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.

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.

scholarly journals Mechanical behaviour and microstructural evolution in fine grain Ti-6Al-4V alloy under superplastic conditions

2020 ◽  
Vol 321 ◽  
pp. 11011
Author(s):  
Laurie Despax ◽  
Vanessa Vidal ◽  
Denis Delagnes ◽  
Moukrane Dehmas ◽  
Hiroaki Matsumoto ◽  
...  
Keyword(s):  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Phase Fraction ◽  
Diffusional Creep ◽  
Dislocation Glide ◽  
Β Phase ◽  
Fine Grain ◽  
Structural Applications ◽  
High Level ◽  
Mechanisms Of Deformation

Ti-6Al-4V is able to support high level of deformations like superplastic deformation for aeronautical structural applications. However, the applied temperature during forming induces changes in phase fraction, which may have an impact on the mechanisms of deformation involved and the final part. Mechanisms described in the literature, like dislocation glide, diffusional creep, Grain Boundary Sliding (GBS) accommodated by dislocation or diffusion, are still controversial as there are mainly based on post mortem analysis or on stress-strain data. The purpose of this work was to combine interrupted tensile tests and heat treatments to improve the understanding of the mechanisms of deformation on each stage of deformation. The chosen test temperatures were 750°C and 920°C which correspond to different β phase fractions. The microstructural features like grain size and phase fraction were studied by Scanning Electron Microscope (SEM) combined with image analysis. Moreover, EBSD was used to follow the change of crystalline orientation of α grains to distinguish the involved mechanisms as a function of the deformation. Indeed, it would appears that several mechanisms could be activated depending on the deformation stage and on the temperature.

Superplastic Behavior in Magnesium Alloy with Dispersion of Quasicrystal Phase Particle

2010 ◽  
Vol 433 ◽  
pp. 291-295
Author(s):  
Hidetoshi Somekawa ◽  
Alok Singh ◽  
Toshiji Mukai
Keyword(s):  
Phase Particle ◽  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Mechanical Anisotropy ◽  
Micro Hardness ◽  
Superplastic Behavior ◽  
Fine Grained ◽  
Microstructure Observation ◽  
Boundary Sliding ◽  
High Possibility

Superplastic behavior was investigated using an extruded Mg-Zn-Y alloy with the dispersion of the quasicrystal phase particle in fine-grained matrix. Tensile tests showed that the low temperature superplasticity was behaved at a temperature of 473 K and maximum elongation was 462 % at 573 K in 1  10-5 s-1. The deformed microstructure observation showed that the dominant deformation process was grain boundary sliding. The present alloy also demonstrated a high possibility for secondary forming, such as superplastic forge forming. Furthermore, the forged alloy had a homogeneous microstructures, no mechanical anisotropy and uniform micro-hardness properties in any portion of a forged product.

Superplasticity of Mg-Zn-Y Alloy Prepared by Extrusion of Machined Chip

2012 ◽  
Vol 735 ◽  
pp. 259-264
Author(s):  
Takaomi Itoi ◽  
Syuichi Fudetani ◽  
Mitsuji Hirohashi
Keyword(s):  
Grain Size ◽  
Hot Extrusion ◽  
Initial Strain Rate ◽  
Grain Boundary Sliding ◽  
Initial Strain ◽  
Strain Rates ◽  
Long Period ◽  
Dominant Deformation Mechanism ◽  
Mean Grain Size ◽  
Boundary Sliding

Mg96Zn2Y2 (at.%) extruded alloy was fabricated by hot-extrusion of the Mg96Zn2Y2 machined chip. The Mg96Zn2Y2 extruded alloy consisted of a long period stacking ordered (LPSO)-, Mg3Zn3Y2- and Mg- phases. The Mg phase with mean grain size of 450 nm was confirmed by TEM. However, the LPSO- and Mg3Zn3Y2- phases had relatively large grain size compared with Mg phase. The Mg96Zn2Y2 extruded alloy also showed superplasticity at temperatures of 623 K and 723 K with initial strain rates from 2×10−1 s−1 to 2×10−3 s−1. The maximum elongation of 450 % was achieved at 723 K with an initial strain rate of 2×10−3 s−1. From TEM observation, it is considered that grain boundary sliding of Mg grains was dominant deformation mechanism of the Mg96Zn2Y2 extruded alloy at high temperature range.

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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