Creep Behavior of MoSi2-SiC Composites

1993 ◽  
Vol 322 ◽  
Author(s):  
Darryl P. Butt ◽  
Stuart A. Maloy ◽  
H. Kung ◽  
David A. Korzekwa ◽  
John J. Petrovic
Keyword(s):  
Creep Behavior ◽  
Grain Boundary Sliding ◽  
Dislocation Motion ◽  
Indentation Creep ◽  
Strain Rates ◽  
Compressive Creep ◽  
Creep Measurements ◽  
Boundary Sliding ◽  
Sic Composites ◽  
Complex Manner

AbstractUsing a cylindrical indenter, the indentation creep behavior of hot pressed and HIPed MoSi2-SiC composites containing 0-40% SiC by volume, was characterized at 1000-1200°C, 258-362 MPa. The addition of SiC affects the creep behavior of MoSi2 in a complex manner by pinning grain boundaries during pressing, thus leading to smaller MoSi2 grains; by obstructing or altering both dislocation motion and grain boundary sliding; and by increasing the overall yield stress of the material. Comparisons are made between indentation and compressive creep studies. It is shown that under certain conditions, compressive creep and indentation creep measurements yield comparable results after correcting for effective stresses and strain rates beneath the indenter.

Impression creep behavior of SiC particle-MoSi2 composites

1996 ◽  
Vol 11 (6) ◽  
pp. 1528-1536 ◽  
Author(s):  
Darryl P. Butt ◽  
David A. Korzekwa ◽  
Stuart A. Maloy ◽  
H. Kung ◽  
John J. Petrovic
Keyword(s):  
Creep Behavior ◽  
Grain Boundary Sliding ◽  
Dislocation Motion ◽  
Impression Creep ◽  
Compressive Creep ◽  
Creep Measurements ◽  
Boundary Sliding ◽  
Sic Composites ◽  
Complex Manner ◽  
Punch Pressure

Using a cylindrical indenter (or punch), the impression creep behavior of MoSi2-SiC composites containing 0–40% SiC by volume, was characterized at 1000–1200 °C, 258–362 MPa punch pressure. Through finite element modeling, an equation that depends on the material stress exponent was derived that converts the stress distribution beneath the punch to an effective compressive stress. Using this relationship, direct comparisons were made between impression and compressive creep studies. Under certain conditions, compressive creep and impression creep measurements yield comparable results after correcting for effective stresses and strain rates beneath the punch. However, rate-controlling mechanisms may be quite different under the two stressing conditions, in which case impression creep data should not be used to predict compressive creep behavior. The addition of SiC affects the impression creep behavior of MoSi2 in a complex manner by pinning grain boundaries during pressing, thus leading to smaller MoSi2 grains and by obstructing or altering both dislocation motion and grain boundary sliding.

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.

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 Dynamic recrystallization behavior of the Ta-containing TiAl alloy in isothermal deformation

2020 ◽  
Vol 321 ◽  
pp. 12008
Author(s):  
Y.Y. Luo ◽  
X.N. Mao ◽  
H.Y. Yang ◽  
Y.F. Yin ◽  
Z.Z. Zhao ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Tial Alloy ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
Recrystallization Behavior ◽  
Compression Process ◽  
Dynamic Recrystallization Behavior ◽  
Boundary Sliding ◽  
Mechanical Twins

The dynamic recrystallization behavior of as-cast Ti-46.5Al-3Ta-2Cr-0.2W alloy during isothermal compression process with nominal deformation of 50% and strain rates from 0.01s to 1s was investigated by electron microscopy. The results showed that the deformation mechanism of this alloy can be concluded as grain boundary sliding and mechanical twins, which induce the final dynamic recrystallization. The phase boundary bulging was found to be the major nucleation mechanism responsible for the lamellar globularization and the formation of recrystallized γ grains inside the lamellar colony under the high strain rate. The recrystallized γ grains induced by the twinning is the main mechanism for refining α2 lamellar microstructures under low strain rate.

High Temperature Deformation Behavior of Pre-Sintered Al-10Si-5Fe Based Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 393-396 ◽  
Author(s):  
Dong Suk Lee ◽  
Gyu-Sam Shim ◽  
Mok Soon Kim ◽  
Won Yong Kim ◽  
Hiroshi Yamagata
Keyword(s):  
Liquid Phase ◽  
Deformation Behavior ◽  
Grain Boundary Sliding ◽  
Compressive Deformation ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Sintered Alloy ◽  
Strain Rates ◽  
Considerable Decrease ◽  
Boundary Sliding

Compressive deformation behavior of pre-sintered Al-10Si-5Fe-1Cu-0.5Mg-1Zr (wt%) alloy containing 15% of porosity was investigated in the temperature range from 753 K to 793 K and at strain rates from 10-4 to 100 s-1. From the microstructural observation, it was revealed that the occurrence of grain boundary sliding accomodated by dynamic recrystallization during the compressive deformation was closely associated with the considerable decrease in the porosity of the pre-sintered alloy. In the specimens deformed at 793 K with 10-4~100 s-1 and at 773 K with 10- 4~10-2 s-1, we have found an evidence of the occurrence of a liquid phase during compressive deformation in the microstructure. The liquid phase was considered to promote particle boundary sliding and hinder the reduction of the pore.

Effect of Si3 N4 Addition on Compressive Creep Behavior of Hot-Pressed ZrB2 -SiC Composites

2014 ◽  
Vol 97 (9) ◽  
pp. 2957-2964 ◽  
Author(s):  
Manab Mallik ◽  
Kalyan Kumar Ray ◽  
Rahul Mitra
Keyword(s):  
Creep Behavior ◽  
Compressive Creep ◽  
Sic Composites

Impression Creep Behavior of Atmospheric Plasma-Sprayed and Hot Pressed MoSi2/Si3N4

1997 ◽  
Author(s):  
K.J. Hollis ◽  
D.P. Butt ◽  
R.G. Castro
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Creep Behavior ◽  
Grain Boundary Sliding ◽  
Atmospheric Plasma ◽  
Second Phase ◽  
Impression Creep ◽  
Creep Mechanisms ◽  
Boundary Sliding ◽  
Plasma Sprayed

Abstract The use of MoSi2 as a high temperature oxidation resistant structural material is hindered by its poor elevated temperature creep resistance. The addition of second phase Si3N4 holds promise for improving the creep properties of MoSi2 without decreasing oxidation resistance. The high temperature impression creep behavior of atmospheric plasma sprayed (APS) and hot pressed (HP) MoSi2/Si3N4 composites was investigated. Values for steady state creep rates, creep activation energies, and creep stress exponents were measured. Grain boundary sliding and splat sliding were found to be the dominant creep mechanisms for the APS samples while grain boundary sliding and plastic deformation were found to be the dominant creep mechanisms for the HP samples.

Deformation Behavior of Fine Grained Al-Mg Alloy under Biaxial Stress

2006 ◽  
Vol 503-504 ◽  
pp. 475-480 ◽  
Author(s):  
Masafumi Noda ◽  
Kunio Funami
Keyword(s):  
Grain Boundary ◽  
Tensile Deformation ◽  
Grain Boundary Sliding ◽  
Biaxial Stress ◽  
Mg Alloy ◽  
Strain Rates ◽  
Fine Grained ◽  
Biaxial Tensile ◽  
Wide Range ◽  
Boundary Sliding

The grain boundary sliding and the formation of slipped bands and cavitations during biaxial tensile deformation were examined in fine grained Al-Mg alloy. Biaxial tensile testing was conducted with cruciform specimens at initial strain rates of 10-4 to 101s-1. It was found that at the same equivalent strain conditions, the number of cavities under biaxial tension is significantly greater than that under uniaxial tension. A greater prevalence of slipped bands and grain separations were clearly observed under biaxial stress than under uniaxial stress. It was suggested that development of slipped bands resulted from the formation of elongated cavities and multiple deformed bands under biaxial stress. Additionally, the m-value under biaxial stress remained at about 0.3 over a wide range of strain rates. The effects of grain separation and formation of cavities were related to the motion of grain boundary sliding, grain size and loading conditions.

Enhanced Tensile Ductility of AZ80 Magnesium Alloy

2011 ◽  
Vol 284-286 ◽  
pp. 1635-1638
Author(s):  
Jun Qiao ◽  
Yu Wang ◽  
Guo Dong Shi ◽  
Bao Xin Nie
Keyword(s):  
Tensile Tests ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Strain Rates ◽  
Premature Failure ◽  
Az80 Magnesium Alloy ◽  
Coarse Grains ◽  
Elongation To Failure ◽  
Boundary Sliding ◽  
Cavity Evolution

Tensile behaviors of extruded and rolled AZ80 Mg alloy were investigated with elongation-to-failure tensile tests at constant temperatures of 300 °C, 350 °C, 400 °C, and 450 °C, and constant strain rates of 10-2s-1and 10-3s-1. Experimental data show that the material exhibits tensile ductilities of over 100% at 400 °C and 450 °C, featured by long steady state deformation. Microstructure studies show that annealed coarse grains were remained in the gauge region during the tensile tests, and the enhanced tensile ductilities resulted from dislocation creep, other than dynamic recrystallization or grain boundary sliding. Cavity evolution and recrystallized coarse grains near fracture end caused premature failure of the material.

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