scholarly journals The Influence of Quench Interruption and Direct Artificial Aging on the Hardening Response in AA6082 during Hot Deformation and In-Die Quenching

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 935
Author(s):  
Benedikte Myrold ◽  
Ola Jensrud ◽  
Knut Erik Snilsberg
Keyword(s):  
Room Temperature ◽  
Artificial Aging ◽  
Temperature Drop ◽  
Specific Strength ◽  
Altered Precipitation ◽  
Die Quenching ◽  
Emission Regulations ◽  
Direct Aging ◽  
Quenching Process ◽  
Temperature Exposure

The automotive industry is searching for lightweight solutions to meet emission regulations. Development of an integrated hot forming and in-die quenching process will leverage use of age-hardenable aluminum alloys with high specific strength for applications in volume car manufacturing. Quench interruption and direct artificial aging may reduce the cycle time in a die-quenching process. However, this alters the temperature exposure of the part and results in an altered precipitation and clustering sequence during hardening. To investigate the effect of modified precipitation and clustering on mechanical properties, the process has been simulated by application of a water-cooled compression tool to control the combination of a temperature drop and simultaneous deformation prior to aging. Extruded 4.6 mm thick AA6082 profiles were deformed during different quenching rates and directly transferred to subsequent artificial aging from various temperatures between room temperature and 200 °C. The results indicate insignificant changes of strength and elongation after direct aging from 200 °C compared to specimens cooled to room temperature before aging.

Strengthening Evaluation in a Composite Mg-RE Alloy Using TEM

2011 ◽  
Vol 678 ◽  
pp. 75-84 ◽  
Author(s):  
Marcello Cabibbo
Keyword(s):  
Electron Microscopy ◽  
Metal Matrix ◽  
Room Temperature ◽  
Strengthening Mechanism ◽  
Composite Alloy ◽  
Specific Strength ◽  
High Specific Strength ◽  
Transmission Electron ◽  
Sic Ceramic

Magnesium alloys containing rare earth elements are known to have high specific strength and corrosion resistance. The addition of SiC ceramic particles makes the metal matrix composite stronger with better wear and creep resistance and a still good machinability. The role of the reinforcement particles to the enhanced strength can be quantitatively evaluated using transmission electron microscopy (TEM). This paper presents a quantitative strengthening evaluation in a SiC Mg-RE composite alloy. The different contributions were determined by TEM inspections. The microstructure strengthening mechanism was studied after room temperature compression specimens. The way of combining the different contributions and the comparison to the measured yield stress, is also discussed and justified.

Thermal Resistance of Fly Ash Geopolymers with Alumina as Additive

2018 ◽  
Vol 281 ◽  
pp. 182-188
Author(s):  
Yong Sing Ng ◽  
Yun Ming Liew ◽  
Cheng Yong Heah ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Kamarudin Hussin
Keyword(s):  
Elevated Temperature ◽  
Fly Ash ◽  
Thermal Resistance ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Room Temperature ◽  
Strength Degradation ◽  
Alumina Addition ◽  
Higher Temperature ◽  
Temperature Exposure

The present work investigates the effect of alumina addition on the thermal resistance of fly ash geopolymers. Fly ash geopolymers were synthesised by mixing fly ash with activator solution (A mixture of 12M sodium hydroxide and sodium silicate) at fly ash/activator ratio of 2.5 and sodium silicate/sodium hydroxide ratio of 2.5. The alumina (0, 2 and 4 wt %) was added as an additive. The geopolymers were cured at room temperature for 24 hours and 60°C for another 24 hours. After 28 days, the geopolymers was heated to elevated temperature (200 - 1000°C). For unexposed geopolymers, the addition of 2 wt % of alumina increased the compressive strength of fly ash geopolymers while the strength decreased when the content increased to 4 wt.%. The temperature-exposed geopolymers showed enhancement of strength at 200°C regardless of the alumina content. The strength reduced at higher temperature exposure (> 200°C). Despite the strength degradation at elevated temperature, the strength attained was relatively high in the range of 13 - 45 MPa up to 1000°C which adequately for application as structural materials.

Tensile Properties at High and Low Temperatures and at Room Temperature after High-Temperature Exposure

2004 ◽  
pp. 211-242
Keyword(s):  
High Temperatures ◽  
Room Temperature ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Data Set ◽  
Casting Alloys ◽  
Subzero Temperatures ◽  
Wide Range ◽  
Temperature Exposure ◽  
High And Low Temperatures

Abstract This data set contains the results of uniaxial tensile tests of a wide range of aluminum casting alloys conducted at high temperatures from 100 to 370 deg C, subzero temperatures from -269 to -28 deg C, and room temperature after holding at high temperatures from 100 to 370 deg C. In most cases, tests were made of several lots of material of each alloy and temper. The results for the several lots were then analyzed together graphically and statistically, and the averages were normalized to the room-temperature typical values. For some alloys, "representative" values (raw data) rather than typical values are provided.

scholarly journals Early life variations in temperature exposure affect the epigenetic regulation of the paraventricular nucleus in female rat pups

2020 ◽  
Vol 287 (1937) ◽  
pp. 20201991
Author(s):  
Samantha C. Lauby ◽  
Patrick O. McGowan
Keyword(s):  
Dna Methylation ◽  
Thyroid Hormone ◽  
Maternal Care ◽  
Hormone Receptor ◽  
Room Temperature ◽  
Thyroid Hormone Receptor ◽  
Female Rat ◽  
Receptor Signalling ◽  
Rat Pups ◽  
Temperature Exposure

Early life maternal care received has a profound effect on later-life behaviour in adult offspring, and previous studies have suggested epigenetic mechanisms are involved. Changes in thyroid hormone receptor signalling may be related to differences in maternal care received and DNA methylation modifications. We investigated the effects of variations in temperature exposure (a proxy of maternal contact) and licking-like tactile stimulation on these processes in week-old female rat pups. We assessed thyroid hormone receptor signalling by measuring circulating triiodothyronine and transcript abundance of thyroid hormone receptors and the thyroid hormone-responsive genes DNA methyltransferase 3a and oxytocin in the paraventricular nucleus of the hypothalamus. DNA methylation of the oxytocin promoter was assessed in relation to changes in thyroid hormone receptor binding. Repeated room temperature exposure was associated with a decrease in thyroid hormone receptor signalling measures relative to nest temperature exposure, while acute room temperature exposure was associated with an increase. Repeated room temperature exposure also increased thyroid hormone receptor binding and DNA methylation at the oxytocin promoter. These findings suggest that repeated room temperature exposure may affect DNA methylation levels as a consequence of alterations in thyroid hormone receptor signalling.

Determination of Creep Parameters of Ti-6Al-4V with Bimodal and Equiaxed Microstructure

2012 ◽  
Vol 326-328 ◽  
pp. 520-524 ◽  
Author(s):  
L.A.N.S. Briguente ◽  
Antônio Augusto Couto ◽  
Nara Miranda Guimarães ◽  
Danieli A.P. Reis ◽  
Carlos de Moura Neto ◽  
...  
Keyword(s):  
Creep Resistance ◽  
Room Temperature ◽  
Life Time ◽  
Constant Load ◽  
Bimodal Microstructure ◽  
Creep Tests ◽  
Equiaxed Microstructure ◽  
Specific Strength ◽  
Heat Treated

Ti-6Al-4V is the most used of titanium alloy and presents some important properties as metallurgical stability, high specific strength, corrosion and creep resistance [. The aim of this study is to evaluate the creep behavior of Ti-6Al-4V alloy with equiaxed and bimodal microstructures and determine the creep parameters of Ti-6Al-4V in these conditions. It was used a Ti-6Al-4V alloy forged and annealed at 190°C for 6 hours and cooled in air. The material in this condition shows an equiaxed microstructure. For bimodal microstructure, the material was heat-treated at 950°C for 60 minutes and cooled in water until room temperature. After this the material was heat-treated at 600°C for 24 hours and cooled in air until room temperature. Creep tests were performed at 600°C in stress conditions of 125, 250 and 319 MPa at constant load. The alloy with Bimodal microstructure shows higher creep resistance with a longer life time in creep.

scholarly journals A Soft X-Ray Photoemission Study of the Chemisorption and Reaction of Diethylsilane on SI(100)

1993 ◽  
Vol 307 ◽  
Author(s):  
D. A. Lapiano-Smith ◽  
F. J. Himpsel ◽  
L. J. Terminello
Keyword(s):  
Room Temperature ◽  
Chemical Vapor ◽  
Subsequent Reaction ◽  
X Ray ◽  
Molecular Precursor ◽  
Band Spectra ◽  
Temperature Exposure ◽  
Photoemission Study ◽  
Deposition Techniques ◽  
Photoemission Experiment

ABSTRACTSoft x-ray synchrotron radiation has been utilized as the excitation source in a high-resolution photoemission experiment designed to investigate the chemisorption and subsequent reaction of diethylsilane on the technologically important Si(100) surface. We have found that diethylsilane chemisorbs dissociatively to form Si-CH2CH3 surface species on Si(100) following a room temperature exposure. These species are identified by two very sharp peaks observed in the valence band spectra positioned at 17.9 and 14.3 eV binding energy. In addition, C Is core level spectra, measured following exposures of Si(100) substrates as a function of surface temperature, show that carbon, in some form, exists on the Si surface following exposures at every temperature from room temperature to about 600°C. While only -CH2CH3 ethyl groups are observed on the surface at room temperature, these species appear to partially dehydrogenate at 300°C, producing a mixture of -CH2CH3 groups and other intermediate carbonaceous species. At a growth temperature of about 400°C the intermixing of elemental carbon with Si begins. At higher temperatures, we observe the continued degradation of diethylsilane to produce a Si + C alloy on the surface at 600°C. Our results indicate that diethylsilane has potential as a molecular precursor for SiC formation by chemical vapor deposition techniques.

Effect of the Metallic Aging on the Microstructure and Mechanical Properties of Titanium Alloy

MRS Advances ◽  
2017 ◽  
Vol 2 (50) ◽  
pp. 2837-2845
Author(s):  
T.J. Sánchez-Rosas ◽  
J.D. Muñoz-Andrade ◽  
M. Aguilar-Sánchez ◽  
B. Vargas-Arista ◽  
E. Garfias-García
Keyword(s):  
Titanium Alloy ◽  
Room Temperature ◽  
Microstructural Analysis ◽  
Structural Refinement ◽  
Α Phase ◽  
Direct Aging ◽  
Second Procedure ◽  
Metallic Bath ◽  
Final Spacing ◽  
Hardness Values

ABSTRACTDifferent aging heat treatments were performed in a Titanium alloy using as aging media metallic baths in comparison to typical furnace aging. As a first step, a Duplex Aging (DA) consisted of solubilization followed by quenching to room temperature after aging heat treatment in different metallic baths (Zn, Sn and Bi). A second procedure was Alternative Aging (AA) which consisted of solubilization and direct aging inside three different aforementioned baths. Microstructural aging variations begins at half hour until 30 h at 550°C inside metallic bath of Zn, Sn or Bi. Both kinds of aging promoted a microstructural variation and so on microhardness values. Microstructural analysis by Optical Microscopy showed a structural refinement after AA treatment. The highest hardness value of 375 HVN was achieved in Alternative Aging with Zn bath, which was found to be dependent on laminar α phase refining. Moreover, after AA treatment for 0.5, 1, 2, 3, 4, 10 and 30 h at 550°C in the metallic bath of Zn and Sn, the results indicated similar hardness values in different times, resulting in the fastest kinetic for Sn metallic bath at 2 h compared to that 4 h in Zn metallic bath. The observed increase in micro-hardness is not very attractive, it is recommended to use large aging times in order to stabilize final spacing of microstructural features in AA treatment.

La2CuO4+δ: Synthesis under high oxygen pressure and study of phase relations and energetics

1994 ◽  
Vol 9 (1) ◽  
pp. 8-12 ◽  
Author(s):  
R.P. Rapp ◽  
A. Mehta ◽  
J. DiCarlo ◽  
A. Navrotsky
Keyword(s):  
Room Temperature ◽  
Temperature Drop ◽  
High Oxygen ◽  
Drop Calorimetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Piston Cylinder ◽  
High Oxygen Pressure ◽  
High Pressure Oxygen ◽  
Capsule Assembly

High oxygen pressures have been achieved in a piston-cylinder apparatus using a double capsule assembly consisting of a sealed outer Au capsule, containing an oxygen source (KMnO4), and an inner, open Pt capsule containing the sample. Using this technique, La2CuO4 was annealed at 800 °C, 5–25 kbar for 2–4 h. Transposed temperature drop calorimetry at 704 °C was used to determine the enthalpy of oxidation, and weight loss measurements characterized the oxygen nonstoichiometry, δ, in La2CuO4+δ, in the high-pressure, oxygen-annealed samples. For samples analyzed at room temperature, x-ray diffraction measurements show that beyond δ ≍ 0.10–0.13, additional oxygen is accommodated in a perovskite-like LaCuO3−α phase. An analysis of the thermochemical measurements indicates that the nature of holes in La2CuO4+δ could change in the range of δ ≍ 0.03–0.06.16,17 It is further suggested that the observed change in the thermochemical behavior in the range of δ ≍ 0.03–0.06 could be the driving influence behind the spinodal decomposition of La2CuO4+δ at low temperatures (Dabrowski et al.10).

Influence of Pulsed Current on the Tensile Behaviors of the 5XXX Aluminum Alloy

2014 ◽  
Vol 709 ◽  
pp. 399-402
Author(s):  
Jung Han Song ◽  
Seo Gou Choi
Keyword(s):  
Flow Stress ◽  
Room Temperature ◽  
Test System ◽  
Al Alloys ◽  
Electric Resistivity ◽  
Al Alloy ◽  
Challenging Problem ◽  
Specific Strength ◽  
High Specific Strength ◽  
Strength And Stiffness

Aluminum (Al) alloys have great potential as ideal structural materials because of their high specific strength and stiffness. However, Al alloys exhibit poor ductility at room temperature. Enhancing the formability is a very important and challenging problem to both automotive and manufacturing engineers. In this study, the electro-plastic effects, which is first discovered in 1960s, of 5xxx Al alloy sheets are investigated to improve the formability. To begin with, a test system is built up to carry out the tensile test with heavy electric current flowing through the specimen. The evolutions of the flow stress and the electric resistivity are obtained using this test system. The significant decrease in the flow stress caused by the heavy flowing through current is observed.

scholarly journals Pre-Analytical Sample Quality: Metabolite Ratios as an Intrinsic Marker for Prolonged Room Temperature Exposure of Serum Samples

PLoS ONE ◽  
2015 ◽  
Vol 10 (3) ◽  
pp. e0121495 ◽  
Author(s):  
Gabriele Anton ◽  
Rory Wilson ◽  
Zhong-hao Yu ◽  
Cornelia Prehn ◽  
Sven Zukunft ◽  
...  
Keyword(s):  
Room Temperature ◽  
Serum Samples ◽  
Sample Quality ◽  
Intrinsic Marker ◽  
Temperature Exposure
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