Properties Of AZ31B Magnesium Alloy Research Articles

Microstructure and Mechanical Properties of AZ31B Magnesium Alloy by Friction Stir Welding

Friction stir welded Mg AZ31B alloy have been investigated. Friction stir welding (FSW) is carried out at different rotational speeds of 900rpm, 1120rpm, 1400rpm and 1800rpm and with change of tool materials such as High speed steel (HSS) and Stainless steel (SS) at a constant welding speed of 40mm/min, tilt angle of 2.50 and axial force of 5 KN. It is observed In this study, the effect of tool material and rotational speed on microstructure and mechanical properties of that the joint fabricated using SS tool material at a rotational speed of 1120rpm obtained higher mechanical properties as compared to those of 900rpm, 1400rpm and 1800rpm and also to those of HSS material.

Characterization of Mechanical Properties and Microstructural Analysis of Friction Stir Welded AZ31B Mg Alloy Thorough Optimized Process Parameters

In this paper, a detailed investigation has been carried out to find out the impact of the process parameters including Tool rotational speed, welding direction at constant axial force and with a taper cylindrical pin profiled HSS tool during the Friction stir welding (FSW) of AZ31B magnesium alloy lap joints. This paper evaluates & examines in an elaborate manner, the influence of these FSW parameters in the microstructure & mechanical properties of AZ31B magnesium alloy. In short, AZ31B Mg alloys were friction stir welded by varying several different process parameters and the effects of these parameters on the joint quality, microstructure & mechanical properties were discussed comprehensively. This paper also experimentally proves & suggests the optimized process parameter values to be adopted for effective lap joining of AZ31B Magnesium alloys using FSW technique.

Mechanical Properties and Microstructure of AZ31B Magnesium Alloy Processed by I-ECAP

Abstract Incremental equal channel angular pressing (I-ECAP) is a severe plastic deformation process used to refine grain size of metals, which allows processing very long billets. As described in the current article, an AZ31B magnesium alloy was processed for the first time by three different routes of I-ECAP, namely, A, BC, and C, at 523 K (250 °C). The structure of the material was homogenized and refined to ~5 microns of the average grain size, irrespective of the route used. Mechanical properties of the I-ECAPed samples in tension and compression were investigated. Strong influence of the processing route on yield and fracture behavior of the material was established. It was found that texture controls the mechanical properties of AZ31B magnesium alloy subjected to I-ECAP. SEM and OM techniques were used to obtain microstructural images of the I-ECAPed samples subjected to tension and compression. Increased ductility after I-ECAP was attributed to twinning suppression and facilitation of slip on basal plane. Shear bands were revealed in the samples processed by I-ECAP and subjected to tension. Tension–compression yield stress asymmetry in the samples tested along extrusion direction was suppressed in the material processed by routes BC and C. This effect was attributed to textural development and microstructural homogenization. Twinning activities in fine- and coarse-grained samples have also been studied.

Effects of melt temperature on as-cast structure and mechanical properties of AZ31B magnesium alloy

The effects of melt temperature on the as-cast structure and mechanical properties of AZ31B magnesium alloy were studied through a home-made electrical resistance furnace. The results show that the equiaxed dendrite size of AZ31B magnesium alloy under water-cooled metal cooling is linearly decreased with increasing the melt temperature below 850 °C, whereas the size changes little over 850 °C. The second phases in the microstructure are firstly refined; however, they are coarsened when the melt temperature exceeds 850 °C. With the increase of melt temperature, the tensile strength, yield strength and elongation of AZ31B magnesium alloy samples are rapidly enhanced first, then are slightly declined. When the melt temperature is increased to 850 °C, the tensile strength, yield strength and elongation reach 260 MPa, 75.4 MPa and 27.57%, respectively. The tensile strength, yield strength and elongation are increased by 15%, 13% and 61%, respectively compared with 750 °C. DSC analysis shows that the nucleation temperature is decreased, the critical nucleus radius is lessened with the increase of melt temperature, which increase the degree of supercooling and heterogeneity nucleation rate in melt, and the growth rate becomes larger with the increase of the degree of supercooling. That is the reason why the grain size is first rapidly decreased, and then is little increased.

Influence of Heat Treatment on Microstrudture and Mechanical Properties of AZ31B Magnesium Alloy Prepared by Solid-State Recycling

This work is to study the influence of heat treatment on microstrudture and mechanical properties of AZ31B magnesium alloy prepared by solid -state recycling. AZ31B magnesium alloy chips were recycled by hot extruding. Three different heat treatments were conducted for recycled alloy. Mechanical properties and microstructure of the recycled specimen and heat treated specimen were investigated. 300°C×2h annealing specimen exhibits finer grain due to static recrystallization, and microstructure of 400°C×2h annealing specimen becomes more coarse. 300°C×2h annealing treatment improves obviously strength and ductility of recycled alloy. Ultimate tensile strength of alloy decreases and elongation to failure increases after 400°C×2h annealing. Grain size, dislocation density and bonding of chips have an effect on the elongation of recycled materials. 190°C×8h ageing has no influence on microstructure and mechanical properties of recycled alloy.

Effects of Melt Superheating Holding Time on Solidification Structure and Mechanical Property of AZ31B Magnesium Alloy

Effects of melt superheating holding time on microstructure and mechanical properties of AZ31B magnesium alloy were studied. The results show that the grain size of AZ31B magnesium alloy is gradually increased with the elongation of holding time. The grain is the finest without insulation work, and the increase amplitude of grain size is the most when holding for 20 minutes in this experiment. The higher is the melt superheating temperature, the larger the increase amplitude of grain size when holding for 20 minutes is. The tensile strength, yield strength and elongation percentage of AZ31B magnesium alloy specimens are small declined with the elongation of holding time under lower melt temperature. At 850°C or 900°C, the mechanical properties are rapidly declined with the elongation of holding time when holding time is less than 20 minutes, whereas the mechanical properties are slight increased when holding time is more than 20 minutes. DSC analysis shows that the elongation of holding time causes the increase of solidification onset temperature and the augment of solidification range, so the undercooling degree and nucleation rate are decreased in the melt, which result in the grain coarsening and the mechanical properties decrease.

Effect of Electron Beam Treatment on the Surface Properties of AZ31B Magnesium Alloy

AZ31B magnesium alloy were irradiated by a high current pulsed electron beam (HCPEB) device with pulse times 10, 15 and 20 respectively. The morphology of the surface and cross-section of modified layer were investigated by optical microscope. The corrosion resistance of modified layer were tested by EG&G M273 potentiostat in 5% NaCl solution. Wear resistance were tested by HRS-2 high speed reciprocation frictional testing machines. The results indicated that magnesium alloy surface hardness obviously enhances, the wear volume reduces 7%, the corrosion resistance also improves obviously after electron beam processing.

Evolution of microstructures and mechanical properties of AZ31B magnesium alloy weldment with active oxide fluxes and GTAW process

In this study, the effect of active oxide fluxes with gas tungsten arc welding on the microstructure and mechanical properties of AZ31B magnesium alloy weldment was investigated. The gas tungsten arc welding process through a flux spray layer was applied to an AZ31B magnesium alloy sheet to produce a bead-on-plate specimen. Oxide (TiO2, SiO2, Fe2O3, Al2O3, and ZrO2) powders were used as the activating fluxes. The macrographs and micrographs of the weld beads were examined using an optical microscope and a scanning electron microscope. The specimens with SiO2 and Fe2O3 fluxes had high depth-to-width ratio welds, followed by those with TiO2 and ZrO2 fluxes and while that with Al2O3 flux had the low ratio weld. The use of 70 A welding current for the specimens with different fluxes produced complete penetration, whereas the specimen without any flux required a 90 A welding current to produce complete penetration. The weld bead microstructure was affected by the activating fluxes, which created different thermal effects that changed the convection direction and promoted the formation of various precipitates in the fusion zone during solidification. Three types of precipitates were found in the fusion zones, that is, a long layer-shaped TiAlMg precipitate with TiO2 flux, a spherical AlMgZn precipitate with Al2O3 flux, and an oval-shaped MgAlMn precipitate with all types of fluxes. The mechanical properties of AZ31B magnesium alloy were measured by tensile testing in the rolling direction. Fractures occurred in the fusion zone near the heat-affected zone interface of specimens welded with TiO2 flux, revealing a brittle fracture with trans-granular cleavage facets and a large number of small, bright dimples at the center. Such brittle fractures also occurred in the fusion zone of specimens welded with Al2O3, ZrO2, SiO2, and Fe2O3 fluxes. Similarly, the specimens welded with Al2O3 exhibited a brittle fracture with trans-granular facets, whereas the other specimens revealed a brittle fracture with inter-granular cleavage facets.

Effect of Differential Speed Rolling on Microstructure and Mechanical Properties of AZ31B Magnesium Alloy Sheets

The grain size and the distribution of crystal orientation have an important effect on the mechanical properties of wrought AZ31B magnesium alloy sheets. Because the AZ31B magnesium alloy sheets rolled by conventional rolling have a poor formability at room temperature, a new rolling technology of differential speed rolling is used to improve the mechanical properties of AZ31B magnesium alloy. The research shows that the number of twinning crystal decreases, the number of the core of dynamically recrystallized grain increases, and the grain size become fine and isotropy by differential speed rolling with the increase of the reduction and the improving of the rolling temperature to some extent. The differential speed rolling not only improves the isotropy of the basal texture and also improves the microstructure and mechanical properties.

Effect of Extrusion Time on Microstructure and Mechanical Properties of AZ31B Magnesium Alloy Prepared by Solid-State Recycling

AZ31B magnesium alloys recycled by solid-state process from oxidized chip were extruded repeately. Microstructures and mechanical properties of recycled alloys for different extrusion times were studied. With the increasing extrusion times, the breaking degree and homogeneity of oxide increase and stream line feature of oxide become less obvious. Second extrusion make dynamic recrystallization microstructure of recycled alloy become more homogeneous and fine, but the microstructure is not refined furtherly after 3 and 4 times extrusion. The ultimate tensile strength increases with the increasing extrusion time, which resulting from the microstructure evolution during repeating extrusion and the enhanced bonding between oxide and magnesium alloy matrix. The elongation to failure of recycled alloy increases after second extrusion and continuously decreases after 3 and 4 time extrusion. This is determined not only by the variation of dynamic recrystallization microstructure and bonding strength between chips but also by the distribution status of oxide.

Metallurgical characterization of pulsed current gas tungsten arc, friction stir and laser beam welded AZ31B magnesium alloy joints

This paper reports the influences of welding processes such as friction stir welding (FSW), laser beam welding (LBW) and pulsed current gas tungsten arc welding (PCGTAW) on mechanical and metallurgical properties of AZ31B magnesium alloy. Optical microscopy, scanning electron microscopy, transmission electron microscopy and X-Ray diffraction technique were used to evaluate the metallurgical characteristics of welded joints. LBW joints exhibited superior tensile properties compared to FSW and PCGTAW joints due to the formation of finer grains in weld region, higher fusion zone hardness, the absence of heat affected zone, presence of uniformly distributed finer precipitates in weld region.

Microstructure and mechanical properties of AZ31B magnesium alloy prepared by solid-state recycling process from chips

AZ31B magnesium alloy chips were recycled by three solid-state recycling processes including cold-pressing, hot-pressing followed by hot extrusion and double extrusion. Microstructure and mechanical properties of the recycled specimens and reference specimens were compared. For the recycled specimen by cold-pressing, the grains are refined to a large extent during hot extrusion due to the presence of twins and high density dislocation. The recycled specimens by hot-pressing and double extrusion do not exhibit finer grain than that the recycled specimen by cold-pressing. Consequently, higher ultimate tensile strength of the recycled specimen by hot-pressing and double extrusion is not achieved. For hot pressing process, more compact billet lowers the porosity in recycled material, so elongation to failure of the recycled specimen increases. The recycled specimen fabricated by double extrusion process shows slightly higher elongation than the reference specimen. The second extrusion makes the oxides further crush and distribute more dispersedly, and minimizes porosity, which is responsible for the improved ductility.

Fatigue performance of pulsed current gas tungsten arc, friction stir and laser beam welded AZ31B magnesium alloy joints

This paper reports the influence of welding processes such as friction stir welding (FSW), laser beam welding (LBW) and pulsed current gas tungsten arc welding (PCGTAW) on fatigue properties of AZ31B magnesium alloy. Fatigue experiment was conducted using servo hydraulic controlled fatigue testing machine. Fatigue strength, fatigue notch factor and notch sensitivity factor were evaluated. The LBW joints showed higher fatigue strength compared to FSW and PCGTAW joints. The formation of very fine grains in weld region, higher fusion zone hardness, uniformly distributed finer precipitates are the main reasons for superior fatigue performance of LBW joints compared to PCGTAW and FSW joints.

An experimental investigation on friction stir welding of AZ31B magnesium alloy

The conventional fusion welding of magnesium alloys often produces porosity in the weld joint, which deteriorates its mechanical properties. To solve this problem, friction stir welding (FSW), a solid-state welding technique, can be applied for joining of magnesium alloys. In this investigation, an attempt was made to understand the effect of FSW process parameters such as tool rotational speed, welding speed, and axial force on tensile properties of AZ31B magnesium alloy. Fourteen joints were fabricated using different levels of tool rotational speed, welding speed, and axial force. Tensile properties of the welded joints were evaluated and correlated with the weld zone microstructure and hardness. From this investigation, it is found that the joints fabricated using a tool rotational speed of 1,600 rpm, a welding speed of 0.67 mm/s, and an axial force of 3 kN yielded superior tensile properties compared to other joints. Optimum level of heat generation, formation of finer grains, and higher hardness are the main reasons for the superior tensile properties of these joints. Fatigue properties of FSW joints were evaluated, and it was found that fatigue properties of FSW joints were slightly lower than the base metal.

Microstructure and mechanical properties of AZ31B magnesium alloy recycled by solid-state process from different size chips

AZ31B magnesium alloy chips of different size were recycled by hot extruding. Mechanical properties and microstructure of the recycled specimens and reference specimen were investigated. Amounts of oxide in recycled materials were estimated. Almost all the recycled specimens exhibit higher strength than reference specimens, this is mainly attributed to grain refinement strengthening whereas particle-dispersion strengthening has few effect. The strength of recycled specimen increases with increasing of total surface area of chips because of different grain size. Recycled specimens show inferior ductility than reference specimens and recycled specimens with medium surface area of chips possess highest elongation. Grain size, oxide amount and density of billet have an effect on the elongation of recycled materials.

Influences of Welding Processes on Microstructure, Hardness, and Tensile Properties of AZ31B Magnesium Alloy

This article reports the influences of welding processes such as gas tungsten arc welding (GTAW), friction stir welding (FSW), and laser beam welding (LBW) on tensile properties of AZ31B magnesium alloy. The lowest hardness distribution profile (LHDP) is constructed across the weld section to identify the fracture path. From this investigation, it is found that LBW joints exhibited superior tensile properties compared to GTAW and FSW joints and this is mainly due to the formation of very fine grains in the fusion zone and absence of heat-affected zone (HAZ).

Increasing significantly the failure strain and work of fracture of solidification processed AZ31B using nano-Al 2O 3 particulates

In the present study, AZ31B magnesium alloy was unified with three different volume fractions of 50-nm Al 2O 3 particulates using the technique of disintegrated melt deposition. Composite samples were then subsequently hot extruded and characterized. Microstructural characterization studies revealed equiaxed grain structure, minimal porosity, reasonably uniform distribution of Al 2O 3 nano-particulates and good matrix-reinforcement interfacial integrity. The presence of Al 2O 3 particulates assisted in improving the thermal stability, microhardness and ductility of AZ31B alloy while 0.2%YS and UTS decreased. The overall tensile properties assessed in terms of work of fracture improved more than four times as a result of presence of 1.5 vol.% of Al 2O 3 nano-particulates. An attempt is made to correlate the effect of amount of Al 2O 3 nano-particulates on the microstructure and properties of AZ31B magnesium alloy.