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Annealing Effects after Various Thermo-Mechanical Treatments on Microstructure and Mechanical Properties of Wrought Magnesium Alloy ZK60

100%
Oo M., Janeček M., Kral R., Wagner L.
Acta Physica Polonica A
|
2012
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vol. 122
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issue 3
606-609
EN
The magnesium alloy ZK60 received from Dead Sea Magnesium in direct-chill cast condition was extruded at T = 350C using an extrusion ratio of ER = 12. The extruded bars were severely plastically deformed at 250C by either equal channel angular pressing or swaging. While swaging led to similar grain refinements as observed after equal channel angular pressing, yield stress and tensile strength values were by far superior in the swaged material. This result is explained by the unfavourable 45° texture component of the (0002) pole figure that develops during the massive shear deformation in equal channel angular pressing. Unlike equal channel angular pressing, the grain orientation after swaging is similar as in the as-extruded condition. Annealing at elevated temperatures indicates very low thermal stability of microstructure and mechanical properties in the equal channel angular pressing material while both properties in the swaged microstructure are as stable as in the as-extruded reference.
2
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Effect of Microstructure on the Corrosion Resistance of the AE42 Magnesium Alloy Processed by Rotary Swaging

76%
Minárik P., Zemková M., Král R., Mhaede M., Wagner L., Hadzima B.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
805-807
EN
Microstructure and corrosion resistance of the AE42 commercial alloy processed by extrusion and rotary swaging were investigated. Microstructure characterization showed an increasing volume fraction of the refined grains with increasing stage of swaging processing. However, their presence was limited solely to the peripheral ring of ≈1 mm in all studied conditions of swaged material. Corrosion resistance investigation showed continuous decrease of polarization resistance that was attributed to the grain refinement and insufficient homogenization of the alloying elements during the swaging process.
3
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The Very High Cycle Fatigue Behaviour of Ti-6Al-4V Alloy

76%
Janeček M., Nový F., Harcuba P., Stráský J., Trško L., Mhaede M., Wagner L.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
497-502
EN
The high cycle and very high cycle fatigue properties of the titanium alloy Ti-6Al-4V with a duplex microstructure were investigated at room temperature. High cycle fatigue tests were performed in the range from 10⁴ to 10⁷ cycles by rotating bending at the frequency of 30 Hz. The very high cycle fatigue tests were carried out in the range from 10⁷ to 10¹⁰ cycles in tension-compression on an ultrasonic fatigue testing machine at the frequency of 20 kHz. The stress amplitude was found to decrease with increasing number of cycles in the whole range from 10⁴ up to 10⁹ cycles and only at the highest number of cycles (N_{F}=10⁹) the alloy exhibits the fatigue limit of 460 MPa. The detail fractographic analysis was performed to characterize the fatigue failure mechanisms. Both subsurface and surface crack initiation were observed in very high cycle fatigue region. No inclusions, but only local chemical inhomogeneity in microstructure was observed at the locations of subsurface fatigue crack initiation in alpha-grains.
4
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Grain Refinement after Various Thermo-Mechanical Treatments in AZ80 and ZK60 Magnesium Alloys

76%
Ryspaev T., Janecek M., Minárik P., Wesling V., Wagner L., Kral R.
Acta Physica Polonica A
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2012
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vol. 122
|
issue 3
622-624
EN
The effect of thermal processing prior to severe plastic deformation by extrusion and swaging on grain refinement in ZK60 and AZ80 alloys was studied. The alloys received in direct-chill cast condition were homogenized at 415C and annealed (over-aged) at temperatures from 200 to 380°C. Both the direct-hill cast and over-aged conditions were extruded at T = 300C using an extrusion ratio of ER = 19. Hot extrusion resulted in substantial grain refinement in both cases, the effect being stronger in the over-aged material. The extruded bars were severe plastically deformed at 250C by swaging. Swaging refined further the grain size depending on the deformation ratio (number of passes). At optimal processing conditions the grain size was 450 nm and 570 nm for the AZ80 and ZK60 alloys, respectively.
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