Microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy by micro-arc oxidation

The microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy obtained in silicate-,borate- and aluminate-based electrolyte without and with nanoadditive Al2O3 and TiO2 by micro-arc oxidation（MAO） were studied by scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDS）,X-ray diffraction（XRD）,microhardness and friction-abrasion tests,respectively.SEM results show that coatings with nanoadditive have less porosities than those without nanoadditive.XRD results reveal that nanoadditive-containing coatings contain more oxides compared with nanoadditive-free coatings in all cases,which are consistent with the EDS analysis.Mechanical properties tests show that nanoadditive Al2O3-containing coatings have higher microhardness values compared with the other coatings obtained in silicate-,borate- and aluminate-based electrolyte.On the other hand,nanoadditive has a positive effect on improving the wearing-resistance of MAO coatings in all cases.Furthermore,the borate-MAO coatings present an inferior anti-wearing property compared with the silicate- and aluminate-MAO coatings for both the nanoadditive-free and nanoadditive-containing coatings.

Comparative Study on the Microstructure and Mechanical Properties of Mg-Li-Al Based Alloys with Yttrium and Strontium Addition

The effects of yttrium and strontium on the microstructure and mechanical properties of Mg- 11Li-3A1 magnesium alloy （LA113） are compared and analyzed. Microstructures and phases of the alloys were studied with optical microscope （OM）, scanning electron microscope （SEM）, X-ray diffractometer （XRD） and energy dispersive spectrometer （EDS）. Mechanical properties of alloys were measured with tensile tester. The results show that yttrium and/or strontium additions produce a strong grain refining effect in LA113 alloy. AI2Y and AI4Sr, etc. phases with different morphologies are verified and exist inside the grain or at the grain boundaries, which directly impact on the mechanical properties of LA113 alloy. The results of tensile tests show that, the as-extruded LA113-1Y-1 Sr alloy obtains the optimal tensile property of which the tensile strength and elongation are 253.56 MPa and 18.12%, the tensile strength is increased by almost 25% compared with the as- extruded LA113 alloy.

Effects of yttrium on microstructure and mechanical properties of Mg-Zn-Cu-Zr alloys

The effects of yttrium addition on microstructure and mechanical properties of as-cast Mg-6Zn-3Cu-0.6Zr-xY(x=0,0.5, 1.0,1.5 and 2.0,mass fraction,%)(ZCK630+xY for short in this study)alloys were investigated by means of OM,XRD and SEM. The results show that the average grain size of Mg-Zn-Cu-Zr magnesium alloy is effectively reduced(from 57μm to 39μm)by Y addition.The analysis of XRD indicates the existence of I-phase(Mg3Zn6Y)and W-phase(Mg3Zn3Y2)in ZCK630 alloys with Y addition.The ultimate tensile strength of ZCK630 alloys is significantly deteriorated with increasing Y addition,which is possibly related to the continuous networks of intergranular phases and the increase of W-phase.

Microstructure and mechanical properties of Fe-doped NiAl-28Cr-6Mo eutectic alloys

Room temperature and high temperature microstructural and mechanical properties of arc melted Ni Al-28Cr-6Mo eutectic alloys doped with 0.1% Fe, 0.2% Fe and 0.5% Fe(mole fraction) were investigated. The homogenization heat treatment of the alloys was conducted at 1300℃ in Ar atmosphere. Microscopic analyses, hardness measurements, XRD measurements and compression tests were used to characterize the alloys. As-cast and homogenized alloys exhibit fine cellular eutectic structures with coarse intercellular eutectic structure. The increase in the content of Fe results in coarsening eutectic layers and the decrease in eutectic cells. All alloys have very high compressive stress and strain at room temperature. The addition of Fe has small negative impact on the strength and ductility of the alloys at room temperature. However, the addition of Fe increases the high temperature strength of the alloy. High temperature XRD patterns show that peaks shift to lower Bragg angles. This indicates that the lattice parameter of the alloys increases.

Effects of yttrium on microstructure and mechanical properties of Mg-6Al magnesium alloy

Since Y has a great solid solubility in magnesium alloys, it helps enhancing the heat-resistant property of magnesium alloys. The effects of Y on microstructures and mechanical properties of Mg-6Al alloy have been studied in this work. The results show that Y addition refines grains of Mg-6Al alloy, and reduces the amount of the Mg 17 Al 12 phase. At the same time, the high melting-point Al 2 Y phase particles are formed. According to the mathematical model of the two-dimensional lattice misfit proposed by Braffit, it is believed that the Al 2 Y particles can serve as the nucleation sites for α-Mg. After T6 treatment, both elongation and ultimate tensile strength of Mg-6Al alloy at the room temperature and high-temperature increased firstly and then decreased, with increasing Y addition. The peak mechanical properties were achieved in the Mg-6Al-1.2Y alloy system. Y addition appears to change the fracture characteristic of Mg-6Al alloy. With 1.2wt%Y, the fracture surface of the alloy showed a lot of dimples and tearing ridges which connected the microscopic dimples and the fracture is mixed fracture of quasi-cleavage and ductile fracture.

Effects of yttrium addition on microstructure and mechanical properties of as-extruded AZ31 magnesium alloys

The effects of yttrium addition on microstructure and mechanical properties of as-extruded AZ31 magnesium alloys were investigated by OM,XRD and SEM.The results show that the addition of yttrium results in the formation of a new phase,Al_2Y. When the addition of yttrium is higher than 1.48%-2.91%(mass fraction),another new phase,Al_3Y_5Mn_7,forms,and the amount ofβ-Mg_(17)Al_(12) phase in the AZ31 alloy decreases sharply.The tensile test at room temperature indicates that the yield strength of as-extruded AZ31 alloys improves with the addition of yttrium,but the elongation decreases,which is possibly related to the formation of coarse blocky compounds containing yttrium and the grain coarsening in the alloys.

Effects of Yttrium on Mechanical Properties and Microstructures of Ti-Si Eutectic Alloy

The effects of rare earth （Y） on Ti-TisSi3 eutectic alloy are studied. The results of microstructure analysis show that the colonies and microstructures of the raw alloy are transformed evidently with the addition of Y. With proper addition of yttrium （0.025at%）, the shape and size of the coarse TisSi3 phases of the colonies change to be fine and round meanwhile the microstructure of the alloy goes into uniformity. The compressive ductility and strength at room temperature are also improved. The effects of yttrium on the alloy are likely due to that Si atoms in TisSi3 phase are partially substituted for yttrium atoms which results in silicide Ti5（Si, Y）3 phases.

Microstructures and mechanical properties of 2014 aluminium alloy forgings made by a new process

The triangular 2014 aluminium alloy forgings were made by a new process and the traditional process. The results showed that the mechanical properties of the forgings made by the new process are far higher than that in the standard of GB223 84, and also higher than that in the standard of EL/53MI 94; moreover, the mechanical properties are almost the same in each direction, and anisotropies are very small. The grains and 2nd phases were analyzed by using TEM and SEM, the results indicate that very fine grains (3～6 μm)appear in an approximately isometric way, and a large number of 2nd submicrophases(0.05～0.15 μm) disappear in no apparently preferred orientation distribution because the new process involves multidirectional heavy plastic deformation (λ=12), solution(500 ℃/400 min) and ageing(165 ℃/10 h) heat treatments for a long time at high temperatures. These refined grains, 2nd submicrophases and their almost homogeneous distribution can make it possible for the forgings to display high mechanical properties.

Effect of Fe addition on microstructure and mechanical properties of Al-9Mg-2.6Si Alloy

This paper presents the effect of Fe on the microstructure and mechanical properties of Al-9Mg-2.6Si alloy.The Feaddition in the Al-9Mg-2.6Si alloy can slightly increase the yield strength but decrease the elongation.With a much higher Feaddition around1.6wt.%,the elongation of the alloy can still maintain a usable level of5%.This alloy has shown a high toleranceon the Fe contamination

Effect of yttrium on microstructures and mechanical properties of hot rolled AZ61 wrought magnesium alloy

The microstructures and mechanical properties of the rolled AZ61 alloys containing different contents of Y (0, 0.5, 0.9, 1.4%Y respectively) were studied. Phase analysis was performed by X-ray diffraction(XRD). Microstructures of experimental materials were observed by optical microscope(OM) and scanning electron microscope(SEM) equipped with energy dispersive spectrometer(EDS). The results show that the alloys with variable Y contents all contain a second-phase Al2Y. The amount of Al2Y increases with the increasing of Y content while that of Mg17Al12 decreases. Moreover, Y refines the microstructures of as-cast and rolled alloys. The finest average grain size is obtained in the alloy containing 0.9%Y with the best mechanical properties. When the Y content is up to 1.4%, Al2Y phase in the alloy coarsens, which leads to the drop of tensile strength.

Microstructure and mechanical properties of AZ81 magnesium alloy with Y and Nd elements

The effects of rare earth(RE)elements Y and Nd(w(Y)/w(Nd)=3-2)with total content of 1%-4%on microstructures and elevated temperature mechanical properties of AZ81 magnesium alloy were investigated.The results show that,proper content of rare earth elements makes the microstructures of AZ81 magnesium alloy refine obviously and the quantity ofβ-Mg17Al12 phases reduce,and Al2Y and Al2Nd form.After solid solution treatment,with increasing content of rare earth elements,the tensile strength and elongation of the alloys(at room temperature,150 ℃and 250℃)increase first,then decrease.When the content of rare earth elements is up to 2%,the values of tensile strength at room temperature and 150 ℃are up to their maxima simultaneously,282 MPa and 212 MPa,respectively.Meanwhile,the values of elongation at room temperature and at elevated temperature are also up to their maxima,13%and 15%,respectively.

Effect of Y content on microstructure and mechanical properties of 2519 aluminum alloy

The effects of yttrium(Y) content on precipitation hardening, elevated temperature mechanical properties and morphologies of 2519 aluminum alloy were investigated by means of microhardness test, tensile test, optical microscopy(OM), transmission electron microscopy(TEM) and scanning electron microscopy(SEM). The results show that the tensile strength increases from 485 MPa to 490 MPa by increasing Y content from 0 to 0.10%(mass fraction) at room temperature, and from 155 MPa to 205 MPa by increasing Y content from 0 to 0.20% at 300 ℃. The high strength of 2519 aluminum alloy is attributed to the high density of fine θ′ precipitates and intermetallic compound AlCuY with high thermal stability. Addition of Y above 0.20% in 2519 aluminum alloy may induce the decrease in the tensile strength both at room temperature (20 ℃) and 300 ℃.

Effects of Y addition on microstructure and properties of Al-Zr alloys

Microstructure and properties of Al-0.30Zr and Al-0.30Zr-0.08Y （mass fraction, %） alloys were investigated by electrical conductivity measurements, microhardness tests, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Micron-sized primary Al3Y phases form within grains and at grain boundaries simultaneously as product of eutectic reaction in as-cast Al-Zr--Y alloys. The addition of Y obviously accelerates the precipitation kinetics of Al3Zr （Ll2） in Al-Zr-Y alloys. The Al-Zr-Y alloys exhibit greater electrical conductivity during aging due to formation of increased volume fractions of Al3（Zr, Y） precipitates. In ternary Al-Zr-Y alloys, spheroidal L l2-structured Al3（Zr, Y） precipitates with increased number density and smaller mean radius were observed. The Al-0.30Zr-0.08Y alloys show improved recrystallization resistance compared with Al-0.30Zr alloys

Effect of trace yttrium on the microstructure,mechanical property and corrosion behavior of homogenized Mg-2Zn-0.1Mn-0.3Ca-xY biological magnesium alloy

The effects of trace yttrium(Y)element on the microstructure,mechanical properties,and corrosion resistance of Mg-2Zn-0.1Mn-0.3Ca-xY(x=0,0.1,0.2,0.3)biological magnesium alloys are investigated.Results show that grain size decreases from 310 to 144µm when Y content increases from 0wt%to 0.3wt%.At the same time,volume fraction of the second phase increases from 0.4%to 6.0%,yield strength of the alloy continues to increase,and ultimate tensile strength and elongation decrease initially and then increase.When the Y content increases to 0.3wt%,Mg_(3)Zn_(6)Y phase begins to precipitate in the alloy;thus,the alloy exhibits the most excellent mechanical property.At this time,its ultimate tensile strength,yield strength,and elongation are 119 MPa,69 MPa,and 9.1%,respectively.In addition,when the Y content is 0.3wt%,the alloy shows the best corrosion resistance in the simulated body fluid(SBF).This investigation has revealed that the improvement of mechanical properties and corrosion resistance is mainly attributed to the grain refinement and the precipitated Mg_(3)Zn_(6)Y phase.

Microstructure and Mechanical Property of 2024 Aluminium Alloy Prepared by Rapid Solidification and Mechanical Milling

Rapidly solidified 2024 aluminium alloy powders were mechanically milled, then consolidated to bulk form. The microstructural changes of the powders in mechanical milling (MM) and consolidation process were characterized by X-ray diffraction analyses and transmission electron microscopy observations. The results showed that mechanical milling reduced the grain size to nanometer, dissolved the Al2Cu intermetallic compound into the aluminium matrix and produced an aluminium supersaturated solid solution. During consolidation process. the grain size increased to submicrometer, and the Al2Cu and Al2(Cu, Mg, Si, Fe, Mn) compounds precipitated owing to heating. Increasing consolidation temperature and time results in obvious grain growth and coarsening of second phase particles. The tensile yield strength of the consolidated alloy with submicrometer size grains increases with decreasing grain size, and it follows the famous HallPetch relation

Additive manufacturing of a high strength Al-5Mg_(2)Si-2Mg alloy:Microstructure and mechanical properties

A novel Al-5 Mg2 Si-2 Mg alloy was processed by selective laser melting(SLM) to understand its representative features of microstructural evolution and mechanical properties during additive manufacturing(AM). The as-SLM fabricated Al-5 Mg_(2) Si-2 Mg alloy is found to deliver much less hot cracks and other defects. Meanwhile, excellent mechanical property is also achieved, i.e. 452 ± 11 MPa for ultimate tensile strength, 295 ± 14 MPa for yield strength, and 9.3 ± 2.5% for elongation. Clearly, these mechanical properties are better than that obtained by high pressure die casting(HPDC), and better than some other alloys obtained by SLM. The as-SLM fabricated Al-5 Mg_(2) Si-2 Mg alloy is featured by the significantly refined microstructures in the compact primary α-Al, the divorced Mg_(2) Si eutectic networks distributing atα-Al grain boundaries, and some α-Al Fe Mn Si phase in association with eutectic Mg_(2) Si phase. The high strength and ductility of the alloy are attributed to its unique features including(a) the reduced solidification range,(b) the possible increase of the eutectic level in the microstructure, and(c) the shift of eutectic point and the maximum solubility point of Mg2 Si in Al matrix.

Microstructure analysis and mechanical characteristics of tungsten inert gas and metal inert gas welded AA6082-T6 tubular joint: A comparative study

The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding （TIG） and metal inert gas welding （MIG） processes. The effect of welding processes was analysed based on optical microscopy image, tensile testing, and Vickers micro-hardness measurements. The results showed that the tensile strengths of the TIG-welded joints were better than those of the MIG-welded joints, due to the contribution of fine equiaxed grains formation with narrower spacing arms. In terms of joint efficiency, the TIG process produced more reliable strength, which was about 25% higher compared to the MIG-joint. A significant decay of hardness was recorded in the adjacent of the weld bead zone, shown in both joints, related to phase transformation, induced by high temperatures experienced by material. A very low hardness, which was about 1.08 GPa, was recorded in the MIG-weldcd specimens. The extent of the heat-affected-zone （HAZ） in the MIG-welded joints was slightly wider than those of the TIG-welded specimens, which corresponded with a higher heat input per unit length.

Microstructure and mechanical properties of novel Al-Y-Sc alloys with high thermal stability and electrical conductivity

The microstructure and mechanical properties of novel Al-Y-Sc alloys with high thermal stability and electrical conductivity were investigated.Eutectic Al3 Y-phase particles of size 100-200 nm were detected in the as-cast microstructure of the alloys.Al3 Y-phase particles provided a higher hardness to as cast alloys than homogenized alloys in the temperature range of 370-440℃.L12 precipitates of the Al3(ScxYy) phase were nucleated homogenously within the aluminium matrix and heterogeneously on the dislocations during annealing at 400℃.The average size of the L12 precipitates was 11±2 nm after annealing for 1 h,and 25-30 nm after annealing for 5 h,which led to a decrease in the hardness of the Al-0.2 Y-0.2 Sc alloy to15 HV.The recrystallization temperature exceeded 350℃and 450℃for the Al-0.2 Y-0.05 Sc and Al-0.2 Y-0.2 Sc alloys,respectively.The investigated alloys demonstrated good thermal stability of the hardness and tensile properties after annealing the rolled alloys at 200 and 300℃,due to fixing of the dislocations and grain boundaries by L12 precipitates and eutectic Al3 Y-phase particles.The good combination of strength,plasticity,and electrical conductivity of the investigated Al-0.2 Y-0.2 Sc alloys make it a promising candidate for electrical conductors.The alloys exhibited a yield stress of 177-183 MPa,ultimate tensile stress of 199-202 MPa,elongation of 15.2-15.8%,and electrical conductivity of 60.8%-61.5% IACS.

Mechanical properties and microstructure analysis of refilling friction stir welding on 2219 aluminum alloy

The 2219 aluminum alloy under refilling friction stir welding （RF-FSW） was investi- gated. The micrographs showed that the bead could be divided into six zones, and the grain size and shape were greatly different in these zones. According to the mi- crostructure analysis, the weld nugget zone and the shoulder stirring zone consisted of equiaxed grains, while the grains in the heat affected zone were seriously coars- ened. It was obvious that bending deformation occurred in the thermo-mechanically affected zone. According to the microhardness analysis, the lowest hardness of the weld was at the thermo-mechanically affected zone, and the microhardness increased with the retraction of the stir-pin. The tensile strength and elongation of the bead were 70% and 80% of the base metal, respectively. The tensile strength was slightly different for the stable stage and the retraction stage, while the elongation decreased in the retraction stage. The mechanical different retraction speed were analyzed, with increasing retraction speed. properties and microstrueture responded to and it showed that the elongation decreased

Microstructure and Mechanical Properties of Galvanized Steel/AA6061 Joints by Laser Fusion Brazing Welding

Laser fusion brazing welding was proposed.Galvanized steel/AA6061 lapped joint was obtained by laser fusion brazing welding technique using the laser-induced aluminium molten pool spreading and wetting the solid steel surface.Wide joint interface was formed using the rectangular laser beam coupled with the synchronous powder feeding.The result showed that the tiny structure with the composition of a-Al and Al–Si eutectic was formed in the weld close to the Al side.And close to the steel side,a layer of compact Fe–Al–Si intermetallics,including the Al-rich FeAl3,Fe2Al5 phases and Al–Fe–Si s1 phase,was generated with the thickness of about 10–20 lm.Transverse tensile shows the brittlefractured characteristic along to the seam/steel interface with the maximum yield strength of 152.5 MPa due to the existence of hardening phases s1 and Al–Fe intermetallics.