channel angular pressing at room temperature are investigated using comparative study of the microstructure before and after tensile testing as well as deformation relief on the pre-polished surface of the sample tested. Deformation behavior and structure evolution during tension suggest development of grain boundary sliding in addition to intragrain dislocation slip. Contribution grain boundary sliding to the overall deformation calculated using the magnitude of shift of grains relative to each other is found to be ~40%.

Research on Surface Microstructures of Nanocomposite Ceramics in Two-Dimensional Ultrasonic Ultraprecision Grinding

2007 ◽  
Vol 364-366 ◽  
pp. 909-913 ◽  
Author(s):  
Bo Zhao ◽  
Jing Lin Tong ◽  
Yan Wu ◽  
Guo Fu Gao
Keyword(s):  
Grain Boundary ◽  
Deformation Mechanism ◽  
Grain Boundary Sliding ◽  
Nano Particles ◽  
Surface Generation ◽  
Second Phase ◽  
Two Dimensional ◽  
Boundary Sliding ◽  
Microscopic Deformation ◽  
Surface Microstructures

Using TEM, SEM and XRD, the surface microstructures of nanocomposite ceramics prepared by heterocoagulation was studied in two-dimensional ultraprecision grinding with ultrasonic assistance. This research was focused on the structure of ground surface degenerating layer, surface generation mechanism and characteristics of nanocomposite ceramic parts. The experimental results showed that the microscopic deformation mechanism of the ordinary Al2O3 parts was grain- boundary twinning and grain-boundary sliding while microscopic deformation mechanism of nanophase ceramic parts was the inner crystal dislocation of strengthened phase with intragranular structure. And its deformation coordination mechanisms were the grain-boundary sliding and coordination deformation of intercrystalline second-phase. The observation on the fracture surfaces of nanocomposite materials with different microscopic structures by TEM and SEM showed that ZrO2 particles had an important effect on the generation and expansion of crack in ceramic parts. The introduction of ZrO2 particles strengthened the interface intensity of grain boundary. If there were rich ZrO2 particles on the grain boundary, the cracks generated during the grinding process would be prevented. Smooth and plastic deformation processing surface was obtained. It was proved further that the nanophase materials behaved transcrystalline fracture due to the nano particles, dispersed in the grain boundary and prevented the expansion of crack. This material’s fracture behavior made favorable surface possible. In the precise grinding of nano materials, the plastic removal mechanism dominated the process. The dislocated depth of the nanocomposite ceramics after grinding was bigger than that of common ceramics, which meant that dislocation increased.

Temperature Dependence of Compressive Deformation Behavior of Mg89Zn4Y7 Extruded LPSO-Phase Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 607-610 ◽  
Author(s):  
Koji Hagihara ◽  
Akihito Kinoshita ◽  
Yuya Sugino ◽  
Michiaki Yamasaki ◽  
Yoshihito Kawamura ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Deformation Behavior ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Petch Relationship ◽  
Lpso Phase ◽  
Boundary Sliding

Deformation mechanisms of Mg89Zn4Y7 (at.%) extruded alloy, which is mostly composed of LPSO-phase, was investigated focusing on their temperature dependence. The yield stress of as-extruded alloy showed extremely high value of ~480 MPa at RT, but it largely decreased to ~130 MPa at 300 °C. The decreasing rate of the yield stress could be significantly reduced, however, by the annealing of specimen at 400 °C, by suppressing the microyielding which is considered to occur related by the grain boundary sliding in restricted regions. The yield stress of the annealed specimens with random textures could be estimated by the Hall-Petch relationship by regarding the length of long-axis of plate-like grains as a grain size between RT and 300 °C. The yield stress of the annealed specimens maintained high values even at 200°C, but it also showed large decreases at 300 °C.

The Compressive Behaviors of the Mg-Zn-Er Alloy Containing I-Phase

2015 ◽  
Vol 1088 ◽  
pp. 227-232
Author(s):  
Ke Liu ◽  
Wen Bo Du ◽  
Zhao Hui Wang ◽  
Shu Bo Li
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Deformation Mechanism ◽  
Basal Plane ◽  
Volume Fraction ◽  
Cast Alloy ◽  
Grain Boundary Sliding ◽  
Moderate Temperature ◽  
Boundary Sliding ◽  
Main Deformation

The microstructure and compressive behaviors of the Mg-Zn-Er alloy reinforced by I-phase were investigated. The XRD results suggested that the as-cast alloy was composed of -Mg and I-phase. During compress test, the deformation mechanism was depended on the test temperature and strain. It indicated that basal plane slip played an important role in deformation at both low and high temperature. However, the main deformation mechanism of the as-cast alloy includes grain boundary sliding and twins forming at the strain of 20% at a moderate temperature (225oC) besides the basal plane slip. Moreover, the DRX occurred at the moderate temperature after the strain of 50%. At high temperature (more than 300oC), the cavity was present, and the volume fraction of the cavities increases with the temperature increasing. At the high temperature, the deformation mechanism of the as-cast alloy is mainly dislocation sliding and climbing.

scholarly journals Syn-kinematic hydration reactions, dissolution-precipitation creep and grain boundary sliding in experimentally deformed plagioclase-pyroxene mixtures

2018 ◽  
Author(s):  
Sina Marti ◽  
Holger Stünitz ◽  
Renée Heilbronner ◽  
Oliver Plümper ◽  
Rüdiger Kilian
Keyword(s):  
Grain Boundary ◽  
Confining Pressure ◽  
Shear Zones ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Dislocation Creep ◽  
Crystallographic Preferred Orientation ◽  
Mafic Rocks ◽  
Boundary Sliding ◽  
Crustal Shear Zones

Abstract. While it is widely observed that mafic rocks are able to exeprience high strains by viscous flow, details on their rheology and deformation mechanisms are poorly constrained. Here, rock deformation experiments on four different, water-added plagioclase-pyroxene mixtures are presented: (i) plagioclase(An60-70) – clinopyroxene – orthopyroxene, (ii) plagioclase(An60) – diopside, (iii) plagioclase(An60) – enstatite and (iv) plagioclase(An01) – enstatite. Samples were deformed in general shear at strain rates of 3 × 10−5 to 3 × 10−6 s−1, 800 °C and confining pressure of 1.0 or 1.5 GPa. Results indicate that dissolution-precipitation creep (DPC) and grain boundary sliding (GBS) are the dominant deformation mechanisms. Coinciding with sample deformation, syn-kinematic mineral reactions yield abundant nucleation of new grains; the resulting intense grain size reduction is considered crucial for the activity of DPC and GBS. In high strain zones dominated by plagioclase, a weak, non-random and geometrically consistent crystallographic preferred orientation (CPO) is observed. Usually, a CPO is considered a consequence of dislocation creep, but the experiments presented here demonstrate that a CPO can develop during DPC and GBS. This study provides new evidence for the importance of DPC and GBS in mid-crustal shear zones within mafic rocks, which has important implications on understanding and modelling of mid-crustal rheology and flow.

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