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1

Effect of continuous annealing process on various structure parameters of martensite of dual-phase steels

Gorain Nemai, Walunj Mahesh Gulab, Soni Manish Kumar, Kumar B. Ravi

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 1

405--414

EN

Industrial continuous annealing process routes for dual-phase steels are mostly found to be non-isothermal in nature. The present study is an effort to understand the importance of non-isothermal annealing process parameters and their impact on the various metallurgical phenomena; such as recrystallisation and phase transformation behaviours of duel-phase steel. These, in turn, are expected to influence various structure parameters of martensite phase which are critical in determining the strength of duel-phase steel. A dual-phase steel sheet in 67% cold rolled full hard condition was subjected to non-isothermal annealing treatment with varying heating rate and inter-critical annealing temperatures. After processing the samples were investigated for structural parameters of martensite phase using a scanning electron microscope, X-ray diffraction, and nano-indentation technique. It was observed that due to non-isothermal nature of continuous annealing process, the hardness of the martensite phase did not follow the hardness trends as determined from conventional carbon concentration. Further, lattice tetragonality of martensite was also affected by increasing its volume fractions. The annealing process apparently influenced the evolution of texture because of the increasing fraction of martensite in dual-phase steel.

2

Structural and electrical properties of chromium substituted nickel ferrite by conventional ceramic method

Jahan N., Chowdhury F. U. Z., Zakaria A. K. M.

Materials Science Poland

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2016

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Vol. 34, No. 1

185--191

EN

Polycrystalline Cr substituted Ni ferrites [NiCrxFe2-xO4 (0.0 ≤ x ≤ 1.0)] were synthesized by conventional ceramic method and sintered at 1350 degrees C in air. X-ray diffraction (XRD) patterns showing sharp peaks confirmed the formation of single phase cubic spinel structure. The lattice parameters of the samples were determined from the XRD data using Nelson-Riley extrapolation technique. They were found to decrease with increasing Cr concentration obeying Vegard's law. X-ray density, bulk density and porosity were also calculated from the XRD data. The variation of DC resistivity with temperature was measured by two-probe method. The DC resistivity was found to decrease with increasing temperature indicating the semiconducting nature of the samples. Activation energy was calculated from the Arrhenius plot. AC resistivity, dielectric constant and loss tangent were measured in the frequency range of 1 kHz to 120 MHz at room temperature.

3

Development and validation of a quantitative dilatometric analysis model of austenite decomposition into ferrite and pearlite

Opara J., Wrożyna A.

Prace Instytutu Metalurgii Żelaza

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2015

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T. 67, nr 4

24--32

EN

The quantitative dilatometric analysis model for the austenite decomposition into ferrite and pearlite during continuous cooling treatment is presented. It is based on measurements of a relative length change of a sample during the progress of phase transformations and calculations of the difference in atomic volume of present phases. The proposed model incorporates crucial effects accompanying the austenite decomposition, i.e. the carbon enrichment of the remaining austenite during ferrite formation, which causes an increase in the definite atomic volume of austenite, while formation of pearlite has a clearly different impact with the volume fractions of cementite and ferrite regulated by constant carbon composition inherited from austenite (enriched in carbon). The analysis results are compared with quantitative microstructure analysis and an excellent convergence has been found. Depicted results state a convincing confirmation that the model is correctly developed by the authors. Additionally, kinetics of phase transformations as function of normalized time were analyzed and a process of carbon enrichment of austenite was demonstrated.

PL

W niniejszej pracy zaprezentowano model ilościowej analizy dylatometrycznej dla rozpadu austenitu w ferryt i perlit podczas ciągłego chłodzenia. Rozwiązanie bazuje na pomiarach względnej zmiany długości próbki w trakcie postępu przemian fazowych oraz obliczeniach różnic objętości atomowych występujących faz. Zaproponowany model uwzględnia kluczowe zjawiska towarzyszące rozpadowi austenitu, tzn. wzbogacanie się austenitu w węgiel podczas powstawania ferrytu, które powoduje wzrost określonej objętości atomowej austenitu, podczas gdy formowanie się perlitu ma wyraźnie odmienny wpływ poprzez udziały objętościowe ferrytu i cementu, które wynikają z ustalonej zawartości węgla dziedziczonej z austenitu (wzbogaconego w węgiel). Rezultaty ilościowej analizy dylatogramów zestawiono z ilościową analizą mikrostruktur i uzyskano doskonałą zbieżność wyników. Przedstawione wyniki stanowią wyraźne potwierdzenie, iż model jest poprawnie opracowany przez autorów. Ponadto, przeprowadzono analizę kinetyk przemian fazowych w funkcji znormalizowanego czasu oraz przedstawiono proces wzbogacania austenitu w węgiel.

4

Coefficient of crystal lattice matching as a parameter of substrate - crystal structure compatibility in silumins

Piątkowski J.

Archives of Foundry Engineering

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2009

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Vol. 9, iss. 4

191-194

EN

Adding high-melting point elements (Mo, Nb, Ni, Ti, W) to complex silumins results in hardening of the latter ones, owing to the formation of new intermetallic phases of the AlxMey type, with refinement of dendrites in \alfa solution and crystals in \beta phase. The hardening is also due to the effect of various inoculants. An addition of the inoculant is expected to form substrates, the crystal lattice of which, or some (privileged) lattice planes and interatomic spaces should bear a strong resemblance to the crystal nucleus. To verify this statement, using binary phase equilibria systems, the coefficient of crystal lattice matching, being one of the measures of the crystallographic similarity, was calculated. A compatibility of this parameter (up to 20%) may decide about the structure compatibility between the substrate and crystal which, in turn, is responsible for the effectiveness of alloy modification. Investigations have proved that, given the temperature range of their formation, the density, the lattice type, and the lattice parameter, some intermetallic phases of the AlxMey type can act as substrates for the crystallisation of aluminium and silicon, and some of the silumin hardening phases.

5

The CuGaSe2-HgSe and CuInSe2-HgSe systems

Olekseyuk I.D., Parasyuk O.V., Galka V.O.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 1

49-54

EN

Phase diagrams in the CuGaSe2-HgSe and CuInSe2-HgSe systems have been constructed using differential thermal, X-ray phase and microstructural analyses. The CuGaSe2-HgSe system is of the peritectic type. Solid solution of the constituent components have been found and their limit compositions have been established. They contain 0-3 ans 63-100 mol. % HgSe at 870 K. The CuInSe2-HgSe system is of the first type, due to Roozeboom classification. A continuous range of solid solutions exists between HgSe and the high-temperature beta-modification of CuInSe2. The solid solution are created on the basis of alpha-CuInSe2 which contains up to 7 mol. % HgSe at 870 K.