Hypoeutectic Al–Fe Alloys: Formation and Characterization of Intermetallics by Dissolution of the Al Matrix

2019 ◽  
Author(s):  
Amauri Garcia ◽  
Pedro Goulart ◽  
Felipe Bertelli ◽  
José Spinelli ◽  
Noé Cheung
Keyword(s):  
Cooling Rate ◽  
Laser Remelting ◽  
Cooling Rates ◽  
Rich Phase ◽  
Wide Range ◽  
Equilibrium Solidification ◽  
Fe Alloys ◽  
Fe Intermetallics ◽  
Al Matrix

A careful technique of dissolution of the Al-rich phase is conducted in hypoeutectic Al–Fe alloys samples, which were solidified under a wide range of cooling rates envisaging deeper investigations on the skeletal arrangement of either Al6Fe intermetallic fibers or Al3Fe plates, and their dependence on solidification thermal parameters. The experiments were carried out with hypoeutectic Al–Fe alloys, subjected to equilibrium solidification from the melt, steady-state solidification (Bridgman growth), transient directional solidification in water-cooled and air-cooled molds and rapid solidification (laser remelting), thus permitting a significant range of microstructural scales to be examined. It is shown that Al6Fe prevails for cooling rates >1.5 K/s, and that a short zone of coexistence of Al3Fe and Al6Fe phases exists for cooling rates <1.5 K/s, which is rapidly replaced with the prevalence of Al3Fe intermetallics with further decrease in cooling rate. In contrast, even with high values of cooling rate, typical of the laser remelting process, the Al–Al3Fe eutectic is shown to prevail.

Effects of the Cooling Rate on the Acoustic Properties of Pb-10Sn Solder

2012 ◽  
Vol 729 ◽  
pp. 356-360
Author(s):  
Endre Harkai ◽  
Tamás Hurtony ◽  
Péter Gordon
Keyword(s):  
Sound Velocity ◽  
Cooling Rate ◽  
Acoustic Microscopy ◽  
Acoustic Properties ◽  
Scanning Acoustic Microscopy ◽  
Cooling Rates ◽  
Reliability Parameters ◽  
Microscopy Characterization ◽  
The Given

Microhardness and sound velocity were measured in case of differently prepared solder samples. The used Pb-10Sn solder samples were melted then cooled down applying different cooling rates. These procedures caused variant microstructure thus different microhardness and sound velocity values. The sound velocity was measured by means of scanning acoustic microscopy. Characterization of solder materials by acoustic microscopy gives the possibility to non-destructively estimate mechanical and reliability parameters of the given material.

Effect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation in Al-6.5% Si-3.5% Cu-Fe alloys

2000 ◽  
Vol 13 (4) ◽  
pp. 231-253 ◽  
Author(s):  
A. M. Samuel ◽  
A. Pennors ◽  
C. Villeneuve ◽  
F. H. Samuel ◽  
H. W. Doty ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Sr Modification ◽  
Fe Alloys ◽  
Fe Intermetallics

scholarly journals Microstructure and Microsegregation Characterization of Laser Surfaced Remelted Al-3wt%Cu Alloys

2021 ◽  
Author(s):  
Zhenjie Yao ◽  
Wenjing Ren ◽  
John Allison
Keyword(s):  
Cooling Rate ◽  
Dendrite Morphology ◽  
Melt Pool ◽  
Cu Alloy ◽  
Fine Microstructure ◽  
Equilibrium Solidification ◽  
Scan Speed ◽  
Far From Equilibrium ◽  
Beam Movement

Abstract Solidification rates during laser remelting of solid metals occur under solidification conditions that are far from equilibrium conditions. The microstructural evolution and microsegregation behaviors are affected by these conditions. This study comprised an experimental characterization of the ultra-fine microstructure and microsegregation in laser surface remelted regions of a hypoeutectic Al-Cu alloy. The laser scan speed, which controls the cooling rate within the remelted region, was observed to have a significant effect on microstructural features and microsegregation. Dendrite arm spacing was determined to decrease with increasing scan speed and depended on location within the melt pool. A transition of the dendrite morphology was also observed in the melt pools. This transition, which is attributed to the grain orientation change influenced by the laser beam movement, was experimentally characterized. The measured microsegregation profiles show decreasing microsegregation as cooling rate increases which is typically of increasing undercooling and non-equilibrium solidification.

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 Effect of Cooling Rate and Slag Modification on the Copper Matte in Smelting Slag

2020 ◽  
Vol 37 (5) ◽  
pp. 1593-1601
Author(s):  
Xiang Gao ◽  
Zhuo Chen ◽  
Junjie Shi ◽  
Pekka Taskinen ◽  
Ari Jokilaakso
Keyword(s):  
Particle Size ◽  
Cooling Rate ◽  
Copper Matte ◽  
Controlled Cooling ◽  
Slow Cooling ◽  
Rich Phase ◽  
Metal Ratio ◽  
Smelting Slag ◽  
Slag Modification

Abstract The amount of copper flash smelting slag has increased during the recent years along with an increasing slag-to-metal ratio. During slag tapping, some copper sulfide is mechanically entrained. As a result, it is necessary to recover copper matte from the slag by suitable methods. At present, the most common way is slow, controlled cooling in a transfer ladle. However, research on the detailed effects of slow cooling and the function of slag modification is rare. This paper described experiments that were performed at different cooling rates (0.5, 1.5, 3, and 7 °C/min), with and without additive. A detailed characterization of the copper-rich phase and its particle size was subsequently made using SEM-EDS micrographs and image analysis software. With a decrease in cooling rate, the particle size of the copper-rich matte phase became larger. The addition of gypsum and carbon as a slag modifier affected the size of the copper-rich phase slightly, and its chemical composition was modified compared with the experiments without additive.

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.

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.

Kinetics of Pb-rich Phase Particle Coarsening in Sn–Pb Solder Under Isothermal Annealing–cooling Rate Dependence

2005 ◽  
Vol 20 (6) ◽  
pp. 1563-1573 ◽  
Author(s):  
Paul Vianco ◽  
Jerome Rejent ◽  
Gary Zender ◽  
Alice Kilgo
Keyword(s):  
Cooling Rate ◽  
Annealing Temperature ◽  
Isothermal Annealing ◽  
Phase Particle ◽  
Bulk Diffusion ◽  
Fast Diffusion ◽  
Cooling Rates ◽  
Particle Coarsening ◽  
Activation Barriers ◽  
Rich Phase

The coarsening behavior of the Pb-rich phase particles in 63Sn–37Pb (wt%) solder was investigated following isothermal annealing treatments. Samples were exposed to cooling rates of 0.1, 1.0, 10, and 100 °C/min. Annealing temperatures were 25, 55, 70, 85, and 100 °C, and times were 2–100 days. The mean particle diameter decreased from 1.8 × 10−3 to 0.8 × 10−3 mm with increased cooling rate, indicating two solidification regimes: one for cooling rates ≤1 °C/min and the other for cooling rates of ≥10 °C/min. The Pb-rich phase particles coarsened more quickly in samples made at the two fastest cooling rates. There was little Pb-rich phase particle coarsening at 25 and 55 °C for all annealing times. Coarsening rate kinetics were examined specifically for the 10 and 100 °C/min data using the expression Atnexp[−ΔH/RT]. The values of n were 0.23 ± 0.11 and 0.36 ± 0.13, respectively; n was not sensitive to annealing temperature. The corresponding 1/n values indicated that the coarsening mechanism changed from a fast diffusion to a bulk diffusion controlled process with a faster cooling rate. The apparent activation energy ΔH ranged from 16 ± 8 to 41 ± 8 kJ/mol; the values increased with cooling rate from 10 to 100 °C/min. The ΔH value was sensitive to annealing temperature only for the faster cooling rate of 100 °C/min. Together, the n and ΔH values indicated that an accelerated, fast diffusion mechanism with low activation barriers characterized the Pb-rich phase coarsening in samples exposed to a slower cooling rate, greater annealing, or a combination of the two conditions. That mechanism likely originated from the in situ development of recover/recrystallization microstructures in the Sn-rich phase. At faster cooling rates, those microstructures were not as well developed, so coarsening was controlled more by the higher activation barriers of bulk diffusion processes.

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.

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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