High Local Stresses Research Articles

Local prestressing of cold forging tools by reinforcements with adapted interference

With contact pressures of more than 3000 MPa cold forging dies belong to the highest loaded components in mechanical engineering. Especially in non-symmetrical dies, this leads to a complex stress state with locally varying stresses. Cyclically occurring tensile stress concentrations cause crack initiation, which is why fatigue is the most important failure mechanism for complex cold forging tools. To reduce tensile stresses and counteract fatigue failure, dies are conventionally prestressed by inserting them into a reinforcement ring with a uniformly distributed interference. However, the compressive prestress is often not enough to compensate the high local stresses occurring in processes for non-symmetrical parts. Therefore, this paper focuses on using a non-uniformly distributed interference to locally increase prestresses in critical areas. To achieve this, gaps are inserted between die and reinforcement, inducing a bending stress. A numerical model is used to analyse how to design the gaps depending on the interference fit and how effective the use of gaps is for different part geometries with an increasing number of functional elements. Results show, that gap angles between 40° and 60° are suitable for locally improving the stress state. For high interferences, too large gap angles increase tensile stresses occurring in other areas of the dies, possibly impeding tool life. Since the adapted interferences work based on a bending effect, gaps are effective for up to four uniformly distributed critical areas. For more local elements, the lever distance is too low to apply an effective bending stress and the stress state does not improve.

Effect of cerebrospinal fluid elements on stress distribution in stress analysis model of brain tissue constrained by skull in infancy

The purpose of this study was to clarify the effect of cerebrospinal fluid elements on the brain stress model, in order to develop a tool to support the treatment of craniosynostosis using the finite element method. The growth of the brain was expressed by the thermal expansion. A soft solid element, which imitates cerebrospinal fluid, was introduced into the model consisting of brain, pia mater, arachnoid mater, dura mater and skull. The thermal expansion coefficient of the brain was set as 0.04049, which corresponds to a volumetric expansion of the brain of 1% when the pia mater element contacts the cerebrospinal fluid elements. As a result, a maximum stress of 2.588×10-5 [MPa] was generated in the brain, and the stress on the brain element was reduced by introducing the cerebrospinal fluid elements. Here, the stress distribution of the cerebrospinal fluid elements was not uniform, due to the coarse meshing, resulting in the generation of the localized high stresses. Therefore, it would be necessary to improve the accuracy of the stress analysis model in the future.

Stacking fault and nano-twins dominating strengthening mechanism of (CuZnMnNi)100-xSnx high entropy brass alloy prepared by mechanical alloying and fast hot pressing sintering

In this work, a new strengthening mechanism is reported in (CuZnMnNi)100-xSnx high entropy brass alloy (HEBA) prepared by mechanical alloying and fast hot pressing sintering. Increasing Sn content can form more BCC phase, but decreases the mechanical property, and the stacking fault and nano-twins dominates the strengthening mechanism. High energy grain boundaries with substantial orientation variation or the lattice distortion caused by different phase transformation can lead to high local stress concentration, which provides driving force for the generation of stacking faults and nano-twins. Some nano-twins can also be formed via stacking growth.

Enhanced output performance of piezoelectric energy harvester based on hierarchical Bi3.15Nd0.85Ti3O12 microspheres/PVDF-HFP composite

The inclusion of inorganic piezoelectric fillers in the polymeric matrix of flexible ferroelectric polymer synergies the piezoelectricity for wearable electronics. Herein, hierarchical Bi3.15Nd0.85Ti3O12 microspheres (H-BNdT MPs) embedded in the polymeric matrix of polyvinylidene fluoride–hexafluoropropylene (PVDF-HFP) based piezoelectric thin films are fabricated by using a facile and cost-effective film-forming method, drop-casting. The composites possess improved dielectric and ferroelectric properties comparing with that of the pure PVDF-HFP film without any electrical poling treatment. More importantly, the highest outputs of an open-circuit voltage of 20 V and a short-circuit current of 1.9 μA under the repeated mechanical force of 10 N at the frequency of 2 Hz were successfully achieved. The maximum power of the optimal PEH can reach as high as 4.6 mW, corresponding to a power density of 938 μW/cm2, and the output electricity can light up 10 LEDs with a full-wave rectifier circuit. The enhanced output performance is attributed to the high local stress around the H-BNdT MPs arising from the hollow hierarchical architecture of the inorganic fillers. The lead-free flexible PEH is also proved to have the ability to harvest the biomechanical energy of human movements, such as finger pinching, finger tapping, and fist punching. In particular, a PEH shoe is made to harvest energy from walking and running. This PEH is confirmed to be a potential energy harvester and effective self-powered generator to drive wearable devices.

Shear waves in a Piezo-Fiber-Reinforced-Poroelastic composite structure with sandwiched Functionally Graded Buffer Layer: Power Series approach

Love wave sensors are highly sensitive devices owing to the concentration of acoustic energy within a few wavelengths of the surface. The basic model of these high-performance devices is layered structures composed of highly sensitive composite and functionally graded materials. Thus the present work aims to establish an analytical framework to investigate the propagation characteristics of horizontally polarized shear waves (SH waves) in a composite structure comprised of a Functionally Graded (FG) buffer layer sandwiched between an overlying transversely isotropic Piezo-Fiber-Reinforced Composite (PFRC) material guiding layer and an underlying transversely isotropic Piezo-Poroelastic (PP) half-space. The motive considering the gradient materials, especially at the interface adjoining the layers, is to avoid the discontinuity of the inter-laminar stress and high local stress fields, which can arise around the edges of the laminates due to material mismatch across the interface. The functional gradient of the buffer layer is configured in terms of volume fractions of the guiding layer and the half-space material. The power series technique is employed to solve the governing equations of the FG-buffer layer. For the propagating SH wave, the dispersion relation relating the wave number with phase velocity through the mechanical and electrical parameters of the PFRC and PP materials, the gradient parameter, and the widths of the guiding and buffer layer is presented for the electrically open (EO) as well as electrically shorted (ES) conditions. Furthermore, mass loading sensitivity is analyzed by coating a fine layer on the free surface of the structure. The obtained results on the dispersion relations are compared and found to be in well-agreement with some of the outcomes available in the extant literature, thus validating the present study. To graphically delineate the impact of all influencing parameters, a layered structure of ZnO-Epoxy (PFRC)/ FG-buffer Layer/PZT-1 (PP) is considered. Also, the mass loading sensitivity is graphically illustrated for the coating of a fine layer of SiO2 on the free surface. The present study may be applied for a myriad of engineering applications like manufacturing and optimizing sensors, actuators, transducers, etc. The obtained results are specifically useful for developing and enhancing the performance of surface acoustic wave (SAW) devices/Love wave sensors.

Sandwich panels with functionally graded strut‐based lattice cores

AbstractDue to their high mechanical performance, sandwich panels are widely utilized in many applications. Among the most frequently used cores in sandwich panels are honeycomb structures. Since the invention of additive manufacturing, new core structures like strut‐based lattices which are not possible by conventional manufacturing processes are also being considered as cores for sandwich panels. Depending on the given boundary conditions and load cases, core struts must transfer different loads. Particularly struts near load introduction points and support points are exposed to high local stresses. In the present study, a graded core is used to reduce the effect of local stress concentration near load introduction points and support points. In the graded core higher loaded areas show a higher relative density. In contrast, low loaded areas represent lower relative density, resulting in a reduction of the core weight and a uniform stress distribution. Only the strut diameters are varied. It is demonstrated that systematic optimization allows a well‐tailored core gradation and some valuable weight reduction.

Effect of Compliance on Residual Stresses in Manufacturing With Moving Heat Sources

Abstract Manufacturing processes involving moving heat sources include additive manufacturing, welding, laser processing (cladding and heat treatment), machining, and grinding. These processes involve high local thermal stresses that induce plasticity and result in permanent residual stress and distortion. The residual stresses are typically calculated numerically at great computational expense despite the fact that the inelastic fraction of the domain is very small. Efforts to decouple the small plastic part from the large elastic part have led to the development of the tendon force concept. The tendon force can be predicted analytically for the case of infinitely rigid components; however, this limitation has prevented the broader use of the concept in practical applications. This work presents a rigorous mathematical treatment using dimensional analysis, asymptotics, and blending which demonstrates that the effect of geometric compliance depends on a single dimensionless group, the Okerblom number. Closed-form expressions are derived to predict the effect of compliance without the need for empirical ad-hoc fitting or calibration. The proposed expressions require input of only material properties and tabulated process parameters and are thus ideally suited for use in metamodels and design calculations, as well as incorporation into engineering codes and standards.

Numerical analysis and multi-objective optimization design of parabolic trough receiver with ribbed absorber tube

Parabolic trough collector (PTC) is the most cost-effective and mature concentrated solar power (CSP) technology for solar thermal utilization. However, the highly concentrated solar irradiation on the bottom of the absorber tube causes high local temperature, thermal stress and deformation, further leading to damage and performance degradation of PTC. In order to alleviate the above problem, a novel parabolic trough receiver (PTR) with ribbed absorber tube is proposed to improve the thermo-mechanical performance of PTC Moreover, the multi-objective optimization is employed to determine the optimal parameter combinations (slant angle (β), size (e), pitch (p), and number of the ribs (N)) of ribbed absorber tube coupled with 3D numerical simulation and the genetic algorithm (GA). Based on the TOPSIS method and performance evaluation criteria (PEC) value, the ribbed absorber tube with the optimal geometric parameters of β=15°, N=6, e=4.5 mm and p=20 mm is selected in the Pareto Front as the suggested optimal design. Furthermore, the performance of the PTRs at different inlet temperature of the fluid (Tin=400–600K), direct normal irradiance (DNI=300–1000 W/m2) and mass flow rate (M=0.62–3.72kg/s) are evaluated. It is found that the ribbed absorber tube can effectively disturb the fluid near the boundary and induce longitudinal vortexes flow, which results in significant improvement in heat transfer between fluid and absorber tube, thereby enhancing the performance of the PTC. Compared to the plain tube, the heat transfer and flow resistance of the optimal ribbed absorber are enhanced by 57%–225% and 222%–630%, and the heat loss is lessened by up to 79.3%, resulting in 2.3% and 2.2% improvement in the heat collecting efficiency and overall efficiency. The findings in this paper may provide practical guidelines for developing efficient PTC.

Tribo-dynamic analysis for aero ball bearing with 3D measured surface roughness

Tribological failures, like wear, scuffing and pitting, etc, often occur in aero ball bearings due to large dry contact area, high friction-flash temperature and stress concentration at the interface between the contacting ball and race. In this paper, a numerical tribo-dynamic analysis procedure is developed for the predictions of dynamic performance, lubrication state, friction-temperature, and subsurface stress of the aero ball bearing with 3D measured roughness. The numerical model is verified by comparing the friction coefficients with the testing results, which show well agreements and proves the presented model is available. The dynamic performance of bearing at different azimuth angle are studied, which indicate the increasing radial load and speed result in more asymmetric distributions of the contact load, stress and slide-roll ratio, the maximum values and the unloaded-region become larger. With the increase of the inner race groove coefficient and the contact angle, the pv value and the radial stiffness decrease clearly. The tribology behaviors of the ball bearing are also investigated, the obtained results indicate that the heavy-load and low-speed lead to large dry contact areas, high friction-temperature, and high local stress peaks, the lubrication state become worse, which may further cause the failures of mass wear, scuffing and micro-pitting.

Crack initiation of neutron-irradiated 304 L stainless steel in PWR primary water

Stress corrosion crack (SCC) initiation of neutron-irradiated 304 L stainless steel was studied following irradiation to various doses. Tensile test results show that SCC susceptibility dependence of the alloy on dose is slight. Grain boundary (GB) oxidation was observed prior to crack initiation and DCs always proceeded before or accompanies crack initiation in the bend test. The DC-GB intersections were the predominant crack initiation sites due to the high local stress. Constant load tests resulted in greater GB oxidation and cracks initiated at applied stress as low as 50% of the irradiated yield strength due to the long exposure time.

Local capacitance-voltage profiling and high voltage stress effect study of SiO2/SiC structures by time-resolved scanning nonlinear dielectric microscopy

We investigate SiO2/SiC structures by a nanoscale capacitance-voltage (CV) profiling method based on time-resolved scanning nonlinear dielectric microscopy (tr-SNDM). Owing to the high sensitivity to the variation in the tip-sample capacitance, wide bandwidth of the measurement, and high flexibility of offline processing, tr-SNDM permits the more accurate acquisition of the microscopic CV characteristics localized below the scanning tip. We demonstrate that tr-SNDM based local CV profiling is able to distinguish the different features of untreated and nitrided SiO2/SiC structures and image intrinsic spatial non-uniformity of the interfaces. We also investigate the nanoscale impacts of high voltage stress on the SiO2/SiC structures. By inspecting the local CV characteristics under high voltage stress, we suggest that the interface defect density locally increases during the stress application.

An alternating ageing-annealing process for enhancing strength and ductility of a Mg-Gd-Y-Zn-Zr alloy

In this paper, an alternating ageing-annealing process was proposed for an extruded Mg-9.5Gd-4Y-2.2Zn-0.5Zr (wt.%) alloy, and then the effects of this process on the microstructure, mechanical properties and fracture mechanism of the alloy were investigated. The results showed that short rod-shaped particles with long period stacking ordered (LPSO) phases and β′ phases were densely and uniformly distributed in the sample and exhibited a homogeneous microstructure after alternating ageing-annealing treatment, while after the traditional ageing treatment only basal γ′ phases were sparsely distributed in the fine grain region of the sample with a bimodal microstructure. Deformed grains with strong basal textures and deformation incompatibility between different regions (deformed grain region, fine grain region and bulk-shaped LPSO phase) were prone to high local stress concentrations, which caused the alloy to fracture without full work hardening. The sample possessed an excellent strength-ductility synergistic effect after alternating ageing-annealing treatment. This is mainly attributed to the coordinated deformation of the homogeneous microstructure and the pinning effect of the short rod-shaped LPSO phases and the prismatic β′ phases on dislocations and grain boundaries, which significantly improved the strength and inhibited the initiation of cracks. In summary, the mechanical properties of the sample were improved after heat treatment, with a yield strength (YS) of 425 MPa, an ultimate tensile strength (UTS) of 493.2 MPa, and an elongation (EL) of 11.2%.

Experimental Investigation on the Low Velocity Impact Response of Fibre Foam Metal Laminates.

The combination of fibre metal laminates (FML) and sandwich structures can significantly increase the performance under impact of FMLs. The goal of this work was to create a material that will combine the superior properties of FMLs and foam sandwich structures in terms of the impact resistance and simultaneously have lower density and fewer disadvantages related to the manufacturing. An extensive impact testing campaign has been done using conventional fibre metal laminates (carbon- and glass-based) and in the proposed fibre foam metal laminates to assess and compare their behaviour. The main difference was observed in the energy absorption mechanisms. The dominant failure mechanism for fibre foam laminates is the formation of delaminations and matrix cracks while in the conventional fibre metal laminate the main failure mode is fibre cracking due to high local stress concentrations. The reduction in the fibre cracking leads to a better after-impact resistance of this type of structure improving the safety of the structures manufactured with these materials.

Unraveling the Transport and Fate of Polycyclic Aromatic Hydrocarbons Through Coupling Fluvial Geomorphic Modeling and Measured Data

Coastal zones receive upstream runoff and sediments, as well as the contaminants transported with sediments and flow. Constant urban growth in many coastal areas has raised an increasing concern about stream and floodplain contamination. This is a particularly challenging issue because fluvial hydraulics in the coastal zone is complex, due to the presence of backwater (BW) conditions which alter flow patterns and sediment transport regime. Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that are widely distributed in urban areas and can be transported through stormwater runoff and by sediment facilitated transport. Even though this is a widespread problem in urban areas, the relationship between fluvial deposition and concentrations of PAHs is largely uninvestigated. To fill this gap, this paper investigates the correlation between PAHs concentration and sediment deposition in a backwater zone, using the lower Darby Creek, PA as a case study. A BW geomorphologic model was used to simulate the hydraulics of the flow in Darby Creek. The model identified locations of high and low shear stresses, erosion, and deposition of fluvial sediment. Twenty-eight core sediment samples, capturing a range of soil depths, were collected from the bed, the banks, and the floodplains of the creek and were analyzed for PAHs on a GC-MS. The results showed that PAHs concentrations were generally highest on depositional banks and were highly variable on the channel bed and in the floodplain. Further, PAH concentrations were more uniform across the cross section (bed, bank, and floodplain) at downstream sites compared to upstream. The results also showed that in erosional sites, unlike the depositional sites, there was little variation in PAHs concentration in the soil column. This analysis provides deeper insight into the transport and fate of PAHs in urban streams and floodplains, ultimately helping mitigate the impacts of pollutants on the environment.

Acute Responses to Cycling Exercise With Blood Flow Restriction During Various Intensities.

Lauver, JD, Moran, A, Guilkey, JP, Johnson, KE, Zanchi, NE, and Rotarius, TR. Acute responses to cycling exercise with blood flow restriction during various intensities. J Strength Cond Res 36(12): 3366-3373, 2022-The purpose of this study was to investigate the acute physiological responses during cycling at various intensities with blood flow restriction (BFR). Subjects ( N = 9; V̇ o2 peak = 36.09 ± 5.80 ml·kg -1 ·min -1 ) performed 5 protocols: high-intensity (HIGH), control (CON-90), 90% of ventilatory threshold (VT) work rate with BFR (90-BFR), 70% of VT with BFR (70-BFR), and 30% V̇ o2 peak with BFR (30-BFR). Protocols consisted of five 2-minute work intervals interspersed with 1-minute recovery intervals. Blood flow restriction pressure was 80% of limb occlusion pressure. V̇ o2 , muscle excitation, tissue oxygen saturation (StO 2 ), discomfort, and level of perceived exertion (RPE) were assessed. Muscle excitation was higher during HIGH (302.9 ± 159.9 %BSL [baseline]) compared with 70-BFR (99.7 ± 76.4 %BSL) and 30-BFR (98.2 ± 70.5 %BSL). StO 2 was greater during 90-BFR (40.7 ± 12.5 ∆BSL), 70-BFR (34.4 ± 15.2 ∆BSL), and 30-BFR (31.9 ± 18.7 ∆BSL) compared with CON-90 (4.4 ± 11.5 ∆BSL). 90-BFR (39.6 ± 12.0 ∆BSL) resulted in a greater StO 2 -Avg compared with HIGH (20.5 ± 13.8 ∆BSL). Also, HIGH (23.68 ± 5.31 ml·kg -1 ·min -1 ) resulted in a greater V̇ o2 compared with 30-BFR (15.43 ± 3.19 ml·kg -1 ·min -1 ), 70-BFR (16.65 ± 3.26 ml·kg -1 ·min -1 ), and 90-BFR (18.28 ± 3.89 ml·kg -1 ·min -1 ); 90-BFR (intervals: 4 = 15.9 ± 2.3; intervals: 5 = 16.4 ± 2.5) resulted in a greater RPE compared with 30-BFR (intervals: 4 = 13.3 ± 1.4; intervals: 5 = 13.7 ± 1.7) during intervals 4 and 5. These results suggest that when adding BFR to various intensities of aerobic exercise, consideration should be given to peak work and VT to provide a balance between high local physiological stress and perceptual responses.

Micro-cantilever testing of microstructural effects on plastic behavior of Ti–6Al–4V alloy

To evaluate the effects of microstructural factors on the plastic behavior of Ti–6Al–4V alloys, micro-cantilevers featuring several grains were machined using a focused ion beam. The equiaxed structure (a mixture of equiaxed α phase and intergranular β phase) and bimodal structure (a mixture of an equiaxed α phase and lamellar phase) were examined to verify the microstructural effects. To determine the slip plane and direction, the crystal structure was evaluated using electron backscattered diffraction, following bending tests of the microcantilever. In addition, the elastic modulus and hardness of each grain were determined via nanoindentation testing. In the equiaxed microstructure, the β-phase deformation often occurred first; then, slips were activated inside the equiaxed α phase. It is concluded that the β phase deforms more easily than the α phase because the elastic modulus and hardness of the former are lower, as indicated by the nanoindentation testing. In the bimodal microstructure, β-lath deformation occurred along the acicular direction in the lamellar-phase region, and slips occurred inside the α grain. The deformation of the lamellar structure was associated with β-phase deformation and affected by the high local stress at the grain boundary and phase interface, owing to the difference in grain orientation within the lamellar structure. The results of this study suggest that the plastic behavior of Ti–6Al–4V alloys depends not only on the slip system of the α grains but also on the deformability of the β phase and the misorientation of adjacent grains in polycrystalline Ti–6Al–4V alloy.

Thermal-Fluid-Solid Coupling Analysis on the Temperature and Thermal Stress Field of a Nickel-Base Superalloy Turbine Blade.

Based on the establishment of the original and improved models of the turbine blade, a thermal-fluid-solid coupling method and a finite element method were employed to analyze the internal and external flow, temperature, and thermal stress of the turbine blade. The uneven temperature field, the thermal stress distribution characteristics of the composite cooling turbine blade under the service conditions, and the effect of the thickness of the thermal barrier coating (TBC) on the temperature and thermal stress distributions were obtained. The results show that the method proposed in this paper can better predict the ablation and thermal stress damage of turbine blades. The thermal stress of the blade is closely related to the temperature gradient and local geometric structure of the blade. The inlet area of the pressure side-platform of the blade, the large curvature region of the pressure tip of the blade, and the rounding between the blade body and the platform on the back of the blade are easily damaged by thermal stress. Cooling structure optimization and thicker TBC thickness can effectively reduce the high temperature and temperature gradient on the surface and inside of the turbine blade, thereby reducing the local high thermal stress.

Effect of precipitates on the cryogenic fracture toughness of 9%Ni steel flux cored arc weld

The microstructure and fracture toughness of 9%Ni steel flux cored arc welds with different heat input were investigated. CTOD results showed that the fracture toughness of the weld decreased with the increasing amount of precipitates at room temperature and at cryogenic temperature. Micro-regional force and deformation (MRFD) of the weld was investigated by finite element analysis. Precipitates have a significant impact on MRFD. In the stretching process, high stress concentration and local plastic deformation occurred around precipitates, which decreased crack propagation resistance in interdendritic region. The increment of precipitate amount enhanced the stress concentration and local plastic deformation. The effect of rod-shaped Laves phase on MRFD is much higher than globular-shaped carbide. For Laves phase, the maximum local plastic strain and peak stress has close relationship with its aspect ratio and its angle between long-axis direction and load-direction. The size of carbide has little influence on MRFD. Due to the high local plastic deformation and peak stress, microcracks formed at interdendritic region near precipitates during stretching at cryogenic temperature.

Dynamic recrystallization by subgrain rotation in olivine revealed by electron backscatter diffraction

We document how dynamic recrystallization by subgrain rotation (SGR) develops in natural olivine-rich rocks deformed in extension to up to 50% bulk finite strain (1473 K, confining pressure of 300 MPa, and stresses between 115 and 180 MPa) using electron backscatter diffraction (EBSD) mapping. SGR occurs preferentially in highly deformed grains (well-oriented to deform by dislocation glide) subjected to local stress concentrations due to interactions with hard neighboring grains (poorly-oriented olivine crystals or pyroxenes). Subgrains (misorientation <15°) are mainly delimited by tilt walls composed of combinations of dislocations of the [100](001), [001](100), [100](010) and [001](010) systems, in order of decreasing frequency. The activation and prevalence of these systems agree with a Schmid factor analysis using data for high-T dislocation creep in olivine. The development of closed 3D subgrain cells by SGR recrystallization requires the contribution of at least three different slip systems, implying the activation of hard slip systems and high (local) stresses. The transition from subgrain to grain boundaries (misorientation ≥15°) is characterized by a sharp change in the misorientation axes that accommodate the difference in orientation between the two subgrains or grains. We propose that this change marks the creation and incorporation of new defects (grain boundary dislocations with different Burger vectors and, likely, disclinations or disconnections) at the newly-formed grain boundaries and that this might be favoured by stress concentrations due to increasing misalignment between slip systems across the boundary. Finally, we document the development of strong misorientations within the parent grains, due to the accumulation of low angle grain boundaries, and between them and the recrystallized grains. SGR recrystallization may thus produce strong dispersion of the crystal preferred orientation without the need for grain boundary sliding.

Comparative study of tensile and high-cycle fatigue properties of extruded AZ91 and AZ91–0.3Ca–0.2Y alloys

Mg–Al–Zn–Ca–Y alloys with excellent ignition and corrosion resistances—termed SEN alloys (where the letters “S,” “E,” and “N” stand for stainless, environmentally friendly, and non-flammable, respectively)—have been developed recently. In this study, the microstructure, tensile properties, and high-cycle fatigue properties of an extruded Mg–9.0Al–0.8Zn–0.1Mn–0.3Ca–0.2Y (SEN9) alloy are investigated and compared with those of a commercial Mg–9.0Al–0.8Zn–0.1Mn (AZ91) alloy extruded under the same conditions. Both the extruded SEN9 alloy and the extruded AZ91 alloy have a fully recrystallized structure comprising equiaxed grains, but the former has a smaller average grain size owing to the promoted dynamic recrystallization during extrusion. The extruded AZ91 alloy contains coarse Mg17Al12 discontinuous precipitate (DP) bands parallel to the extrusion direction, which are formed during its cool down after extrusion. In contrast, the extruded SEN9 alloy contains relatively fine undissolved Al2Ca, Al8Mn4Y, and Al2Y second-phase particles, which are formed during the solidification stage of the casting process. The tensile strength of the extruded SEN9 alloy, which has finer grains and more abundant particles, is slightly higher than that of the extruded AZ91 alloy. However, the difference in their strengths is relatively small because the stronger solid-solution hardening and precipitation hardening effects in the extruded AZ91 alloy offset the stronger grain-boundary hardening and dispersion hardening effects in the extruded SEN9 alloy to some extent. The tensile elongation of the extruded AZ91 alloy is significantly lower than that of the extruded SEN9 alloy because the large cracks formed in the DP bands in the former cause its premature fracture. Although the extruded SEN9 alloy has higher tensile properties than the extruded AZ91 alloy, the high-cycle fatigue life and fatigue strength of the former are shorter and lower, respectively, than those of the latter. The DP bands in the extruded AZ91 alloy do not act as fatigue crack initiation sites, and therefore, fatigue cracks initiate on the specimen surface at all stress amplitude levels. In contrast, in most of the fatigue-fractured specimens of the extruded SEN9 alloy, fatigue cracks initiate on the undissolved Al2Ca and Al2Y particles present on the surface or subsurface of the specimens because of the high local stress concentration on the particles during cyclic loading. This particle-initiated fatigue fracture eventually decreases the high-cycle fatigue resistance of the extruded SEN9 alloy.