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Papers by Petr Kratochvíl

The research of the high temperature mechanical properties of Fe28Al4Cr with additives Ce, TiB2 a... more The research of the high temperature mechanical properties of Fe28Al4Cr with additives Ce, TiB2 and Zr is completed using as additive Zr combined with TiB2. The alloy was prepared using vacuum induction melting and rolling at 1200 °C and finally applying annealing at 1150°C for 2 hours. During alloying the majority of Ti in TiB2 was replaced by Zr. The majority

Metallurgical and Materials Transactions A, 2015

ABSTRACT The final microstructure of cold rolled intermetallic disordered alloy Fe17Al4Cr0.3Zr wa... more ABSTRACT The final microstructure of cold rolled intermetallic disordered alloy Fe17Al4Cr0.3Zr was rebuilt during the annealing at moderate temperatures in the range of 800 to 900 °C. The time necessary to obtain recrystallized structure was determined at several annealing temperatures to optimize the processing technology of the plates. The phases present in the material during this process were identified. The grain growth (grain boundary movement) during static recrystallization (SRX) is connected with the interaction with an array of the Laves phase λ1(Fe,Al)2Zr and ZrC particles. The Avrami-based phenomenological model describing kinetics of SRX was developed. The activation energy for recrystallization was estimated.

International Journal of Materials Research, 2009

V. Sima et al.: FeAl-based alloys cast in an ultrasound tield FeAl-based alloys cast in an ultras... more V. Sima et al.: FeAl-based alloys cast in an ultrasound tield FeAl-based alloys cast in an ultrasound field An ultrasonic device was designed to fabricate relatively small (about 0.7 kg) vacuum chill castings of FeAl-based alloys with improved microstructure. The influence of ultrasound on the solidification microstructure of the Fe-40 at.Va AI based castings was investigated. The subsequent hot-rolling of such an as-cast alloy was made using a special stainless steel bandage of the casting. This effectively prevents fraying and cracking caused by the thermal shock arising at the surface of the hot casting, when it comes in contact with a cold roller. The efficiency of ultrasonic vacuum casting, based on the influence of the acoustic cavitation on the solidification of the melt, is manifested by a refined microstructure of the prepared iron aluminides Fe-40 at.Vo Al with addition of C or Zr and B. First results of improved mechanical properties of these alloys are presented and discussed.

Intermetallics, 2010

The creep behaviour of a rolled Fe–Al alloy containing (at. %) 17.3 Al, 3.81 Cr, 0.29 Zr and 0.13... more The creep behaviour of a rolled Fe–Al alloy containing (at. %) 17.3 Al, 3.81 Cr, 0.29 Zr and 0.13 C was examined at temperatures ranging from 550°C to 700°C. The applied stress dependence of the creep rate at a given temperature could be described by the power function. The values of the power n decreased with increasing temperature: n equalled

Intermetallics, 2006

Creep of an alloy based on the intermetallic compound FeAl with Ti addition was studied by compre... more Creep of an alloy based on the intermetallic compound FeAl with Ti addition was studied by compressive tests at constant stress in the temperature range from 873 to 973 K. The stress exponent n and the activation energy of creep Q were determined for the minimum creep rate. The stress exponent is slightly decreasing with increasing temperature. Its value is in agreement with stress exponents reported for FeeAl alloys with similar additions of titanium. The values of n together with the observed shapes of the creep curves are consistent with the expected behaviour for solid solution hardened alloys where the dislocation motion is controlled by viscous glide of dislocations. Annealing of the alloy for 2 h at 1423 K with subsequent oil-quenching had no influence on the minimum creep rate in comparison with the as-cast material. On the other hand, this annealing accelerated ''the inverse primary behaviour''.

Intermetallics, 2010

The research of the high temperature mechanical properties of Fe28Al4Cr with additives Ce, TiB2 a... more The research of the high temperature mechanical properties of Fe28Al4Cr with additives Ce, TiB2 and Zr is completed using as additive Zr combined with TiB2. The alloy was prepared using vacuum induction melting and rolling at 1200 °C and finally applying annealing at 1150°C for 2 hours. During alloying the majority of Ti in TiB2 was replaced by Zr. The majority

ABSTRACT The structure of four Fe–30Al alloys with different contents of Zr has been studied. Lig... more ABSTRACT The structure of four Fe–30Al alloys with different contents of Zr has been studied. Light optical microscopy (LOM), scanning electron microscopy (SEM) with EDX module, measurement of microhardness as well as X-ray diffraction (XRD) was used to determine the structure and phase composition. Addition of Zr to Fe–30Al leads, in the cast state, to the formation of a Fe–Al matrix with a hard lamellar eutectic skeleton. The eutectic is composed of thin lamellae of λ1-Laves phase Zr(Fe,Al)2 and Fe–Al (B2/D03). Annealing at 1000 °C for 200 h results in the formation of the equilibrium phase τ1 Zr(Fe,Al)12. The presence of these phases in the matrix leads to increase of high temperature yield stress and strength.

The research of the high temperature mechanical properties of Fe28Al4Cr with additives Ce, TiB2 a... more The research of the high temperature mechanical properties of Fe28Al4Cr with additives Ce, TiB2 and Zr is completed using as additive Zr combined with TiB2. The alloy was prepared using vacuum induction melting and rolling at 1200 °C and finally applying annealing at 1150°C for 2 hours. During alloying the majority of Ti in TiB2 was replaced by Zr. The majority

Metallurgical and Materials Transactions A, 2015

ABSTRACT The final microstructure of cold rolled intermetallic disordered alloy Fe17Al4Cr0.3Zr wa... more ABSTRACT The final microstructure of cold rolled intermetallic disordered alloy Fe17Al4Cr0.3Zr was rebuilt during the annealing at moderate temperatures in the range of 800 to 900 °C. The time necessary to obtain recrystallized structure was determined at several annealing temperatures to optimize the processing technology of the plates. The phases present in the material during this process were identified. The grain growth (grain boundary movement) during static recrystallization (SRX) is connected with the interaction with an array of the Laves phase λ1(Fe,Al)2Zr and ZrC particles. The Avrami-based phenomenological model describing kinetics of SRX was developed. The activation energy for recrystallization was estimated.

International Journal of Materials Research, 2009

V. Sima et al.: FeAl-based alloys cast in an ultrasound tield FeAl-based alloys cast in an ultras... more V. Sima et al.: FeAl-based alloys cast in an ultrasound tield FeAl-based alloys cast in an ultrasound field An ultrasonic device was designed to fabricate relatively small (about 0.7 kg) vacuum chill castings of FeAl-based alloys with improved microstructure. The influence of ultrasound on the solidification microstructure of the Fe-40 at.Va AI based castings was investigated. The subsequent hot-rolling of such an as-cast alloy was made using a special stainless steel bandage of the casting. This effectively prevents fraying and cracking caused by the thermal shock arising at the surface of the hot casting, when it comes in contact with a cold roller. The efficiency of ultrasonic vacuum casting, based on the influence of the acoustic cavitation on the solidification of the melt, is manifested by a refined microstructure of the prepared iron aluminides Fe-40 at.Vo Al with addition of C or Zr and B. First results of improved mechanical properties of these alloys are presented and discussed.

Intermetallics, 2010

The creep behaviour of a rolled Fe–Al alloy containing (at. %) 17.3 Al, 3.81 Cr, 0.29 Zr and 0.13... more The creep behaviour of a rolled Fe–Al alloy containing (at. %) 17.3 Al, 3.81 Cr, 0.29 Zr and 0.13 C was examined at temperatures ranging from 550°C to 700°C. The applied stress dependence of the creep rate at a given temperature could be described by the power function. The values of the power n decreased with increasing temperature: n equalled

Intermetallics, 2006

Creep of an alloy based on the intermetallic compound FeAl with Ti addition was studied by compre... more Creep of an alloy based on the intermetallic compound FeAl with Ti addition was studied by compressive tests at constant stress in the temperature range from 873 to 973 K. The stress exponent n and the activation energy of creep Q were determined for the minimum creep rate. The stress exponent is slightly decreasing with increasing temperature. Its value is in agreement with stress exponents reported for FeeAl alloys with similar additions of titanium. The values of n together with the observed shapes of the creep curves are consistent with the expected behaviour for solid solution hardened alloys where the dislocation motion is controlled by viscous glide of dislocations. Annealing of the alloy for 2 h at 1423 K with subsequent oil-quenching had no influence on the minimum creep rate in comparison with the as-cast material. On the other hand, this annealing accelerated ''the inverse primary behaviour''.

Intermetallics, 2010

The research of the high temperature mechanical properties of Fe28Al4Cr with additives Ce, TiB2 a... more The research of the high temperature mechanical properties of Fe28Al4Cr with additives Ce, TiB2 and Zr is completed using as additive Zr combined with TiB2. The alloy was prepared using vacuum induction melting and rolling at 1200 °C and finally applying annealing at 1150°C for 2 hours. During alloying the majority of Ti in TiB2 was replaced by Zr. The majority

ABSTRACT The structure of four Fe–30Al alloys with different contents of Zr has been studied. Lig... more ABSTRACT The structure of four Fe–30Al alloys with different contents of Zr has been studied. Light optical microscopy (LOM), scanning electron microscopy (SEM) with EDX module, measurement of microhardness as well as X-ray diffraction (XRD) was used to determine the structure and phase composition. Addition of Zr to Fe–30Al leads, in the cast state, to the formation of a Fe–Al matrix with a hard lamellar eutectic skeleton. The eutectic is composed of thin lamellae of λ1-Laves phase Zr(Fe,Al)2 and Fe–Al (B2/D03). Annealing at 1000 °C for 200 h results in the formation of the equilibrium phase τ1 Zr(Fe,Al)12. The presence of these phases in the matrix leads to increase of high temperature yield stress and strength.