scholarly journals A Comparative Study on the Hot Deformation Behavior of As-Cast and Twin-Roll Cast Mg-6.8Y-2.5Zn-0.4Zr Alloy

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3628
Author(s):  
Kristina Kittner ◽  
Madlen Ullmann ◽  
Ulrich Prahl
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Hot Deformation Behavior ◽  
Cast Material ◽  
Continuous Dynamic Recrystallization ◽  
Roll Casting ◽  
Continuous Dynamic ◽  
Twin Roll Cast ◽  
Twin Roll

The Mg-6.8Y-2.5Zn-0.4Zr (WZ73) alloy exhibits different microstructure characteristic after conventional casting compared to the twin-roll cast (TRC) state. Twin-roll casting results in a finer microstructure, where the LPSO phases are more finely distributed and less strongly connected. A transfer of the hot deformation behavior from the as-cast condition to the TRC condition is only possible to a limited extent due to the microstructural differences. Both states show differences in the recrystallization behavior during hot deformation. In the conventional cast state, dynamic recrystallization (DRX) is assumed to be delayed by the occurrence of coarse blocky LPSO phases. Main DRX mechanisms are continuous dynamic recrystallization (CDRX), particle stimulated nucleation (PSN) and twin induced dynamic recrystallization (TDRX). The deformed TRC sample showed pronounced DRX at almost all deformation conditions. Besides the TDRX and the PSN mechanism, kink induced dynamic recrystallization (KDRX) can be observed. Optimum deformation conditions for both states are temperatures from 500 °C to 520 °C, and strain rates ranging from 0.01 s−1 to 0.1 s−1 for the as-cast material as well as a strain rate of 1 s−1 for the TRC material.

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

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 307
Author(s):  
Madlen Ullmann ◽  
Kristina Kittner ◽  
Ulrich Prahl
Keyword(s):  
Dynamic Recrystallization ◽  
Power Dissipation ◽  
Hot Deformation ◽  
Deformation Behaviour ◽  
Rate Sensitivity ◽  
Cast Material ◽  
Continuous Dynamic Recrystallization ◽  
Forming Temperature ◽  
Twin Roll Cast ◽  
Twin Roll

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.

scholarly journals Microstructure and Hot Deformation Behavior of Twin Roll Cast Mg-2Zn-1Al-0.3Ca Alloy

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1020 ◽  
Author(s):  
Kristina Kittner ◽  
Madlen Ullmann ◽  
Thorsten Henseler ◽  
Rudolf Kawalla ◽  
Ulrich Prahl
Keyword(s):  
Hot Deformation ◽  
Deformation Behavior ◽  
Flow Instability ◽  
Grain Structure ◽  
Strain Rates ◽  
Compression Tests ◽  
Cast State ◽  
Hot Deformation Behavior ◽  
Twin Roll Cast ◽  
Twin Roll

In the present work, the microstructure, texture, mechanical properties as well as hot deformation behavior of a Mg-2Zn-1Al-0.3Ca sheet manufactured by twin roll casting were investigated. The twin roll cast state reveals a dendritic microstructure with intermetallic compounds predominantly located in the interdendritic areas. The twin roll cast samples were annealed at 420 °C for 2 h followed by plane strain compression tests in order to study the hardening and softening behavior. Annealing treatment leads to the formation of a grain structure, consisting of equiaxed grains with an average diameter of approximately 19 µm. The twin roll cast state reveals a typical basal texture and the annealed state shows a weakened texture, by spreading basal poles along the transverse direction. The twin roll cast Mg-2Zn-1Al-0.3Ca alloy offers a good ultimate tensile strength of 240 MPa. The course of the flow curves indicate that dynamic recrystallization occurs during hot deformation. For the validity range from 250 °C to 450 °C as well as equivalent logarithmic strain rates from 0.01 s−1 to 10 s−1 calculated model coefficients are shown. The average activation energy for plastic flow of the twin roll cast and annealed Mg-2Zn-1Al-0.3Ca alloy amounts to 180.5 kJ/mol. The processing map reveals one domain with flow instability at temperatures above 370 °C and strain rates ranging from 3 s−1 to 10 s−1. Under these forming conditions, intergranular cracks arose and grew along the grain boundaries.

scholarly journals Hot Deformation Behavior Considering Strain Effects and Recrystallization Mechanism of an Al-Zn-Mg-Cu Alloy

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1743 ◽  
Author(s):  
Lei Luo ◽  
Zhiyi Liu ◽  
Song Bai ◽  
Juangang Zhao ◽  
Diping Zeng ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Processing Parameters ◽  
Strain Rate Range ◽  
Hot Compression ◽  
Processing Maps ◽  
Hot Deformation Behavior ◽  
Recrystallization Mechanism ◽  
Cu Alloy

The hot deformation behavior of an Al-Zn-Mg-Cu alloy was investigated by hot compression test at deformation temperatures varying from 320 to 440 °C with strain rates ranging from 0.01 to 10 s−1. The results show that the Mg(Zn, Cu)2 particles as a result of the sufficient static precipitation prior to hot compression have an influence on flow softening. A constitutive model compensated with strain was developed from the experimental results, and it proved to be accurate for predicting the hot deformation behavior. Processing maps at various strains were established. The microstructural evolution demonstrates that the dominant dynamic softening mechanism stems from dynamic recovery (DRV) and partial dynamic recrystallization (DRX). The recrystallization mechanism is continuous dynamic recrystallization (CDRX). The microstructure observations are in good agreement with the results of processing maps. On account of the processing map and microstructural observation, the optimal hot processing parameters at a strain of 0.6 are at deformation temperature range of 390–440 °C and strain rate range of 0.010–0.316 s−1 with a peak efficiency of 0.390.

scholarly journals Hot Deformation Behavior of Cu–Sn–La Polycrystalline Alloy Prepared by Upcasting

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3739
Author(s):  
Siming Hua ◽  
Pingze Zhang ◽  
Zili Liu ◽  
Lin Yang
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Testing Machine ◽  
Shear Bands ◽  
Strain Curve ◽  
Extrusion Process ◽  
Hot Deformation Behavior ◽  
Polycrystalline Alloy ◽  
Promising Application

In this study, the hot deformation of a Cu–0.55Sn–0.08La (wt.%) alloy was studied using a Gleeble-3180 testing machine at deformation temperatures of 400–700 °C and various strain rates. The stress–strain curve showed that the hot deformation behavior of the Cu–0.55Sn–0.08La (wt.%) alloy was significantly affected by work hardening, dynamic recovery, and dynamic recrystallization. The activation energy Q was 261.649 kJ·mol−1 and hot compression constitutive equation was determined as  ε˙=[sinh(0.00651σ)]10.2378·exp(33.6656−261.649RT). The microstructural evolution of the alloy during deformation at 400 °C revealed the presence of both slip and shear bands in the grains. At 700 °C, dynamic recrystallization grains were observed, but recrystallization was incomplete. In summary, these results provide the theoretical basis for the continuous extrusion process of alloys with promising application prospects in the future.

Sign in / Sign up

Export Citation Format

Share Document