Alloy AZ31B Research Articles

Crystal Plasticity Simulation of the AZ31B Alloy Sheet under Uniaxial Deformation Considering Grain Boundary Sliding

The aim of present work is to develop a crystal plasticity modeling approach to integrate slip, dynamic recrystallization (DRX) and grain boundary sliding (GBS) for simulating the deformation and texture evolution of magnesium alloys deformed at the high temperature. A GBS model is developed to evaluate strain and grains’ rotation induced by GBS, and implemented into the polycrystal plasticity framework VPSC. The VPSC-DRX-GBS model can well reproduce the stress-strain curves and texture evolution. The calculated GBS contribution ratio in tension is obviously higher than in compression due to easier cavity nucleation on grain boundaries under tensile creep-aging conditions. The significantly different texture development in tension and compression deformation due to GBS is well reproduced by the proposed model.

Surface chemistry, film morphology, local electrochemical behavior and cytotoxic response of anodized AZ31B magnesium alloy

This work investigates the effect of current density on the surface chemistry, film morphology, cytotoxic response, global and local electrochemical behaviors of AZ31B alloy anodized in 1.0 M NaOH + 0.5 M Na2SiO3 solution. Three different current densities, namely 5, 10 and 20 mA cm−2 were tested. The surface morphology and thickness of the anodized layers were examined by scanning electron microscopy. The surface chemical states were assessed by X-ray photoelectron spectroscopy. The corrosion resistance was evaluated in phosphate-buffered saline (PBS) based on electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The use of scanning probe techniques with physicochemical resolution, the scanning electrochemical microscopy (SECM) and the scanning Kelvin probe (SKP), allowed the best corrosion behavior to be assigned to the sample anodized using a current density of 20 mA cm−2. Altogether, these methods allowed to establish that the anodizing current density imposed to the magnesium alloy had a major effect on the morphology and composition of the surface layers, and produced changes in their electrochemical behavior. In vitro cytotoxicity tests using the MTS assay demonstrated that the good biocompatibility of the AZ31B magnesium alloy was not damaged by the surface layers formed during the anodization treatment.

Effect of pin diameter and different cooling media on friction stir welding of dissimilar Al-Mg alloys

Abstract Friction Stir welding (FSW) is preferred over conventional welding process for dissimilar materials joining. This is due to controlled heat input which restricts the brittle intermetallic compound (IMC) formation. In the present study, aluminum alloy 6061-T6 and magnesium alloy AZ31B were friction stir welded at the tool rotation speed of 545 rpm, feed speed of 31.5 mm/min, 20 tilt angle and 2 mm offset towards Mg alloy (advancing side) with different tool pin diameter and cooling conditions. Compressed air and CO2 cooling conditions were used to control the heat input. Visual inspection, weld interface, tensile and microhardness measurement were carried out. In-process temperature measurement was carried out for different cooling conditions to relate the heat input. It indicated decreased peak temperature on the advancing side with increased cooling severity. With increasing cooling severity, tensile strength increased to 108.94 MPa. However, microhardness decreased with increased cooling severity due to the possibility of reduced Al/Mg IMC formation.

Mechanical and Corrosion Assessment of Friction Self-Piercing Rivet Joint of Carbon Fiber-Reinforced Polymer and Magnesium Alloy AZ31B

Abstract In the present work, thermoset carbon fiber–reinforced polymer (CFRP) was spot joined to magnesium alloy AZ31B by a friction self-piercing riveting (F-SPR) process. Lap shear tensile and cross-tension testing were used to evaluate the mechanical joint performance. An average lap shear tensile load of 5.18 kN was achieved, while an average of 2.81 kN was found from cross-tension testing. All F-SPR samples showed a pullout of AZ31B after mechanical testing, indicating good mechanical interlocking between the steel rivet and AZ31B. Corrosion potential was measured for each material to establish the galvanic corrosion characteristics. As expected, AZ31B was found to be the most active, while thermoset CFRP was the most noble. The steel rivet fell between the AZ31B (active) and the thermoset CFRP (noble). Salt fog corrosion testing (ASTM B-117) was performed to evaluate the corrosion performance of the uncoated F-SPR joint. With up to 200 h of exposure, the post-corroded F-SPR joint integrity retained 81.2% of the pre-exposure F-SPR joint strength with AZ31B pullout failure mode. From cross-sectional analysis of the F-SPR joint, extensive corrosion of AZ31B was observed at the joint and other exposure areas. However, steel rivet was not significantly corroded due to sacrificial anode effect by which AZ31B corroded first in the galvanic couple.

Fabrication and mechanical properties of novel CFRP/Mg alloy hybrid laminates with enhanced interface adhesion

To enhance the interfacial and mechanical properties of magnesium alloy based fiber-metal laminates, a novel of AZ31B magnesium alloy-based hybrid fiber metal laminates (Mg-FMLs) bonded with Mg-Zn-Al eutectic alloy solder based on carbon fiber woven/polymer (epoxy resin) prepregs (CFRP) and AZ31B alloy sheets were prepared by using ultrasonic vibration assisted hot pressing technology. Interlaminar performance of the hybrid composite laminates was measured using double cantilever beam (DCB) and three-point end notched flexure (3ENF) tests. The interface morphologies and tensile behavior of the Mg-FMLs were evaluated. Results show that metallurgically-bonded interfaces have been formed in the Mg alloy-based hybrid FMLs. The present Mg-FMLs bonded with Mg alloy solder exhibit higher interlaminar and tensile performance than traditional Mg-FMLs bonded with epoxy resin. The enhanced tensile properties of the present Mg-FMLs can be attributed to the synergistic effect from the Mg alloy sheet and CFRP layer because of high interlaminar properties. For the same reason, the tensile fracture of the novel Mg-FMLs exhibits matrix and CFRP dominated mixed-mode failure.

FE-DE coupling analysis of AZ31B sheet solid granule medium forming based on GTN model

In order to solve the problem of forming parts with complex shape and small local feature size, solid granules medium forming (SGMF) was adopted. A part of magnesium alloy AZ31B with double-cone shape was taken as an example to analyze the forming process. The parameters of Gurson–Tvergaard–Needleman (GTN) were identified by an inverse method, comparing the experimental results with the numerical results. Based on the GTN model, the coupled finite element and discrete element (FE-DE) method was applied to simulate the forming process of the double-cone part with SGMF technology, and the relevant forming experiments were carried out. The results show that the quality of the workpiece can be improved with different friction coefficient of different area of the part. The fracture behavior and final wall thickness distribution obtained by experiment consist with those by simulation. So, it demonstrates the applicability of the FE-DE method with GTN damage model in analyzing formability of magnesium alloy, and the FE-DE method could embody the medium discrete characteristics fully during SGMF technology.

Tribological analysis on magnesium alloy AZ31B with reinforced ZrSiO4 through Taguchi technique

Optimization of the wear characteristics of composites (AZ31B/ZrSiO4) prepared through stir casting process using Taguchi’s S/N analysis was examined. L9 OA has been chosen to perform dry sliding wear experiments using pin on the disk device. The foremost goal is to employ S/N ratio and analysis of variance to inspect the impact of sliding distance, applied load and mass fraction of incorporation particles on wear rate (WR). The microstructure exploration revealed that there is a ZrSiO4 particle which diminishes wear of the specimens. Wear tests were functioned on a pin on a disc machine according to ASTM G99 – 05 standard. Wear rate were calculated from the ANOVA study as strongly contributing parameters to interrupt the composite properties.

Investigation of material flow and thermomechanical behavior during friction stir welding of an AZ31B alloy for threaded and unthreaded pin geometries using computational solid mechanics simulation

In the friction stir welding process, the tool role in the material flow and its thermomechanical behavior is still not entirely understood. Several modeling approaches attempted to explain the material and tool relationship, but to this date, insufficient results were provided in this matter. Regarding this issue and the urgent need for trustful friction stir welding models, a computational solid mechanic's model capable of simulating material flow and defect formation is presented. This model uses an Arbitrary Lagrangian-Eulerian code comparing a threaded and unthread pin profile. The model was able to reproduce the tool's torque, temperatures, and material flow along the entire process, including the underreported downward flow effect promoted by threaded pin's. A point tracking analysis revealed that threads increase the material velocity and strain rate to almost 30% compared to unthreaded conditions, promoting a temperature increment during the process, which improved the material flow and avoided filling defects. The presented results showed the model's capability to reproduce the defects observed in real welded joints, material thermomechanical characteristics and high sensitivity to welding parameters and tool geometries. Nevertheless, the outcomes of this work contribute to essential guidelines for future friction stir welding modeling and development, tool design, and defect prediction.

Influence of laser shock peening on the surface energy and tribocorrosion properties of an AZ31B Mg alloy

The present study investigates the influence of laser shock peening (LSP) on surface energy (SE) of AZ31B Magnesium alloy and its resilience to corrosion and tribocorrosion. AZ31B alloy was treated at different laser intensities. The SE and its interfacial components of treated surfaces were analyzed. The SE was found to be least at low laser intensity LSP. Lower interfacial SE showed decreased wettability, providing enhanced tribocorrosion resistance with respect to untreated surface. However, higher laser intensities increased the surface roughening effect, causing an increase in the interfacial SE and wettability of the surfaces, decreasing the tribocorrosion resistance. The study finds LSP can enhance tribological properties and mitigate the effects of corrosion and tribocorrosion.

Electrodeposition of micro-nano hierarchically structured fluoridated hydroxyapatite coating on AZ31B alloy

ABSTRACT In this study, a novel micro-nano hierarchically structured fluoridated hydroxyapatite (FHAp) coating on AZ31B substrate was successfully synthesized via a simple one-step electrochemical deposition method. And the formulation of the electrodeposition solution is simple and environment-friendly without any harmful additives. The FHAp coating consists of a large amount of nanorods and some micro-structured spherical aggregates composed of nanorods. Electrochemical tests demonstrated that the FHAp coating exhibited higher anti-corrosion property and lower degradation rate than that of pure HAp coating. Moreover, the FHAp coating with micro-nano hierarchically structured surface displayed good cell biocompatibility. The addition of fluorine ion into HAp coating can further promote the cell adhesion and proliferation. This work provides a simple, environment-friendly, and efficient way to prepare FHAp coating on AZ31B alloy with improved corrosion resistance and biocompatibility.

Forming limits of magnesium alloy AZ31B sheet at elevated temperatures

Magnesium alloy sheets usually has to be processed by warm forming, and change of strain path and evolution of microstructure can significantly influence their warm formability. Forming limit test for an AZ31B alloy sheet under strain path changes was configured and implemented, and the effects of strain paths and microstructure evolution on the forming limit diagram are investigated. The sheet was pre-strained under in-plane uniaxial, plane strain and biaxial tension loading paths at 150 °C, 200 °C and 300 °C, followed by hemispherical punch stretching experiments at the three temperatures using specimens extracted from the pre-strained samples. A crystal plasticity model that incorporates dynamic recrystallization (DRX) and annealing recovery was combined with the Marciniak-Kuczyński (M-K) approach to calculate the FLDs. The evolution of dislocation density during annealing in the pre-strained FLD test at 200 °C was evaluated, through which the predictions of pre-strained FLDs were considerably improved. The present work provides experimental as well as crystal plasticity based methods for evaluating warm formability of magnesium alloys influenced by temperature, pre-straining, DRX and recovery.

Low cycle fatigue behavior of magnesium matrix nanocomposite at ambient and elevated temperatures

AZ31B alloy reinforced by 1.5 vol.% nano-sized Al2O3 particles has been subjected to fully-reversed strain-controlled uniaxial tension-compression cyclic loading at room temperature, 100 °C, and 200 °C. A combination of mechanical and magnetic stir casting methods followed by a hot-extrusion process was used to fabricate the composite material. Cyclic and fatigue behaviors of the composite were studied at the strain ranges of 0.8%–2.5%. The experimental results of the fatigue lives were used to assess and compare the life prediction capabilities of different existing strain-based and energy-based fatigue models. The results exhibited that the presence of the nano-sized reinforcing particles leads to a homogenously fine microstructure and slightly changes the texture of the composite extrusion, compared to the typical microstructure and texture of monolithic AZ31B extrusion. The cyclic behavior of the composite is altered from an asymmetric shape at room temperature to a symmetric one at 200 °C, resulting in reduction of mean stress. Unlike the room-temperature behavior, twinning and detwinning are not governing plastic deformation mechanisms at the elevated temperatures, especially at 200 °C. Cyclic softening occurs by increasing the temperature, in a manner similar to the monotonic tensile tests. Due to the strain-controlled loading and increasing the composite ductility at the elevated temperatures, the fatigue lives are comparable at the different temperatures. Finally, considering the results at all the temperatures, Jahed-Varvani (JV) as an energy-based model shows a more promising life prediction.

Corrosion and Biocompatibility Behavior of the Micro-Arc Oxidized AZ31B Alloy in Simulated Body Fluid

Corrosion and Biocompatibility Behavior of the Micro-Arc Oxidized AZ31B Alloy in Simulated Body Fluid

Energy Absorption at High Strain Rate of Magnesium Alloy AZ31B

Energy Absorption at High Strain Rate of Magnesium Alloy AZ31B

Mechanical and Tribological Behavior of Mg-Matrix Composites Manufactured by Stir Casting

In the recent decades, magnesium matrix composites present a plenty of applications in automotive, marine and aerospace industries. In this work, AZ31B is selected as Mg matrix material and hard Tungsten carbide (WC) particles as reinforcement material. Mg/WC composites are reinforced with different weight proportions (0, 5, 10 and 15% wt.) using stir casting method. The worn surface of manufactured Mg/WC composites and base Mg material were examined by scanning electron microscope (SEM). The wear test results denote that AZ31B/15% wt. WC composites have excellent tribological behaviour when compared to the base magnesium matrix AZ31B alloy. The yield tensile strength, flexural strength, ultimate tensile strength and micro-hardness of the manufactured composites are improved by increasing the WC content. Further, SEM analysis revealed the homogeneous distribution of WC particles throughout the Mg matrix.

Silicon oxide multilayer coatings doped with carbon nanotubes and graphene nanoplatelets for corrosion protection of AZ31B magnesium alloy

Magnesium (Mg) AZ31B alloy substrates were coated by the dip-coating method to obtain four different coating configurations. Three different sol-gels were synthesized to create different monolayer and multilayer coating configurations from two silicon alkoxides, tetraethyl orthosilicate (TEOS) and methyl-triethoxysilane (MTES). Two of these sol-gel solutions were doped with nanocharges. The final concentration of nanocharges in the coatings was 0.045 wt% and 0.046 wt% for multiwall carbon nanotubes (MWCNTs) and functionalized graphene nanoplatelets (COOH-GNPs), respectively. The anti-corrosion behaviour of these coatings was assessed by electrochemical and hydrogen evolution tests in 3.5 wt% NaCl solution. All of the coating configurations significantly improved the behaviour against corrosion compared with the bare substrate, especially the SG + SG/GNP (sol-gel + sol-gel doped with 0.046 wt% COOH-GNPs) multilayer coating system. The sol-gel synthesis combined with the dip-coating method was demonstrated to be an effective way to generate compact and homogeneous coatings for corrosion protection.

Effect of cyclic frequency on uniaxial ratcheting behavior of a textured AZ31B magnesium alloy under stress control

The ratcheting behavior of magnesium alloy AZ31B was investigated under controlled cyclic stress at frequencies of 0.5 Hz, 1.0 Hz and 2.0 Hz. The result showed that cyclic loading accelerates strain accumulation as compared with static creep at room temperature, and the effect of cyclic frequency on strain rate dεr/dt, represented by strain in a unit time, is of multiplicity due to the diversification of deformation mechanisms. However, strain rate dεr/dN, represented by strain in one cycle, decreases evidently with increasing frequency at steady strain accumulative stage. High frequency promotes twinning-detwinning, and is favorable for prolonging the fatigue life in terms of cyclic number to failure. The fatigue life increases linearly with decrease of plastic strain energy density under all frequency conditions. This leads to conclude that frequency affects the fatigue life via changing plastic strain energy stored in the deformed microstructure.

Characterization of indigenously coated biodegradable magnesium alloy primed through novel additive manufacturing assisted investment casting

The present study explored the potential of a novel additive manufacturing (AM) assisted investment casting (IC) process for developing indigenously hydroxyapatite (HA)/titanium dioxide (TiO2) coated magnesium AZ31B alloy for biomedical applications. The as-produced HA and HA/TiO2 indigenous coatings exhibited higher biomechanical properties (hardness and adhesion strength) as compared to un-coated samples. Further, the in-vitro corrosion and cell-culture test highlighted that the obtained coatings improved the corrosion resistance, reduced the degradation rate, and enhanced the bioactivity of AZ31B alloy. The results of the present study strongly advocated that the adopted methodology can be used for potential orthopaedic applications.

A method for the simultaneous identification of anisotropic yield and hardening constitutive parameters for sheet metal forming

Sheet metal forming processes and their simulations often require knowledge of both anisotropic yield and hardening constitutive parameters. The identification of these properties, however, involves a large number of homogeneous tests as well as various expensive testing machines. In this paper, a novel method is proposed to enable a simultaneous identification of the multiple anisotropic yield and hardening constitutive parameters from a single test and using the simplest uniaxial testing machine, which significantly simplifies the conventional complex constitutive identification procedures. In particular, the test configuration is elaborately designed to exhibit both heterogeneous stress states and insignificant buckling under compressive loadings based on the plate buckling theory. The virtual fields method is adopted as the inverse problem solution for the selected anisotropic yield and hardening laws, namely, Hill1948 and the nonlinear kinematic hardening models. The proposed identification scheme is first validated through the simulated full-field strain and load data of the designed bridge-like test configuration. Its identification sensitivity is analyzed with respect to the influences of measurement noise, type and combination of virtual fields. The results show that using the designed test configuration it is possible to identify all the target anisotropic parameters from a single test despite a noticeable level of error. This however can be markedly improved by combining the two tests performed in the rolling and transverse directions, and with the multiple virtual fields constraints, from which accurate and robust identification results are obtained for the selected models. The validity of this method is then illustrated experimentally with the application on the wrought magnesium alloy AZ31B sheet specimens. Finally, potential improvements and applications of this method are suggested.

Laser patterned hydroxyapatite surfaces on AZ31B magnesium alloy for consumable implant applications

Currently, materials employed for use as consumable prosthetic devices possess uncontrolled degradation via corrosive action and inferior bio-integration characteristics. A material that is biocompatible and mechanically rigid is necessary for osseointegration. In an attempt to address these issues, a novel laser surface engineering approach was used to produce physically patterned hydroxyapatite coatings on the magnesium AZ31B alloy. Variations of two different laser processing parameters, namely laser power (800–1200 W) and laser track separation (0.15–0.9 mm), were explored in conjunction to determine the optimal processing combination. Biocompatibility was subsequently examined via contact angle measurements and performing in-vitro immersions in simulated body fluid. The surface characteristics, microstructure, and phase evolution of post-processed and post-immersed samples were examined using optical profilometry and scanning electron microscopy. It was confirmed that samples with hydrophilic contact angles correlated to higher degrees of biomineralization and minimal corrosion. These hydrophilic contact angles were realized in samples processed either with low laser power and a higher degree of track overlap or with high laser power and no laser track overlap.