Fatigue of rare‐earth containing magnesium alloys: a review

Abstract

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)

Interfacial Characterization of Dissimilar Joints Between Al/Mg/Al-Trilayered Clad Sheet to High-Strength Low-Alloy Steel

“…However, some challenges such as poor corrosion resistance and low room-temperature formability limit the widespread structural applications of Mg alloys in the transportation industry. [10][11][12][13][14][15] Recently, a novel process-roll cladding-was considered to improve the corrosion resistance and formability of Mg alloys. 16,17 Specifically, Al-cladding of Mg alloy sheet could combine the superior corrosion resistance and formability of Al with the high strength-to-weight ratio of Mg substrate.…”

Precipitation Hardening on Mechanical and Corrosion Properties of Extruded Mg10Gd Modified with Nd and La

“…Vickers hardness (HV1) was used to determine changes during heat treatment with approximately 30 indents each, under a load of 1 kg (9.807 N), and the average values are reported. 3-point bending was conducted using a span of 40 mm on 70 × 10 × 8 mm 3 samples at a speed of 1 mm/min (plates were tested in the upright position to guarantee longer crack propagation). Micrographs revealed the microstructure, and with this, the influence of twins and larger precipitates on crack propagation was determined.…”

“…Here it is used as the reference material, and is often alloyed with Nd, Y, and Zr to increase creep, fatigue, and corrosion properties. A review by Mirza et al [3] on Mg-RE alloys, on the basis of a higher Gd content for fatigue studies, presented promising results: Effectively weakened crystallographic textures; suppressed twinning; and enhanced fatigue strength. The role of Nd and/or La in Mg10Gd, in the mechanical properties and corrosion behavior during precipitation hardening, is of interest in this study, especially its influence on crack propagation.…”

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

“…Structural components for the transport industry, such as camshaft covers, clutch and transmission housings, intake manifolds, engine blocks, steering components, radiator supports, and automobile wheels, are inevitably subjected to cyclic stresses in service. For this reason, investigation on the fatigue behaviour of both cast and wrought Mg alloys has recently drawn considerable interest [5][6][7][8][9]. Recent studies [7,9,10] have demonstrated that the addition of rare earth (RE) elements, such as Nd, Gd, Y, can remarkably enhance both the tensile and fatigue strength of Mg alloys.…”

“…For this reason, investigation on the fatigue behaviour of both cast and wrought Mg alloys has recently drawn considerable interest [5][6][7][8][9]. Recent studies [7,9,10] have demonstrated that the addition of rare earth (RE) elements, such as Nd, Gd, Y, can remarkably enhance both the tensile and fatigue strength of Mg alloys. In the case of castings, this improvement was related both to the microstructural refinement and to the decreased size and amount of porosity and inclusions induced by RE elements [7,11,12], while in wrought Mg alloys it seems mainly due to the corresponding weakness of crystallographic textures and the reduction of twinning [13][14][15][16].…”