Effects of Gd on microstructure and mechanical property of ZK60 magnesium alloy

Microstructures and phase compositions of as-cast and extruded ZK60-xGd （x=0-4） alloys were investigated. Meanwhile, the tensile mechanical property was tested. With increasing the Gd content, as-cast microstructure is refined gradually. Mg-Zn-Gd new phase increases gradually, while MgZn2 phase decreases gradually to disappear. The second phase tends to distribute along grain boundary by continuous network. As-cast tensile mechanical property is reduced slightly at ambient temperature when the Gd content does not exceed 2.98%. After extrusion by extrusion ratio of 40 and extrusion temperature of 593 K, microstructure is refined further with decreasing the average grain size to 2 μm for ZK60-2.98Gd alloy. Broken second phase distributes along the extrusion direction by zonal shape. Extruded tensile mechanical property is enhanced significantly. Tensile strength values at 298 and 473 K increase gradually from 355 and 120 MPa for ZK60 alloy to 380 and 164 MPa for ZK60-2.98Gd alloy, respectively. Extruded tensile fractures exhibit a typical character of ductile fracture.

Effect of applied pressure on microstructure and mechanical properties of Mg-Zn-Y quasicrystal-reinforced AZ91D magnesium matrix composites prepared by squeeze casting

The Mg-Zn-Y quasicrystal-reinforced AZ91 D magnesium matrix composites were prepared by squeeze casting process. The effects of applied pressure on microstructure and mechanical properties of the composites were investigated. The results show that squeeze casting process is an effective method to refine the grain. The composites are mainly composed of α-Mg, β-Mg17Al12 and Mg3Zn6Y icosahedral quasicrystal phase（I-phase）. With the increase of applied pressure, the contents of β-Mg17Al12 phase and Mg3Zn6 Y quasicrystal particles increase, further matrix grain refinement occurs and coarse dendritic α-Mg transforms into equiaxed grain structure. The composite exhibits the maximum ultimate tensile strength and elongation of 194.3 MPa and 9.2% respectively when the applied pressure is 100 MPa, and a lot of dimples appear on the tensile fractography. Strengthening mechanisms of quasicrystal-reinforced AZ91 D magnesium matrix composites are chiefly fine-grain strengthening and quasicrystal particles strengthening.

Effect of hot plastic deformation on microstructure and mechanical property of Mg-Mn-Ce magnesium alloy

Hot plastic deformation was conducted using a new solid die on a Mg-Mn-Ce magnesium alloy. The results of microstructural examination through OM and TEM show that the grain size is greatly refined from 45 μm to 1.1 μm with uniform distribution due to the occurrence of dynamic recrystallization. The grain refinement and high angle grain boundary formation improve the mechanical properties through tensile testing with the strain rate of 1.0×10?4 s?1 at room temperature and Vickers microhardness testing. The maximum values of tensile strength, elongation and Vickers microhardness are increased to 256.37 MPa, 17.69% and HV57.60, which are 21.36%, 133.80% and 20.50% more than those of the as-received Mg-Mn-Ce magnesium alloy, respectively. The SEM morphologies of tensile fractured surface indicate that the density and size of ductile dimples rise with accumulative strain increasing. The mechanism of microstructural evolution and the relationship between microstructure and mechanical property of Mg-Mn-Ce magnesium alloy processed by this solid die were also analyzed.

Influence of Ce addition on microstructure and mechanical properties of high pressure die cast AM50 magnesium alloy

The influence of Ce addition on the microstructure and mechanical properties of AM50 magnesium alloy was investigated to improve its mechanical properties.The results show that the addition of Ce to AM50 alloy results in the grain refinement and the mechanical properties of the Ce-modified AM50 at room and elevated temperatures are remarkably improved.AM50 magnesium alloy containing 1% Ce（mass fraction） shows better refinement and mechanical properties compared with the AM50 magnesium alloy with 0.5% Ce and even AM50 alloy without any Ce.

On the deformation behavior of heterogeneous microstructure and its effect on the mechanical properties of die cast AZ91D magnesium alloy

Both a conventional flow distributer and an improved one with a flow buffer were applied respectively during the high pressure die casting(HPDC)process,and samples of AZ91D magnesium alloy with different microstructure mainly consisting ofα-Mg grains,β-phase and porosities were obtained.According to the grain orientation analysis,the predominant deformation behavior inα-Mg grains was dislocation slip,supplemented by deformation twinning.Dislocation slip was more difficult to occur in the samples with the improved flow distributer on account of the fact that the size ofα-Mg grains in the microstructure was finer and more uniform.During the in situ tensile deformation test,cracks were observed to initiate from gas-shrinkage pore and island-shrinkage,and two main crack propagation mechanisms,porosity growth and coalescence were found accordingly.When the crack was in contact with theβ-phase,it would pass through and fracture the networkβ-phase,whereas bypass the islandβ-phase by detaching it from the surroundingα-Mg grains.Mechanical property tests showed that the samples with relatively more homogeneous microstructure would perform higher mechanical properties,which was the combined effect of matrixα-Mg grains,β-phase,and porosities.

Effects of Bi on the microstructure and mechanical property of ZK60 alloy

Microstructures and phase compositions of as-cast and extruded ZK60-xBi(x=0-1.64)alloys were investigated.Meanwhile,the tensile mechanical property and hardness were tested.With increasing the Bi content,the as-cast microstructure is first refined obviously,and then becomes coarse slightly.New small block compound which is rich in Zr,Zn,Bi and poor in Mg increases gradually,and MgZn_(2) phase decreases gradually.The second phase mainly precipitates along the grain boundary.The as-cast tensile mechanical property is first enhanced obviously,where the tensile strengthσb,yield strengthσ0.2 and elongationδcan reach 265 MPa,151 MPa and 13.5%for ZK60-0.23Bi alloy,respectively,then remains the high value for ZK60-(0.37-1.09)Bi alloys,and finally decreases obviously for ZK60-1.64Bi alloy.After hot extrusion,the obvious dynamic recrystallization occurs.Broken block compound distributes along the extrusion direction by zonal shape.The average grain size can reach only 4-6μm.The extruded tensile mechanical property is enhanced significantly,where σ_(b),σ_(0.2) and δ are at the range of 345-360 MPa,285-300 MPa and 15.5-19.5%,respectively.Extruded tensile fracture exhibits a typical character of ductile fracture.

Effects of Calcium and Yttrium on Microstructure and Mechanical Properties of High Strain-Rate Rolled AZ91D Magnesium Alloy

Effects of calcium( Ca) and yttrium( Y) on microstructure and mechanical properties of high strain-rate rolled AZ91 D magnesium alloy were studied. High strain-rate rolling can improve the strength and plasticity of magnesium alloy sheets.Additions of Ca and Y into AZ91 D can refine grains and modify the size and the distribution of the precipitated phases. After solution treatment( 418 ℃ and 20 h) and high strain-rate rolling( heating at420 ℃ for 10 min firstly and then rolling from 10 mm to 2 mm in thickness via a single pass),the tensile strength of the AZ91 D-0. 2%Ca alloy was 1. 3% higher than that of the AZ91 D-0. 4 D%Y alloy,and the tensile strength of the AZ91 D-0. 2%Ca-0. 4%Y alloy was about 8. 3% and 6. 9% higher than those of the AZ91 D-0. 4%Y and the AZ91 D-0. 2%Ca alloys respectively.

Optimization on microstructure,mechanical properties and damping capacities of duplex structured Mg–8Li–4Zn–1Mn alloys

Optimizing the mechanical properties and damping capacity of the duplex-structured Mg–Li–Zn–Mn alloy by tailoring the microstructure via hot extrusion was investigated.The results show that the Mg–8Li–4Zn–1Mn alloy is mainly composed ofα-Mg,β-Li,Mg–Li–Zn and Mn phases.The microstructure of the test alloy is refined owing to dynamic recrystallization(DRX)during hot extrusion.After hot extrusion,the crushed precipitates are uniformly distributed in the test alloy.The yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)of as-extruded alloy reach 156 MPa,208 MPa,and 32.3%,respectively,which are much better than that of as-cast alloy.Furthermore,the as-extruded and as-cast alloys both exhibit superior damping capacities,with the damping capacity(Q^(-1))of 0.030 and 0.033 at the strain amplitude of 2×10^(-3),respectively.The mechanical properties of the test alloy can be significantly improved by hot extrusion,whereas the damping capacities have no noticeable change,which indicates that the duplex-structured Mg–Li alloys with appropriate mechanical properties and damping properties can be obtained by alloying and hot extrusion.

Effect of B_2O_3 on microstructures and mechanical properties of cast Mg-Al-Ti-B alloys

The Mg-Al-Ti-B alloy prepared by mechanical alloying is poor in microstructural uniformity and compactness. In order to improve the microstructural uniformity and compactness of Mg-Al-Ti-B alloy and thus to improve the mechanical properties, effect of B2O3 on microstructure and mechanical properties of cast Mg-9Al-6Ti alloy was studied by optical microscopy, scanning electron microscopy, X-ray diffraction and mechanical property testing. The results show that due to the addition of B2O3, the average grain size of Mg-Al-Ti-B alloys is refined to 12μm, dispersed Ti phases completely disappear, the amount of precipitation phase Mgl7All2 is reduced and TiA13 is increased, and new phases MgB6 and TiaB4 are precipitated. The average hardness, average tensile strength, yield strength and elongation of the alloy are HV 77.1, 171.2 MPa, 113.5 MPa and 5.2%, respectively.

Influence of recycled carbon fiber addition on the microstructure and creep response of extruded AZ91 magnesium alloy

In this study,the recycled short carbon fiber(CF)-reinforced magnesium matrix composites were fabricated using a combination of stir casting and hot extrusion.The objective was to investigate the impact of CF content(2.5 and 5.0 wt.%)and fiber length(100 and 500μm)on the microstructure,mechanical properties,and creep behavior of AZ91 alloy matrix.The microstructural analysis revealed that the CFs aligned in the extrusion direction resulted in grain and intermetallic refinement within the alloy.In comparison to the unreinforced AZ91 alloy,the composites with 2.5 wt.%CF exhibited an increase in hardness by 16-20%and yield strength by 5-15%,depending on the fiber length,while experiencing a reduction in ductility.When the reinforcement content was increased from 2.5 to 5.0 wt.%,strength values exhibited fluctuations and decline,accompanied by decreased ductility.These divergent outcomes were discussed in relation to fiber length,clustering tendency due to higher reinforcement content,and the presence of interfacial products with micro-cracks at the CF-matrix interface.Tensile creep tests indicated that CFs did not enhance the creep resistance of extruded AZ91 alloy,suggesting that grain boundary sliding is likely the dominant deformation mechanism during creep.

Influence of Ca addition on microstructure,mechanical properties and corrosion behavior of Mg-2Zn alloy

The microstructure,mechanical properties and corrosion behaviors of as-cast ternary Mg-2Zn-x Ca(x=0,0.2,0.4,0.8)alloys have been investigated in this study.Results indicate that the microstructure of Mg-Zn-Ca alloys can be significantly refined with increasing Ca concentration.Moreover,the alloys with different contents of Ca exhibit the different phases formation behaviors,i.e.α-Mg+Ca_2Mg_6Zn_3 phases for Mg-2Zn-0.2Ca and Mg-2Zn-0.4Ca alloys,andα-Mg+Ca_2Mg_6Zn_3+Mg_2Ca phases for Mg-2Zn-0.8Ca alloy,respectively.Among all the alloys,the maximum ultimate tensile strength and elongation(161 MPa and 9.1%)can be attained for the Mg-2Zn-0.2Ca alloy.Corrosion tests in Hanks’balanced salt solution indicated that Ca addition is detrimental to corrosion resistance of Mg-2Zn alloy.The relationship between as-cast microstructure and properties for different Ca-containing alloys is also discussed in detail.

Effects of calcium addition on as-cast microstructure and mechanical properties of Mg-5Zn-5Sn alloy

The effects of Ca addition on the as-cast microstructure and mechanical properties of the Mg-5Zn-5Sn (mass fraction,%) alloy were investigated.The results indicate that an addition of 0.5%-1.5% (mass fraction) Ca to the Mg-5Zn-5Sn alloy not only refines the as-cast microstructure of the alloy but also causes the formation of the primary and/or eutectic CaMgSn phases with high thermal stability;an increase in Ca amount from 0.5% to 1.5% (mass fraction) increases the amount and size of the CaMgSn phase.In addition,Ca addition to the Mg-5Zn-5Sn alloy improves not only the tensile properties at room temperature and 150 ℃ but also the creep properties.Among the Ca-containing Mg-5Zn-5Sn alloys,the one added 0.5% (mass fraction) Ca obtains the optimum ultimate tensile strength and elongation at room temperature and 150 ℃,however,the alloy added 1.5% (mass fraction) Ca exhibits the optimum yield strength and creep properties.

Effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy

The effect of Ca addition on the as-cast micmstructure and creep properties of Mg-5Zn-5Sn magnesium alloy was investigated. The results indicate that adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can effectively refine the as-cast microstructure of the alloy, and the CaMgSn phase with high thermal stability is formed in the alloy. In addition, adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can also improve the creep properties of the alloy. After adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy, the second creep rate of the alloy at 150℃ and 50 MPa for 100 h decreases from 4.67 ×10^-8 to 1.43 × 10^-8 s^-1. The strengthening mechanism is mainly attributed to the microstructural refinement and the formation of CaMgSn phase.

Effect of ageing treatment on microstructures,mechanical properties and corrosion behavior of Mg-Zn-RE-Zr alloy micro-alloyed with Ca and Sr

Effects of ageing treatment on the microstructures,mechanical properties and corrosion behavior of the Mg-4.2Zn-1.7RE-0.8Zr-xCa-ySr[x=0,0.2(wt.%),y=0,0.1,0.2,0.4(wt.%)]alloys were investigated.Results showed that Ca or/and Sr additions promoted the precipitation hardening behavior of Mg-4.2Zn-1.7RE-0.8Zr alloy and shortened the time to reaching peak hardness from 13 h to 12 h.The maximum hardness of 77.1±0.6 HV for the peak-aged Mg-4.2Zn-1.7RE-0.8Zr-0.2Ca-0.2Sr alloy was obtained.The microstructures of peak-aged alloys mainly consist ofα-Mg phase,Mg_(51)Zn_(20) phase and ternary T-phase.The Zn-Zr phase is formed within theα-Mg matrix,and the Mg_(2)Ca phase is formed near T-phase due to the enrichment of Ca in front of the solid-liquid interface.Furthermore,fine short rod-shapedβ′1 phase is precipitated within theα-Mg matrix in the peak-aged condition.The peak-aged Mg-4.2Zn-1.7RE-0.8Zr-0.2Ca-0.2Sr alloy exhibits optimal mechanical properties with an ultimate tensile strength of 208 MPa,yield strength of 150 MPa and elongation of 3.5%,which is mainly attributed to precipitation strengthening.In addition,corrosion properties of experimental alloys in the 3.5wt.%NaCl solution were studied by the electrochemical tests,weight loss,hydrogen evolution measurement and corrosion morphology observation.The results suggest that peak-aged alloys show reduced corrosion rates compared with the as-cast alloys,and minor additions of Ca and/or Sr improve the corrosion resistance of the Mg-4.2Zn-1.7RE-0.8Zr alloy.The peak-aged Mg-4.2Zn-1.7RE-0.8Zr-0.2Ca-0.2Sr alloy possesses the best corrosion resistance,which is mainly due to the continuous and compact barrier wall constructed by the homogeneous and continuous second phases.

Influence of Ca Element on Microstructure and Mechanical Properties of AZ61-1.2Y

The effects of Ca element on the microstructure and mechanical properties of AZ61-1. 2Y alloy were investigated by microstructure observation, tensile tests and fracture analysis. The results show that, with the addition of Ca element, the microstructure of AZ61-1.2Y was obviously refined, high melting point Al2Ca intermetallic compound formed, and/3-Mg17 Al12 phase disappeared. With 1. 0% Ca addition, the values of tensile strength at 25, 150 and 175 ℃ reached their maxima simultaneously, 225, 182, and 175 MPa, respectively. Meanwhile, the values of elongation at room temperature and elevated temperature were also up to their peaks. The enhancement of the mechanical properties of AZ61-1.2Y with Ca can be attributed to the functions of grain refmement strengthening and dispersion strengthening.

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.

Influence of high frequency vibration on microstructure and mechanical properties of TIG welding joints of AZ31 magnesium alloy

A device for superimposing vibration on workpiece in both horizontal and vertical directions during tungsten-arc inert gas （TIG） welding was developed, with maximum power output of 2 kW at frequency of 15 kHz. AZ31 sheets with thickness of I and 3 mm were used in the vibratory welding. Microstructures along with the mechanical properties of the weld joints under different vibrating conditions （vibration direction, vibration amplitude and groove angle） were examined. It is observed that the grain size in welding zone decreases remarkably with the application of vibration, while the amount of second phase β-Mg_17Al_12 within the zone decreases slightly; meanwhile, microhardness of the weld joints, macroscopic tensile strength and elongation of the weldment increase. Vibration, especially the one along vertical direction, has more impact on the performance of the thick weldments. Influence of vibration on mierostructure and mechanical properties of weldments is affected by wave energy transferring in the melt and depends on the processing and geometric parameters including amplitude and direction of vibration, thickness, and groove angles.

Effect of heat treatment on microstructures and mechanical properties of sand-cast Mg-10Gd-3Y-0.5Zr magnesium alloy

The microstructure, mechanical properties and fracture behavior of sand-cast Mg-10Gd-3Y-0.5Zr alloy （mass fraction,%） under T6 condition （air cooling after solid solution and then aging heat treatment） were investigated. The optimum T6 heat treatments for sand-cast Mg-10Gd-3Y-0.5Zr alloy are （525 ℃, 12 h＋225 ℃, 14 h） and （525 ℃, 12 h＋250 ℃, 12 h） according to age hardening curve and mechanical properties, respectively. The ultimate tensile strength, yield strength and elongation of the Mg-10Gd-3Y-0.5Zr alloy treated by the two optimum T6 processes are 339.9 MPa, 251.6 MPa, 1.5%and 359.6 MPa, 247.3 MPa, 2.7%, respectively. The tensile fracture mode of peak-aged Mg-10Gd-3Y-0.5Zr alloy is transgranular quasi-cleavage fracture.

Influence of aging on microstructure and mechanical properties of AZ80 and ZK60 magnesium alloys

The effect of aging on the microstructure and mechanical properties of AZ80 and ZK60 wrought magnesium alloys was studied with optical microscope and mechanical testers. The results demonstrate that both the tensile strength and elongation of AZ80 alloy increase firstly and then decrease as the aging temperature rises, the peak values appear when the aging temperature is 170 ℃ The hardness of ZK60 alloy increases firstly and then decreases as the aging temperature rises, and the hardness reaches its peak value at 170 ℃. However, the toughness of the alloy is just the opposite. Moreover, ZK60 alloy has good performances in both impact toughness and other mechanical properties at the aging temperature from 140 ℃ to 200 ℃.

Effect of Nd addition on microstructures and mechanical properties of AZ80 magnesium alloys

The influence of Nd addition on the microstructures and mechanical properties of AZ80 magnesium alloys was investigated. The results show that the microstructure of as-cast AZS0 magnesium alloy is modified effectively with the addition of 1.0% Nd, the grain size is decreased from 448 to 125 ~tm, new rod-shaped A111Nd3 phase and block-shaped A12Nd phase are observed in the as-cast microstructure, and fl-Mgl7All2 phases are refined and become discontinuous. The addition of Nd suppresses the discontinuous precipitations at grain boundaries during aging, and the time of reaching the peak hardness is delayed. With the addition of 1.0% Nd, the combined properties reach an optimum, the yield strength, tensile strength and elongation are 103.7 MPa, 224.0 MPa and 8.4%, respectively. After T6 heat treatment, the yield strength and tensile strength of the AZ80-1.0%Nd alloy are increased to 141.1 and 231.1 MPa, respectively.