A study of the α ↔ γ transformation in pure iron: rate variations revealed by means of thermal analysis

Papandrea, C.; Battezzati, Livio

doi:10.1080/14786430601080260

Cited by 10 publications

(2 citation statements)

References 21 publications

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“…The DSC curve in Figure 8 shows endothermic peak around 297 • C upon heating the 30 h milled and pressed Co powder, followed by a small and large exothermic peaks at 426 and 707 • C, respectively. It is well known that endothermic peaks show phase transformation in certain pure metals [42,43] including Co [5]. However, since our powder has no HCP phase after milling, this endothermic peak at 297 • C cannot be related to allotropic HCP to FCC phase transition.…”

Section: Resultsmentioning

confidence: 79%

Effect of Mechanical Milling and Cold Pressing on Co Powder

Bolokang

Phasha

Motaung

et al. 2012

Journal of Metallurgy

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Cold pressing (CP) of the amorphous-like Co powder suppressed most of the XRD peaks, in particular the peak along (100) plane. The DSC curve of unmilled CP Co powder has shown a distinct sharp exothermic peak at615C°. Upon annealing at700C°, only the FCC phase with lattice parameter of 3.51 Å was detected by XRD. Our results implied that the exotherm at615C°corresponds to compaction-pressure-assisted HCP to FCC first-order phase transition. The XRD analysis of 30 h milled powder revealed for the first time the FCC phase witha=3.80 Å. However, due to presence of (100) and (210) peaks, this phase is thought to be FCT with lattice parametersa=b=3.80andc=3.07 Å. Consequently, the high-energy milling carried out in the current work induced for the first time HCP to FCT transition in Co. Upon CP of milled powder, the lattice parameterashrunk from 3.80 to 3.75 Å. However, during annealing of the CP milled Co powder at750C°, the FCT to FCC transition occurred, yielding the FCC phase witha=3.51 Å.

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Section: Resultsmentioning

confidence: 79%

Effect of Mechanical Milling and Cold Pressing on Co Powder

Bolokang

Phasha

Motaung

et al. 2012

Journal of Metallurgy

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“…30,31 This was confirmed in EDS (Figure 4) where FCC is the darker phase and rich in Fe, Al and Vas was reported in another study. 32 It will be noted that sintering temperature of 900°C was a transformation phase in this HEA because all the crystal peaks present in the sample sintered at 800°C disappeared leaving only one FCC peak. This is because crystallization of γ-Fe had started but the peaks are yet to evolve fully.…”

Section: Resultsmentioning

confidence: 89%

Mechanical and thermal behaviors of Ti36-Al16-V16-Fe16-Cr16 high entropy alloys fabricated by spark plasma sintering: An advanced material for high temperature/strength applications

Ujah

Popoola

Uyor

2022

Journal of Composite Materials

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Conventional superalloys possess high strength, high oxidation resistance and high creep resistance. Nonetheless, some lose strength at elevated temperatures, while others suffer high temperature oxidation and creep. This work was aimed at developing high entropy alloy (HEA) of Ti36-Al16-V16-Fe16-Cr16 at near equi molar configuration using spark plasma sintering technique which would be able to address the challenges of conventional superalloys. The powders were mixed with Turbular mixer at 69 rpm for 10 h. The sintering was carried out with the same sintering pressure of 40 MPa, time of 10 min, heating rate of 100°C/mins on all the samples. Only the sintering temperature was varied. The temperatures used included 700°C, 800°C, 900°C, 1000°C and 1100°C, respectively. The powders and sintered samples were characterized with Scanning electron microscopy connected to Energy Dispersive Spectroscopy and X-ray diffractometer. The mechanical properties were tested with Nano indenter using ASTM D785 standard; while the thermal stability was investigated with thermogravimetric analyzer. Results showed that HEA sintered at 1000°C possessed the best nanomechanical, thermal and microstructural properties while that sintered at 700°C had the weakest properties. The best developed alloy had an improved elastic modulus of 671.17 ± 50 GPa and 930.12 ± 38 GPa at darker flakey phase and white phase, respectively. It had creep resistance of 1.82%, densification of 98.96% and porosity of 1.04%. It was concluded that the developed alloy can perform much better than most superalloys in high temperature and high strength and applications.

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