The Creep Behaviour of Extruded Mg-5Li-3Al-1.5Zn-2RE Alloy

2011 ◽  
Vol 213 ◽  
pp. 492-496 ◽  
Author(s):  
Ting Qu Li ◽  
Yong Bing Liu ◽  
Zhan Yi Cao ◽  
Li Ren Cheng ◽  
Dong Mei Jiang
Keyword(s):  
Electron Microscopy ◽  
Creep Behaviour ◽  
Microstructural Analysis ◽  
Extrusion Process ◽  
Intermetallic Phases ◽  
Tensile Creep ◽  
Dislocation Creep ◽  
Creep Tests ◽  
Creep Properties ◽  
Transmission Electron

The Mg-5Li-3Al-1.5Zn-2RE (LaPrCe) alloy was prepared by hot-chamber extrusion process after casting. The alloy consists of α-Mg solid solution and intermetallic phases (Al11RE3 phase and Al2RE phase). The microstructural analysis of the alloy reveals the correlation between microstructure and creep properties. The stress exponent of n varies from 4.25 to 6.23, and the activation energy varies from 104 to 134 kJ/mol. There is a transition between dislocations climb dominated creep mechanism and dislocation creep controlled by non-basal planes slip. Tensile creep tests were combined with detailed transmission electron microscopy in order to characterize the Al11RE3 phase, which had thermal stability at 448K during the creep test. The dislocations pinned and cross-slip dislocations were observed.

Microstructure Stability and Creep Behaviour of a Cu-0.2wt.%Zr Alloy Processed by Equal-Channel Angular Pressing

2010 ◽  
Vol 667-669 ◽  
pp. 821-826 ◽  
Author(s):  
Jiří Dvořák ◽  
Petr Král ◽  
Marie Kvapilová ◽  
Milan Svoboda ◽  
Vàclav Sklenička
Keyword(s):  
Electron Microscopy ◽  
Equal Channel Angular Pressing ◽  
Creep Behaviour ◽  
Tensile Creep ◽  
Creep Tests ◽  
Creep Properties ◽  
Angular Pressing ◽  
Microstructure Stability ◽  
Transmission Electron ◽  
Zr Alloy

A dispersion-strengthened Cu-0.2 wt.% Zr alloy was subjected to equal-channel angular pressing (ECAP) at room temperature for up to 12 passes through route BC using a die having a channel angle of 90°. The microstructural investigations were performed using both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Tensile creep tests were conducted at temperature 673 K and at the applied stress in the range from 80 to 180 MPa. The migration of boundaries and subsequent grain growth were restricted by Cu9Zr2 precipitates. The study was performed in order to evaluate the effects of severe plastic deformation and precipitation on creep behaviour and microstructure of the pressed alloy. It was found that creep behaviour is strongly dependent on number of ECAP passes. The pressed alloy after up to 4 ECAP passes exhibited a considerable improvement in creep properties in comparison with the unpressed alloy.

Microstructure and Creep Resistance of Mg-Al-Ca-Sr Alloys

2014 ◽  
Vol 59 (1) ◽  
pp. 329-334 ◽  
Author(s):  
T. Rzychoń ◽  
B. Adamczyk-Cieślak
Keyword(s):  
Electron Microscopy ◽  
Creep Resistance ◽  
Volume Fraction ◽  
Intermetallic Phases ◽  
Phase Identification ◽  
Quantitative Metallography ◽  
Creep Tests ◽  
Creep Properties ◽  
Transmission Electron ◽  
Ebsd Technique

Abstract Microstructure and creep properties of cast Mg-Al-Ca-Sr alloys have been investigated. The microstructure was characterized using light microscopy, scanning and transmission electron microscopy. Phase identification was made by EBSD technique and by SAED analysis. The measurement of volume fraction of intermetallic phases was performed using quantitative metallography. Creep tests were performed at 180°C and at applied stress between 45 and 90 MPa. Microstructure of tested alloys composed of α-Mg grains and intermetallic compounds in the interdendritic regions. It was found that the addition of calcium and strontium improves creep resistance at 180°C.

scholarly journals Dislocation Creep of Olivine and Amphibole in Amphibole Peridotites from Åheim, Norway

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1018
Author(s):  
Sejin Jung ◽  
Takafumi Yamamoto ◽  
Jun-ichi Ando ◽  
Haemyeong Jung
Keyword(s):  
Electron Microscopy ◽  
Slip System ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Dislocation Creep ◽  
Transmission Electron ◽  
Electron Backscatter ◽  
Different Types ◽  
Localized Shear Deformation ◽  
Backscatter Diffraction

Amphibole peridotite samples from Åheim, Norway, were analyzed to understand the deformation mechanism and microstructural evolution of olivine and amphibole through the Scandian Orogeny and subsequent exhumation process. Three Åheim amphibole peridotite samples were selected for detailed microstructural analysis. The Åheim amphibole peridotites exhibit porphyroclastic texture, abundant subgrain boundaries in olivine, and the evidence of localized shear deformation in the tremolite-rich layer. Two different types of olivine lattice preferred orientations (LPOs) were observed: B- and A-type LPOs. Electron backscatter diffraction (EBSD) mapping and transmission electron microscopy (TEM) observations revealed that most subgrain boundaries in olivine consist of dislocations with a (001)[100] slip system. The subgrain boundaries in olivine may have resulted from the deformation of olivine with moderate water content. In addition, TEM observations using a thickness-fringe method showed that the free dislocations of olivine with the (010)[100] slip system were dominant in the peridotites. Our data suggest that the subgrain boundaries and free dislocations in olivine represent a product of later-stage deformation associated with the exhumation process. EBSD mapping of the tremolite-rich layer revealed intracrystalline plasticity in amphibole, which can be interpreted as the activation of the (100)[001] slip system.

The High Temperature Creep Behavior of Mg-5Li-3Al-2Zn-2Cu Alloy

2013 ◽  
Vol 760-762 ◽  
pp. 759-762
Author(s):  
Ting Qu Li ◽  
Xiang Ling Liu ◽  
Zhan Yi Cao
Keyword(s):  
Creep Behavior ◽  
Room Temperature ◽  
Microstructural Analysis ◽  
Dislocation Creep ◽  
High Temperature Creep ◽  
Creep Properties ◽  
X Ray ◽  
Transmission Electron ◽  
The Matrix ◽  
Dislocation Movement

The room-temperature mechanical properties of the extruded Mg-5Li-3Al-2Zn-2Cu alloy (LAZ532-2Cu) were researched previously. In this paper, the creep behavior of the extruded LAZ532-2Cu alloy was studied at the temperature range from 398K to 448K, with the stress 60MPa, 80MPa and 100MPa. The microstructure of the alloy consists of the matrix α-Mg solid solution and the intermetallic compounds on the grain boundary or in the grain. The microstructural analysis of the alloy reveals the correlation between microstructure and creep properties. The stress exponent n 3.72, 4.8, 6.1, the activation energy Qc 94.8kJ/mol, 123.9kJ/mol, 128 kJ/mol were calculated at the test condition. The creep test samples were combined with detailed transmission electron microscopy and X-ray diffractometry in order to characterize the precipitated AlLi phase, which contributes to the creep resistance by obstructing the dislocation movement in dislocation creep.

The Effect of Severe Plastic Deformation Processing on Creep Properties of Metallic Materials

2015 ◽  
Vol 651-653 ◽  
pp. 639-644
Author(s):  
Jiri Dvorak ◽  
Petr Král ◽  
Vaclav Sklenička ◽  
Milan Svoboda ◽  
Marie Kvapilová
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Electron Backscatter Diffraction ◽  
Bulk Material ◽  
Creep Behaviour ◽  
Tensile Creep ◽  
Severe Plastic Deformation Processing ◽  
Processing Route ◽  
Creep Tests ◽  
Creep Properties

Processing by severe plastic deformation (SPD) may be defined as such metals forming procedure in which a very high strain is imposed on a bulk material. This paper investigates the effect of different equal channel angular pressing (ECAP) routes and number of ECAP passes on resulting microstructure, mechanical properties and creep behaviour of selected materials. The distinction between various ECAP routes (A, B and C) and the difference in number of ECAP passes applied may lead to variations both in the macroscopic distortions of the individual grains and in the capability to develop a reasonably homogeneous and equiaxed ultrafine-grained microstructure. Experimental materials were processed by ECAP at room temperature using a die with an internal angle of 90° between the two parts of the channel. The ECAP pressing was performed by different routes up to 12 ECAP passes. Tensile creep tests were conducted at temperatures 473 - 673 K and at different applied stresses on ECAP materials and, for comparison purposes, on their unpressed states. Microstructure of samples was characterized by scanning electron microscope (SEM) equipped with the electron backscatter diffraction (EBSD) unit. In conclusion, the ECAP processing route and number of applied ECAP passes could play an important role in creep behaviour and their effect may be different for particular materials. The highest differences in processing routes were revealed for materials especially at lower number of ECAP passes. However, a little apparent dependence of the creep properties was observed during subsequent pressing.

Microstructural Analysis of SiO2-Al2O3 Glasses

1982 ◽  
Vol 40 ◽  
pp. 562-563
Author(s):  
C. M. Jantzen ◽  
D. G. Howitt
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Microstructural Analysis ◽  
Liquid Immiscibility ◽  
Metastable Region ◽  
Transmission Electron ◽  
Liquidus Temperatures

The mullite-SiO2 liquidus has been extensively studied, and it has been shown that the flattening of the liquidus is related to the existence of a metastable region of liquid immiscibility at sub-liquidus temperatures which is detectable by transmission electron microscopy (TEM) (Fig. 1).

Microstructure and Strengthening of Creep-Tested Cryomilled NiAl-AlN

1996 ◽  
Vol 460 ◽  
Author(s):  
Anita Garg ◽  
J. Daniel Whittenberger ◽  
Michael J. Luton
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Subgrain Size ◽  
Tensile Creep ◽  
Strain Rates ◽  
Mechanical Grinding ◽  
Intermetallic Matrix ◽  
Transmission Electron ◽  
Intermetallic Matrix Composite ◽  
Nial Powder

ABSTRACTThe mechanical grinding of prealloyed NiAl powder in liquid nitrogen (cryomilling) results in an intermetallic matrix composite where micron sized particle free aluminide cores (grains) are surrounded by thin mantles comprised of nanometer sized A1N particles and NiAl grains. Under high temperature, slow strain rate conditions both compressive and tensile creep testing have shown that the mechanical strength of hot extruded cryomilled NiAl approaches the levels exhibited by advanced NiAl-based single crystals and simple Ni-based superalloys. Transmission electron microscopy of cryomilled materials tested between 1100 and 1300 K revealed little, if any, dislocation structure within the mantle regions, while the NiAl cores contained subgrains and dislocation networks after testing at all strain rates between 10-4 and 10-8 s-1. These and other microstructural observations suggest that creep strength is the result of a fine NiAl grain/subgrain size, the inability of dislocations to move through the mantle and stabilization of the microstracture by the A1N particles.

Microstructure and Creep Properties of Selected Gravity Casting Magnesium Alloys

2016 ◽  
Vol 682 ◽  
pp. 372-379
Author(s):  
Tomasz Rzychoń
Keyword(s):  
Magnesium Alloys ◽  
Creep Resistance ◽  
Low Cost ◽  
Xrd Analysis ◽  
Phase Identification ◽  
Creep Tests ◽  
Gravity Casting ◽  
Creep Properties ◽  
Transmission Electron ◽  
Primary Crystals

In this paper microstructure and creep properties of Mg-Al-Ca-Sr, Mg-Zn-RE-Zr and Mg-Sn-Si gravity casting magnesium alloys are presented. The microstructure was characterized using light microscopy, scanning and transmission electron microscopy. Phase identification was made by SAED and XRD analysis. Creep tests were carried out in the temperature range from 180°C to 200°C at applied stress of 60 MPa. Microstructure of Mg-Al-Ca-Sr alloys composed of α-Mg grains and C36, C15 and C14 intermetallic compounds in the interdendritic regions. In case of Mg-Zn-RE-Zr alloys the dominant intermetallic compound is (Mg,Zn)12RE phase also located in the interdendritic regions. Microstructure of Mg-Sn-Si alloys after T6 heat treatment consists of plate-like precipitates of Mg2Sn phase, primary crystals of Mg2Si phase and globular Mg2Si phase. Among the alloys in this study, the low-cost Mg-5Al-3Ca-0.7Sr alloy has the best creep resistance. The other alloys, excluding the Mg-5Si-7Sn alloy, are characterized by a poorer creep resistance in compared to Mg-5Al-3Ca-0.7Sr alloy, however their creep resistance is better if compared to typical Mg-Al alloys. Creep resistance of Mg-5Si-7Sn alloy is very low.

The Effect of Interfacial Free Energies on the Stability of Microlaminates

2000 ◽  
Vol 652 ◽  
Author(s):  
A. C. Lewis ◽  
A. B. Mann ◽  
D. van Heerden ◽  
D. Josell ◽  
T. P. Weihs
Keyword(s):  
Electron Microscopy ◽  
Grain Boundary ◽  
High Temperatures ◽  
Free Energies ◽  
Microstructural Stability ◽  
Creep Tests ◽  
Interfacial Energies ◽  
Transmission Electron ◽  
The Stability ◽  
Interfacial Free Energies

ABSTRACTLaminated composites with polycrystalline layers typically break down at high temperatures through grain boundary grooving and the pinch-off of individual layers. Such materials, when exposed to high temperatures, develop grooves where grain boundaries meet the interfaces between layers. The depths of the grooves are controlled by the ratios of grain boundary and interfacial free energies, γgb/γint. Depending on the dimensions of the grains, these grooves can extend through the entire layer, causing pinch-off at the grain boundary. This pinch-off destroys the layering and eventually leads to a gross coarsening of the microstructure. Because microstructural stability is critical to performance for most applications, the ability to understand and predict the stability of microlaminates is a necessary tool. An existing model of this capillarity-driven breakdown requires the interfacial free energies, γgb and γint, as input parameters. Both biaxial and uniaxial zero creep tests have been used in conjunction with transmission electron microscopy to measure these interfacial energies in Ag/Ni and Nb/Nb5Si3 microlaminates.

Microstructure and Creep Properties of AJ62 and AE44 Die-Casting Magnesium Alloys

2010 ◽  
Vol 638-642 ◽  
pp. 1546-1551 ◽  
Author(s):  
Andrzej Kiełbus ◽  
Tomasz Rzychoń
Keyword(s):  
Magnesium Alloys ◽  
Creep Resistance ◽  
Cell Structure ◽  
Creep Behaviour ◽  
Die Casting ◽  
Tensile Creep ◽  
Creep Properties ◽  
Die Cast ◽  
Subgrain Formation ◽  
Good Creep Resistance

Microstructure and tensile creep behaviour of the die-cast AE44 and AJ62 magnesium alloys has been studied at temperatures between 175°C and 200°C and at stresses in the range from 60 to 75 MPa. At the 175°C the AJ62 and AE44 alloys exhibit good creep resistance after 120h creep deformation. At 200°C the AE44 alloy shows still good creep resistance, whereas in the case of AJ62 alloy the rapid decreasing of creep resistance has been observed. TEM observations reveal dislocations cell structure in AE44 alloy after creep test. In AJ62 alloy subgrain formation and decreasing the dislocation density have been observed.

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