scholarly journals Initiation and Suppression of Crack Propagation during Magnesium Alloy Rolling

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5217
Author(s):  
Jing Tian ◽  
Quan-Xin Shi ◽  
Li-Xin Meng ◽  
Jia-Fei Deng ◽  
Wei Liang ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Engineering Application ◽  
Effective Mechanism ◽  
Basal Surface ◽  
High Deformation ◽  
Micro Cracks ◽  
Three Stages ◽  
Edge Cracks ◽  
Edge Cracking ◽  
Conventional Rolling

The conventional rolling of magnesium alloy with a single pass and large reduction will cause severe edge cracking. The sheet without cracks can be achieved by limited width rolling. The microstructure evolution of the sheet with cracks after conventional rolling and the sheet without cracks after limited width rolling is explored, and an effective mechanism for solving edge cracks is proposed. Conventional rolling can fully develop twin evolution due to high deformation, and three stages of twinning evolution can be observed and the secondary twins easily become the nucleation points of micro cracks, resulting in a large number of cracks propagating along the twin lamellae. Cracks terminate at dislocation accumulation because the accumulation of a large number of dislocations can hinder propagation. Dislocation shearing of twins to eliminate the high localization caused by twins and induce the tensile twins to weaken the basal surface texture provides an effective plastic deformation mechanism of crack inhibition, which is useful for expanding the engineering application of magnesium alloy rolled sheets.

Morphology of Edge Cracks of Rolled Magnesium Alloy Sheet

2014 ◽  
Vol 922 ◽  
pp. 469-474 ◽  
Author(s):  
Sho Manabe ◽  
Hiroshi Utsunomiya ◽  
Tetsuo Sakai ◽  
Ryo Matsumoto
Keyword(s):  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
High Speed ◽  
Heating Temperature ◽  
Thin Sheet ◽  
Contact Length ◽  
Alloy Sheet ◽  
Different Temperatures ◽  
Edge Cracks ◽  
Critical Reduction

Magnesium alloys show low deformability at low temperature because of hcp structure and inactiveness of basal slip. Manufacturing of thin sheet is difficult in industries. Some approaches, such as small-draft multi-pass rolling, intermediate annealing, isothermal rolling and high-speed rolling were proposed to overcome the deformability. However, small edge cracks are still formed on the sheet. In this study, rolling speed of 1000m/min was employed to warm-roll AZ31B magnesium alloy in a single pass at different temperatures. The edge cracks formed after the rolling were classified into three main groups: minor, regular and zigzag edge cracks. ‘Crack contact length’ are introduced to explain the morphology of edge cracks. The results show that the critical reduction for crack initiation depends on the pre-heating temperature. The spacing between edge cracks increases linearly with the crack contact length regardless of roll diameter, speed and reduction. It is suggested that this approach is useful to understand the formation mechanism of edge cracks and to evaluate the rollability of magnesium alloys.

Effect of Stress State in Rolling Deformation Zone of AZ31 Magnesium Alloy Plate on Edge Cracking

2020 ◽  
Vol 29 (6) ◽  
pp. 3906-3912
Author(s):  
Zhiquan Huang ◽  
Chuanlu Qi ◽  
Guowei Yang ◽  
Hongyu Lai ◽  
Yanchun Zhu ◽  
...  
Keyword(s):  
Stress State ◽  
Magnesium Alloy ◽  
Deformation Zone ◽  
Az31 Magnesium Alloy ◽  
Alloy Plate ◽  
Edge Cracking ◽  
Rolling Deformation

SUPERPLASTIC FORMABILITY OF AZ31 MAGNESIUM ALLOY SHEETS PRODUCED BY TWIN ROLL CASTING AND SEQUENTIAL HOT ROLLING

2013 ◽  
Vol 27 (19) ◽  
pp. 1341020
Author(s):  
YANDONG YU ◽  
KAI LIN ◽  
PENG JIANG
Keyword(s):  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Hot Rolling ◽  
Tensile Testing ◽  
Az31 Magnesium Alloy ◽  
Twin Roll Casting ◽  
Roll Casting ◽  
Three Stages ◽  
The Common ◽  
Twin Roll

In this paper, superplastic tensile testing and gas bulging forming of AZ31 and AZ31 + Y + Sr magnesium alloys produced by twin roll casting (TRC) and sequential hot rolling were carried out. At 673 K, the superplastic formability of the TRC AZ31 magnesium alloy sheets added Y and Sr elements has improved significantly compared to the common TRC AZ31 sheets. Formations of cavities on the bulging part go through three stages of the nucleation, growth and aggregation, finally cavities merging lead to rupture at the top of the bulging part.

In Situ Detection of Surface Micro-Cracking in Ultrafine-Grained AZ31 Magnesium Alloy by Resonant Ultrasound Spectroscopy

2014 ◽  
Vol 606 ◽  
pp. 87-90 ◽  
Author(s):  
Hanuš Seiner ◽  
Petr Sedlák ◽  
Lucie Bodnárová ◽  
Michal Landa ◽  
Jitka Stráská ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Az31 Magnesium Alloy ◽  
Threshold Temperature ◽  
Strong Increase ◽  
Resonant Ultrasound Spectroscopy ◽  
Reliable Determination ◽  
Micro Cracks ◽  
Ultrafine Grained ◽  
Resonant Ultrasound ◽  
Cracking Process

Resonant ultrasound spectroscopy (RUS) was applied to monitor the micro-cracking process occurring during cooling at polished surfaces of an ultrafine-grained AZ31 magnesium alloy. It was observed that although the net of micro-cracks covered only narrow regions along the edges of the sample, its appearance resulted in a strong increase of the attenuation of the free elastic vibrations, and was, thus, sensitively detectable from the evolution of the RUS resonant spectra with temperature. This approach enabled a reliable determination of the threshold temperature for micro-cracking.

Effect of Rolling Speed on Deformability and Microstructure in Rolling of AZ31B Magnesium Alloy

2010 ◽  
Vol 89-91 ◽  
pp. 227-231 ◽  
Author(s):  
Go Hamada ◽  
Tetsuo Sakai ◽  
Hiroshi Utsunomiya
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
High Speed ◽  
Rolling Speed ◽  
Single Pass ◽  
Specific Strength ◽  
Superior Mechanical Properties ◽  
Hcp Structure ◽  
Edge Cracking

Magnesium alloys are expected to be used widely as structural materials because of their lowest density (1.8g/cm3) among all practical alloys and superior specific strength. However, magnesium alloys exhibit poor ductility due to its hcp structure and inactiveness of non-basal slip systems below 523K. Accordingly, magnesium alloy sheets had to be rolled at elevated temperature to avoid edge cracking and fracture during rolling. The present authors succeeded in single pass large draught rolling of AZ31 magnesium alloy sheets below 473K without heating rolls by rolling at the speed higher than 1000m/min. The rolled and quenched sheets had fine recrystallized microstructure and exhibited excellent mechanical properties. It was found that the high speed rolling is a promising method not only for increasing productivity but also for controlling microstructures and improving mechanical properties. If the above mentioned advantages of high speed rolling can be drawn from the rolling at the speed lower than 1000m/min, it is possible to mass-produce magnesium alloy sheets having superior mechanical properties at lower cost. In this study, we tried to determine the lower limiting rolling speed at which we can obtain advantages of high speed rolling. We revealed that the thickness could be reduced about 60% by single pass operation even at 250m/min without heating rolls. The rolled and quenched sheets had equiaxed fine recrystallized microstructure. For example, the mean grain size of 2.1m was obtained in the AZ31B sheet rolled at 250m/min at room temperature to the reduction of 60%.

scholarly journals Formation Process of an LDHs Coating on Magnesium Alloy by a CO2 Pressurization Method

Coatings ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 47 ◽  
Author(s):  
Xiaochen Zhang ◽  
Jiaoxiang Wang ◽  
Chunyan Zhang ◽  
Bin Liu ◽  
Peng Jiang ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Formation Process ◽  
Growth Stage ◽  
Solubility Curve ◽  
Layer By Layer ◽  
Micro Structure ◽  
Co2 Solubility ◽  
Periodic Growth ◽  
Three Stages ◽  
Apparent Activation Energies

The formation process of LDHs (layered double hydroxides) coating on magnesium alloy by the CO2 pressurization method was studied. The micro-structure was observed by OM, SEM and GAXRD. The weighted gain curve, apparent activation energy, and CO2 solubility curve were all calculated by equations. The potentiodynamic polarization curve, hydrogen evolution data, and immersion were analyzed by an electrochemical method. The results show that the LDHs coating was formed layer-by-layer. The formation positions were initially on the α-Mg phase, and then on the β-Mg17Al12 phase. It was found to be the most compact after 30 min. The LDHs coating began to appear to have severe cracks and holes over time. The formation process of the LDHs coating can be divided into three stages: a rapid growth stage (0–10 min), slow growth stage (10–20 min), and periodic growth stage (30 min, 1 h). The apparent activation energies in each of the three stages are 21.78, 31.86 and 34.92 kJ mol−1, respectively. The LDHs coating has a compact micro-structure and better anti-corrosion at a pressure of 3 MPa, a temperature of 50 °C and a time of 30 min. The CO2 pressurization promotes a formation reaction rate and achieves a high formation efficiency and good formation stability under the condition of zero pollution.

Research of Brittle Shear Failure Strength of Rock Materials

2013 ◽  
Vol 454 ◽  
pp. 125-128
Author(s):  
Yuan Li ◽  
Zhen Li ◽  
Tie Jun Xu
Keyword(s):  
Shear Failure ◽  
Rock Material ◽  
Strength Analysis ◽  
Strength Theory ◽  
Micro Cracks ◽  
Good Consistency ◽  
Shear Characteristics ◽  
Three Stages ◽  
Relationship Of ◽  
The Relationship

In order to get brittle shear characteristics of rock material, acoustic emission accompanied with triaxial stress-strain test was applied to monitor the emergence and development of micro cracks. Theoretical analysis and data processing were conducted based on the theories of fracture mechanics and general rock mechanics, relations between the feature strength of three stages and the stress state were obtained, and a method was put forward for analyzing the brittle shear failure of rock material. The relationship of the Mohr-Coulomb strength theory, Griffith strength theory and Hoek-Brown criterion with the brittle-shear strength model were established. Strength analysis of mixed granite in Shuichang slope was carried out by the brittle shear failure model, and the theoretical value and experimental value has a good consistency.

Deformation Characteristics of Concrete under Uniaxial Compression

2014 ◽  
Vol 670-671 ◽  
pp. 428-431
Author(s):  
Guo Jun Liu
Keyword(s):  
Uniaxial Compression ◽  
Research Work ◽  
Crack Development ◽  
Future Research ◽  
Deformation Characteristics ◽  
Unstable Crack ◽  
Development Period ◽  
Micro Cracks ◽  
Depth Study ◽  
Three Stages

Depth study of deformation characteristics of concrete can reveal failure mechanism of concrete materials based on strain. This paper studies the deformation characteristics of concrete under uniaxial compression, and draw conclusions that deformation can cause the expansion of internal micro cracks, in accordance with the expansion of micro cracks, the law of cracks development of concrete under uniaxial loads is divided into three stages, micro-cracks relatively stable, stable crack development period and unstable crack development period. The research results can provide valuable reference for future research work.

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