Fatigue Crack Propagation in Die-Cast AZ91D Magnesium Alloy

Shibusawa, Toshinori; Kobayashi, Yasuo; Ishikawa, Keisuke

doi:10.2320/jinstmet1952.61.4_298

Cited by 5 publications

(4 citation statements)

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“…The fatigue response of magnesium alloys is considerably sensitive to the testing environment. Several researchers [1,10,13] have shown that long fatigue-crack growth rates are higher and fatigue-crack-growth thresholds are lower in laboratory air, compared to a vacuum or inert gas environment. Cycling magnesium alloys in the presence of a NaCl solution further increases long-crack growth rates compared to laboratory air and also results in accelerated crack formation at corrosion pits.…”

Section: Introductionmentioning

confidence: 98%

“…The use of cast magnesium as a structural material requires a detailed understanding of the material response to cycling loading conditions. Previous work has characterized the fatigue properties of various wrought [1][2][3][4][5][6] and cast [5][6][7][8][9][10][11][12][13][14][15] magnesium alloys. However, a detailed understanding of fatigue mechanisms operating in cast magnesium alloys is still needed in order to develop microstructure-based fatigue-life prediction tools, and thus, facilitate optimal casting design.…”

Section: Introductionmentioning

confidence: 99%

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In-situ observations of low-cycle fatigue damage in cast AM60B magnesium in an environmental scanning electron microscope

Gall

Biallas

Maier

et al. 2004

Metall Mater Trans A

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We present in-situ observations of low-cycle fatigue damage in cast AM60B magnesium. The in-situ fatigue tests were conducted in an environmental scanning electron microscope under both high vacuum and 20 Torr of water vapor. In both environments, fatigue cracks were observed to form and grow within the dendrite cells and through the interdendritic regions. Crack formation and growth through the dendrite cells proceeded along persistent slip bands. The persistent slip bands were typically oriented at about 45 deg with respect to the loading axis and were more frequently observed in relatively large dendrite cells. Crack formation and growth through the Mg interdendritic regions, laden with Al-Mg intermetallic particles, was facilitated by slip incompatibilities in adjacent dendrite cells, microporosity, and damaged second-phase particles. The detectable "crack-formation" size at slip bands and within interdendritic regions was typically equivalent to the dendrite cell size (DCS), since cracks rapidly spanned this distance once nucleated. Cracks formed during cycling in vacuum were more uniformly distributed and showed a lack of complete closure upon unloading, in contrast to cracks formed during cycling in water vapor. The cracks formed in water vapor were much more isolated and showed indication of significant environmental attack and associated embrittlement at the crack tip, as evidenced by the near-perfect mating of crack faces upon unloading. Final fracture occurred by the coalescence of numerous cracks throughout the microstructure, distributed differently depending on the testing environment. The water-vapor environment accelerated the formation of selected, isolated cracks, leading to more localized damage compared to the highly distributed damage growth and coalescence observed in the material cycled in vacuum.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

In-situ observations of low-cycle fatigue damage in cast AM60B magnesium in an environmental scanning electron microscope

Gall

Biallas

Maier

et al. 2004

Metall Mater Trans A

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“…Because of this, there has been growing interest recently in evaluating the fatigue behaviour of magnesium alloys. These studies include crack‐growth behaviour in die cast AZ91D, 4 low‐cycle fatigue behaviour of die cast AZ91E‐T6 5 and high‐cycle fatigue behaviour of die cast AZ91 6 . Hilpert and Wagner 7 examined the performance of extruded high strength AZ80 magnesium alloy under fatigue loading in ambient air as well as in an aggressive environment created by using a spray of aqueous NaCl solution.…”

Section: Introductionmentioning

confidence: 99%

Effects of humidity and temperature on the fatigue behaviour of an extruded AZ61 magnesium alloy

Sajuri

Miyashita

Mutoh

2005

Fatigue Fract Eng Mat Struct

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A B S T R A C T Load-controlled fatigue tests were performed at 20 and 50 • C using two relative humidity levels of 55 and 80% to characterize the influence of humidity and temperature on the fatigue behaviour of an extruded AZ61 magnesium alloy. Fatigue tests were also conducted at 150 • C. No significant variation in fatigue properties was noticed with respect to temperature over the range from 20 to 50 • C for both the humidity levels. Fatigue limits in the range 140-150 MPa were observed for relative humidity of 55%. Fatigue strength decreased significantly with increase in temperature to 150 • C. Further, a significant reduction in fatigue strength with a fatigue limit of ∼110 MPa was observed with increase in relative humidity to 80% at 20 and 50 • C. The crack initiation and propagation remained transgranular under all test conditions. The fatigue fracture at low stress amplitudes and high relative humidity of 80% results from the formation of corrosion pits at the surface and their growth to a critical size for fatigue-crack initiation and propagation. The observed reduction in fatigue strength at high humidity is ascribed to the effects associated with fatigue-environment interaction.

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“…4,5 The S ± N (stress ± number of cycles to failure) curve for AZ91 has indicated that precipitation from supersaturated solution results in little improvement in fatigue strength, although the yield stress may signi®cantly increase (treatment designated T6). 6 It is known that the mechanical properties of die casting alloy AZ91HP can be improved by a supersaturated solution and arti®cial aging treatment. 7 The present paper is concerned with the low cyclic deformation behaviour of alloy AZ91HP in the -F, -T4, and -T6 conditions in comparison with alloy AM50HP(-F).…”

Section: Introductionmentioning

confidence: 99%

Cyclic deformation behaviour and fatigue crack propagation in AZ91HP and AM50HP

Liu

Wang²,

Wang

et al. 2001

Materials Science and Technology

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The purpose of the present work was to investigate room temperature cyclic deformation and crack propagation behaviour in the most widely used die casting magnesium alloy AZ91HP with different heat treatments. In addition, examination of the low cycle fatigue properties of solid solution treated alloy AZ91HP-T4 was emphasised in comparison with AM50HP. Obvious cyclic strain hardening was found in low cycle fatigue tests, especially for AZ91HP-T4 at high cyclic strain amplitudes. Nevertheless, it was very dif®cult to evaluate differences in low cycle fatigue behaviour between die casting alloy AZ91HP-F, arti®cially aged alloy AZ91HP-T6, solution treated alloy AZ91HP-T4, and AM50HP(-F) because of the scatter of test data. However, it may be concluded that the last two alloys had greater plastic strain components during cyclic deformation, and AZ91HP-T4 exhibited a longer fatigue life than that of AM50HP at the highest strain amplitude. According to results of tests carried out on AZ91HP compact tension (CT) specimens, it was concluded that solution treatment could reduce the fatigue crack propagation rate, and plasticity induced crack closure was considered to have a predominant effect on fatigue crack propagation.MST/4480

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Fatigue Crack Propagation in Die-Cast AZ91D Magnesium Alloy

Cited by 5 publications

References 0 publications

In-situ observations of low-cycle fatigue damage in cast AM60B magnesium in an environmental scanning electron microscope

In-situ observations of low-cycle fatigue damage in cast AM60B magnesium in an environmental scanning electron microscope

Effects of humidity and temperature on the fatigue behaviour of an extruded AZ61 magnesium alloy

Cyclic deformation behaviour and fatigue crack propagation in AZ91HP and AM50HP

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