Alloy AZ31B Research Articles

In vitro biocompatibility and degradation assessment of tantalum oxide coated Mg alloy as biodegradable implants

In the present study, the sputtering process deposited tantalum oxide thin film onto AZ31B alloy, and the biocompatibility and degradation resistance were evaluated. The phase analysis by X-ray diffraction (XRD) and transmission electron microscopy (TEM) was carried out to understand the Ta-based thin films’ crystalline and amorphous nature thin film. The thin film surface chemical composition was investigated by X-ray Photoelectron Spectroscopy (XPS) which showed the elemental signals of O, Ta without any other impurities. Contact angle measurements verified the hydrophobic nature of the coated specimens. The corrosion studies revealed that corrosion resistance was significantly enhanced for the Ta-based thin-film coated Mg alloys than the uncoated bare counterpart by reducing corrosion current density from 2.886 × 10−4 to 1.20 × 10−5 A/cm2. Bioactivity of the coated specimens in SBF immersion showed apatite formation in 5 days. The hemocompatibility studies of the coatings showed the echinocytes morphology of the RBCs. In vitro, MTT assay exhibited more significant cell proliferation and cell viability of 100% at 7 days of incubation. The cell morphology studies showed improved cell attachment and cell growth by controlling magnesium ions' release into the cell culture media.

Experimental investigation on magnesium AZ31B alloy during ultrasonic vibration assisted turning process

ABSTRACT Magnesium alloys generate harmful emissions while using coolants during the machining process and it affects both the operator and the environment. Ultrasonic vibration assisted turning (UVAT) is an eco-friendly and advanced machining process to machine various materials than conventional turning (CT). In this study, experimental analysis is carried out to investigate the machinability of the magnesium AZ31B alloy during CT and UVAT processes. The effect of cutting speed during the processing of magnesium AZ31B alloy is analyzed and compared with CT in terms of machining forces, machining temperature, tool wear, chip morphology, surface roughness, microstructure, and microhardness. Results showed that compared with CT, machining forces and surface roughness is reduced significantly in UVAT. However, higher machining temperature is obtained during UVAT than CT. Flank wear is observed during CT although negligible tool wear is observed for UVAT. Chip segmentation is obtained for both CT and UVAT whereas higher chip thickness is observed for UVAT than CT process. Finer grains and higher microhardness are obtained in UVAT than the coarse grains and lower microhardness in CT. The results showed that the processing of magnesium AZ31B alloy during the UVAT process leads to enhanced machining performance compared to the CT process.

Research on the Composite Performance of Aluminum Alloy Plate and Concrete-Based Material

The effects of 1061, 6061, and AZ31B alloy plates on the apparent properties of sleeve grouting material, the corrosion of concrete on fluorocarbon aluminum alloy plates, and the influence of fluorocarbon aluminum alloy plates on concrete’s strength and carbonization properties were studied. The deformation between the fluorocarbon aluminum alloy plate and the concrete was theoretically analyzed. The results show that there is no obvious corrosion of concrete with the aluminum alloy plate coated with fluorocarbon paint within a certain period of time. After the concrete is covered with the fluorocarbon aluminum alloy plate, there is a hydration space that is not affected by the outside world, and its compressive strength and anti-carbonization performance are further improved. When aluminum alloy plates are used for composite concrete in areas with higher temperatures, anchoring measures should be used to disperse the temperature expansion stress between the aluminum alloy plates and the hardened concrete.

Biocompatibility and corrosion evaluation of niobium oxide coated AZ31B alloy for biodegradable implants

Biodegradable magnesium (Mg) based implants have considerable interest in the biomedical field as their use nullifies the necessity for implant removal surgery and avoids the long-standing adverse reaction of permanent bioimplants. The degradation resistance and biocompatibility of the Mg alloys can be improved by coating them with a suitable thin film. Here, thin films of niobium and niobium oxide were developed on the AZ31B Mg alloy by sputtering technique and their biocompatibility and corrosion resistance was examined. X-ray diffraction (XRD) and Transmission electron microscope (TEM) techniques confirmed the crystallinity of the thin films. Subsequently, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques were employed to evaluate the morphology and chemical composition of the thin film surfaces, respectively. Thin-film coated Mg alloys revealed good corrosion resistance compared to their uncoated bare counterparts in simulated body fluid (SBF). The contact angle study was performed on the coated specimens to investigate their wettability which revealed their hydrophobic character. The cell viability studies on thin-film coated specimens exhibited significant cell proliferation, and cell morphological studies showed good cell attachment and growth. The in vitro MTT assay on mouse osteoblast precursor cells (MC3T3-E1) indicated that the Nb-based coatings are cytocompatible and promote cell proliferation.

Microstructure, mechanical and corrosion behaviour of friction stir welding of AA6061 Al alloy and AZ31B Mg alloy

The present investigation emphasizes studying the impact of the rotational tool speed and traverse speed on microstructure, mechanical properties, and corrosion behaviour of Al alloy AA6061 to Mg alloy AZ31B friction-stir welds. Results indicated that the use of the 1000 rpm rotation speed of the tool and 40 mm/min traverse speed led to increased weld strength and corrosion resistance. Owing to more heat generation, the surface of every friction stirs welded joint became rougher, and a keyhole can be observed. A maximum temperature of 311°C was observed for 1000 rpm of rotation speed and 40 mm/min of traverse speed, and a minimum temperature of 191°C was observed for 600 rpm of rotation speed and 80 mm/min of traverse speed. A minor tunnel defect can be partially observed at traverse speeds of 60 mm/min; the size of the tunnel defect becomes more prominent as the traverse speed rises to 80 mm/min. The joint with little or no defects was extracted at any rotational tool speed and a low traverse speed of 40 mm/min. The maximum value of UTS of 121 MPa was observed due to the better mechanical interlocking phenomena. It is approximately 41% of UTS of Al alloy AA6061 and 50% of UTS of Mg alloy AZ31B. Frictional heat, heavy plastic distortion, and grain refinement in the nugget zone are the reasons for the higher hardness value found mostly in weld nuggets. The FSW specimens indicate a primarily brittle type of failure, and a fracture of the cleavage type was seen with an excessive volume of intermetallic layer. Compared to both alloy side weld regions, the Mg alloy area weld zone was more corroded and had more cracks and gaps than the Al alloy side.

Influence of cutting parameters on end milling of magnesium alloy AZ31B

Magnesium alloys are having the characteristics like light weight, wear, and corrosion resistance. Mg alloys find usage in a wide range of applications such as engine block of automobile parts, laptop cases, aircraft fuselages and mobile outer cases. However, in dry machining, many challenges restrict its development during fitment. In this research work, conventional vertical milling machine was used to conduct end milling operation on Mg AZ31B alloy with coated carbide insert. End milling operations were performed by varying spindle speed, feed per tooth, and constant cutting depth. The chip morphology and tool chip interface temperature were investigated for various cutting conditions. Also, feed force (Fx), thrust force (Fy) and cutting force (Fz) was analyzed to understand the proper material deformation characteristics.

Temperature and Strain Rate Dependent Anisotropic Plastic Deformation Behavior of AZ31B Mg Alloy

In the present study, the plastic deformation of commercially available AZ31B alloy at different temperatures (300K-473K) and strain rates (0.1s-1-0.01s-1-0.001s-1) under uniaxial tensile test has been carried out. Three different sheet orientations, viz., rolling direction (RD), transverse direction (TD), and 45° to rolling direction have been used. The outcomes of the experiments have demonstrated a temperature-dependent relationship between mechanical properties such as yield strength, ultimate tensile strength, and percentage elongation. The yield strength and ultimate tensile strength has decreased by 28.58% and 31.03% respectively as temperature increased from 300 K to 473 K. At elevated temperature (473 K) the material has exhibited highest ductility (64.88%) as compare to 300 K. The hardening exponent has been found to decrease with increasing temperature. The flow stress behaviour has been predicted using work hardening models such as the Hollomon and Ludwik. Two-stage work hardening behavior has been observed at all the temperatures. According to statistical parameter comparison, Ludwik equation prediction capability of correlation coefficient (0.9959) has been found to be best in agreement with the experimental results.

Welding studies on dissimilar magnesium alloys for improving corrosion behaviour

Dissimilar friction stir and tungsten inert gas between Magnesium alloys AZ31B and ZM21 plates with a thickness of 5 mm was performed. The friction stir welding tool is rotated at 2100 rpm under a constant transverse speed of 140 mm/min. A salt fog corrosion test is used to determine weldments' material losses and corrosion behavior in various zones using different welding processes for magnesium alloys like AZ31B and ZM21, which use friction stir welding (FSW) tungsten inert gas (TIG) welding. AZ31B weldment area is more susceptible to corrosion than ZM21. Both welds' macro and microstructures are analyzed to understand the metallurgical characteristics of the two different welds. Taguchi L9 orthogonal design improves process parameters for both the FSW and TIG welding processes. The rotating speed, tool shape, and axial load are the input process parameters for FSW, while the welding speed is kept constant. By single goal optimization, the maximum tensile strength of the dissimilar joints is 208 MPa. FSW welds of Dissimilar Magnesium alloys AZ31B and ZM21 were successfully manufactured with no defects.

Influence of Microstructure and Texture on Mechanical and Corrosion Properties in SSFSWed Joints of Thick-Plate AZ31B Alloy

Influence of Microstructure and Texture on Mechanical and Corrosion Properties in SSFSWed Joints of Thick-Plate AZ31B Alloy

FE analysis of Ultrasonic vibration assisted turning of magnesium AZ31B alloy

Ultrasonic vibration assisted turning (UVAT) is advanced machining process where vibrational assistance of high frequency and low amplitude is provided to tool. In the present study, a two dimensional (2D) numerical simulation is carried out in ABAQUS/Explicit to compare the machinability of AZ31B magnesium alloy with tungsten carbide as a cutting tool during the conventional turning (CT) and UVAT processes. The objective of this study is to compare the effective stress distribution, cutting and thrust forces, and machining temperature during the CT and UVAT processes. The simulation results showed that the average stress distribution during UVAT is reduced to about 40% compared with CT. However, the average stress distribution is comparable during CT and the penetration stage of the UVAT process. Furthermore, the average cutting and thrust forces were reduced by 69% and 65% respectively in UVAT than CT. Although, the machining temperature in UVAT is found to be around 37% higher than that in CT. The results revealed that the UVAT has many advantages over CT and the machinability can be improved significantly by incorporating vibrations to the conventional turning process.

Effect of Tool Pin Geometry and Process Parameters During FSW of Dissimilar Alloys of Mg

Effect of two distinctive tool designs along with other tool related parameters including speed of traverse of tool and offset distance of tool pin during friction stir welding of dissimilar AZ91C and AZ31B alloys of Mg were investigated. Experimental recordings revealed that all the joints fabricated during 1st set of investigations employing cylindrically tapered pin geometry and their offset distances being 0.5 mm or 1mm towards any one of the parent metals possessed flaws. Joint No: II-3 fabricated in 2nd set of investigations by employing 15mm diameter inner shoulder tool with threaded cylindrical tapered pin geometry at a tool offset distance of 0 mm was found be free from flaws. This joint exhibited a tensile strength of 186 MPa which was 78.81% of AZ91C and 70.72% of another parent metal AZ31B. Existence of intermetallic phased constituents, namely, Mg17Al12 in several regions of fractured surfaces have contributed to the supplementary brittleness in the zone of nugget, and have reduced the tensile strength of the joint.

Recrystallization Behavior and Mechanical Properties of Az31b Alloy During the Hot-Rolling Process

Recrystallization Behavior and Mechanical Properties of Az31b Alloy During the Hot-Rolling Process

Dual Frequency Domain Characteristics of Ratcheting Behavior of Az31b Alloy Under Asymmetrically Stress-Controlled Loading Mode

Dual Frequency Domain Characteristics of Ratcheting Behavior of Az31b Alloy Under Asymmetrically Stress-Controlled Loading Mode

Effect of friction stir processing on the high cycle fatigue behavior of AZ31B alloy

The low-weight metal magnesium alloy finds extensive use in aircraft vehicles, defense vehicles, biomedical, and sporting equipment industries. The friction stir process (FSP), as plastic deformation, has a wide range of influence on mechanical systems and microstructure properties of the material. One of the most essential properties for analysing the failure behaviour of FSP-ed structures is the fatigue life of FSP. The rolling shoulder profile design of the stirring tool with three different cooling mediums was used. This work aims to study the effect of FSP on the fatigue properties of AZ31B alloy under different mediums. Finally, fractographic analysis was performed on different cooling medium samples. The fatigue results show that the SFSP-ed sample has a longer fatigue life compared with the CFSP-ed sample.

Experimental investigations of WEDM process parameters for magnesium alloy AZ31B biomedical material

Wire Electrode Discharge Machining (WEDM) is a modernized conventional machining process having the capability to machine complex profiles on conductive material in an accurate and precise way, which is hard to achieve on the conventional type of machining process. The process takes place by cutting through the wire which acts as an electrode. Further process analyses are being done to find the control factors for magnesium alloy AZ31 by using a one-factor approach at a time (OFAT). In the current study, the effect of various parameters like wire feed (WF), wire tension (WT), peak current (IP), servo voltage (SV), pulse off-time (Toff), and pulse on-time (Ton) on cutting rate has been studied by using OFAT on magnesium alloy AZ31B. The experiments show that the Ton, Toff, SV, and SF plays a significant role in the evaluation of cutting rate, while other parameters viz.: IP, WT, and WF are observed to be insignificant during the investigation of CR. The CR found to be increased from 9.93 mm/min to 10 mm/min with the increase in Ton from 102 µs to 110 µs.

Deposition temperature effect on sputtered hydroxyapatite coatings prepared on AZ31B alloy substrate

The corrosion of Mg alloys is a provocative topic and it is still a challenge to find a solution for the improvement of their degradation rate into solution found in human body (Simulated Body Fluid, SBF). The aim of the present paper is to coat AZ31B alloy by hydroxyapatite (HAp) as a possible solution in order to change its degradation behaviour for medical implants. Since the Mg alloy is sensible to temperature while the HAp properties depend on the deposition temperature, in this study, the effect of deposition temperature on the properties of the AZ31Balloy was evaluated. The HAp coatings were prepared using the RF magnetron sputtering technique, ranging the temperature from the room one to 400 °C. It was found that the grain size of the investigated Mg alloy increased more than 100% when the deposition temperature was increased. By increasing the temperature, the hardness level was reduced of about 15%. All HAp coatings revealed corrosion behaviour much better than the uncoated AZ31B alloy; in particular, the coating deposited at 200 °C exhibited the best corrosion behavior. Moreover, the best protection to the corrosive attack of SBF was found for the HAp coating deposited at 200 °C (97.3%), which was also characterized by the lowest porosity. To conclude, HAp coatings can be used to improve the properties of AZ31B alloys, but just up to 200 °C; beyond this temperature, the mechanical and the anticorrosion properties are lost.

Effect of Rolling Orientation on the Microstructure and Mechanical Properties of AZ31B Mg Alloy

The magnesium AZ31B alloy has been utilized in a variety of applications within the automotive and aviation industries due to its high specific strength, low-cost processing, and low density. However, the AZ31B alloy generally has poor ductility and limited workability at room temperature. The objective of this study was to develop a manufacturing processing technique to increase the potential uses of this alloy. The methodology includes cold rolling and annealing using small pass reductions until the samples reached a final thickness of 1.78 mm (0.07 in). The samples were cut into 10.16 mm (0.4 in), 7.62 mm (0.3 in), and 5.08 mm (0.2 in) thicknesses prior to cold rolling and were rolled in 0-, 45-, and 90-degree rolling directions. The grain shapes and sizes were examined via optical microscopy. Tensile testing was conducted to determine the strength and ductility. Scanning electron microscopy (SEM) images were taken to evaluate fractured surfaces. All processes including rolling direction and furnace cooling or air cooling after annealing produced similar results of medium strength (245-250 MPa in ultimate strength, 122-127 MPa in yield) and greater than 22.5% elongations in very thin sheets. Samples rolled along the 45-degree direction produced the highest percent reduction in thickness.

Microstructural and Mechanical Properties of a Solid-State Additive Manufactured Magnesium Alloy

Abstract In recent years, additive manufacturing (AM) has gained prominence in rapid prototyping and production of structural components with complex geometries. Magnesium alloys, which have a strength-to-weight ratio that is superior compared with steel and aluminum alloys, have shown potential in lightweighting applications. However, commercial beam-based AM technologies have limited success with magnesium alloys due to vaporization and hot cracking. Therefore, as an alternative approach, we propose the use of a near net-shape solid-state additive manufacturing process, additive friction stir deposition (AFSD), to fabricate magnesium alloys in bulk. In this study, a parametric investigation was performed to quantify the effect of process parameters on AFSD build quality including volumetric defects and surface quality in magnesium alloy AZ31B. In order to understand the effect of the AFSD process on structural integrity in the magnesium alloy AZ31B, in-depth microstructure and mechanical property characterization was conducted on a bulk AFSD build fabricated with a set of acceptable process parameters. Results of the microstructure analysis of the as-deposited AFSD build revealed bulk microstructure similar to wrought magnesium alloy AZ31 plate. Additionally, similar hardness measurements were found in AFSD build compared with control wrought specimens. While tensile test results of the as-deposited AFSD build exhibited a 20% drop in yield strength (YS), nearly identical ultimate strength was observed compared with the wrought control. The experimental results of this study illustrate the potential of using the AFSD process to additively manufacture Mg alloys for load bearing structural components with achieving wrought-like microstructure and mechanical properties.

Impact of asymmetry deformation on microstructure and mechanical properties of AZ31B alloy sheets deformed by on-line heating rolling

The effect of asymmetry deformation on microstructure and mechanical properties of AZ31 sheet was investigated in the present paper. Two AZ31 sheets were rolled together with an on-line heating rolling mill and separated from each other afterwards. For each sheet, the strain on both surface during rolling was asymmetry and this rolling method is called asymmetry rolling (AR) in present work. For comparison, symmetry rolling (SR) was also carried out on the same rolling mill that only one sheet was rolled in one pass. The sheets deformed by AR showed more homogeneous microstructure with higher recrystallization level and symmetry distributional basal texture. Moreover, SR sheets showed many narrow shear bands which distributed as “V” shape along rolling direction, while less shear bands with wider size are observed in AR sheet. The shear bands in AR sheet distributed as a line and across the entire thickness of the sheet, resulting in layered bimodal structure. Based on the unique microstructure and texture characteristics, AR sheet has lowest mechanical property anisotropy and a good balance of strength and elongation.

Anomalous effect of grain size on the room-temperature bendability of Mg–Gd alloy sheet

In this work, grain size impacted on the bendability of the Mg-2Gd (wt. %) alloy sheets was investigated. The microstructures and textures evolution during the bending test were analyzed by the electron back-scattered diffraction (EBSD) and the scanning electron microscopy (SEM) technique. The results showed an anomalous grain size-dependent bendability in this alloy. The coarser grain size sample corresponded to a poorer bendability in the Mg–Gd alloys, which was dramatically different from the traditional Mg alloys (such as AZ31B alloys). This opposite mode between the Mg–Gd and traditional rare earth (RE) free Mg alloys was mainly attributed to the difference of microcracks nucleation mechanism during the bending test. The nucleation sites of microcracks were almost in the grain boundaries for the Mg–Gd alloys, while in the intragranular for the traditional Mg alloys. Furthermore, the larger size of initial microcracks and the more heterogeneous strain distributions in the coarser grain Mg–Gd samples led to a premature failure in the bending process and gave rise to this anomalous grain size-dependent bendability.