AZ31 Alloy Research Articles

Silicon carbide-embedded AZ91E alloy nanocomposite hybridised with chopped basalt fibre: performance measures

ABSTRACT This study uses vacuum stir casting to manufacture magnesium alloy hybrid nanocomposites of silicon carbide nanoparticles (50 nm) and chopped basalt fibre. The different weight percentages (0 wt%, 3 wt%, 6 wt% and 9 wt%) of chopped basalt fibres with a constant weight percentage of 7.5 wt.% silicon carbide nanoparticles were added into molten AZ91E magnesium alloy at 600 rpm constant stirring speed. During the final casting process, 0.1 MPa vacuum pressure was applied to all the composites to reduce the casting defects. The prepared hybrid composite was characterised by physical, mechanical, microstructural and wear properties. The Quanta FEG model SEM apparatus was used to examine the distribution of silicon carbide nanoparticles and basalt fibre. The mechanical characteristics, such as ultimate tensile strength (UTS), yield strength and impact strength, were obtained for 7.5 wt% SiCnp/9 wt% basalt fibre reinforced AZ91E magnesium alloy matrix hybrid nanocomposite. Adding chopped basalt fibre enhanced the wear properties of conventional AZ91E magnesium alloy.

Effect of Single-Pass Rolling on Microstructure and Mechanical Properties of AZ31 Alloy Processed by Equal Channel Angular Pressing

Effect of Single-Pass Rolling on Microstructure and Mechanical Properties of AZ31 Alloy Processed by Equal Channel Angular Pressing

Role of combinative In and Sm additions in tailoring the discharge performance of extruded AZ31 alloys as anodes for seawater batteries

The discharge behaviors of AZ31 alloys, modified by the addition of In and Sm elements in conjunction with equal channel angular pressing (ECAP) processing, were systematically explored. The incorporation of In suppressed the formation of cathodic second phases. In contrast, Sm promoted the precipitation process and therefore led to higher microstructure uniformity following ECAP processing. The solid-solution In contributed to the activated dissolution of Mg matrix and the inhibited hydrogen evolution during discharge, while Sm was beneficial for the uniform dissolution and the alleviation of chunk effect. The results indicated that the 12-pass ECAP processed AZ31-In-Sm anode revealed the most enhanced discharge performance with a discharge voltage of 0.889 V and a utilization of 66.94% at 100 mA cm−2. This improvement can be primarily attributed to the combined effects of the decreased precipitations of cathodic phases by In addition and the enhanced microstructure homogeneity by Sm addition, collaborated with significant microstructure refinement.

Ageing Characteristics of Stir Cast AZ 61 Alloy with Minor Additions

Background: Knowing that magnesium (Mg) alloys and its composites bear the potential of being used simultaneously for light structural as well as biomedical applications, it appears prudent to look for developing a novel Mg alloy; the concurrent demand is to monitor recent trend in development of functional Mg-alloy and its composite materials through extensive patent search. Review of recent patents in the related field makes it relevant to investigate this aspect. Objective: The authors aim to study the evolution of structure and properties in stir cast of AZ- 61 alloy with minor additions of scandium, calcium and manganese. This paper reports the results of this investigation. Methods: The castings are prepared by stirring the molten alloy at 600 rpm for 10 minutes, followed by pouring into a preheated metal mould. The solidified alloys are homogenized at 550°C for 12 hours. The homogenized alloys are then subjected to solutionising treatment at 500°C for 5 hours; subsequently, the alloys are quenched in iced water. The quenched alloys are subjected to ageing treatment at different temperatures between 100°C to 400°C at an interval of 100°C. Similar experiments are conducted with its statically cast counterparts. The structure and properties of all the samples have been characterized by optical and scanning electron microscopy, and XRD analysis; DSC heating run is conducted to study the kinetics of phase transformation. Mechanical behaviour of castings is studied with the aid of tensile testing and fractography. Moreover, tribological behaviour of alloys is assessed by wear testing with the help of pin on disc method. Results: The results show that the stir cast alloy produces a homogeneous structure with significant improvement in properties. The precipitates of Mg17Al12, Al Mn, Mg Zn2, Al2 Ca and Mg2 Ca are formed due to the ageing of both stir cast and statically cast alloy. It is found that the diffusion of Al in magnesium controls the precipitation process. The tribological properties are found to be satisfactory for the stir cast alloy. Conclusion: The modified AZ61 alloy with minor additives, achieves excellent structural homogeneity and mechanical properties after stir casting followed by quench ageing.

Improved corrosion resistance of hydroxyapatite-reinforced plasma electrolytic oxide coatings on AZ31 alloy from one-step and two-step fabrications

The improved corrosion resistance of AZ31 alloy by plasma electrolytic oxidation (PEO) counteracts its apatite-forming ability. To overcome the issue, apatite-containing coatings were fabricated. One-step and two-step fabrications were compared to incorporate the nanoparticle hydroxyapatite (HA) in the coating and to evaluate their effect on the corrosion resistance. The corrosion resistance was evaluated by polarization test and EIS measurement in 0.9% NaCl solution. The electron microscopy and chemical analysis revealed that the HA particles were dispersed in the one-step coatings, while an interspersed HA distribution was observed in the two-step coatings. The dispersed particles enhanced the coating’s hardness from 490 to 554 HV. In the two-step coatings, the HA particles mainly accumulated inside the pores, reducing the coating porosity down to 3.9%. The one-step coatings were more stable in the corrosive solution, offering a remarkably higher corrosion resistance, than the two-step coatings. Moreover, the one-step coating required a shorter (half) processing time (10 min) than the two-step process (20 min) to achieve a similar order of corrosion current density of 10−7 A cm−2. The results demonstrated that the arrangement of reinforcement in the PEO coatings and its effect on the corrosion resistance can be adjusted.

Revealing the heterogeneous nucleation mechanism of Mg17Al12 on impurity Mg2Si particles in commercial AZ31 alloy

Silicon (Si) is an inevitable impurity element in the AZ31 alloy. In this study, the Si impurity was detected mainly as fine Mg2Si particles dispersed widely within the central region of the Mg17Al12 phase. During the solidification process, the Mg2Si particle precipitates at about 565 °C, before the Mg17Al12 phase of 186 °C, potentially acting as the heterogeneous nucleation core for the Mg17Al12 phase. The orientation relationship between Mg2Si and Mg17Al12 was investigated using the edge-to-edge matching model (E2EM) calculations, which showed a misfit of only 0.1 %. This low misfit suggests that Mg2Si can serve as a heterogeneous nucleation site for Mg17Al12. The surface and interface structures of Mg2Si (220) and Mg17Al12 (332) were constructed, and then investigated through the first-principles calculation. The theoretical results indicate that Mg and Al are easily adsorbed on the surface of Mg2Si, with Al showing higher adsorption energy than Mg. Furthermore, the interface between Mg2Si and Mg17Al12 exhibits favorable thermodynamic stability. Combined with experiments and theoretical calculations, it is confirmed that the Mg2Si particles, formed due to the Si impurity, provide effective heterogeneous nucleation sites for the Mg17Al12 phase.

Electrophoretic deposition of MXene coating on Mg alloy 2,5 PDCA-LDH film for enhanced anticorrosion/wear

Two-dimensional (2D) MXene, employed as protective coatings for anticorrosion and wear resistance, outperforms most state-of-the-art 2D nanomaterials. In this work, MgAl-LDH film modified with the 2,5 PDCA inhibitor was synthesized on Mg alloy AZ31 via in-situ hydrothermal methods. Subsequently, MXene Ti3C2 at various concentrations was electrophoretically deposited onto the as-prepared 2,5 PDCA-LDH film. The successful incorporation of the 2,5 PDCA inhibitor resulted in MgAl-LDH nanosheets with a low growth angle, facilitating the electrophoretic deposition of MXene Ti3C2. After deposition, Ti3C2 nanomaterials uniformly coated the 2,5 PDCA-LDH film, forming a protective barrier against corrosive species while simultaneously establishing a lubricating layer. Notably, Ti3C2 nanosheets exhibit a tendency to self-agglomerate at higher concentrations, resulting in the 1.0 wt% Ti3C2 coating displaying the highest anticorrosion and lubrication capacities.

Microstructure Evolution and Creep Properties of AZ61 Magnesium Matrix Composites Reinforced with Bimodal-Sized SiC Particles

In the scope of this exploration, AZ61 magnesium matrix composites fortified with bimodal size SiC particles were synthesized using ultrasonic-assisted mixing in the semi-solid state, which exhibited optimal grain refinement and exceptional creep resistance. We examined the impact of bimodal SiC particles on the microscopic structure and creep deformation of the resulting composites. Our findings indicated that incorporating bimodal SiC particles resulted in the refinement of the matrix grains and alteration of the morphology of the Mg17Al12 phase. Furthermore, the micron-sized SiC particles exhibited a typical necklace-like particle distribution around the grain boundaries of the bimodal SiC particle/AZ61 composites, while the nano-sized SiC particles were mainly located around the micron-sized particles. As the volumetric percentage of micron SiC particles increased, the quantity of nano-sized particle clusters diminished noticeably. Creep analysis at 200 °C and 50 MPa revealed that the creep life of M−6+N−1 composite was increased by 111.9% compared to the AZ61 alloy. Additionally, the M−6+N−1 combination exhibited a significantly lower steady-state creep rate compared to the matrix alloy, with a reduction of approximately 11 times. These results indicate that the bimodal SiC particle/AZ61 composites have superior creep resistance, which is a consequence of the grain refinement and grain boundary pinning effects of SiC particles.

Effect of Electropulsing on the Microstructure and Mechanical Properties of AZ31 Alloys Manufactured by Cold Drawing

Effect of Electropulsing on the Microstructure and Mechanical Properties of AZ31 Alloys Manufactured by Cold Drawing

Analysis and optimization of machining parameters of AZ91 alloy nanocomposite with the Influences of nano ZrO2 through vacuum diecast process

The magnesium alloy composite is a vital material for automotive applications due to its features like high stiffness, superior damping resistance, high strength, and lightweight. Here, the motto of research is to establish the AZ91 alloy nanocomposite with the exposures of 0, 1, 3, and 5 volume percentages (vol%) of nano zirconium dioxide (ZrO2) particles (50nm) through fluid stir metallurgy route associated with 1x105 Pa vacuum die cast process. Exposures on structural morphology, hardness, and impact toughness of composite are analyzed and identified as the nano AZ91 alloy composite enclosed with 5vol% is homogenous particle dispersion, enhanced hardness (97.6HV), and optimum toughness of 21.2J/mm2. However, composite faces machining difficulties due to the hard abrasive particles with higher hardness, resulting in tool wear. This experiment predicts the optimum mill parameters during the end mill operation of magnesium alloy nanocomposite (AZ91/5vol%) by using a tungsten carbide coated end mill cutter to attain the maximum metal removal rate with low surface roughness and tool wear analyzed via the general linear model (GLM) ANOVA approach. The input conditions for end milling operation vary, like feed rate (0.1 -0.4mm/rev), depth of cut (0.05 -0.2mm), and spindle speed (250-1000rpm). During the ANOVA GLM approach, the L16 design experiment is fixed for further interaction analysis. The results predicted by the depth to cut and feed rate were dominant and played a major role in deciding the tool wear, surface roughness, and MRR.

Microstructure and mechanical properties of hammer-forging assisted wire-arc directed energy deposition AZ91 alloy

ABSTRACT With the development of lightweight aerospace equipment, magnesium alloys are receiving increasing attention. Wire-arc directed energy deposition (Wire-arc DED) is a highly promising manufacturing method for magnesium alloy parts, but its development has been severely restricted by the problems of coarse grain size and low mechanical properties. To address these issues, a hammer-forging assisted Wire-arc DED technology for magnesium alloy AZ91 is proposed. The effects of interlayer hammer-forging and synchronous hammer-forging on macrostructure, microstructure and mechanical properties of the Wire-arc DED samples are compared, and the microstructure evolution and performance enhancement mechanism are discussed. The results show that the maximum plastic deformation caused by hammer forging reaches 11.7%. Hammer forging can significantly refine grains, and the average grain size decreases from 27.7 μm to 13.5 μm. Synchronous hammer-forging is better than interlayer hammer-forging in terms of performance enhancement, the UTS reaches 301.8 MPa, an increase of 10.9%, which is comparable to that of traditional forged parts, mainly attributed to the grain refinement and increased dislocation density.

Effect of SiC content on the microstructure and wear behavior of cold-sprayed Al-SiC coatings deposited on AZ31 alloy substrate

As a promising and recently developed deposition technique, cold spray deposition method is among the most recently implemented approaches to enhance the poor hardness and wear resistance of AZ31B magnesium alloy. This study investigated the effect of SiC content on the microstructural characteristics, microhardness, and wear behavior of cold-sprayed Al-(16, 28, and 38 wt%) SiC composite coatings. The incorporation of SiC particles into the Al-matrix coating led to the development of a mechanical interlocking mechanism and improved coating-substrate interfacial bonding. The microhardness of the Al-38 wt% SiC coating was approximately 80 % higher than that of the bare substrate due to reduced porosity and a uniform distribution of SiC particles. For coatings with higher SiC content, the dominant wear mechanism transitioned from adhesive to abrasive wear, as evidenced by the friction coefficient (COF) values and wear track micromorphology. The Al-16 wt% SiC coating exhibited the lowest COF and wear rate values, indicating superior wear resistance among the specimens.

Effect of texture on bending behavior of Mg alloy sheets

The effect of Li elements on the microstructure and texture evolution of AZ31 alloy sheets during room-temperature three-point bending was investigated. The results showed that the conventional c-axis//ND basal texture of the extruded AZ31 sheet could be modified to a TD-elongated fiber texture with a 5 wt% Li addition. As a result, the room-temperature bendability of the Mg–3Al–5Li sheet was improved effectively, and this sheet showed a minimum bending radius of only 2 mm. The superior bendability exhibited surpasses the room-temperature bending capabilities commonly observed in the majority of commercial Mg alloys. The improvement in bendability of the Mg–3Al–5Li sheet was attributed to the TD-elongated texture distribution. This type of texture distribution may offer more effective deformation modes to alleviate thickness strain during bending in comparison to the texture in extruded AZ31 sheets. This study could provide insights into developing Mg alloys with high room-temperature bendability by tailoring texture distribution rather than texture weakening.

Influence of rotational speed on the microstructural, mechanical and wear behaviour of FSPed cast AZ91 magnesium alloy

ABSTRACT In this study, the Magnesium AZ91 alloy underwent a process known as Friction Stir Processing (FSP) at different tool rotational speeds: 1160 r.p.m., 850 r.p.m., and 580 r.p.m. subjected to a constant transverse speed/feed rate (50 mm/min). The average grain size of the FSP-processed samples fell dramatically due to dynamic recrystallisation (DRX), from 43.65 μm in the as-received Mg AZ91 to less than 4.21 μm in the alloy processed at 850 rotational speed. The UTS was enhanced from 145.49 MPa to 184.51 MPa for as-received material to alloy processed at 850 rotational speeds due to the dissolution of secondary phases and the grain refinement. Also, this increase in rotational speed resulted in an increase in total elongation (TE), which increased from 5.465% to 9.92% due to the removal of defects during the processing. The wear resistance of FSPed materials was better than that of the as-received material at all tool rotational speeds. Better wear resistance was observed in the case of samples processed at 850 r.p.m. All these alterations in properties were found due to the existence of refined grains and the removal of defects due to stirring action.

Study on the surface layer properties of magnesium alloys after impulse shot peening

Shot peening is a commonly used method of finishing machine elements in the manufacturing process. One variation of shot peening is the impulse shot peening. This paper presents the influence of impulse shot peening technological conditions on the surface roughness (parameters Ra and Rt), topography, and microhardness. The FEM was used to determine the S11 stresses. In the experiment and simulation tests, AZ31 and AZ91HP magnesium alloy samples were used. Variable parameters in the impulse shot peening process were impact energy E (15–185 mJ), ball diameter d (3–15 mm), and impact density j (3–44 mm−2). As a result of the tests carried out, it was found that after impulse shot peening, the surface topography is change, microirregularities are flattened, and numerous depressions are formed, which can be potential lubrication pockets. The 2D surface roughness parameters for most impulse shot peening conditions are lower than for the pre-machining. The roughness parameters for magnesium alloy AZ91HP are lower than for AZ31. This is most likely due to the lower elongation A. The microhardness after impulse shot peening increased by 20 to 87 HV. As a result of FEM of the impulse shot peening, compressive stresses S11 were created in the surface layer. The depth of occurrence of S11 stresses is from 1.5 to 3.5 mm, and their values for the AZ91HP magnesium alloy samples are 10 to 25% lower than for the AZ31 alloy samples. The most favorable results of the tested properties of the surface layer were obtained for E = 100 mJ, d = 10 mm, and j = 11 mm−2. The abstract serves both as a general introduction to the topic and as a brief, non-technical summary of the main results and their implications.

Investigating the role of fine grain structure on mineral deposition and resistance to corrosion initiated mechanical failure of the fine grained AZ31 magnesium alloy

ABSTRACT In the present work, fine grained AZ31 magnesium (Mg) alloy was produced by equal channel angular pressing (ECAP) and exposed to simulated physiological conditions to investigate the role of refined microstructure on biomineralisation, degradation and corrosion initiated mechanical failure. ECAP was carried out at 200°C in Bc route for up to four passes (one complete cycle) and a grain refinement up to 1.9 ± 1.1 μm was achieved in AZ31 Mg alloy from a starting size of 36 ± 4.1 μm. X-ray diffraction (XRD) analysis confirms the development of non-basal texture in the ECAPed AZ31 alloy. The phases deposited on the surface of the samples after immersion carried out in simulated physiological environment were analysed by XRD and scanning electron microscopy which confirms the higher level of mineral phase deposition on ECAPed AZ31 alloy due to increased surface energy (39.11 ± 2.1 mJ/cm2) compared with base alloy (20.5 ± 5.3 mJ/cm2). Higher tensile strength (169.9 ± 5.5 MPa) was observed for the fine grained AZ31 Mg alloy compared with the base alloy (120.5 ± 3.7 MPa) to resist the corrosion initiated mechanical failure after exposing the samples to corroding simulated physiological environment for 1 day.

Enhancing the mechanical properties and thermal conductivity of Ti/AZ91 composites through integrated extrusion and rolling continuous deformation processing

With the increasing demand for highly integrated circuits to optimize energy efficiency, reduce weight, and improve mechanical properties, finding a Magnesium (Mg) matrix material with excellent mechanical strength and high thermal conductivity poses a significant challenge. In this work, titanium (Ti) particles were introduced into AZ91 (Mg-9Al-1Zn) alloy to fabricate Ti/AZ91 composites, employing a combination of stir casting, extrusion and rolling processes. This strategy simultaneously enhances the mechanical properties and thermal conductivity of the Ti/AZ91 composites compared with AZ91 alloy. The incorporation of Ti particles serves to refine grains, expediting the formation of Mg17Al12 phase within the Mg matrix. Optimal comprehensive mechanical properties are attained in 10 wt% Ti/AZ91 composite, exhibiting an ultimate tensile strength of 365 MPa, an elongation of 11.9 %, and a significantly low wear rate of 4.548×10−3 mm3/m. Notably, the 10 wt% Ti/AZ91 composite shows a 41.1 % reduction in wear rate relative to the AZ91 alloy, attributed to the incorporation of hard Ti particles. Furthermore, the thermal conductivity of the 2.5 wt% Ti/AZ91 composite exhibits a significant enhancement over that of the AZ91 alloy. Detailed discussions are provided on the fundamental mechanisms responsible for strengthening, wear resistance, and thermally conductive in Ti/AZ91 composites. These results highlight the substantial potential of Ti/AZ91 composites for lightweight structural applications, such as highly integrated circuits requiring excellent mechanical properties and high thermal conductivity.

Effect of sliding speed and sliding distance on wear behavior of AZ31-B4C composite

Emphasis of current research is to investigate the dry sliding behavior of AZ31 magnesium alloy and AZ31–1.5B4C magnesium metal matrix composites (MMCs) at varying sliding speeds and sliding distances. Magnesium alloy and composite are fabricated through ultrasonic assisted stir casting method. Optical microscope (OM), scanning electron microscopy (SEM), and energy dispersive x-ray analysis (EDAX) are used to characterize developed materials. Microhardness of all materials is measured using a Vickers microhardness tester. Wear-friction behavior is investigated in dry sliding mode using pin-on-disc tribometer at room temperature. Magnesium alloy and composite are tested over a range of sliding speeds (0.25–1.25 m s−1) and distances at a moderate normal load (20N). Wear morphology is finally investigated for composites and alloy under SEM and EDAX. SEM micrographs of as-cast AZ31-1.5B4C composite reveals uniform distribution of B4C particles with noticeable refinement in grain structure. EDAX spectra of AZ31-1.5B4C composite depict the presence of boron and carbon along with existing elements of AZ31 alloy. Microhardness has enhanced around 30% for Mg-MMC by incorporating 1.5 wt% B4C in AZ31 alloy. Furthermore, the use of B4C as reinforcement increases the density of the composite. Wear rate is reduced by around 20% and COF is reduced by around 25% for AZ31-1.5B4C composite compared to AZ31 alloy for all experimental conditions. Abrasion, oxidation, adhesion and delamination wear mechanisms are observed as dominant mechanism for varying sliding speeds and distances.

Regulating the grain refinement and rolling properties of coarse-crystalline Mg-Zn-Gd-Ca-Mn alloy through multi-pass cold rolling and annealing

The newly developed Mg–Zn-RE (rare earth) alloy sheet shows significant prospects for 3C applications due to its superior room-temperature malleability compared to the commercial AZ31 alloy. However, the casting ingots of these alloys often exhibit coarse grains due to low alloying element content and the absence of the grain-refining element Zr, making them susceptible to significant cracking while hot-rolling. This study applies a multi-pass cold rolling technique with minimal reduction to a cast Mg–Zn-Gd-system alloy characterized by coarse grains, followed by a static annealing process to enhance its rolling capability. The impact of cold rolling and annealing temperatures on microstructure, plastic deformation mechanism, and static recrystallization (SRX) behavior were studied. It was found that multi-pass cold rolling with minimal decrease promoted the generation of more twins and slip lines, resulting in more uniform deformation and a substantial accumulated rolling strain of 10 %. Consequently, the significant accumulated strain, coupled with stress concentration at positions such as grain boundaries, twin boundaries, and dislocation tangles, acted as nucleation sites for complete static recrystallization at a specific annealing temperature of 375 °C. As a result, the coarse cast grains were successfully refined from 400 μm to 37 μm. Fortunately, this improvement has significantly enhanced the hot-rolling qualities, removing fractures throughout the process. This advancement not only enables industrial-scale rolling but also enhances production efficiency.

Detwinning and Anneal-Hardening Behaviors of Pre-Twinned AZ31 Alloys under Cryogenic Loading

Detwinning and Anneal-Hardening Behaviors of Pre-Twinned AZ31 Alloys under Cryogenic Loading