Influence of Deformation on Aging Precipitation Behavior of an Al-Cu-Mg-Si Alloy

2014 ◽  
Vol 936 ◽  
pp. 1247-1251 ◽  
Author(s):  
Xi Wu Li ◽  
Bai Qing Xiong ◽  
Yong An Zhang ◽  
Yan Qi Zeng ◽  
Feng Wang ◽  
...  
Keyword(s):  
Cold Deformation ◽  
Temperature Stability ◽  
High Temperature Stability ◽  
Precipitation Behavior ◽  
Scanning Calorimetry ◽  
Σ Phase ◽  
Aerospace Applications ◽  
Transmission Electron ◽  
Aging Precipitation ◽  
Stretching Deformation

To meet the stringent requirements of heat-resistance products for aerospace applications, an Al-4.0Cu-1.3Mg-0.6Si alloy containing a cubic σ phase (Al5Cu6Mg2) with excellent high temperature stability was developed. Influence of deformation on aging precipitation behavior of the alloy was investigated by transmission electron microscope (TEM) and differential scanning calorimetry (DSC). The results indicated that cold deformation had great effect on aging precipitation behavior in the alloy. When the alloy was processed a pre-stretching deformation before aging, the precipitation of σ phase was restrained while the S′ phase (Al2CuMg) was promoted. And the nucleation sites played an important role on them.

Hexaaluminate Catalysts for Fuel Reforming

2008 ◽  
Author(s):  
Nicholas E. McGuire ◽  
Neal P. Sullivan ◽  
Robert J. Kee ◽  
Huayang Zhu ◽  
James A. Nabity ◽  
...  
Keyword(s):  
Flow Reactor ◽  
Exchange Process ◽  
Catalyst Support ◽  
Temperature Stability ◽  
Metal Exchange ◽  
High Temperature Stability ◽  
Fuel Reforming ◽  
Transmission Electron ◽  
Wide Range ◽  
Hexaaluminate Catalysts

Hexaaluminate catalysts offer excellent high-temperature stability compared to the equivalent metal-based catalysts. Their stability also lends well to use as a catalyst support. However, use of novel hexaaluminates is limited in fuel processing for fuel-cell applications. In this paper, we report on the performance of hexaaluminates as a catalyst support in the steam reforming of methane. The hexaaluminates are synthesized by a metal-exchange process using alumoxane precursors that enable a wide range of metal substitutions. Performance is evaluated using a unique stagnation-flow reactor that enables detailed probing of the boundary layer above the catalyst-impregnated stagnation surface. Experimental results are compared with models to understand fundamental reaction kinetics and optimize catalyst performance. RhSr-substituted hexaaluminates with a Rh impregnation are shown to yield the best performance. Scanning- and Transmission-Electron Microscopy are used to characterize the different types of hexaaluminates, and to examine the effect of aging on catalyst structure.

scholarly journals Effect of a Trace Addition of Sn on the Aging Behavior of Al–Mg–Si Alloy with a Different Mg/Si Ratio

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 913 ◽  
Author(s):  
Lehang Ma ◽  
Jianguo Tang ◽  
Wenbin Tu ◽  
Lingying Ye ◽  
Haichun Jiang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Room Temperature ◽  
Number Density ◽  
Precipitation Behavior ◽  
Aging Behavior ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Positive Effect ◽  
Room Temperature Tensile Test

In this paper, the effect of trace Sn on the precipitation behavior and mechanical properties of Al–Mg–Si alloys with different Mg/Si ratios aged at 180 °C was investigated using hardness measurements, a room-temperature tensile test, transmission electron microscopy and differential scanning calorimetry. The results shown that Sn reduces the precipitation activation energy, increases the number density of β″ precipitates, and then increased the aging hardenability and mechanical properties of the Al–Mg–Si alloy. However, the positive effect of Sn on the mechanical properties of the Al–Mg–Si alloy drops with the decrease of the Mg/Si ratio of the alloy.

scholarly journals A Low-Temperature Alumina/Copper Diffusion Bonding Process using La-Doped Titanium Interlayers

Coatings ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 401 ◽  
Author(s):  
Cherng-Yuh Su ◽  
Jia-Liang Huang ◽  
Po-Chun Chen ◽  
Hsin-Jung Yu ◽  
Dai-Liang Ma ◽  
...  
Keyword(s):  
Low Temperature ◽  
Diffusion Bonding ◽  
Bonding Temperature ◽  
Oxygen Affinity ◽  
Temperature Stability ◽  
High Strength ◽  
High Temperature Stability ◽  
Transmission Electron ◽  
Temperature Diffusion ◽  
La Doped

Ceramic-to-metal heterojunctions have been established to improve high-temperature stability for applications in aerospace and harsh environments. In this work, we employed low-temperature diffusion bonding to realize an alumina/Cu heterogeneous joint. Using a thin layer of lanthanum-doped titanium (La-doped Ti) to metallize the alumina surface, we achieved the bonding at a temperature range of 250–350 °C. We produced a uniform, thermally stable, and high-strength alumina/Cu joint after a hot-press process in vacuum. Signals from X-ray diffraction (XRD) suggested the successful diffusion of Ti and La into the alumina substrate, as Ti can easily substitute Al in alumina, and La has a better oxygen affinity than that of Al. The transmission electron microscopy and XRD results also showed the existence of CuxTiyO phases without CuxTiy or LaOx. In addition, the bonding strength of alumina/copper hot-pressed at 250, 300, and 350 °C were 7.5, 9.8 and 15.0 MPa, respectively. The process developed in this study successfully lowered the bonding temperature for the alumina/copper joint.

scholarly journals Multiscale Study on the Effect of Nano-Organic Montmorillonite on the Performance of Rubber Asphalt

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Xiaoge Tian ◽  
Ren Zhang ◽  
Zhen Yang ◽  
Yantian Chu ◽  
Yichao Xu ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Storage Stability ◽  
Temperature Stability ◽  
High Temperature Stability ◽  
Scanning Calorimetry ◽  
Microscopic Mechanism ◽  
Organic Montmorillonite ◽  
Temperature Performance ◽  
And Storage

In order to improve the high-temperature performance, antiaging performance, and storage stability of rubber asphalt, nano-organic montmorillonite (NOMMT) was mixed with rubber asphalt. Macroscopic influences of NOMMT on rubber asphalt were measured through penetration, softening point, ductility, rotational viscosity tests, dynamic shear rheology test, and bending beam rheology test at low temperature and were conducted on rubber asphalt with different contents of NOMMT. Then, the microscopic mechanism of NOMMT on the microscopic performance of rubber asphalt was studied through using scanning electron microscopy (SEM), infrared spectroscopy (IR), and differential scanning calorimetry (DSC). The results showed that the rubber particles were smoother, uniform, and dispersed after NOMMT was introduced, and the compatibility between NOMMT and crumbed rubber powder was good. Some stable structures were formed in the composite modified asphalt. The disappearance of alcohol phenol and the increase in related groups such as alkane, benzene, and hydrocarbon indicated that chemical reaction occurred between NOMMT and rubber asphalt, resulting in the changes of the performance of the composite modified system, so that high-temperature stability, antiaging properties, and storage stability were improved but its low-temperature performance was decreased.

Synthesis and characterization of pure and nanosized hydroxyapatite bioceramics

2017 ◽  
Vol 6 (2) ◽  
pp. 149-157 ◽  
Author(s):  
Aneela Anwar ◽  
Qudsia Kanwal ◽  
Samina Akbar ◽  
Aisha Munawar ◽  
Arjumand Durrani ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Calcium Nitrate ◽  
Temperature Stability ◽  
Molar Ratio ◽  
Calcium Nitrate Tetrahydrate ◽  
High Temperature Stability ◽  
X Ray ◽  
Transmission Electron ◽  
Nanosized Hydroxyapatite ◽  
Co Precipitation

AbstractSynthetic nanosized hydroxyapatite (HA) particles (<120 nm) were prepared using a co-precipitation technique by adopting two different routes – one from an aqueous solution of calcium nitrate tetrahydrate and diammonium hydrogen phosphate at pH 10 and the other by using calcium hydroxide and phosphoric acid as precursors at pH 8.5 and reaction temperature of 50°C. The lattice parameters of HA nanopowder were analogous to reference [Joint Committee on Powdered Diffraction Standards (JCPDS)] pattern no. 09-432. No decomposition of HA into other phases was observed even after heating at 1000°C in air for 1 h. This observation revealed the high-temperature stability of the HA nanopowder obtained using co-precipitation route. The effects of preliminary Ca/P molar ratio, precipitation, pH and temperature on the evolution of phase and crystallinity of the nanopowder were systematically examined and optimized. The product was evaluated by techniques such as X-ray-diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and Raman spectroscopy analyses. The chemical structural analysis of the as-prepared HA sample was performed using X-ray photoelectron spectroscopy (XPS). After heat treatment at 1000°C for 1 h and ageing for 15 h, the product was obtained as a phase-pure, highly crystalline HA nanorods.

Research on Microstructure Evolution of Spray Forming FVS0812 Alloy Varies with Temperature

2014 ◽  
Vol 543-547 ◽  
pp. 3729-3732
Author(s):  
Rong Hua Zhang ◽  
Biao Wu ◽  
Xiao Ping Zheng
Keyword(s):  
Electron Microscope ◽  
High Temperature ◽  
Energy Dispersive Spectrometer ◽  
Temperature Stability ◽  
Optical Microscope ◽  
Spray Forming ◽  
Effect Of Temperature ◽  
High Temperature Stability ◽  
Transmission Electron ◽  
Microstructure Of The Material

Heat-resistant FVS0812 alloys were prepared by spray forming technique. The effect of temperature on microstructure the alloys was studied by optical microscope (OM), transmission electron microscope (TEM) with energy dispersive spectrometer (EDS), differential scanning calorimeter (DSC) in this paper. The research results show that the microstructure of the material doesnt change obviously after being hold for 3 hours at 420°C temperature. When the temperature is over 420°C, the second coarse phases are found in the alloy. The studies on the microstructure of the alloy exposed at 400°C for 100 hours show that the alloy has excellent high temperature stability.

Effect of Cold Deformation on Precipitation of 7050 Aluminum Alloy during Aging Process

2015 ◽  
Vol 1120-1121 ◽  
pp. 1014-1018
Author(s):  
Hong Wei Yan ◽  
Liang Zhen ◽  
Jian Tang Jiang
Keyword(s):  
Electron Microscopy ◽  
Aluminum Alloy ◽  
Aging Process ◽  
Cold Deformation ◽  
Research Topic ◽  
Strengthening Mechanisms ◽  
Scanning Calorimetry ◽  
Main Research ◽  
Transmission Electron ◽  
7050 Aluminum Alloy

Strengthening of aluminum alloy has always been an interesting research topic. There might be interactions between different strengthening mechanisms. In this paper, the effect of large cold deformation on the precipitation of as-quenched 7050 aluminum alloy was studied. Differential scanning calorimetry was used as the main research technique, accompanied by tensile test and transmission electron microscopy. It was found that clusters and precipitation had formed in the cold deformation, and dislocations accelerated the precipitation dynamics.

Analysis of Ageing Precipitation Behavior of an Aluminum Alloy

2014 ◽  
Vol 488-489 ◽  
pp. 243-247
Author(s):  
Hong Xing Liu ◽  
Jian Bo Zhang ◽  
Qi Ming Liang ◽  
Hai Jun Hu
Keyword(s):  
Electrical Conductivity ◽  
Ageing Time ◽  
Precipitation Behavior ◽  
Scanning Calorimetry ◽  
Exothermic Reactions ◽  
Transmission Electron ◽  
Different Temperatures ◽  
One Step ◽  
Electrical Conductivity Change

The characterization of Al-Cu-Mg-Ag alloy with high Cu:Mg in the process of one-step ageing at the different temperatures has been studied by hardness, electrical conductivity test combining with transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results show that one endothermic and three exothermic reactions are involved in the curve of DSC experiment for a sample quenched from 520°C. Four samples were aged at the different temperatures greater or less than the peak temperatures of the four reactions. Hardness and electrical conductivity change slowly with ageing time at the low temperature and change fast at the high temperature. GP zones at {100} ɑ planes are the main precipitates in the microstructure of the sample aged at 80°C. Ω and θ phases dominant the microstructure of the samples aged at 170°C, 230°C and 280°C. In addition, the size of precipitates increases fast when the sample aged at higher temperatures.

Inorganically filled carbon nanotubes: Synthesis and properties

2010 ◽  
Vol 82 (11) ◽  
pp. 2097-2109 ◽  
Author(s):  
Ujjal K. Gautam ◽  
Yoshio Bando ◽  
Pedro M. F. J. Costa ◽  
Xiaosheng Fang ◽  
Benjamin Dierre ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
High Temperature ◽  
Mechanical Response ◽  
Chemical Vapor ◽  
Temperature Stability ◽  
Inorganic Materials ◽  
High Temperature Stability ◽  
Heating Rates ◽  
Transmission Electron ◽  
Synthesis Strategy

Since the discovery of carbon nanotubes (CNTs) in 1991, widespread research has been carried out to understand their useful physical and electronic properties and also to explore their use in devices. CNTs have many unique properties such as tunable electrical resistance, mechanical robustness, and high thermal conductivity, which when combined with other inorganic materials such as phosphors or superconductors could lead to hetero-structures with diverse functionality. We have been able to obtain mass production of such materials wherein CNTs form core-shell heterostructures with metals, semiconductors, insulators, and even metal-semiconductor heterojunctions. The emerging strategy employs a high-temperature chemical vapor deposition (CVD) technique and high heating rates. Interestingly, due to their high temperature stability, CNTs can act as a nanoreactor for production of exotic materials inside it. In this article, we take ZnS-filled CNTs as an example to explain our synthesis strategy. We explore the optical behavior of these complex materials, analyzing both their luminescence and degradation upon exposure to an electron beam. In addition, the mechanical response of filled CNTs has been evaluated individually inside a transmission electron microscope fitted with an atomic force microscopy–transmission electron microscopy (AFM–TEM) sample holder. Many applications can be envisioned for these nanostructures ranging from nanothermometers to photo-protective storage and delivery devices.

Sign in / Sign up

Export Citation Format

Share Document