Relationship between Fatigue Strength and Grain Size in AZ31 Magnesium Alloys

Tsushida, Masayuki; Shikada, Kei; Kitahara, Hiromoto; Ando, Shinji; Tonda, Hideki

doi:10.2320/matertrans.mc2007101

Cited by 23 publications

(10 citation statements)

References 13 publications

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“…Comprehensive studies have concentrated on the effects of strain amplitude [23][24][25], mean stress [26][27][28], strain ratio [8,9,28,29], strain rate [29], microstructure [8,30,31], grain size [32,33], rare earth elements [34,35], hysteresis energy [26], heat-treatment [36], temperature [5], environment [37,38] and initial texture [39][40][41][42] on the fully reversed strain-controlled low-cycle fatigue behavior of the wrought Mg alloys. Moreover, in the last decade, progress has been made in theoretical modeling to predict the slip, twinning, and detwinning behavior in the hcp-structured material during strain-path changes and cyclic loading [11,22,39,[43][44][45][46][47].…”

Section: Introductionmentioning

confidence: 99%

Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

Liaw

2015

Acta Materialia

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In the current study, the deformation mechanisms of a rolled magnesium alloy were investigated under cyclic loading using real-time in situ neutron diffraction under a continuous-loading condition. The relationship between the macroscopic cyclic deformation behavior and the microscopic response at the grain level was established. The neutron diffraction results indicate that more and more grains are involved in the twinning and detwinning deformation process with the increase of fatigue cycles. The residual twins appear in the early fatigue life, which is responsible for the cyclic hardening behavior. The asymmetric shape of the hysteresis loop is attributed to the early exhaustion of the detwinning process during compression, which leads to the activation of dislocation slips and rapid strain-hardening. The critical resolved shear stress for the activation of tensile twinning closely depends on the residual strain developed during cyclic loading. In the cycle before the sample fractured, the dislocation slips became active in tension, although the sample was not fully twinned. The increased dislocation density leads to the rise of the stress concentration at weak spots, which is believed to be the main reason for the fatigue failure. The deformation history greatly influences the deformation mechanisms of hexagonal-close-packed-structured magnesium alloy during cyclic loading.

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Section: Introductionmentioning

confidence: 99%

Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

Liaw

2015

Acta Materialia

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“…Depending on their texture, wrought magnesium alloys show unique deformation behavior such as mechanical anisotropy, [2][3][4] pseudoelasticity in compression and tension loading-unloading, [4][5][6][7][8] and asymmetricity of stress-strain hysteresis loops in strain controlled low-cycle fatigue tests [9][10][11][12][13][14] and even in load controlled high-cycle fatigue tests, 4,9) etc. The orientation dependence of fatigue crack propagation behavior of magnesium single crystals, [15][16][17] and the effect of grain size [18][19][20][21] and texture [22][23][24][25] on fatigue properties of polycrystalline magnesium alloys have been reported in previous works. However, the effect of texture on the fatigue crack propagation behavior of textured polycrystalline magnesium alloys is still poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Fatigue Crack Propagation Behavior of Textured Polycrystalline Magnesium Alloys

et al. 2010

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This paper describes the fatigue crack propagation behavior of rolled and extruded AZ31B magnesium alloys (grain size: approximately 20 and 15 mm, respectively). Fatigue crack propagation tests were performed on center cracked plate tension specimens at a stress ratio of R ¼ 0:1 and a frequency of 10 Hz at room temperature. Loading axes were parallel to the rolling and extrusion directions; fatigue cracks propagated parallel to the transverse direction (L-T specimen of rolled AZ31B), parallel to the short transverse direction (L-S specimen of rolled AZ31B), and perpendicular to the extrusion direction (E-R specimen of extruded AZ31B). The crack growth rate (da=dN) of the L-S specimen was approximately 10 times lower than that of the L-T specimen in the examined stress intensity factor (ÁK) range. Fracture surfaces of the L-T and L-S specimens showed many steps parallel and perpendicular, respectively, to the macroscopic crack growth direction. The plot of the da=dN versus the ÁK range for the E-R specimen shows two regimes with different slopes in the examined ÁK range. The fracture surface was covered by various directional steps independent of macroscopic crack growth direction, and the fracture surface roughness at low ÁK was larger than that at high ÁK. SEM-EBSD observations revealed that the c-axis direction is unfavorable for the fatigue crack propagation in rolled AZ31B magnesium alloy. Free deformation twins were observed around the fatigue crack path in the L-T, L-S, and E-R specimens.

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“…Depending on their texture, rolled magnesium alloys show unique deformation behavior such as mechanical anisotropy [2][3][4], pseudoelasticity in cyclic loading-unloading [4][5][6][7][8], and asymmetricity of stress-strain hysteresis loops in strain controlled low-cycle fatigue tests [9][10][11][12][13][14] and even in load controlled high-cycle fatigue tests [3,9], etc. The orientation dependence of fatigue crack propagation behavior of magnesium single crystals [15][16][17], and the effect of grain size [18][19][20][21] and texture [22][23][24][25] on fatigue properties of polycrystalline magnesium alloys have been reported in previous works. However, the effect of texture on the fatigue crack propagation behavior of magnesium alloy is still poorly understood.…”

Section: Introductionmentioning

confidence: 83%

Microstructure dependence of fatigue crack propagation behavior in wrought magnesium alloy

Morita

Fujiwara

Hori

et al. 2015

Frattura Ed Integrità Strutturale

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This paper deals with the fatigue crack propagation behavior of rolled AZ31B magnesium alloy (grain size: approximately 40 m). Fatigue crack propagation tests were performed on single edge notched tension specimens at a stress ratio of R = 0.1 and a frequency of 10 Hz at room temperature. Loading axes were parallel to the rolling direction; fatigue cracks propagated parallel to the transverse direction (L-T specimen), parallel to the short transverse direction (L-S specimen). Loading axis was perpendicular to the rolling direction; fatigue cracks propagated parallel to the transverse direction (S-T specimen). The crack growth rate (da/dN) of the L-S specimen was several times lower than that of the L-T specimen in the examined stress intensity factor range (K). Fracture surfaces of the L-T and L-S specimens showed many steps parallel and perpendicular, respectively, to the macroscopic crack growth direction. The da/dN of the S-T specimen was higher than that of the L-T and L-S specimens in the examined K. The fracture surface was covered by quasi-cleavage facets independent of macroscopic crack growth direction, and the fracture surface roughness at low K was larger than that at high K.

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Relationship between Fatigue Strength and Grain Size in AZ31 Magnesium Alloys

Cited by 23 publications

References 13 publications

Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

Fatigue Crack Propagation Behavior of Textured Polycrystalline Magnesium Alloys

Microstructure dependence of fatigue crack propagation behavior in wrought magnesium alloy

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