Compressive properties at elevated temperatures of porous aluminum processed by the spacer method

Compressive properties at 573–773 K of porous aluminum produced by the spacer method were investigated and compared with those of bulk reference aluminum with the same chemical compositions. The stress exponent and activation energy for deformation at elevated temperatures in the porous aluminum were in agreement with those in the bulk reference aluminum. In addition, the plateau stress of the porous aluminum was comparable to the stress of the bulk reference aluminum upon compensation by the relative density. Therefore, it is conclusively demonstrated that the mechanism of deformation at elevated temperatures in the porous aluminum is the same as that in the bulk reference aluminum. This is likely due to the homogeneous microstructure in the porous aluminum produced by the spacer method.

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Study on Quasi-Static Uniaxial Compression Properties and Constitutive Equation of Spherical Cell Porous Aluminum-Polyurethane Composites

Materials ◽

10.3390/ma11071261 ◽

2018 ◽

Vol 11 (7) ◽

pp. 1261 ◽

Cited By ~ 3

Author(s):

Haiying Bao ◽

Aiqun Li

Keyword(s):

Constitutive Equation ◽

Relative Density ◽

Uniaxial Compression ◽

Spherical Cell ◽

Plateau Stress ◽

Porous Aluminum ◽

Linear Elastic ◽

Compression Properties ◽

Three Stages ◽

Polyurethane Composites

Quasi-static uniaxial compression properties and the constitutive equation of spherical cell porous aluminum-polyurethane composites (SCPA-PU composites) were investigated in this paper. The effects of relative density on the densification strain, plateau stress and energy absorption properties of the SCPA-PU composites were analyzed. It is found that the stress-strain curves of SCPA-PU composites consist of three stages: The linear elastic part, longer plastic plateau segment and densification region. The results also demonstrate that both the plateau stress and the densification strain energy of the SCPA-PU composites can be improved by increasing the relative density of the spherical cell porous aluminum (SCPA), while the densification strain of the SCPA-PU composites shows little dependence on the relative density of the SCPA. Furthermore, the applicability of three representative phenomenological models to the constitutive equations of SCPA-PU composites are verified and compared based on the experimental results. The error analysis result indicates that the Avalle model is the best model to characterize the uniaxial compression constitutive equation of SCPA-PU composites.

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Creep Properties of a High Niobium Containing γ-TiAl Alloy Sheet Material

MRS Proceedings ◽

10.1557/proc-753-bb3.3 ◽

2002 ◽

Vol 753 ◽

Cited By ~ 3

Author(s):

A. Bartels ◽

S. Bystrzanowski ◽

R. Gerling ◽

F.-P. Schimansky ◽

H. Kestler ◽

...

Keyword(s):

Activation Energy ◽

Stress Exponent ◽

Elevated Temperatures ◽

Sheet Material ◽

Rolling Direction ◽

Constant Load ◽

Alloy Sheet ◽

Tensile Creep ◽

Creep Tests ◽

Fine Grained

ABSTRACTIn this study Ti-46Al-9Nb (at%) sheet material processed by a powder metallurgical route was examined. Subsequent to hot rolling the sheets were subjected to a stress-relief treatment at 1273K for 3 hours. During this heat treatment a fine-grained near gamma microstructure has been formed. 100 hours tensile creep tests under constant load were carried out at 700°C in rolling direction, transverse direction as well as 45° direction. Using the method of load changes a stress exponent of 4.1 was determined. Furthermore, the apparent activation energy was determined in the temperature range of 715 – 775°C. Both stress exponent and activation energy suggest that diffusion assisted dislocation climb is the dominant creep mode. A comparison of these results with those of so-called conventional or so-called “2nd generation” γ-TiAl based alloys, e.g. Ti-46.5Al-4(Cr,Nb,Ta,B) (at%) and Ti-47Al-4(Cr,Mn,Nb,Si,B) (at%), indicates a significantly better creep resistance and a higher activation energy of the high Nb containing alloy. Additionally, internal friction experiments were conducted in order to analyze the deformation behavior under very small strains at elevated temperatures.

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Compressive Properties of Porous Metals with Homogeneous Pore Characteristics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.340-341.415 ◽

2007 ◽

Vol 340-341 ◽

pp. 415-420

Author(s):

Masataka Hakamada ◽

Yuuki Asao ◽

Tetsumune Kuromura ◽

Yasuo Yamada ◽

Y. Chen ◽

...

Keyword(s):

Aluminum Alloy ◽

Relative Density ◽

High Porosity ◽

Compression Tests ◽

Porous Metals ◽

Compressive Properties ◽

Pore Characteristics ◽

Porous Aluminum ◽

Cyclic Compression ◽

Porous Copper

Spacer method is excellent technique of processing porous metals with well-controlled pore characteristics such as porosity (up to 90%) and pore size (as small as several hundred micrometers). Compressive properties of porous aluminum fabricated by the spacer method are investigated. They were subjected to monotonic compression tests at room temperature, and showed less fluctuated flow stress during their compressive deformation than conventional porous aluminum alloy, reflecting their homogeneous pore characteristics. Also, shortening behavior of the porous aluminum fabricated by the spacer method during cyclic compression was significantly differed from that of conventional porous aluminum alloy. Therefore, it can be concluded that the homogeneity of pore characteristics is responsible for compressive properties of porous metals. Monotonic compression tests on porous copper specimens with various porosities, which were made by the spacer method, were also conducted. The yield stress of the porous copper with high porosity (or low relative density) depended on the relative density more strongly than that of the porous copper with low porosity (or high relative density). It is presumed that porous metals with high porosity and ones with low porosities have different deformation mechanisms.

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On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

Journal of Elastomers & Plastics ◽

10.1177/00952443211020330 ◽

2021 ◽

pp. 009524432110203

Author(s):

Sudhir Bafna

Keyword(s):

Mechanical Properties ◽

Activation Energy ◽

Weight Loss ◽

Oxygen Consumption ◽

Dwell Time ◽

Room Temperature ◽

Elevated Temperatures ◽

Degradation Mechanism ◽

Kinetics Of ◽

Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

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Thermodynamic Behavior of Fe-Mn and Fe-Mn-Ag Powder Mixtures during Selective Laser Melting

Metals ◽

10.3390/met11020234 ◽

2021 ◽

Vol 11 (2) ◽

pp. 234

Author(s):

Jakob Kraner ◽

Jožef Medved ◽

Matjaž Godec ◽

Irena Paulin

Keyword(s):

Selective Laser Melting ◽

Manganese Oxides ◽

Elevated Temperatures ◽

Manganese Content ◽

Chemical Compositions ◽

Metal Powders ◽

Laser Melting ◽

Powder Mixtures ◽

Ε Martensite ◽

The Impact

Additive manufacturing is a form of powder metallurgy, which means the properties of the initial metal powders (chemical composition, powder morphology and size) impact the final properties of the resulting parts. A complete characterization, including thermodynamic effects and the behavior of the metal powders at elevated temperatures, is crucial when planning the manufacturing process. The analysis of the Fe-Mn and Fe-Mn-Ag powder mixtures, made from pure elemental powders, shows a high susceptibility to sintering in the temperature interval from 700 to 1000 °C. Here, numerous changes to the manganese oxides and the αMn to βMn transformation occurred. The problems of mechanically mixed powders, when using selective laser melting, were highlighted by the low flowability, which led to a less controllable process, an uncontrolled arrangement of the powder and a large percentage of burnt manganese. All this was determined from the altered chemical compositions of the produced parts. The impact of the increased manganese content on the decreased probability of the transformation from γ-austenite to ε-martensite was confirmed. The ε-martensite in the microstructure increased the hardness of the material, but at the same time, its magnetic properties reduce the usefulness for medical applications. However, the produced parts had comparable elongations to human bone.

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Monotonic and cyclic compressive properties of porous aluminum fabricated by spacer method

Materials Science and Engineering A ◽

10.1016/j.msea.2007.03.027 ◽

2007 ◽

Vol 459 (1-2) ◽

pp. 286-293 ◽

Cited By ~ 34

Author(s):

Masataka Hakamada ◽

Tetsumune Kuromura ◽

Yasumasa Chino ◽

Yasuo Yamada ◽

Youqing Chen ◽

...

Keyword(s):

Compressive Properties ◽

Porous Aluminum

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Microstructures and Creep of AM50-Sb-Gd Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.488-489.749 ◽

2005 ◽

Vol 488-489 ◽

pp. 749-752 ◽

Cited By ~ 2

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.

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Tool Wear Mechanisms during Machining of Alloy 625

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.275.204 ◽

2011 ◽

Vol 275 ◽

pp. 204-207 ◽

Cited By ~ 1

Author(s):

Lenka Fusova ◽

Pawel Rokicki ◽

Zdeněk Spotz ◽

Karel Saksl ◽

Carsten Siemers

Keyword(s):

Wear Mechanisms ◽

Gas Turbines ◽

Metal Cutting ◽

Elevated Temperatures ◽

Orthogonal Cutting ◽

Cutting Speed ◽

Production Costs ◽

Chemical Compositions ◽

Alloy 625 ◽

Wide Range

Nickel-base superalloys like Alloy 625 are widely used in power generation applications due to their unique properties especially at elevated temperatures. During the related component manufacturing for gas turbines up to 50% of the material has to be removed by metal cutting operations like milling, turning or drilling. As a result of high strength and toughness the machinability of Alloy 625 is generally poor and only low cutting speeds can be used. High-speed cutting of Alloy 625 on the other hand gets more important in industry to reduce manufacturing times and thus production costs. The cutting speed represents one of the most important factors that have influences on the tool life. The aim of this study is the analyses of wear mechanisms occurring during machining of Alloy 625. Orthogonal cutting experiments have been performed and different process parameters have been varied in a wide range. New and worn tools have been investigated by stereo microscopy, optical microscopy and scanning electron microscopy. Energy-dispersive X-ray analyses were used for the investigation of chemical compositions of the tool's surface as well as the nature of reaction products formed during the cutting process. Wear mechanisms observed in the machining experiments included abrasion, fracture and tribochemical effects. Specific wear features appeared depending on the mechanical and thermal conditions generated in the wear zones.

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Study on Compressive Properties of SiC Particle Reinforced ZAlCu5Mn Composite Foams

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.395-396.3 ◽

2013 ◽

Vol 395-396 ◽

pp. 3-6

Author(s):

Rong Zhen Jin ◽

Nian Suo Xie ◽

Jiao Jiao Li ◽

Jing Che

Keyword(s):

Relative Density ◽

Volume Fraction ◽

Testing Machine ◽

Average Diameter ◽

Compressive Property ◽

Compressive Properties ◽

Sic Particles ◽

Composite Foams ◽

Universal Material Testing Machine ◽

Sic Particle

SiC particle reinforced AlCu5Mn composite foams (SiCp/ZAlCu5Mn composite foams) were fabricated by the direct foaming of the melt. The quasi-static compressive properties of SiCp/ZAlCu5Mn composite foams were tested by compressive test. The effects of SiC particle, the average diameter of pores, and the relative density on the quasi-static compressive properties of SiCp/ZAlCu5Mn composite foams were performed with the universal material testing machine. The microstructure of SiCp/ZAlCu5Mn composite was studied by SEM. The results show that choosing small size of SiC particles as reinforced material, thinning pore diameter, and increasing the relative density of SiCp/ZAlCu5Mn composite foams with the same volume fraction of SiC particles can improve the energy absorption ability under the quasi-static loading. SiCp/ZAlCu5Mn composite foams are of well compressive property. The compressive deformation course of SiCp/ZAlCu5Mn composite foams involves three stages that are the linearly elastic deformation region, the collapse plateau region, and the densification region. The test results may be influenced by strain gauge, data processing method, shape of incident wave etc.

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