Microstructure and Texture Evolution during Twin-Roll Casting and Annealing of a Mg–6.8Y2.5Zn–0.4Zr Alloy (WZ73)

Kittner, Kristina; Ullmann, Madlen; Arndt, Falko; Kawalla, Rudolf; Prahl, Ulrich

doi:10.3390/cryst10060513

Cited by 17 publications

(13 citation statements)

References 37 publications

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“…Figure 1 shows the microstructure of the twin-roll cast Mg-6.8Y-2.5Zn-0.4Zr alloy after heat treatment at 500 °C for 2 h. The microstructure after twin-roll casting consisted primarily of α-magnesium matrix material, which was pervaded by a fine network of LPSO phases. A detailed description of the microstructural composition and the texture of twin-roll cast strips of Mg-6.8Y-2.5Zn-0.4Zr alloy can be found in [ 19 ]. On the basis of X-ray diffraction investigations, the LPSO phases that occurred after twin-roll casting could be assigned to the 18R or 14H structures.…”

Section: Resultsmentioning

confidence: 99%

“…The network-like LPSO phases remained intact. Higher temperatures (525 °C) and/or longer holding times (6 h) are required to dissolve such phases [ 19 ].…”

Section: Resultsmentioning

confidence: 99%

“…The chemical composition of the Mg-6.8Y-2.5Zn-0.4Zr alloy is shown in Table 1 . Details on the production of twin-roll cast strips of Mg-6.8Y-2.5Zn-0.4Zr alloy are described in detail in [ 19 ].…”

Section: Methodsmentioning

confidence: 99%

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Hot Deformation and Dynamic Recrystallisation Behaviour of Twin-Roll Cast Mg-6.8Y-2.5Zn-0.4Zr Magnesium Alloy

2021

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In this work, the deformation behaviour of a twin-roll cast (TRC) Mg-6.8Y-2.5Zn-0.4Zr alloy during plane strain compression was characterised by high-temperature testing. Based on the experimental data, the values of strain-rate sensitivity, the efficiency of power dissipation and the instability parameter were investigated under the conditions of various hot deformation parameters. In contrast to conventionally cast material, no lamellae of the LPSO (long period stacking ordered) phase were precipitated in the magnesium matrix after TRC. The precipitation of fine lamellar LPSO phases only occurred during cooling to forming temperature after the heat treatment. Dynamic recrystallization (DRX) hardly occurred during deformation at temperatures between 350 °C and 400 °C. This can be attributed to the precipitation of the lamellar LSPO phases, which contribute to retardation of the DRX process. At higher deformation temperatures and strain rates DRX is pronounced and the twin-induced (TRDX) as well as continuous dynamic recrystallization could be identified as the dominant softening mechanisms. The processing maps were established by superimposing the instability map over the power dissipation map, this being associated with microstructural evolution analysis in the hot deformation processes. Two instability zones could be recognised for the twin-roll cast and heat-treated Mg-6.8Y-2.5Zn-0.4Zr alloy: (1) 350 °C to 460 °C and 0.01 s−1 to 0.3 s−1 and (2) 485 °C to 525 °C and 2.5 s−1 to 10 s−1, where deformation is not favourable.

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Section: Resultsmentioning

confidence: 99%

“…The network-like LPSO phases remained intact. Higher temperatures (525 °C) and/or longer holding times (6 h) are required to dissolve such phases [ 19 ].…”

Section: Resultsmentioning

confidence: 99%

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Hot Deformation and Dynamic Recrystallisation Behaviour of Twin-Roll Cast Mg-6.8Y-2.5Zn-0.4Zr Magnesium Alloy

2021

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“…According to previous investigations, the chemical composition of the LPSO phase corresponds to 65% Mg, 21% Y, and 14% Zn (mass fractions) and can be assigned to the 18R or the 14H LPSO phase. 28,36…”

Section: Center-line Segregationmentioning

confidence: 99%

Analysis of defects in a twin roll cast Mg‐Y‐Zn magnesium alloy

Kittner

Ullmann

Arndt

et al. 2021

Engineering Reports

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Twin roll casting (TRC) enables the production of magnesium strips in an economic manner. TRC has enormous potential for the production of thin strip material from magnesium alloys. However, a range of defects may arise during casting. Internal and surface defects also influence the final properties of TRC strips. In this work, the magnesium alloy Mg‐6.8Y‐2.5Zn‐0.4Zr (WZ73) containing long‐period stacking ordered (LPSO) structures was twin roll cast with different process parameters, and the defects that arose were investigated. In particular, defects such as surface bleeds, center‐line segregations and deformation segregations in the mid‐thickness of the strip were observed and analyzed with regard to the TRC parameters applied. The latter may have developed due to the solidification of solute‐rich liquid in the center of the strip. X‐ray diffraction analysis was carried out to determine the phase compositions within the casting defects. A (Mg,Zn)3Y phase was found to precipitate in a blocky or lamellar shape within large, plate‐like LPSO phases. Wavy lines resulting from high specific rolling forces can be avoided if specific rolling force does not exceed a value of 8 kN/mm. Casting speed of 1.5 m/min has proven to be favorable to prevent the occurrence of center‐line segregation.

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“…Studies on cast and extruded Mg-RE-Zn alloys show, in dependence on their initial microstructure, their thermo-mechanical treatment or post-heat treatment changes in the morphology of the LPSO phases. Blocky and lamellar LPSO phases can dissolve into the Mg-matrix and saturated solid solution is formed [17,18], blocky LPSO phases can transform into lamellar LPSO structures [19][20][21][22], the lamellar structure can change its periodical intervals [23] and higher blocky and lamellar LPSO structures can form during ageing treatment [24].…”

Section: Introductionmentioning

confidence: 99%

Crack Propagation in As-Extruded and Heat-Treated Mg-Dy-Nd-Zn-Zr Alloy Explained by the Effect of LPSO Structures and Their Micro- and Nanohardness

et al. 2021

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The investigation of the crack propagation in as-extruded and heat-treated Mg-Dy-Nd-Zn-Zr alloy with a focus on the interaction of long-period stacking-ordered (LPSO) structures is the aim of this study. Solution heat treatment on a hot extruded Mg-Dy-Nd-Zn-Zr (RESOLOY®) was done to change the initial fine-grained microstructure, consisting of grain boundary blocky LPSO and lamellar LPSO structures within the matrix, into coarser grains of less lamellar and blocky LPSO phases. C-ring compression tests in Ringer solution were used to cause a fracture. Crack initiation and propagation is influenced by twin boundaries and LPSO lamellae. The blocky LPSO phases also clearly hinder crack growth, by increasing the energy to pass either through the phase or along its interface. The microstructural features were characterized by micro- and nanohardness as well as the amount and location of LPSO phases in dependence on the heat treatment condition. By applying nanoindentation, blocky LPSO phases show a higher hardness than the grains with or without lamellar LPSO phases and their hardness decreases with heat treatment time. On the other hand, the matrix increases in hardness by solid solution strengthening. The microstructure consisting of a good balance of grain size, matrix and blocky LPSO phases and twins shows the highest fracture energy.

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Microstructure and Texture Evolution during Twin-Roll Casting and Annealing of a Mg–6.8Y2.5Zn–0.4Zr Alloy (WZ73)

Cited by 17 publications

References 37 publications

Hot Deformation and Dynamic Recrystallisation Behaviour of Twin-Roll Cast Mg-6.8Y-2.5Zn-0.4Zr Magnesium Alloy

Hot Deformation and Dynamic Recrystallisation Behaviour of Twin-Roll Cast Mg-6.8Y-2.5Zn-0.4Zr Magnesium Alloy

Analysis of defects in a twin roll cast Mg‐Y‐Zn magnesium alloy

Crack Propagation in As-Extruded and Heat-Treated Mg-Dy-Nd-Zn-Zr Alloy Explained by the Effect of LPSO Structures and Their Micro- and Nanohardness

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