Cyclic Deformation Behavior of a Rare-Earth Containing Extruded Magnesium Alloy: Effect of Heat Treatment

Mirza, F.A.; Chen, D.L.; Li, D. J.; Zeng, Xiaoqin

doi:10.1007/s11661-014-2687-1

Cited by 37 publications

(61 citation statements)

References 91 publications

(201 reference statements)

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“…. Figure a shows a typical microstructure of an as‐extruded Mg‐10Gd‐3Y‐0.5Zr (GW103K) alloy . It is seen that uniform equiaxed grains with an average grain size of about 12 µm were obtained in this alloy due to the occurrence of DRX in the hot extrusion process at 400 °C.…”

Section: Microstructures Of Re–mg Alloysmentioning

confidence: 97%

Fatigue of rare‐earth containing magnesium alloys: a review

Mirza

Chen

2014

Fatigue Fract Eng Mat Struct

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A B S T R A C T Lightweighting in ground vehicles is today considered as one of the most effective strategies to improve fuel economy and reduce anthropogenic environment-damaging and climate-changing emissions. Magnesium (Mg) alloy, as a strategic ultra-lightweight metallic material, has recently drawn a considerable interest in the transportation industry to reduce the weight of vehicles due to their high strength-to-weight ratio, dimensional stability, good machinability and recyclability. However, the hexagonal close-packed crystal structure of Mg alloys gives only limited slip systems and develops sharp deformation textures associated with strong mechanical anisotropy and tension-compression yield asymmetry. For the vehicle components subjected to dynamic loading, such asymmetry could exert an unfavourable influence on the material performance. This problem could be conquered through weakening the texture via addition of rare-earth (RE) elements. Thus, a number of RE-containing Mg alloys have recently been developed. To guarantee the structural integrity, durability and safety of highly loaded structural components, understanding the characteristics and mechanisms of cyclic deformation and fatigue fracture of such RE-Mg alloys is of vital importance. In this review, the available fatigue properties including stress-controlled fatigue strength, strain-controlled cyclic deformation characteristics and fatigue crack propagation behaviour are summarized, along with the microstructural change and crystallographic texture weakening in the RE-containing Mg alloys in different forms (cast, extruded and heat-treated states), in comparison with those of RE-free Mg alloys.Keywords fatigue; magnesium alloy; rare-earth element; texture; tension-compression yield asymmetry. N O M E N C L A T U R Eb = fatigue strength exponent (-) c = fatigue ductility exponent (-) E = Young's modulus (GPa) HCF = high cycle fatigue (-) K′ = cyclic strength coefficient (MPa) LCF = low cycle fatigue (-) n′ = cyclic strain hardening exponent (-) N f = number of cycles to failure (-) R ε = strain ratio (-) S = stress (MPa) α, β = phase designations (-) Δε e /2 = elastic strain amplitude (%) Δε p /2 = plastic strain amplitude (%) Δε t /2 = total strain amplitude (%) Δσ/2 = stress amplitude (MPa) ε′ f = fatigue ductility coefficient (-) σ′ f = fatigue strength coefficient (MPa) σ′ y = cyclic yield strength (MPa)

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Section: Microstructures Of Re–mg Alloysmentioning

confidence: 97%

Fatigue of rare‐earth containing magnesium alloys: a review

Mirza

Chen

2014

Fatigue Fract Eng Mat Struct

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“…While Stage A was linked to the formation of extension twinning during compression in the extrusion direction, the presence of Stage B was mainly ascribed to the twin-twin and twin-dislocation interactions as well as the subsequent twin growth. [111] Since the addition of rare earth metals such as Y, Gd, and Nd is known to hinder twin formation, [15,16,[112][113][114][115][116][117] it was likely that the value of maximum strain hardening rate between Stages B and C would gradually decline with increasing amount of alloying element Y. [106][107][108] Whereas, when deformation is dominated by extension twinning, the true stress-true strain curve is represented by a lower yield point and the strain hardening rate demonstrates the above-mentioned three well-defined stages.…”

Section: Strain Hardeningmentioning

confidence: 99%

A Critical Review of Mg–Zn–Y Series Alloys Containing I, W, and LPSO Phases

Tahreen

Chen

2016

Adv Eng Mater

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Magnesium and its alloys are playing an increasingly important role in the transportation industry due to the pressing demand of lightweight structures to improve fuel efficiency and reduce CO 2 emissions. But the shortcomings of poor room temperature (RT) formability and high temperature strength, tension-compression asymmetry, and anisotropy are among the major issues which are currently limiting their widespread applications. Recently, research and development activities of Mg-Zn-Y series alloys have significantly increased because of their superior mechanical properties arising from the formation of different ternary phases known as I (Mg 3 YZn 6 ), W (Mg 3 Y 2 Zn 3 ), and LPSO (Mg 12 YZn). In this review article, the crystal structure of these phases and their orientation relationships with hexagonal magnesium matrix are discussed. Recent advances about I, W, and LPSO phase containing Mg alloys are presented, along with the effects of these phases on the microstructural evolution and mechanical properties including tensile, compressive, fatigue, and creep resistance. Important aspects involving thermal stability, phase transformation, and influence of heat treatment are also described. Based on the current status, some existing issues are pointed out and further studies are suggested so as to warrant safe and reliable lightweight structural applications of Mg-Zn-Y alloys in the automotive industry.

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“…Representative SEM images of the crack growth region for the PEO treated and untreated samples are, instead, reported in Fig 13 a-b, showing the presence of classic fatigue striations. In Mg alloys their formation is generally associated with the dislocation slip and twinning mechanisms in the plastic zone ahead of the fatigue crack tip [4,6,48]. In this region also secondary transgranular cracks are clearly visible, as shown by representative OM images on longitudinal sections of fatigue samples ( Fig.…”

Section: Fracture Surfaces Analysismentioning

confidence: 86%

Fatigue Behavior of the Rare Earth Rich EV31A Mg Alloy: Influence of Plasma Electrolytic Oxidation

Ceschini¹,

Morri²,

Angelini³

et al. 2017

Preprint

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Rare earth rich magnesium alloys are used in aerospace and automotive fields because of their high specific strength and good castability. However, due to their low corrosion resistance, protective surface treatments, such as conversion coating or electroless plating are necessary, when they have to be used in humid or corrosive environments. The present study was aimed to evaluate the effect of Plasma Electrolytic Oxidation (PEO) and different surface roughness (Ra≈0.8 μm and Ra≈0.3 μm) on the rotating bending fatigue of an innovative Mg alloy, with a high content of Nd (up to 3.1 wt%) and Gd (up to 1.7 wt %). Fatigue tests revealed a 15% decrease in the fatigue strength of the PEO treated alloy (fatigue strength = 88 MPa) with respect to the bare alloy (fatigue strength = 103 MPa). The reduction of fatigue strength was mainly due to the residual tensile stresses induced by the PEO treatment. The effect of surface roughness on the bare alloy was, instead, negligible. The mechanisms of crack initiation were similar in the untreated and PEO treated alloy, with crack nucleation sites located in correspondence of large facets of the cleavage planes.

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Cyclic Deformation Behavior of a Rare-Earth Containing Extruded Magnesium Alloy: Effect of Heat Treatment

Cited by 37 publications

References 91 publications

Fatigue of rare‐earth containing magnesium alloys: a review

Fatigue of rare‐earth containing magnesium alloys: a review

A Critical Review of Mg–Zn–Y Series Alloys Containing I, W, and LPSO Phases

Fatigue Behavior of the Rare Earth Rich EV31A Mg Alloy: Influence of Plasma Electrolytic Oxidation

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