scholarly journals Creep Behavior and Microstructural Evolution of Al–Cu–Mg–Ag Alloys with Various High Cu Contents

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 487
Author(s):  
Fangle Peng ◽  
Jiefang Wang ◽  
Ruibin Yang ◽  
Yage Xia ◽  
Guopeng Zhang ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
Creep Behavior ◽  
Creep Resistance ◽  
Solution Treatment ◽  
Aged Alloy ◽  
Number Density ◽  
Solid Solubility Limit ◽  
Cu Content ◽  
Ω Phase ◽  
Increasing Temperature

The creep behavior and microstructural evolution of three Al–Cu–Mg–Ag alloys with Cu content around its solid solubility limit in Al (5.65 wt %) were investigated at 180–240 °C and applied stress of 150–300 MPa. The creep resistance of aged alloy, which is mainly determined by the number density of Ω phase, is the best for 6.00 wt % Cu, better for 5.30 wt % Cu, and the worst for 5.65 wt % Cu. After solid-solution treatment, the lowest Cu content in the Al matrix for the alloy with 5.65 wt % Cu is observed due to the existence of more residual phases. It results in the lowest number density of Ω phase the following aging and poor creep resistance. Increasing temperature from 180 to 240 °C at the same stress (225 MPa), the steady creep rate of alloys increases by 225 times, which is apparently larger than that (26 times) for increasing stress from 225 to 300 MPa at the same temperature (180 °C). It indicates that the coarsening of the Ω phase with increasing temperature should be more serious than that with increasing stress. The creep mechanism of Al–Cu–Mg–Ag alloy can be attributed to the dislocation climb with the existence of threshold stress.

Variation of Hardness with Microstructure Evolutions in Metastable β Titanium Alloy TIMETAL®LCB

2007 ◽  
Vol 561-565 ◽  
pp. 2067-2070 ◽  
Author(s):  
Tatsuaki Sakamoto ◽  
Kiyomichi Nakai ◽  
Munehiro Maeda ◽  
Sengo Kobayashi
Keyword(s):  
Titanium Alloy ◽  
Orientation Relationship ◽  
Aging Time ◽  
Aging Temperature ◽  
Solution Treatment ◽  
Alpha Phase ◽  
Number Density ◽  
Hardness Variation ◽  
Ω Phase ◽  
Α Phase

Microstructure evolutions and hardness variation during aging in metastable β titanium alloy TIMETAL®LCB have been examined. In as-quenched specimen after solution treatment, athermal ω phase formed. Isothermal ω phase formed during aging at 623 K, and α phase formed after precipitation of isothermal ω phase during aging at 673 and 773 K. Alpha phase nucleated at isothermal ω phase, and had the orientation relationship with β and ω, (111)β//(0001)ω//(1120 )α and [10 1 ]β//[1120 ]ω//[0001]α . During aging at 873 K, α phase formed without isothermal ω phase. Hardness increased with increasing aging time and decreasing aging temperature, partly because number density of isothermal ω or α precipitates increased with increasing aging time and decreasing aging temperature.

Microstructures and Creep of AM50-Sb-Gd Alloys

2005 ◽  
Vol 488-489 ◽  
pp. 749-752 ◽  
Author(s):  
Su Gui Tian ◽  
Keun Yong Sohn ◽  
Hyun Gap Cho ◽  
Kyung Hyun Kim
Keyword(s):  
Activation Energy ◽  
Creep Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Mechanism ◽  
Creep Resistance ◽  
Fine Particles ◽  
Dislocation Climb ◽  
The Matrix

Creep behavior of AM50-0.4% Sb-0.9%Gd alloy has been studied at temperatures ranging from 150 to 200°C and at stresses ranging from 40 to 90 MPa. Results show that the creep rate of AM50-0.4%Sb-0.9%Gd alloy was mainly controlled by dislocation climb at low stresses under 50 MPa. The activation energy for the creep was 131.2 ± 10 kJ/mol and the stress exponent was in the range from 4 to 9 depending on the applied stress. More than one deformation-mechanism were involved during the creep of this alloy. Microstructures of the alloy consist of a–Mg matrix and fine particles, distinguished as Mg17Al12, Sb2Mg3, and Mg2Gd or Al7GdMn5 that were homogeneously distributed in the matrix of the alloy, which effectively reduced the movement of dislocations, enhancing the creep resistance. Many dislocations were identified to be present on non-basal planes after creep deformation.

The Compression Creep Behavior of Ni3Al-X Single Crystals

1990 ◽  
Vol 213 ◽  
Author(s):  
Seiji Miura ◽  
Tohru Hayashi ◽  
Mitsuhiro Takekawa ◽  
Yoshinao Mishima ◽  
Tomoo Suzuki
Keyword(s):  
Activation Energy ◽  
Single Crystals ◽  
Power Law ◽  
Creep Behavior ◽  
Creep Resistance ◽  
Constant Strain Rate ◽  
State Equation ◽  
Ternary Alloys ◽  
Plastic Behavior ◽  
Compression Tests

ABSTRACTCompressive creep behavior is investigated in ternary Ni3Al single crystals containing Ti, Si, Hf and Cr with stress axes parallel to the crystallographic orientation near [001]. Then a comparison is made with the results of high temperature compression tests under a constant strain rate for the same orientation where plastic behavior is characterized by a distinct yield drop followed by steadystate deformation. It is found that the deformation mechanism for the two cases is identical, namely octahedral viscous flow being expressed by the state equation of the power-law type with a stress exponent of about 3 to 4. The effect of offstoichiometry on the creep resistance is then examined in Ni3(Al,5 at%Ti) alloys with different Ni concentrations. The results support the observation in the polycrystalline compound where the creep resistance increases with Ni concentration on both sides of stoichiometry exhibiting a discontinuity at stoichiometry. Finally, the apparent activation energy in the power-law type state equation for the steady state creep deformation is estimated for all the ternary alloys examined. They are in general in good agreement with that for diffusion of ternary elements in Ni3Al. However, the relative magnitude of the value can not simply be compared since the activation energy depends on deviations from stoichiometry.

scholarly journals Long-Term Creep Behavior Prediction of Sol-Gel Derived SiO2- and TiO2-Wood Composites Using the Stepped Isostress Method

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1215 ◽  
Author(s):  
Ke-Chang Hung ◽  
Tung-Lin Wu ◽  
Jyh-Horng Wu
Keyword(s):  
Creep Behavior ◽  
Creep Resistance ◽  
Flexural Modulus ◽  
Sol Gel ◽  
Untreated Wood ◽  
Behavior Prediction ◽  
Inorganic Composites ◽  
Sol Gel Process ◽  
Term Creep

In this study, methyltrimethoxysilane (MTMOS), methyltriethoxysilane (MTEOS), tetraethoxysilane (TEOS), and titanium(IV) isopropoxide (TTIP) were used as precursor sols to prepare wood-inorganic composites (WICs) by a sol-gel process, and subsequently, the long-term creep behavior of these composites was estimated by application of the stepped isostress method (SSM). The results revealed that the flexural modulus of wood and WICs were in the range of 9.8–10.5 GPa, and there were no significant differences among them. However, the flexural strength of the WICs (93–103 MPa) was stronger than that of wood (86 MPa). Additionally, based on the SSM processes, smooth master curves were obtained from different SSM testing parameters, and they fit well with the experimental data. These results demonstrated that the SSM was a useful approach to evaluate the long-term creep behavior of wood and WICs. According to the Eyring equation, the activation volume of the WICs prepared from MTMOS (0.825 nm3) and TEOS (0.657 nm3) was less than that of the untreated wood (0.832 nm3). Furthermore, the WICs exhibited better performance on the creep resistance than that of wood, except for the WICMTEOS. The reduction of time-dependent modulus for the WIC prepared from MTMOS was 26% at 50 years, which is the least among all WICs tested. These findings clearly indicate that treatment with suitable metal alkoxides could improve the creep resistance of wood.

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