Superplastic Deformation of YBa2Cu3O7−x in a Superplastic Metal Matrix

1990 ◽  
Vol 196 ◽  
Author(s):  
J. Emilio Moreno ◽  
G. Torres-Villasefor
Keyword(s):  
Grain Boundaries ◽  
Room Temperature ◽  
Meissner Effect ◽  
Grain Boundary Sliding ◽  
New Class ◽  
Fine Grain ◽  
The Matrix ◽  
High Transition ◽  
Boundary Sliding ◽  
Zn Alloy

ABSTRACTThe new class of high-transition-temperature ceramic superconductors (e.g. Y-Ba-Cu-O) show a fine grain size polycrystalline structure, similar to that shown by the superplastic metals. The material behaves in a brittle manner with a strain to fracture below 0.5 % at room temperature. One of the reasons for this mechanical behavior is that the grain boundaries are easily separated when a stress is applied. It was found in this work that a deformation of the superconductor ceramic (scc) in superplastic metal (spin) matrix reduces the separation of the grain boundaries in such materials so that they can be deformed at room temperature. The spin matrixes used in this work were Zn-Cd, Bi-Sn and Cd-Sn. It was found that the highest the yield point of the matrix the highest the deformation induced in the scc. The Cd-Zn alloy was the most effective in avoiding the separation of the grain boundaries during the deformation of a composite formed by a cylinder of scc embedded in a spin matrix. Meissner effect was observed in the scc, after more than 160 % of plastic deformation. SEM observations show that deformation takes place by grain boundary sliding and some grain refinement was observed.

Microstructure and Mechanical Properties of Ni3Al-Ai2O3 Composites Produced by Hot Extrusion

1990 ◽  
Vol 194 ◽  
Author(s):  
C. G. McKamey ◽  
E. H. Lee
Keyword(s):  
Room Temperature ◽  
Hot Extrusion ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Diffusional Creep ◽  
Superplastic Behavior ◽  
Fine Grain ◽  
Boundary Sliding ◽  
Microstructural Studies ◽  
Better Than

AbstractHot extrusion of premixed charges of 10–20 vol% chopped A12O fiber and Ni3Al powder has resulted in composite alloys of near theoretical density. In tensile tests at room temperature, density-compensated yield strengths of some of these composite alloys are as good or better than those of as-cast Ni3Al without reinforcement; however strengths at 1000°C in vacuum are lower. The low strength at 1000°C and fine grain size (2–3/μm) suggest the presence of superplastic behavior and the accompanying diffusional creep and grain boundary sliding. This presentation discusses our findings to date and includes microstructural studies and tensile properties, both at room temperature in air and 1000°C in vacuum.

scholarly journals Is Superplasticity in the Future of Nanophase Materials?

1990 ◽  
Vol 196 ◽  
Author(s):  
R. W. Siegel
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Atomic Clusters ◽  
Diffusional Creep ◽  
Ultrafine Grain ◽  
Grain Sizes ◽  
Nanophase Materials ◽  
Boundary Sliding

ABSTRACTThe ultrafine grain sizes and high diffusivities in nanophase materials assembled from atomic clusters suggest that these materials may have a strong tendency toward superplastic mechanical behavior. Both small grain size and enhanced diffusivity can be expected to lead to increased diffusional creep rates as well as to a significantly greater propensity for grain boundary sliding. Recent mechanical properties measurements at room temperature on nanophase Cu, Pd, and TiO2, however, give no indications of superplasticity. Nonetheless, significant ductility has been clearly demonstrated in these studies of both nanophase ceramics and metals. The synthesis of cluster-assembled nanophase materials is described and the salient features of what is known of their structure and mechanical properties is reviewed. Finally, the answer to the question posed in the title is addressed.

Microstructure of Friction Stir Processed Mg-Y-Zn Alloy

2007 ◽  
Vol 558-559 ◽  
pp. 777-780 ◽  
Author(s):  
Taiki Morishige ◽  
Masato Tsujikawa ◽  
Sung Wook Chung ◽  
Sachio Oki ◽  
Kenji Higashi
Keyword(s):  
Equal Channel Angular Extrusion ◽  
Second Phase ◽  
Ingot Metallurgy ◽  
Friction Stir ◽  
Fine Grained ◽  
Probe Diameter ◽  
Fine Grain ◽  
Second Phase Particles ◽  
The Matrix ◽  
Zn Alloy

Friction stir processing (FSP) is the effective method of the grain refinement for light metals. The aim of this study is to acquire the fine grained bulk Mg-Y-Zn alloy by ingot metallurgy route much lower in cost. Such bulk alloy can be formed by the superplastic forging. The microstructure of as-cast Mg-Y-Zn alloy was dendrite. The dendrite arm spacing was 72.5 [(m], and there are the lamellar structures in it. FSP was conducted on allover the plate of Mg-Y-Zn alloy for both surfaces by the rotational tool with FSW machine. The stirring passes were shifted half of the probe diameter every execution. The dendrite structures disappeared after FSP, but the lamellar structure could be observed by TEM. The matrix became recrystallized fine grain, and interdendritic second phase particles were dispersed in the grain boundaries. By using FSP, cast Mg-Y-Zn alloy could have fine-grained. This result compared to this material produced by equal channel angular extrusion (ECAE) or rapid-solidified powder metallurgy (RS P/M). As the result, as-FSPed material has the higher hardness than materials produced by the other processes at the similar grain size.

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.

Enhanced Grain-Boundary Sliding at Room Temperature in AZ31 Magnesium Alloy

2003 ◽  
Vol 419-422 ◽  
pp. 237-242 ◽  
Author(s):  
R. Ohyama ◽  
Junichi Koike ◽  
T. Kobayashi ◽  
Mayumi Suzuki ◽  
Kouichi Maruyama
Keyword(s):  
Magnesium Alloy ◽  
Grain Boundary ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Az31 Magnesium Alloy ◽  
Boundary Sliding

Superplasticity of Aerospace 7075 (Al-Zn-Mg-Cu) Aluminium Alloy Obtained by Severe Plastic Deformation

2018 ◽  
Vol 385 ◽  
pp. 39-44 ◽  
Author(s):  
Fernando Carreño ◽  
Oscar A. Ruano
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Aluminium Alloy ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
Aerospace Applications ◽  
Boundary Sliding ◽  
Processing Stress

The 7075 (Al-Zn-Mg-Cu) aluminium alloy is the reference alloy for aerospace applications due to its specific mechanical properties at room temperature, showing excellent tensile strength and sufficient ductility. Formability at high temperature can be improved by obtaining superplasticity as a result of fine, equiaxed and highly misoriented grains prone to deform by grain boundary sliding (GBS). Different severe plastic deformation (SPD) processing routes such as ECAP, ARB, HPT and FSP have been considered and their effect on mechanical properties, especially at intermediate to high temperatures, are studied. Refined grains as fine as 100 nm and average misorientations as high as 39o allow attainment of high strain rate superplasticity (HSRSP) at lower than usual temperatures (250-300oC). It is shown that increasing misorientations are obtained with increasing applied strain, and increasing grain refinement is obtained with increasing processing stress. Thus, increasing superplastic strains at higher strain rates, lower stresses and lower temperatures are obtained with increasing processing strain and, specially, processing stress.

scholarly journals Slip-stimulated grain boundary sliding in Ti-6Al-4 V at room temperature

Materialia ◽  
2019 ◽  
Vol 5 ◽  
pp. 100189 ◽  
Author(s):  
Samuel Hémery ◽  
Christophe Tromas ◽  
Patrick Villechaise
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Boundary Sliding
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