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Kinetics of static recrystallization in the coarse-grained Fe–40 at.%Al–Zr–B alloy

Schindler I., Kopeček J., Kawulok P., Jabłońska M., Hadasik E., Jóźwik P., Opěla P., Hanus P., Polkowski W., Bojar Z.

Archives of Civil and Mechanical Engineering

2017

Vol. 17, no. 4

816--826

The aim of works was to describe mathematically the kinetics of static recrystallization of the alloy type Fe–40 at.%Al–Zr–B (with 24.6 Al–0.01 B–0.18 Zr–0.01 C in wt.%) with the coarse-grained structure. The microstructure of the laboratory castings made of this extremely brittle alloy was homogenized by hot rolling of the material in the protective capsules and by the long-term annealing at 1200 °C. An initial microstructure with average grain size 0.77 ± 0.27 mm was obtained. Based on the isothermal plastic deformation tests and EBSD analysis, the static recrystallization kinetics of the prepared coarse-grained B2 iron aluminide after strain 0.20 was mathematically described. Recrystallized fraction depends on deformation/annealing temperature (900–1100 °C) as well as on annealing time. The activation energy of static recrystallization was calculated as 255 kJ mol−1. Competition between dynamic recovery and static recrystallization was proved after strain 0.35 and annealing temperature 1100 °C. Static recrystallization starts relatively easily in the studied alloy, but a very long-term annealing is quite necessary for the complete course of recrystallization. The mean size of recrystallized grains falls with the decreasing annealing temperature (0.47 ± 0.15 mm for temperature 1100 °C, and 0.22 ± 0.04 mm for 900 °C). Even at a temperature of 1200 °C the annealing after deformation should last approx. 1 min for obtaining the fully recrystallized microstructure. That is why the standard hot forming technologies should be combined by an interpass annealing in order to refine sufficiently the coarse grains.

Plastyczność i mikrostruktura odkształcanego na gorąco stopu magnezu AZ61

Kuc D., Tkocz M., Bednarczyk I., Hadasik E., Śliwa R.

Rudy i Metale Nieżelazne

2012

R. 57, nr 5

298-304

W artykule zaprezentowano wyniki badań dotyczących wpływu parametrów odkształcenia na zmianę naprężenia uplastyczniającego oraz mikrostrukturę stopu magnezu AZ61 (oznaczenie wg norm ASTM). Próby jednoosiowego ściskania na gorąco przeprowadzono w zakresie temperatury od 250 do 400 [stopni] C i prędkości odkształcenia od 0,01 do 1 s-1. Analiza wyników badań plastometrycznych oraz obserwacja mikrostruktury w pozwoliły ustalić, który mechanizm odkształcenia plastycznego - poślizg czy bliźniakowanie - dominuje w określonych warunkach kształtowania stopu AZ61. Otrzymane wyniki porównano z rezultatami prowadzonymi wcześniej dla stopu typu AZ31 o mniejszej zawartości aluminium.

The current trends in the automotive and aircraft focus first and foremost on a reduction of the vehicle weight and saving energy, thereby protecting the environment. Such a set of technical, economical and ecological aspects arouses a considerable interest of the industry in light alloys. Owing to a number of their advantageous mechanical properties including, first of all, low density (1.74 g/cm3), magnesium alloys are more and more frequently used as an engineering material. There is a regular increase visible in the number of components made of magnesium alloys in the car structure. However, for the production of components from magnesium alloys, casting processes are still most often applied. Alloys used for plastic working are less popular compared to those processed via casting and therefore, the number of their grades is much smaller. The number of alloying components in cast magnesium alloys is always higher than in alloys subject to plastic working. Alloys from the group Mg?Al?Zn?Mn have the best set of properties, for they contain as much as 8 % Al with an addition of Mn (up to 2 %) and Zn (up to 1.5 %). From among elements subjected to plastic working, sheet metal deserves special attention, for it can be applied for the construction of light vehicles. In connection with the complexity of the phenomena which take place in the microstructure, a number of studies in the field of Mg-Al-Zn alloys subjected to plastic working are focused on detecting the mechanisms of deformation and structure reconstruction during deformation. There are two main mechanisms of deformation of magnesium alloy - slip and twinning. Magnesium alloys crystallize with hexagonal close pack (HCP) structure and they have very limited number of slip systems. The paper presents the research results on the effect of deformation parameters on flow stress and microstructure of AZ61 magnesium alloy. Hot compression tests were conducted at the temperature range of 250 to 400 [degrees] C and at the strain rate range of 0.01 to 10 s-1. Analysis of the plastometric tests results as well as examination of microstructure at different deformation phases allowed to determine what kind of deformation mechanism - slip or twinning - dominates in the specific conditions of AZ61 alloy forming. The results were compared to the ones obtained for AZ31 magnesium alloy.

Badania plastyczności i mikrostruktury stopu AZ80 po odkształceniu na gorąco

Kuc D., Bednarczyk I., Niewielski G.

Hutnik, Wiadomości Hutnicze

2012

Vol. 79, nr 8

613--619

W artykule przedstawiono wyniki badań wpływu parametrów odkształcenia na strukturę i plastyczność technologiczną stopu AZ80. Strukturę badanego stopu analizowano po jednoosiowym ściskaniu na symulatorze Gleeble. Próby na gorąco przeprowadzono w zakresie temperatury od 250 °C do 400 °C i prędkości odkształcenia 0,01, 0,1, 1 s-1. Uzyskane wyniki pozwoliły na wyznaczenie krzywych płynięcia oraz wskaźników charakteryzujących technologiczną plastyczność.

In the article results of the influence of deformation parameters range structure and plasticity during anneling hot deformation alloy AZ80. Structural examination after annealing and compression test on Gleeble thermo-mechanical simulator. Hot torsion test was performed on torsion plastometer at the temperature range 250÷400 °C and strain rate of 0.01÷1 s-1. The results allowed the determination of flow curves and indices characterizing the technological plasticity.