scholarly journals Microstructural evolution during high-temperature tensile creep at 1,500°C of a MoSiBTiC alloy

2020 ◽  
Vol 39 (1) ◽  
pp. 136-145 ◽  
Author(s):  
Sojiro Uemura ◽  
Shiho Yamamoto Kamata ◽  
Kyosuke Yoshimi ◽  
Sadahiro Tsurekawa
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Grain Boundary Sliding ◽  
Primary Creep ◽  
Tensile Creep ◽  
Tertiary Creep ◽  
Continuous Dynamic Recrystallization ◽  
Continuous Dynamic ◽  
Creep Regime

AbstractMicrostructural evolution in the TiC-reinforced Mo–Si–B-based alloy during tensile creep deformation at 1,500°C and 137 MPa was investigated via scanning electron microscope-backscattered electron diffraction (SEM-EBSD) observations. The creep curve of this alloy displayed no clear steady state but was dominated by the tertiary creep regime. The grain size of the Moss phase increased in the primary creep regime. However, the grain size of the Moss phase was found to remarkably decrease to <10 µm with increasing creep strain in the tertiary creep regime. The EBSD observations revealed that the refinement of the Moss phase occurred by continuous dynamic recrystallization including the transformation of low-angle grain boundaries to high-angle grain boundaries. Accordingly, the deformation of this alloy is most likely to be governed by the grain boundary sliding and the rearrangement of Moss grains such as superplasticity in the tertiary creep regime. In addition, the refinement of the Moss grains surrounding large plate-like T2 grains caused the rotation of their surfaces parallel to the loading axis and consequently the cavitation preferentially occurred at the interphases between the end of the rotated T2 grains and the Moss grains.

scholarly journals Finite element modelling of microstructural changes during equal channel angular drawing of pure aluminium

2021 ◽  
Author(s):  
Serafino Caruso ◽  
Stano Imbrogno
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Finite Element ◽  
Size Variation ◽  
Fe Model ◽  
Pure Aluminium ◽  
Continuous Dynamic Recrystallization ◽  
Research Activities ◽  
Hardness Change ◽  
Continuous Dynamic

AbstractGrain refinement by severe plastic deformation (SPD) techniques, as a mechanism to control microstructure (recrystallization, grain size changes,…) and mechanical properties (yield strength, ultimate tensile strength, strain, hardness variation…) of pure aluminium conductor wires, is a topic of great interest for both academic and industrial research activities. This paper presents an innovative finite element (FE) model able to describe the microstructural evolution and the continuous dynamic recrystallization (CDRX) that occur during equal channel angular drawing (ECAD) of commercial 1370 pure aluminium (99.7% Al). A user subroutine has been developed based on the continuum mechanical model and the Hall-Petch (H-P) equations to predict grain size variation and hardness change. The model is validated by comparison with the experimental results and a predictive analysis is conducted varying the channel die angles. The study provides an accurate prediction of both the thermo-mechanical and the microstructural phenomena that occur during the process characterized by large plastic deformation.

Numerical Modeling of Continuous Dynamic Recrystallization in Sn-Based Solder Connection Under Cyclic Loading

2021 ◽  
Author(s):  
Marta Kuczynska ◽  
Ulrich Becker ◽  
Youssef Maniar ◽  
Steffen Weihe
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Cyclic Load ◽  
Fe Simulation ◽  
Operation Time ◽  
Inelastic Strain ◽  
Parameter Study ◽  
Continuous Dynamic Recrystallization ◽  
Gradual Evolution ◽  
Continuous Dynamic

Abstract The reoccurring cyclic load imposed onto soldered electronic components during their operation time leads to accumulation of inelastic strains in the structure. On a microscale level, the degree of plastic deformation is determined by the formation and annihilation of dislocations, leading to continuous refinement by creation of new grain boundaries, precipitates relocation and growth. This microstructure rearrangement, triggered by an increasing amount of inelastic deformation, is defined as dynamic recrystallization. This work presents a macroscale modelling approach for the description of continuous dynamic recrystallization observed in Sn-based solder connections. The model used in this work describes kinetics of macroscopic gradual evolution of equivalent grain size, where the initial grain size is continuously refined with increasing accumulated inelastic strain until a saturation grain size is reached. The rate and distribution of dynamic recrystallization is further numerically modelled dependent on the effective accumulated inelastic strain and governing stress multiaxiality. A parameter study of the presented model and its employment in finite element (FE) simulation is further described. Finally, FE simulation of the grain size evolution is demonstrated on an example of a bulky sample under isothermal cyclic mechanical loading, as well as a BGA-like structure under tensile, shear and mixed mode cyclic load.

scholarly journals Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing

Solid Earth ◽  
2017 ◽  
Vol 8 (6) ◽  
pp. 1193-1209 ◽  
Author(s):  
James Gilgannon ◽  
Florian Fusseis ◽  
Luca Menegon ◽  
Klaus Regenauer-Lieb ◽  
Jim Buckman
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Finite Strain ◽  
Grain Boundary Sliding ◽  
Large Strains ◽  
Cavity Formation ◽  
Phase Mixing ◽  
Transient Phenomena ◽  
Boundary Sliding

Abstract. Establishing models for the formation of well-mixed polyphase domains in ultramylonites is difficult because the effects of large strains and thermo-hydro-chemo-mechanical feedbacks can obscure the transient phenomena that may be responsible for domain production. We use scanning electron microscopy and nanotomography to offer critical insights into how the microstructure of a highly deformed quartzo-feldspathic ultramylonite evolved. The dispersal of monomineralic quartz domains in the ultramylonite is interpreted to be the result of the emergence of synkinematic pores, called creep cavities. The cavities can be considered the product of two distinct mechanisms that formed hierarchically: Zener–Stroh cracking and viscous grain-boundary sliding. In initially thick and coherent quartz ribbons deforming by grain-size-insensitive creep, cavities were generated by the Zener–Stroh mechanism on grain boundaries aligned with the YZ plane of finite strain. The opening of creep cavities promoted the ingress of fluids to sites of low stress. The local addition of a fluid lowered the adhesion and cohesion of grain boundaries and promoted viscous grain-boundary sliding. With the increased contribution of viscous grain-boundary sliding, a second population of cavities formed to accommodate strain incompatibilities. Ultimately, the emergence of creep cavities is interpreted to be responsible for the transition of quartz domains from a grain-size-insensitive to a grain-size-sensitive rheology.

scholarly journals Microstructural Evolution and Mechanical Properties of Friction Stir Welded Butt Joints of 5A06 Alloy Ultra-Thin Sheets

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3906 ◽  
Author(s):  
Yang Han ◽  
Xiaoqing Jiang ◽  
Tao Yuan ◽  
Shujun Chen ◽  
Dongxiao Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Welding Speed ◽  
Base Material ◽  
Thin Plates ◽  
Al Alloy ◽  
Minimum Thickness ◽  
Friction Stir

Ultra-thin plates have great potential for applications in aircraft skin, the packaging industry, and packaging of electronic products. Herein, 1 mm-thick 5A06 Al alloy was welded with friction stir welding. The microstructural evolution of the welds was investigated in detail with optical microscopy, scanning electron microscopy, and electron backscatter diffraction. The results showed that the friction stir welds of 1 mm-thick 5A06 Al alloy were well formed without obvious defect and with a minimum thickness reduction of 0.025 mm. Further, the grain size and the proportion of low-angle grain boundaries decreased with decreasing welding speed, because of the increasing degree of dynamic recrystallization. Among all of the welded joints, the welding speed of 100 mm/min yielded the smallest grain size and the highest proportion of high-angle grain boundaries, and thus the best mechanical properties. Specifically, the tensile strength of the joint was greater than that of the base material, while the elongation reached 80.83% of the base material.

Characterization of Zinalco Alloy Superplastically Deformed Using Orientation Imaging Microscopy

2009 ◽  
Vol 1242 ◽  
Author(s):  
Ramos A. Mitsuo ◽  
Martínez F. Elizabeth ◽  
Negrete S. Jesús ◽  
Torres-Villaseñor G.
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Superplastic Deformation ◽  
Orientation Imaging Microscopy ◽  
Grain Boundary Sliding ◽  
Boundary Misorientation ◽  
Average Grain Size ◽  
Grain Boundary Misorientation ◽  
Misorientation Angles

ABSTRACTZinalco alloy (Zn-21mass%Al-2mass%Cu) specimens were deformed superplastically with a strain rate (ε) of 1×10-3 s-1 at homologous temperature (TH) of 0.68 (5 ). It was observed neck formation that indicate nonhomegeneus deformation. Grain size and grain boundaries misorientation changes, due superplastic deformation, were characterized by Orientation Imagining Microscopy (OIM) technique. It was studied three regions in deformed specimens and the results were compared with the results for a specimen without deformation. Average grain size of 1 mm was observed in non-deformed specimen and a fraction of 82% for grain boundary misorientation angles with a grain boundaries angles between 15° and 55° was found. For deformed specimen, the fraction of angles between 15° and 55° was decreced to average value of 75% and fractions of low angle (<5°) and high angle (>55°) misorientations were 10% and 15% respectively. The grain size and high fraction of grain boundary misorientation angles between 15° and 55° observed in the alloy without deformation, are favorable for grain rotation and grain boundary sliding (GBS) procces. The changes observed in the fraction of favorable grain boundary angles during superplastic deformation, shown that the superplastic capacity of Zinalco was reduced with the deformation.

Microstructural Evolution and Deformation Mechanisms for Superplasticity of NiAl Intermetallic

2005 ◽  
Vol 475-479 ◽  
pp. 2995-2998
Author(s):  
Jian Ting Guo ◽  
Rong Shi Chen ◽  
Xing Hao Du ◽  
Gu Song Li ◽  
Lan Zhang Zhou
Keyword(s):  
Electron Microscopy ◽  
Microstructural Evolution ◽  
Superplastic Deformation ◽  
Tensile Elongation ◽  
Deformation Mechanisms ◽  
High Angle ◽  
Continuous Dynamic Recrystallization ◽  
Transmission Electron ◽  
Continuous Dynamic ◽  
Temperature Strain

The microstructural evolution during superplastic deformation of the extruded stoichiometric NiAl polycrystals were systemically investigated in various conditions of temperature, strain rate and strain by means of optical microscopy (OM) and transmission electron microscopy (TEM). Consequently, The deformation microstructures corresponding to the large tensile elongation consisted of subgrains, low angle grains as well as high angle grains, which indicated that continuous dynamic recrystallization (CDRX) process was operating during superplastic deformation.

scholarly journals Effects of Repetitive Upsetting Extrusion on the Microstructure and Texture of GWZK124 Alloy under Different Starting Temperatures

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2437
Author(s):  
Guanshi Zhang ◽  
Zhimin Zhang ◽  
Yingze Meng ◽  
Zhaoming Yan ◽  
Xin Che ◽  
...  
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Bimodal Microstructure ◽  
Continuous Dynamic Recrystallization ◽  
Average Grain Size ◽  
Second Phases ◽  
Continuous Dynamic ◽  
Weak Texture

The effects of repetitive upsetting extrusion under different starting temperatures on the microstructure and texture of GWZK124 alloy were investigated. The results clearly showed that the particles and second phases induced dynamic recrystallization (DRX), which can be explained by the particle-stimulated nucleation (PSN) mechanism. It was shown that grain refinement during repetitive upsetting extrusion (RUE) is dominated by a complicated combination of continuous dynamic recrystallization and discontinuous dynamic recrystallization. The RUEed alloys under different starting temperatures exhibited a bimodal microstructure comprising fine DRXed grains with weak texture and coarse deformed grains with strong texture. The DRXed grains could weaken the texture. As the RUE starting temperature decreased, the average grain size increased and the volume fraction of DRXed grains decreased.

β Microtexture Analysis in Correlation with HCP Textured Regions Observed in a Forged Near Alpha Titanium Alloy

2005 ◽  
Vol 105 ◽  
pp. 127-132 ◽  
Author(s):  
Philippe Bocher ◽  
Mohammad Jahazi ◽  
Lionel Germain ◽  
Priti Wanjara ◽  
Nathalie Gey ◽  
...  
Keyword(s):  
Grain Size ◽  
Titanium Alloy ◽  
Thermomechanical Processing ◽  
Continuous Dynamic Recrystallization ◽  
Orientation Image Microscopy ◽  
Average Grain Size ◽  
Alpha Titanium ◽  
Imi 834 ◽  
Continuous Dynamic ◽  
The Relationship

The presence of hcp regions with grains having relatively close orientations has been reported in commercial near alpha titanium billets (IMI 834, Ti 6246, etc). The size of these textured regions (called macrozones) is significantly larger than the average grain size of the microstructure observed after thermomechanical processing. The elongated shape of these large hcp regions suggests that they are eventually related to large prior b grains that pancaked during the ingot break down process. In this contribution, Orientation Image Microscopy was used to study the relationship between the hcp local microtexture heterogeneities and the prior b orientations. Specifically, the orientations of the primary (equiaxed) ap grains and the secondary (lamellar) as colonies produced after the transformation of the b phase were discriminated from OIM maps. Furthermore, from the as inherited OIM map, it was possible to reconstruct the corresponding b OIM map over large regions. The analysis showed that the large hcp macrozones observed in the as received material are not related to corresponding bcc macrozones. However, within an hcp macrozone, various clusters of b grains with similar orientations can be found. In such coherent regions, randomly orientated b grains were also observed, which could be related to microstructural changes during deformation (continuous dynamic recrystallization) as suggested by hot deformation results.

scholarly journals The effect of particles on dynamic recrystallization and fabric development of granular ice during creep

2005 ◽  
Vol 51 (174) ◽  
pp. 377-382 ◽  
Author(s):  
Min Song ◽  
Ian Baker ◽  
David M. Cole
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Mechanical Behavior ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Nucleation Rate ◽  
Random Orientation ◽  
Water Ice ◽  
Average Grain Size ◽  
Prepared Particle

AbstractThe mechanical behavior and microstructural evolution of laboratory-prepared, particle-free fresh-water ice and ice with 1 wt.% (~0.43 vol.%) silt-sized particles were investigated under creep with a stress level of 1.45 MPa at −10°C. The particles were present both within the grains and along the grain boundaries. The creep rates of specimens with particles were always higher than those of particle-free ice. Dynamic recrystallization occurred for both sets of specimens, with new grains nucleating along grain boundaries in the early stages of creep. The ice with particles showed a higher nucleation rate. This resulted in a smaller average grain-size for the ice with particles after a given creep strain. Fabric studies indicated that ice with particles showed a more random orientation of c axes after creep to ~10% strain than the particle-free ice.

scholarly journals Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing

2017 ◽  
Author(s):  
James Gilgannon ◽  
Florian Fusseis ◽  
Luca Menegon ◽  
Klaus Regenauer-Lieb ◽  
Jim Buckman
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Finite Strain ◽  
Grain Boundary Sliding ◽  
Cavity Formation ◽  
Phase Mixing ◽  
Creep Cavity ◽  
Boundary Sliding

Abstract. The dispersal of monomineralic quartz domains in a quartzofeldspathic ultramylonite is interpreted to be the result of the emergence of syn-kinematic pores, called creep cavities. The cavities can be considered the product of two distinct mechanisms that formed hierarchically: Zener-Stroh cracking and viscous grain boundary sliding. In initially thick and coherent quartz ribbons deforming by grain size-insensitive creep, cavities were generated by the Zener-Stroh mechanism on grain-boundaries aligned with the YZ plane of finite strain. The opening of creep cavities promoted the ingress of fluids to sites of low stress. The local addition of a fluid lowered the adhesion and cohesion of grain-boundaries and promoted viscous grain boundary sliding. With the increased contribution of viscous grain boundary sliding, a second population of cavities formed to accommodate strain incompatibilities. Ultimately, the emergence of creep cavities is interpreted to be responsible for the transition of quartz domains from a grain size-insensitive, to a grain size-sensitive rheology.

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