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Rapid solidification behavior of Fe-Cr-Mn-Mo-Si-C alloys
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2007 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 6, 917-926 p.Article in journal (Refereed) Published
Abstract [en]

The rapid solidification behavior of alloys in the Fe-Cr-Mn-Mo-Si-C system was investigated for different compositions and cooling rates. The C content was varied and alloying additions of Mo and B were studied with respect to their effect on the microstructure. The alloys were cast as either melt-spun ribbons or as 1-mm-thick plates after levitation or as rods 2 to 4 mm in diameter by injection into copper molds. A homogeneous single-phase structure was obtained for the alloy of composition 72.8Fe-8Cr-6Mn-5Si-5Mo-3.2C (wt pct), for a sample diameter of 2.85 mm, at a cooling rate of approximate to 1100 K/s. The single-phase structure was identified as a metastable solid solution, exhibiting the characteristics of the e phase. Upon reheating, decomposition of the single-phase structure into fine bainite plates and secondary carbides was observed between 600 degrees C and 700 degrees C. The annealed structure obtained showed high hardness values (> 850 HV).

Place, publisher, year, edition, pages
2007. Vol. 38, no 6, 917-926 p.
Keyword [en]
bulk metallic glasses; amorphous-alloys; epsilon-phase; steel
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-7309DOI: 10.1007/s11663-007-9108-4ISI: 000251925700009Scopus ID: 2-s2.0-37449031278OAI: oai:DiVA.org:kth-7309DiVA: diva2:12278
Note
QC 20100805Available from: 2007-06-07 Created: 2007-06-07 Last updated: 2017-12-14Bibliographically approved
In thesis
1. On the effect of nitrogen, hydrogen and cooling rate on the solidification and pore formation in Fe-base and Al-base alloys
Open this publication in new window or tab >>On the effect of nitrogen, hydrogen and cooling rate on the solidification and pore formation in Fe-base and Al-base alloys
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Experiments on the production of porous metallic materials were performed on Fe-base and Al-base alloys. The method involves dissolution of gases in the liquid state and solidification at various cooling rates. The alloy compositions were selected to induce solidification of primary particles intended to control the pore distribution. For the Fe-base alloys, nitrogen was introduced into the melt by dissolution of chromium nitride powder. Fe-Cr-Mn-Si-C alloys featuring M7C3 carbide particles were selected. For the Al-base alloys, hydrogen gas was dissolved into the melt by decomposition of water vapor. Al-Ti and Al-Fe alloys featuring primary Al3Ti and Al3Fe intermetallic particles, respectively, were considered. In the Fe-base alloys, a homogeneous distribution of gas pores through the specimens’ volume was obtained at high cooling rate (water quenching) and after introduction of external nucleating agents. In the case of the Al-base alloys, a good pore distribution was observed at all cooling rates and without addition of nucleating agents. Calculations of the variation of nitrogen (respectively hydrogen) solubility based on Wagner interaction parameters suggest that pore nucleation and growth occur during precipitation of the primary particles (M7C3 carbides, Al3Ti or Al3Fe intermetallics), due to composition changes in the melt and resultant supersaturation with gas atoms. Microscopic analyses revealed that the primary particles control the pore growth in the melt and act as barriers between adjacent pores, thereby preventing pore coalescence and promoting a fine pore distribution. Uniaxial compression testing of the porous Al-Ti and Al-Fe materials showed the typical compressive behavior of cellular metals. Further work is needed to improve the quality and reproducibility of the porous structures which can possibly be used in energy absorption or load-bearing applications.

As a corollary result of the quenching of hypereutectic Fe-Cr-Mn-Si-C alloys in the experiments of synthesis of porous metals, a homogeneous featureless structure was observed in some parts of the samples, instead of the equilibrium structure of M7C3 and eutectic phases. Subsequent investigations on rapid solidification of Fe-base alloys at various alloy compositions and cooling rates led to the formation of a single-phase structure for the composition Fe-8Cr-6Mn-5Mo-5Si-3.2C (wt.%), at relatively low cooling rates (≈103 K/s) and for large sample dimensions (2.85 mm). The single phase, which is likely to be the hcp ɛ-phase, was found to decompose into a finely distributed structure of bainite and carbides at ≈600 °C. The annealed structure showed very high hardness values (850 to 1200 HV), which could be exploited in the development of high-strength Fe-base materials.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. xii, 52 p.
Series
KTH/MSE, 2007:27
Keyword
Porous metals; Metal foams; Gas solubility; Fe-base alloys; Al-base alloys; M7C3 carbides; Al3Ti; Al3Fe; Rapid solidification; Metastable phases
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-4428 (URN)978-91-7178-684-5 (ISBN)
Public defence
2007-06-15, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100809Available from: 2007-06-07 Created: 2007-06-07 Last updated: 2010-08-09Bibliographically approved
2. Rapid solidification behaviour of Fe and Al based alloys
Open this publication in new window or tab >>Rapid solidification behaviour of Fe and Al based alloys
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Rapid solidification experiment on Fe-Cr-Mo-Mn-Si-C alloy was performed to investigate metastable phases formed during the solidification. A wide range of cooling rate was used to analyse the sample from melt spinning technique (~107 K/s) to water quenching method (~102 K/s). A single phase featureless structure was obtaind initially in the melt spinning experiment for 77Fe-8Cr-6Mn-5Si-4C alloy. Reduction of C and addition of Mo led to form a complete featureless structure for 2.85 mm rod for 72.8Fe-8Cr-5Mo-6Mn-5Si-3.2C. Subsequent investigation of influence of Mo, Cr and Mn on the single phase featureless structure concludes that 7.5 mm thick complete featureless phase could be formed at 63.8Fe-15Cr-7Mo-6Mn-5Si-3.2C alloy composition. In a separate attempt, powder samples of 40 μm dia. size complete featureless powders were produced for three slightly different compostions for the same alloy system.

Characterisation of the featureless phases reveals that it could be a single phase metastable structure of ε phase or austenitic solid solution with high amount of alloying element dissolved in it. Subsequent heat treatment of this featureless phase of the rod and the powder at different temperatures formed bainitic ferrite with fine carbides dispersed in the austenitic matrix. Hardness values measured on featureless phase found to have influenced by the alloying element specially Mo, Cr and Mn.

In an attempet to improve clean melting condition to extend the featureless phase and to form amorphous, an elliptic short arc lamp vaccum furnace was designed with 10 kW lamp power. Around 30 g of iron based alloy system was melted and cast as a 7 mm rod sample in a copper mould. Design details of new mirror and the lamp furnace are presented.

In a separate study, influence of the melt temperature on Al-Y and Al-Si alloys were investigated by levitaion casting in a silver mould at around 2000 K/s cooling rate. Plate like structure of Al8Y3 primary phase was observed at low melt temperature with small percentage of peritectic transformation of Al8Y3 and liquid melt into Al9Y2. A pre-dentritic star like crystal of Al3Y was observed in a fine eutectic matrix at very high melt temperature. Amount and number of primary Si crystals formed in a unit area during the solidification increases as the melt temperature increases.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 46 p.
Series
Trita-MG, ISSN 1104-7127 ; 2009:04
Keyword
Rapid solidification, Melt spinning, Metastable phases, Fe based alloys.
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-11325 (URN)978-91-7415-464-1 (ISBN)
Public defence
2009-11-13, F3, Lindstedtsvägen 26, KTH, 13:00 (English)
Opponent
Supervisors
Note
QC 20100805Available from: 2009-10-26 Created: 2009-10-26 Last updated: 2010-08-05Bibliographically approved

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