The cyclic frequency sensitivity of low cycle fatigue (LCF) behavior of the AZ31B magnesium alloy

Jiang

Materials Science and Engineering: A

et al. 2014

Monotonic and fully reversed strain-controlled cyclic deformation experiments were conducted on a ZK60 magnesium (Mg) alloy in as-extruded and T5 aged conditions in ambient air. It was observed that the aging process had a significant influence on the stress-strain response and the fracture stress and strain under both monotonic tension and monotonic compression but a marginal influence on the stabilized cyclic deformation and fatigue of the material. An Electron Backscatter Diffraction (EBSD) analysis revealed that double twins were formed under a large compression strain in the as-extruded Mg but were not observed in the aged state under monotonic compression. A kink point in the strain-life fatigue curve demarcates the influence of twinning-detwinning deformation on fatigue. No twinning occurred throughout the fatigue life of the material when the strain amplitude was lower than the kink point value. With a strain amplitude slightly above the kink point, twinning-detwinning occurred but the process diminished as the loading cycle increased. The aging process enhanced the kink point slightly from a strain amplitude of 0.32% to 0.35%. Only small amount residual twins were observed in the material after fatigue loading when the strain amplitudes were lower than 4%.

Section: Introductionmentioning

confidence: 99%

Cyclic deformation and fatigue of extruded ZK60 magnesium alloy with aging effects

Jiang

Materials Science and Engineering: A

et al. 2014

Fatigue Fract Eng Mat Struct

“…MAO‐pH 4 specimen had the highest Cl − ion content, due to the porous loose layer on the MAO coating surface forming the channel where Cl − ions reaching the matrix through the coating. The LSP/MAO‐pH 4 specimen had the lowest Cl − ion content, because the nanocrystalline layer produced on the surface of material after LSP treatment can reduce the adsorption capacity of Cl − ions 35 …”

Section: Discussionmentioning

confidence: 99%

“…The LSP/MAO-pH 4 specimen had the lowest Cl À ion content, because the nanocrystalline layer produced on the surface of material after LSP treatment can reduce the adsorption capacity of Cl À ions. 35 For the specimens pre-corroded in pH 7.4 environment (Figure 8), the surface of the BM-pH 7.4 specimen (Figure 8A) had cracks similar to the BM-pH 4 specimen (Figure 7A); however, the crack gap is smaller than the latter. The numbers of micropore and crack on the surface of MAO-pH 7.4 specimen (Figure 8B) is reduced compared to the MAO-pH 4 specimen, and some micropores are blocked by white corrosion products.…”

Section: Corrosion Protection Mechanism Of Modified Layermentioning

confidence: 91%

“…The MAO coating surface has many defects such as micropores and microcracks (Figure 8B), and many cracks will occur at these defect sites when the specimen is subjected to cyclic loading. 35 In addition, a large number of corrosive ions corrode the matrix through the micropores on the MAO coating, which also promotes the crack extension. 36 At the stress ratio of À0.8, the deformation mechanism of the same specimens after the pre-corrosion in pH 4 or pH 7.…”

Section: Effect Of Modified Layer On Cyclic Deformationmentioning

confidence: 99%

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Ratcheting behavior of surface‐modified AZ80 magnesium alloy after pre‐corrosion in simulated body fluids with various pH values

Xiong,

2023

AZ80 magnesium alloy was surface treated by micro‐arc oxidation (MAO) and composite of laser shock penning (LSP) and MAO techniques. Untreated and treated specimens were pre‐corroded in simulated body fluids (SBF) with different pH values (pH 4, 7.4, and 9). The ratcheting behavior of all test specimens was experimentally investigated under stress‐controlled loading. The positive or negative value of the ratcheting strain reflects the mechanism of cyclic deformation. The ratcheting strain with negative values is associated with the cyclic deformation being dominated by twinning–detwinning, while the ratcheting strain with positive values is due to dislocation slip playing a dominant role in the cyclic deformation. A higher absolute value of the ratcheting strain means a lower the ratcheting life. Single MAO coating is not conducive to the fatigue life of magnesium alloy in acidic SBF environment, while LSP/MAO composite coating can improve the fatigue life of magnesium alloy under various loading conditions and different pH environment.

“…In the last decade, a great number of studies were conducted to understand the cyclic deformation behavior and low-cycle fatigue of wrought Mg alloys. The most studied wrought Mg alloys include extruded and rolled AZ31 (Albinmousa et al, 2011a, b;Begum et al, 2009a;Begum et al, 2009b;Chamos et al, 2008;Chen et al, 2012;Duan et al, 2014;Geng et al, 2013;Gu et al, 2014;Hama et al, 2012;Hasegawa et al, 2007;Hazeli et al, 2015;Hong et al, 2011;Huang et al, 2014;Huppmann et al, 2010a;Huppmann et al, 2010b;Hyuk Park et al, 2010;Ishihara et al, 2013;Kang et al, 2014;Kwon et al, 2011;Lee et al, 2015;Li et al, 2016;Lin and Chen, 2008;Lin et al, 2013b;Lin et al, 2013c;Lin et al, 2015;Lv et al, 2009;Lv et al, 2011a;Lv et al, 2011b;Matsuzuki and Horibe, 2009;Muhammad et al, 2015;Ozaki et al, 2014;Park et al, 2010a;Park et al, 2010b;Wu et al, 2010a;Wu et al, 2013;Wu et al, 2012;Wu et al, 2014;Wu et al, 2010b;Xie et al, 2016;Xiong et al, 2012;Yin et al, 2008a;…”

Section: Introductionmentioning

confidence: 99%

Characteristic cyclic plastic deformation in ZK60 magnesium alloy

International Journal of Plasticity

Jiang

et al. 2017

A detailed analysis of the plastic deformation characteristics was performed for an extruded ZK60 magnesium alloy under uniaxial cyclic loading along the extrusion direction. The experiments used for the analysis were performed under single-step strain-controlled loading, two-step strain-controlled loading, and stress-controlled loading. An elastic limit with an offset of plastic strain is used for the demarcation of elastic and elastic-plastic deformation. An inflection point is used to signify a transition of the dominated deformation mechanism from twinning-detwinning to dislocation slips. The macroscopic stress-strain response of the material is intrinsically related to the microstructures of the material during cyclic loading. The elastic limit range is closely related to the microstructure of the material at the peak stress prior to the loading reversal. If the microstructure at the peak stress displays a strong basal a-texture, yielding is dominantly associated with the activation of basal slips. The elastic limit range to activate basal slips for the ZK60 magnesium alloy under investigation is 100 MPa. If the microstructure at the peak stress contains tension twins, the elastic limit range during subsequent loading reversal reflects the activation stress of detwinning/retwinning process, which can be interpreted as the critical stress to activate the gliding of twin boundaries. The stability of twin boundaries is influenced by twin volume fraction, twin morphology, and cyclic hardening. Dependent on the twin volume fraction and loading history, the elastic limit range varies from 20 MPa to 100 MPa for the material under investigation.