scholarly journals On the extraordinary low quench sensitivity of an AlZnMg alloy

2021 ◽  
Author(s):  
Christian Rowolt ◽  
Benjamin Milkereit ◽  
Armin Springer ◽  
Mami Mihara-Narita ◽  
Hideo Yoshida ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Natural Aging ◽  
Temperature Reaction ◽  
Scanning Calorimetry ◽  
Medium Temperature ◽  
Cooling Rates ◽  
Quench Sensitivity ◽  
High Temperature Reaction ◽  
Wide Range ◽  
Wrought Aluminum

AbstractThe scope of this work was to investigate the quench sensitivity of a high-purity wrought aluminum alloy Al6Zn0.75 Mg (in this work called 7003pure). This is compared to a similar alloy with the additions of Fe, Si, and Zr at a sum less than 0.3 at.% (in this work called 7003Fe,Si,Zr). Differential scanning calorimetry (DSC) was used for an in situ analysis of quench induced precipitation in a wide range of cooling rates varying between 0.0003 and 3 K/s. In 7003pure, three main precipitation reactions were observed during cooling, a medium temperature reaction with a distinct double peak between 325 and 175 °C and a very low temperature reaction starting at about 100 °C. An additional high temperature reaction related to the precipitation of Mg2Si starting at 425 °C has been observed for 7003Fe,Si,Zr. In terms of hardness after natural as well as artificial aging, alloy 7003pure shows a very low quench sensitivity. Hardness values on the saturation level of about 120 HV1 are seen down to cooling rates of 0.003 K/s. The as-quenched hardness (5 min of natural aging) shows a maximum at a cooling rate of 0.003 K/s, while slower and faster cooling results in a lower hardness. In terms of hardness after aging, 0.003 K/s could be defined as the technological critical cooling rate, which is much higher for 7003Fe,Si,Zr (0.3–1 K/s). The physical critical cooling rates for the suppression of any precipitation during cooling were found to be about 10 K/s for both variants.

Crystallization Behaviour of Polytetrafluoroethylene over very Large Cooling Rate Domains

2013 ◽  
Vol 747 ◽  
pp. 201-204
Author(s):  
Nicolas Bosq ◽  
Nathanaël Guigo ◽  
Nicolas Sbirrazzuoli
Keyword(s):  
Cooling Rate ◽  
Glassy State ◽  
Crystalline Polymer ◽  
Sem Analysis ◽  
Scanning Calorimetry ◽  
Theoretical Dependence ◽  
Cooling Rates ◽  
Fast Scanning Calorimetry ◽  
Wide Range ◽  
Fast Cooling

Polytetrafluoroethylene (PTFE) is a semi-crystalline polymer that demonstrates a very fast crystallization process on cooling. This study investigates the nonisothermal PTFE ultra-fast crystallization over a wide range of cooling rates via conventional Differential Scanning Calorimetry (DSC), Fast Scanning Calorimetry (FSC) and Ultra-Fast Scanning Calorimetry (UFSC). A new knowledge about crystallization kinetics of PTFE is obtained from the data obtained under very fast cooling rates. The shift of the melting peak to lower temperature shows that the crystals formed under fast cooling rates are slightly less stable than those produced under slower cooling rates. SEM analysis allows to observe these differences in crystal morphologies. According to the results, the crystallization is still present even for the fastest cooling rate employed and in consequences it is impossible to reach a metastable glassy state. The effective activation energy (Eα) displays a variation with the relative extent of crystallization (α) that is characteristic of a transition of PTFE crystallization from regime II to regime III around 312°C. Following the Hoffman-Lauritzen theory the Eα dependency obtained from the crystallizations under the different cooling rates was fitted in order to study the theoretical dependence of the growth rate.

The effect of cooling rate on crystallization behavior and tensile properties of CF/PEEK composites

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Guangming Dai ◽  
Lihua Zhan ◽  
Chenglong Guan ◽  
Minghui Huang
Keyword(s):  
Cooling Rate ◽  
Crystallization Temperature ◽  
Crystallization Behavior ◽  
Crystalline Polymer ◽  
Scanning Calorimetry ◽  
Nonisothermal Crystallization ◽  
Cooling Rates ◽  
Control Range ◽  
Temperature Range ◽  
Transverse Tensile

Abstract In this study, the differential scanning calorimetry (DSC) tests were performed to measure the nonisothermal crystallization behavior of carbon fiber reinforced polyether ether ketone (CF/PEEK) composites under different cooling rates. The characteristic parameters of crystallization were obtained, and the nonisothermal crystallization model was established. The crystallization temperature range of the material at different cooling rates was predicted by the model. The unidirectional laminates were fabricated at different cooling rates in the crystallization temperature range. The results showed that the crystallization temperature range shifted to a lower temperature with the increase of cooling rate, the established nonisothermal crystallization model was consistent with the DSC test results. It is feasible to shorten the cooling control range from the whole process to the crystallization range. The crystallinity and transverse tensile strength declined significantly with the increase of the cooling rate in the crystallization temperature range. The research results provided theoretical support for the selection of cooling conditions and temperature control range, which could be applied to the thermoforming process of semi-crystalline polymer matrixed composites to improve the manufacturing efficiency.

scholarly journals Development of Precipitation Hardening Parameters for High Strength Alloy AA 7068

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 918
Author(s):  
Julia Osten ◽  
Benjamin Milkereit ◽  
Michael Reich ◽  
Bin Yang ◽  
Armin Springer ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Cooling Rate ◽  
Maximum Yield ◽  
High Strength ◽  
Tensile Tests ◽  
Age Hardening ◽  
Scanning Calorimetry ◽  
Cooling Rates ◽  
Critical Cooling Rate ◽  
Kinetics Of

The mechanical properties after age hardening heat treatment and the kinetics of related phase transformations of high strength AlZnMgCu alloy AA 7068 were investigated. The experimental work includes differential scanning calorimetry (DSC), differential fast scanning calorimetry (DFSC), sophisticated differential dilatometry (DIL), scanning electron microscopy (SEM), as well as hardness and tensile tests. For the kinetic analysis of quench induced precipitation by dilatometry new metrological methods and evaluation procedures were established. Using DSC, dissolution behaviour during heating to solution annealing temperature was investigated. These experiments allowed for identification of the appropriate temperature and duration for the solution heat treatment. Continuous cooling experiments in DSC, DFSC, and DIL determined the kinetics of quench induced precipitation. DSC and DIL revealed several overlapping precipitation reactions. The critical cooling rate for a complete supersaturation of the solid solution has been identified to be 600 to 800 K/s. At slightly subcritical cooling rates quench induced precipitation results in a direct hardening effect resulting in a technological critical cooling rate of about 100 K/s, i.e., the hardness after ageing reaches a saturation level for cooling rates faster than 100 K/s. Maximum yield strength of above 600 MPa and tensile strength of up to 650 MPa were attained.

Detection of Quench Induced Precipitation in Al Alloys by Dilatometry

2016 ◽  
Vol 877 ◽  
pp. 147-152 ◽  
Author(s):  
Benjamin Milkereit ◽  
Michael Reich ◽  
Olaf Kessler
Keyword(s):  
Cooling Rate ◽  
High Strength ◽  
Al Alloys ◽  
Age Hardening ◽  
Controlled Cooling ◽  
Scanning Calorimetry ◽  
Cooling Rates ◽  
Precipitation Behaviour ◽  
In Situ Detection

Quenching is a critical step during the strengthening age hardening of Aluminium alloys. To obtain optimal technological results, parts should be quenched with the upper critical cooling rate. The precipitation behaviour of Al alloys during cooling from solution annealing and thereby the critical cooling rates are typically investigated by in-situ measurements with differential scanning calorimetry (DSC). Conventional DSCs are limited at cooling rates below 10 Ks-1. Unfortunately, medium to high strength Al alloys typically have critical cooling rates between 10 and some 100 Ks-1. Recently it was shown that dilatometry is generally able for in-situ detection of precipitation in Al alloys. Dilatometry allows controlled cooling up to some 100 Ks-1 and therefore covers the cooling rate range relevant. In this work, we aim to show up and discuss possibilities and limitations of dilatometric detection of quench induced precipitates in 2xxx, and 7xxx Al alloys. The basic method will be presented and results will be compared with DSC work.

Influence of Cooling Rates on Phase Transitions of Bent-Core Liquid Crystal 1,3-Phenylene-bis[4-(hexylcarboyloxyl)benzylideneamine]

2010 ◽  
Vol 428-429 ◽  
pp. 247-250 ◽  
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
Liquid Crystal ◽  
Optical Microscopy ◽  
Cooling Rate ◽  
Scanning Calorimetry ◽  
Slow Cooling ◽  
Cooling Rates ◽  
Polarized Optical Microscopy ◽  
Fast Cooling

The influence of cooling rate on the phase transitions of a three-benzene-ring containing bent-core liquid crystal 1,3-phenylene-bis[4-(hexylcarboyloxyl)benzylideneamine] has been investigated by means of differential scanning calorimetry and polarized optical microscopy. Our results show that the cooling rates in the second cooling run pose significant effects on the phase transitions of the bent-core liquid crystal despite the cooling rates in the first cooling run pose little effects on the phase transitions. In the second cooling run, the banana phases survived only when the cooling rates were in the range of 14~15oC/min whereas both slow cooling rates which were less than 13oC/min and fast cooling rates which were higher than 16oC/min made the banana phases disappeared.

scholarly journals Influence of Cooling Rate on Nature and Morphology of Intercellular Precipitates in Si-Mo Ductile Irons

2018 ◽  
Vol 925 ◽  
pp. 231-238
Author(s):  
Mervat Youssef ◽  
Adel Nofal ◽  
Abdelhamid Hussein
Keyword(s):  
Cooling Rate ◽  
Lamellar Structure ◽  
Wide Spectrum ◽  
State Transformation ◽  
Solid State Transformation ◽  
Scanning Calorimetry ◽  
Cooling Rates ◽  
Eutectic Carbides ◽  
Thermo Calc Software ◽  
Scanning Electron

This work is designed to better understand the influence of cooling rate on the nature and morphology of intercellular precipitates in Silicon-Molybdenum ferritic ductile iron (SiMo). Plates of 3, 6, 9 mm thickness were cast in greensand and investment casting molds to give a wide spectrum of cooling rates. It was found that at higher cooling rates, the intercellular regions have a lamellar structure typical of pearlite. With decreasing cooling rates, the precipitate contains complex (Fe-Mo-Si) carbides of fine spheroidal or rod-like structure surrounding the eutectic carbides.Intensive Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) and Optical Microscopy (OM) investigations showed that the eutectic carbides are mainly (Fe, Mo, Si) C containing up to 48% Mo, whereas the fine precipitates contain lower Mo-contents. Both carbide types did not show to have a strict stoichometric composition. The solidification and solid-state transformation path was determined using both phase diagram calculated from Thermo-Calc software as well as Differential Scanning Calorimetry (DSC).

scholarly journals Effect of Cooling Rate on Phase and Crystal Morphology Transitions of CaO–SiO2-Based Systems and CaO–Al2O3-Based Systems

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 62 ◽  
Author(s):  
Mei Leng ◽  
Feifei Lai ◽  
Jiangling Li
Keyword(s):  
Cooling Rate ◽  
Mold Flux ◽  
Crystal Morphology ◽  
Confocal Scanning Laser Microscopy ◽  
Scanning Calorimetry ◽  
Cooling Rates ◽  
Mold Fluxes ◽  
Confocal Scanning ◽  
Confocal Scanning Laser ◽  
Primary Crystals

The phase and crystal morphology transitions of two typical types of mold fluxes were investigated fundamentally using differential scanning calorimetry (DSC) and confocal scanning laser microscopy (CSLM) techniques. For the traditional CaO–SiO2–CaF2-based mold flux, different cooling rates can change the phases and the crystal morphologies. Faceted cuspidine and CaSiO3 are co-precipitated when the cooling rate is less than 50 °C·min−1. The phases transform from Ca4Si2O7F2 and CaSiO3 to Ca4Si2O7F2 at the cooling rate of 50 °C·min−1. Cuspidine shows four different morphologies: faceted shape, fine stripe, fine stripe dendrite, and flocculent dendrite. The crystalline phases of CaAl2O4 and Ca3B2O6 are co-precipitated in the CaO–Al2O3-based mold flux. Neither the phases nor the crystal morphologies change in the low cooling rate range (5 °C·min−1 to 50 °C·min−1). With decreasing temperature, the morphology of CaAl2O4 firstly becomes dendritic, and then the dendritic quality gradually changes to a large-mesh blocky shape at the cooling rates of 100 °C·min−1, 200 °C·min−1, and 500 °C·min−1. Different cooling rates do not show an obvious impact on the morphology transition of CaAl2O4. The strong crystallization ability and large rate of crystallization affect the control of the heat transfer of the CaO–Al2O3-based mold flux during casting. The big morphology difference between primary crystals of the CaO–SiO2–CaF2-based mold flux and the CaO–Al2O3-based mold flux is probably one of the biggest factors limiting lubrication between the CaO–Al2O3-based mold flux and high-Al steel during casting.

scholarly journals Influence of Cooling Rate on Microstructure Formation of Si–Mo Ductile Iron Castings

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1634
Author(s):  
Marcin Górny ◽  
Magdalena Kawalec ◽  
Beata Gracz ◽  
Mirosław Tupaj
Keyword(s):  
Cooling Rate ◽  
Ductile Iron ◽  
Metallic Matrix ◽  
Graphite Nodule ◽  
Microstructure Formation ◽  
Cooling Rates ◽  
Iron Castings ◽  
Cooling Conditions ◽  
Wide Range ◽  
Longitudinal Ultrasonic Wave

The present study highlights the effect of the cooling rate on the microstructure formation of Si–Mo ductile iron. In this study, experiments were carried out for castings with different wall thicknesses (i.e., 3, 5, 13, and 25 mm) to achieve various cooling rates. The simulation of the cooling and solidification was performed through MAGMASOFT to correlate the cooling conditions with the microstructure. The phase diagram of the investigated alloy was calculated using Thermo-Calc, whereas the quantitative metallography analyses using scanning electron microscopy and optical microscopy were performed to describe the graphite nodules and metallic matrix morphologies. The present study provides insights into the effect of the cooling rate on the graphite nodule count, nodularity, and volumetric fractions of graphite and ferrite as well as the average ferritic grain size of thin-walled and reference Si–Mo ductile iron castings. The study shows that the cooling rates of castings vary within a wide range (27 °C–1.5 °C/s) when considering wall thicknesses of 3 to 25 mm. The results also suggest that the occurrence of pearlite and carbides are related to segregations during solidification rather than to cooling rates at the eutectoid temperature. Finally, the present study shows that the longitudinal ultrasonic wave velocity is in linear dependence with the number of graphite nodules of EN-GJS-SiMo45-6 ductile iron.

scholarly journals Welding thermal stress diagrams as a means of assessing material proneness to residual stresses

2020 ◽  
Vol 56 (2) ◽  
pp. 1694-1712
Author(s):  
Andrii Mishchenko ◽  
Américo Scotti
Keyword(s):  
Thermal Stress ◽  
Cooling Rate ◽  
Thermal Stresses ◽  
Physical Simulation ◽  
Deformation Behaviour ◽  
Stress Generation ◽  
Cooling Rates ◽  
Wide Range ◽  
Quantitative Manner ◽  
Critical Regions

Abstract In this work, the proposal and appraisal of a method to describe in a quantitative manner the phenomenon of thermal stresses formation in welding at different heat-affected zone (HAZ) regions and under different cooling rates, by means of physical simulation, are explained. Under the denomination of welding thermal stress diagrams (WTSD), initially the concept and experimental arrangements needed to use the idea, based on a Gleeble simulator, are revealed. An approach to determine more realistic thermal cycles (peak temperature and heating/cooling rates) is introduced and applied. The method assessment was carried out by using specimens of a HSLA quenchable steel subjected to different cooling rates (covering a wide range of typical welding heat inputs) and peak temperatures (representing regions progressively farther away from the fusion line). The different thermal stress (TS) curves proved the concept based on the justification of the results. In addition, it was physically demonstrated that TS curves are governed mainly by two complex concurrent phenomena, namely contraction under restriction of heated areas and the expansibility of phase transformation. It was concluded that due to this balance, the highest residual stress (RS) does not occur either at slowest cooling rate or at fastest cooling rate. Nevertheless, the highest RS may not occur at the coarse grain zone either. TS progressively drops along the HAZ regions away from critical regions, and even at sub-critical regions there is tensile RS. Complementarily, it was also concluded that WTSD by physical simulation allows one to determine the deformation behaviour of a material as a function of temperature. This information can be used as input or calibration in modelling for thermal stress generation in steels.

Effect of Cooling Rate on Glass Formation for Some Oxynitride Glasses

2007 ◽  
Vol 554 ◽  
pp. 25-30 ◽  
Author(s):  
Wynette Redington ◽  
Murt Redington ◽  
Stuart Hampshire
Keyword(s):  
Cooling Rate ◽  
Glass Formation ◽  
Resistance Furnace ◽  
Slow Cooling ◽  
Cooling Rates ◽  
X Ray ◽  
Glass Forming ◽  
Wide Range ◽  
Fast Cooling ◽  
Nd Systems

Rapid cooling rates and quenching have traditionally been associated with glass formation. Hampshire et al. [1] investigated oxynitride glasses cooled in a tungsten resistance furnace at approximately 200oC/min and found that fast cooling rates were only important near the limits of the glass-forming region. In the current work on various M-Si-Al-O-N (M=Y, La, Yb, Nd) systems, it was found that even at a relatively slow cooling rate glass formation was still possible for a wide range of compositions. Different cooling rates were investigated to determine the minimum cooling rate at which a glass will form. Quantitative X-ray analysis of melted compositions indicated the relative amounts of amorphous phase and crystalline phase.

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