Optimization of Ageing Parameters of a Low Nickel Maraging Steel

2010 ◽  
Vol 636-637 ◽  
pp. 471-477 ◽  
Author(s):  
M. Cabeza ◽  
G. Castro ◽  
P. Merino ◽  
G. Pena ◽  
M. Román ◽  
...  
Keyword(s):  
Maraging Steel ◽  
Structural Changes ◽  
Precipitation Hardening ◽  
Age Hardening ◽  
Scanning Calorimetry ◽  
Hardening Treatment ◽  
Depth Study ◽  
Final Selection ◽  
Selection Of

In the present work the age hardening parameters of a 14Ni (200) maraging steel are studied in order to optimize mechanical properties of the steel. The initial characterization of the as received solution annealed steel has been carried out by optical and scanning electron microscopy (LOM and SEM), and hardness measurements. To identify the structural changes during ageing, differential scanning calorimetry (DSC) tests were performed. Different time-temperature combinations were considered for the precipitation hardening treatment of as-quenched material samples. After hardness measurements, three of these treatments were selected for an in depth study. The obtained microstructure at the maximum hardness peaks then analysed (LOM, SEM and TEM) and mechanical behaviour (strength, toughness and wear resistance) was studied for the final selection of the age hardening conditions.

Thermo-Optical Properties of Perfluorinated Sulfonic Acid Membranes: An Investigation of Hydration Based on Absorption Spectra

2017 ◽  
Vol 71 (11) ◽  
pp. 2504-2511 ◽  
Author(s):  
Daniele T. Dias ◽  
Guy Lopes ◽  
Tales Ferreira ◽  
Ivanir L. Oliveira ◽  
Caroline D. Rosa
Keyword(s):  
Sulfonic Acid ◽  
Room Temperature ◽  
Water Retention ◽  
Structural Changes ◽  
Optical Characterization ◽  
Scanning Calorimetry ◽  
Experimental Procedure ◽  
Nafion Membranes ◽  
Perfluorinated Sulfonic Acid

The Nafion membranes are widely used in electrochemical applications such as fuel cells, chlor-alkali cells, and actuators–sensors. In this work, the thermal-optical characterization of Nafion in acid form was performed by photoacoustic spectroscopy, thermogravimetry, and differential scanning calorimetry. In the experimental procedure three distinct hydration levels were considered: (1) pristine membrane (λ ≅ H2O/–SO3H ≅ 5.6); (2) swelling process (λ ≅ 17.4); and (3) drying at controlled room temperature after swelling process (λ ≅ 6.5). The discovered behaviors showed significant irreversible structural changes induced by water retention in the membrane. These structural changes depend on the water population present in the clusters and also affect the directional thermal diffusivity of the membrane irreversibly.

Investigation on Modified Humic Substances Based Binders for Iron Ore Agglomeration

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Guihong Han ◽  
Tao Jiang ◽  
Guanghui Li ◽  
Yanfang Huang ◽  
Yuanbo Zhang
Keyword(s):  
Chemical Analysis ◽  
Humic Substances ◽  
Optical Density ◽  
Iron Ore ◽  
Structural Changes ◽  
Density Ratio ◽  
Hydroxyl Groups ◽  
Scanning Calorimetry ◽  
Optical Density Ratio

Characterization of modified humic substances based binders for iron ore agglomeration was examined by chemical analysis, optical density, Fourier transform infrared spectrum (FTIR), and thermogravimetry and differential scanning calorimetry (TG–DSC). Chemical analysis displays the proportion of fulvic acid (FA) to humic acid (HA) in the binder is 1:10. Compared with the HA, the FA possesses more functional groups. Meantime, optical density ratio analysis shows that the molecular weight and aromatization degree of the FA are smaller than those of the HA. FTIR spectra further confirm aromatic and aliphatic fractions are associated with various types of oxygen-rich groups including carboxyl and hydroxyl groups. TG–DSC and chemical analysis indicate structural changes of the binder including thermal decomposition, dehydroxylation and/or decarboxylation are caused during heating. The structural characterization of the binder ensures its good performance in the field of iron ore agglomeration.

Preparation and Crystallization Kinetics of FeSiB Amorphous Ribbons under Non-Isothermal Regime

2014 ◽  
Vol 605 ◽  
pp. 35-38
Author(s):  
Eirini Varouti
Keyword(s):  
Thermal Stability ◽  
Differential Scanning Calorimetry ◽  
Chemical Composition ◽  
Crystallization Kinetics ◽  
Structural Changes ◽  
Scanning Calorimetry ◽  
Amorphous Ribbons ◽  
Isothermal Regime ◽  
Kinetics Of

The aim of the present work was the preparation and characterization of FeSiB amorphous magnetic ribbons with the following chemical composition: Fe80SixB20-x, x=5,6,8 and Fe75Si15B10. Differential Scanning Calorimetry was employed in order to study the thermal stability and structural changes during the transformations that took place. Much emphasis is placed on the analysis of the crystallization kinetics.

scholarly journals Characterization of Li2O-Al2O3-SiO2 glass-ceramics produced from a Brazilian spodumene concentrate

Cerâmica ◽  
2019 ◽  
Vol 65 (375) ◽  
pp. 366-377 ◽  
Author(s):  
L. B. Rebouças ◽  
M. T. Souza ◽  
F. Raupp-Pereira ◽  
A. P. Novaes de Oliveira
Keyword(s):  
Structural Changes ◽  
Glass Ceramics ◽  
Nucleating Agent ◽  
Raw Material ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Heating Microscopy ◽  
Shock Resistance ◽  
High Thermal Shock Resistance

Abstract Glass-ceramics in the LAS (Li2O-Al2O3-SiO2) system with high thermal shock resistance were successfully obtained using Brazilian spodumene concentrate as the main raw material (80-70 wt%). Two compositions (Li2O.Al2O3.nSiO2) were produced with n= 2 and 4, near to the stoichiometric compositions of β-eucryptite and β-spodumene. The characteristic temperatures of parent glasses were determined by contact dilatometry, differential scanning calorimetry and heating microscopy. The crystallization mechanism and the effect of the nucleating agent (TiO2.2ZrO2) required to promote volume crystallization in the parent glasses were investigated. Microstructural and structural changes with temperature were also evaluated by optical microscopy and X-ray diffraction. The obtained glass-ceramics presented coefficients of thermal expansion between -0.370x10-6 and 4.501x10-6 °C-1 in the 22 to 700 °C range.

Characterization of Amorphous, Magnetic Fe-Si-B Ribbons

2013 ◽  
Vol 543 ◽  
pp. 476-478
Author(s):  
Eirini Varouti
Keyword(s):  
Structural Changes ◽  
Amorphous State ◽  
Barkhausen Noise ◽  
Chemical Compositions ◽  
Magnetic Barkhausen Noise ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Noise Measurements ◽  
Shed Light

The aim of this study is to contribute to a better understanding of the properties, structure and crystallization process of the amorphous Fe-based ribbon with the following chemical compositions: Fe80SixB20-x (x=5,6,8) and Fe75Si15B10. Thermal analysis, including Differential Scanning Calorimetry and Magnetic-Thermogravimetric Analysis, were used to shed light in the thermal stability and structural changes taking place during the transformation from the amorphous state to the crystalline state. The arising microstructure was observed via X-ray diffraction. Finally, Magnetic Barkhausen Noise measurements took place so as conclusions to be derived relevant to the dependence between the parameters of the Magnetic Barkhausen Noise and the chemical composition of the amorphous ribbons.

Effect of Combined Pre-Straining and Pre-Aging on the Precipitation Behavior and Age Hardening Response for Al-Mg-Si Alloys

2021 ◽  
Vol 1026 ◽  
pp. 74-83
Author(s):  
Guan Jun Gao ◽  
Xi Wu Li ◽  
Li Zhen Yan
Keyword(s):  
Electron Microscopy ◽  
Natural Aging ◽  
Hardness Test ◽  
Age Hardening ◽  
Precipitation Behavior ◽  
Strengthening Phase ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Hardening Treatment ◽  
Cluster 2

Pre-strain (PS) and pre-aging (PA) treatments are often applied during the preparation of Al-Mg-Si automotive aluminum alloy. In this study, the effect of combined PS and PA on the precipitation behavior and age hardening response for Al-Mg-Si alloys was investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile test, Vickers hardness test, and differential scanning calorimetry (DSC). It was found that the dislocations introduced by PS treatment and the cluster (2) formed during PA treatment effectively inhibited the cluster (1), which further strengthened the inhibition of natural aging hardening at room temperature (RT). The strength increment of the alloys was kept below 10.0 MPa during two weeks RT storage. The dislocations provided heterogeneous nucleation for the precipitates forming and the cluster (2) transformed into β″ strengthening phase during bake hardening treatment. With the acceleration response of the dislocations and the cluster (2), the age hardening response of Al-Mg-Si alloys obviously improved with the denser and larger β″ strengthening phase formed.

Effects of Cu Addition on the Precipitation Process of Al-9Zn-4Mg-xCu (wt. %) Alloys at 130°C

2016 ◽  
Vol 835 ◽  
pp. 222-229
Author(s):  
Bondan Tiara Sofyan ◽  
Immalatul Husna ◽  
Muhammad Syahid
Keyword(s):  
Grain Boundaries ◽  
Optical Microscope ◽  
Age Hardening ◽  
Peak Hardness ◽  
Precipitation Process ◽  
High Concentration ◽  
Scanning Calorimetry ◽  
Microstructural Observation ◽  
Cu Content ◽  
Hardening Treatment

Aluminium is a light-weight material and possesses high corrosion resistance, so that it is widely used in manufacturing industries. The Al-Zn series have the highest strength compared to other aluminium alloys. To further increase the strength of Al-Zn alloys, Mg and Cu are added and age hardening treatment is applied. This research studied the precipitation process in Al-9Zn-4Mg (wt. %) alloys with Cu content of 0, 1, 3 and 5 wt.%. The alloys were produced through investment casting taking the shape of turbine impeller. The samples were solution treated at 460 °C for 2 hours and then aged at 130 °C. The characterization included hardness testing to observe response of age hardening, microstructural observation and Differential Scanning Calorimetry (DSC) testing. Microstructural observation was conducted by optical microscope and Scanning Electron Microscope (SEM) which was combined with Energy Dispersive Spectroscopy (EDS). The results showed that addition of Cu initially decreased the hardness during early ageing (2 hours) due to segregation of Cu-V complexes toward the grain boundaries which then decreased the hardness and enlarged the grain boundary phases. However, the peak hardness of the alloys was not affected by the increase in Cu content. due to high concentration of Zn and Mg. Exothermic reactions of formation of GP zones, η", η' and η (MgZn2) were found during precipitation process while endothermic reaction were observed due to dissolution of the phases. Presence of MgZn2 and Al7Cu2Fe second phases were observed in grain boundaries.

scholarly journals Characterization of the Density and Spatial Distribution of Dispersoids in Al-Mg-Si Alloys

Metals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 26
Author(s):  
Magnus Remøe ◽  
Ida Westermann ◽  
Knut Marthinsen
Keyword(s):  
Spatial Distribution ◽  
Age Hardening ◽  
Careful Selection ◽  
Homogenization Procedure ◽  
Heating Rates ◽  
Spatial Uniformity ◽  
Nucleation Sites ◽  
Precipitation Behaviour ◽  
Selection Of

Al-Mg-Si alloys often contain small additions of, for example, Mn or Cr, to form dispersoids, which may act as nucleation sites for Mg2Si particles after homogenization. The purpose of adding Mn and Cr is to ensure a high density of uniformly distributed small β’-particles, which can be dissolved during further processing prior to the final age hardening step. However, their density and spatial distribution are critically dependent on the homogenization procedure. It is therefore important to have a robust and reliable method for assessing their spatial distribution. In the present work, an existing methodology for assessing spatial uniformity, the Global Shannon Entropy (GSE), was implemented and evaluated for different dispersoid structures characterized by scanning electron microscopy. This metric is highly dependent on the parameters used, but by careful selection of adequate parameters, it can be effective in detecting non-uniformity. An important weakness with the GSE was identified, and a modification to improve on the ability to differentiate degrees of non-uniformity is suggested. To evaluate the proposed methodology, the effect of heating rate on dispersoid precipitation behaviour during homogenisation of four Al-Mg-Si alloys with different Mn/Cr-content was investigated. In general, the dispersoid density increased with decreasing heating rates as longer times in the furnace resulted in particle coarsening. Slower heating rates were found to promote a more uniform dispersoid structure for most alloys investigated in this study. The metric with the new term demonstrated promising results, and improved the ability to differentiate degrees of spatial uniformity.

Measurements of the Cape Astrometric Survey of the Southern Hemisphere

1978 ◽  
Vol 48 ◽  
pp. 515-521
Author(s):  
W. Nicholson
Keyword(s):  
Southern Hemisphere ◽  
Automatic Measuring ◽  
Measuring Machine ◽  
Final Selection ◽  
Selection Of

SummaryA routine has been developed for the processing of the 5820 plates of the survey. The plates are measured on the automatic measuring machine, GALAXY, and the measures are subsequently processed by computer, to edit and then refer them to the SAO catalogue. A start has been made on measuring the plates, but the final selection of stars to be made is still a matter for discussion.

Applications of Transmission Electron Microscopy in the Characterization of Metal Machinability

1968 ◽  
Vol 26 ◽  
pp. 442-443 ◽  
Author(s):  
L.E. Murr ◽  
A.B. Draper
Keyword(s):  
Electron Microscopy ◽  
State Physics ◽  
Test Material ◽  
Milling Machine ◽  
Rotary Table ◽  
Solid State Physics ◽  
Materials Properties ◽  
Transmission Electron ◽  
Selection Of

The industrial characterization of the machinability of metals and alloys has always been a very arbitrarily defined property, subject to the selection of various reference or test materials; and the adoption of rather naive and misleading interpretations and standards. However, it seems reasonable to assume that with the present state of knowledge of materials properties, and the current theories of solid state physics, more basic guidelines for machinability characterization might be established on the basis of the residual machined microstructures. This approach was originally pursued by Draper; and our presentation here will simply reflect an exposition and extension of this research.The technique consists initially in the production of machined chips of a desired test material on a horizontal milling machine with the workpiece (specimen) mounted on a rotary table vice. A single cut of a specified depth is taken from the workpiece (0.25 in. wide) each at a new tool location.

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