Intermediary phases formation in Fe–Al–Si alloys during reactive sintering

Novák, Pavel; Knotek, Vítězslav; Voděrová, Milena; Kubásek, Jiří; Šerák, Jan; Michalcová, Alena; Vojtěch, Dalibor

doi:10.1016/j.jallcom.2010.03.028

Cited by 37 publications

(29 citation statements)

References 19 publications

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“…%. As proved in our previous works, reaction of aluminium or silicon with iron produces usually highly porous materials [12]. The porosity increase in the case of iron aluminides was found to be connected with volume changes when the crystal lattice changes from iron to more complex structures of aluminides or silicides.…”

Section: Experimental Materials and Conditionssupporting

confidence: 69%

EFFECT OF ALLOYING ELEMENTS ON PROPERTIES OF PM Ti-Al-Si ALLOYS

Novák¹,

Kříž²,

Michalcová³

et al. 2013

Acta Metall Slovaca

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This work was devoted to the description of the effect of alloying by transition metals (Cr, Cu, Fe) on the structure and properties of TiAl15Si15 alloy. Alloying elements does not form separate phases, being dissolved in titanium silicide or aluminide. Cu was found predominantly in aluminide phase, while iron was found to bethe silicide-former. Chromium dissolved in both aluminide and silicide in almost comparable amounts. All applied alloying elements increased the wear resistance, but reduced the room-temperature compression strength. The addition of iron and chromium strongly increase the thermal stability at 1000°C by stabilizing the silicide phase.Keywords: reactive sintering; mechanical properties testing; intermetallic compounds; oxidation 1 Introduction Alloys based on titanium aluminides (Ti 3 Al and TiAl) are modern materials for hightemperature applications. Due to low density, good mechanical properties and oxidation resistance at high temperatures, these alloys already found its application in the aerospace industry. The application limits of Ti 3 Al phase are 760°C in inert atmosphere (creep limit) and approx. 600°C in air (oxidation limit) [1]. Application range of TiAl phase is 750°C in air and approx. 900°C in inert atmosphere or vacuum [1]. It shows that the temperature range of application of all Ti-Al phases is strongly limited by their high-temperature oxidation. To improve the high-temperature oxidation behaviour of these materials, additions of various alloying elements are applied. Previously, it was reported that niobium and tantalum increase the high-temperature oxidation resistance [2] and creep behaviour [3] of Ti-Al alloys. It led to the development of new generation of Ti-Al alloys [4]. However these heavy and expensive elements undesirably increase the density and cost. Other possibility how to improve hightemperature behaviour is alloying with silicon. When Ti-Al-Si alloys are produced by conventional melting metallurgy techniques, coarse sharp-edged particles of Ti 5 Si 3 silicide are formed, having negative impact on mechanical properties such as ductility or fracture toughness. Simple production route leading to the fine structure is a reactive sintering powder metallurgy. In our previous works [5], [6], production route for Ti-Al-Si alloys with aluminium content between 8 and 20 wt. % and silicon in the range of 10-20 wt. % was developed and roomtemperature properties were described [5]. There are many papers dealing with the influence of various alloying elements on the structure and selected properties of Ti-Al and Ti-Si binary alloys. In addition to the effect of Nb and Ta,

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Section: Experimental Materials and Conditionssupporting

confidence: 69%

EFFECT OF ALLOYING ELEMENTS ON PROPERTIES OF PM Ti-Al-Si ALLOYS

Novák¹,

Kříž²,

Michalcová³

et al. 2013

Acta Metall Slovaca

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“…The big advantage of this technology is the initiation of the reactions leading to the formation of FeeAl intermetallics at significantly lower temperature than the melting temperature of iron and FeeAl phases. In addition to this fact, the Fe þ Al reactions are strongly exothermal and the evolved heat sustains and propagates further reaction across the compressed powder mixture [8]. Therefore, this process is also called Self-sustainable High-temperature Synthesis (SHS) [6].…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, this process is also called Self-sustainable High-temperature Synthesis (SHS) [6]. Due to highly exothermal nature of the processes, this technology is less energy-consuming than common melting metallurgy and conventional powder metallurgy using pre-alloyed powders [8]. In the case of ironealuminium alloys, extremely high porosity is achieved, especially when pressureless reactive sintering is applied (over 25 vol.%) [9].…”

Section: Introductionmentioning

confidence: 99%

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On the formation of intermetallics in Fe–Al system – An in situ XRD study

et al. 2013

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a b s t r a c tSelf-propagating high-temperature synthesis (SHS) was previously proposed as alternative preparation route for FeeAl intermetallics. However, this process was not optimized and the mechanism and kinetics of the phases' formation was not fully clarified up to current days. In this work, in situ high energy X-ray diffraction analysis was carried out during the SHS process and the mechanism of the intermetallic' formation in FeAl25 powder mixture was described during rapid heating and isothermal annealing at 800 C as well as during a slower continuous heating to 900 C. During slower heating, the formation of Fe 2 Al 5 and FeAl 2 intermetallics starts below the melting point of aluminium. When the heating rate is high, intermetallics are created after melting of aluminium. During long-term annealing, all of the phases can be transformed to FeAl phase when fine powders were applied. Detailed mechanism is proposed in this paper and kinetics of the intermetallics' formation is described.

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“…18,19 In the mentioned papers, the experimental model consisted of an iron or titanium sample submerged in molten aluminium or Al-Si alloy. The aim of these experiments was to describe the kinetics of the formation of intermetallics in these particular alloys systems, because directly in reactive sintering process it is not possible.…”

Section: Methodsmentioning

confidence: 99%

Formation of Ni-Ti intermetallics during reactive sintering at 800–900 °C

Novák¹,

Vojtěch²,

Pecenová³

et al. 2017

Mater. Tehnol.

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In this work the formation of intermetallics in the Ni-Ti system by reactive sintering at 800-900°C was studied. The mechanism and kinetics of the reactions, which led to Ni-Ti phases, were determined by thermal analysis, in-situ XRD and the application of an experimental model consisting of nickel-plated titanium. It was found that the formation of Ni-Ti phases below the transformation temperature of titanium is controlled by diffusion. Above this temperature, the reactions switch to the rapid Self-propagating High-temperature Synthesis (SHS) mode. Keywords: reactive sintering, powder metallurgy, NiTi V delu je bil raziskan nastanek intermetalnih zlitin v sistemu NiTi pri reaktivnem sintranju na 800-900°C. S termi~no analizo, XRD-in situ analizo in uporabo eksperimentalnega modela, nikljanega s titanom, sta bila dolo~ena mehanizem in kinetika reakcij, ki sta vodila k NiTi fazam. Ugotovljeno je bilo, da je tvorba NiTI faze pod transformacijsko temperaturo titana, nadzorovana z difuzijo. Nad to temperaturo se reakcije spremenijo na hitro rasto~i temperaturno -sintezni na~in (SHS). Klju~ne besede: reaktivno sintranje, metalurgija prahov, NiTi

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Intermediary phases formation in Fe–Al–Si alloys during reactive sintering

Cited by 37 publications

References 19 publications

EFFECT OF ALLOYING ELEMENTS ON PROPERTIES OF PM Ti-Al-Si ALLOYS

EFFECT OF ALLOYING ELEMENTS ON PROPERTIES OF PM Ti-Al-Si ALLOYS

On the formation of intermetallics in Fe–Al system – An in situ XRD study

Formation of Ni-Ti intermetallics during reactive sintering at 800–900 °C

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