The transformation of LPSO type in Mg-4Y-2Er-2Zn-0.6Zr and its response to the mechanical properties and damping capacities

The transformation of LPSO type in Mg-4Y-2Er-2Zn-0.6Zr during heat treatment and its influence on damping and mechanical properties are reported in this work.Prior to heat treatment,the alloy consisted of a-Mg matrix and lamellar 14H LPSO phases.After 510℃heat treatment,lamellae shortened,and their content decreased.Upon 8h heat treatment,block 18R LPSO phases formed at the grain boundaries while 14H LPSO lamellae disappeared.Presence of block 18R LPSO phases improved mechanical and damping properties of the alloy.The corresponding mechanisms of the influence of LPSO type and morphology on mechanical and damping capacities are discussed.

Low frequency damping capacities of commercial pure magnesium

The amplitude-dependent and temperature-dependent low frequency damping capacities of magnesium with 99.96% purity were studied by a dynamic mechanical analyzer. The pure magnesium alloys include CPM1 and CPM2 castings having textures of columnar grains which extraordinarily influence the damping behaviours. The commercial pure magnesium alloy CPM was re-melted to obtain equiaxed grains, which could remove the effect of texture orientation on the damping behaviours of these pure magnesium alloys. The results of strain amplitude-dependent damping spectrums of these pure magnesium alloys show that the pure magnesium with equiaxed grains possesses the highest damping capacity. In temperature-dependent damping plot for all these three pure magnesium alloys, there are two damping peaks P1 and P2 located at 80 and 230 °C, respectively. These two damping peaks are considered to be caused by the interaction between dislocation and point defects, and the movement of grain boundaries, respectively.

Influence of B4C particle size on microstructure and damping capacities of(B_(4)C+Ti)/Mg composites

To study the influence of B4C particle size on the microstructure and damping capacities of(B_(4)C+Ti)/Mg composites,in situ reactive infiltration technique was utilized to prepare Mg-matrix composites.The microstructure,produced phases and damping capacities of the composites prepared with different particle size of B4C were characterized and analyzed.The results show that the reaction between B4C and Ti tends to be more complete when finer B_(4)C particle was used to prepare the composites.But the microstructure of the as-prepared composites is more homogenous when B4C and Ti have similar particle size.The strain-dependent damping capacities of(B_(4)C+Ti)/Mg composites improve gradually with the increase of strain amplitude,and composites prepared with coarser B4C particles tend to have higher damping capacities.The temperature-dependent damping capacities improve with increasing the measuring temperatures,and the kind of damping capacities of the composites prepared with 5mm B4C are inferior to those of coarser particles.The dominant damping mechanism for the strain-damping capacity is dislocation damping and plastic zone damping,while that for the temperature-damping capacity is interface damping or grain boundary damping.

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 ANNEALING ON DAMPING CAPACITIES OF AS-CAST ZA27 ALLOY

ZA27 alloy was prepared by casting with permanent mold and then annealed at 250℃ for 1-4h. The damping capaciG of the alloy was measured using a testing apparatus based on the cantilever beam technique. It was found that the as-cast ZA27 alloy possesses high damping capacity with the value of 1.3 × 10^4 at 320Hz. After annealed at 250℃ for lh, the damping capacity decreases to 1.1 × 10^-3 and then remains constant even when the annealing time is increased to 4h. The microstructure of the as-cast ZA27 alloy consists of large dendrites of Al-rich PrimaG （x-phases, eutectoid （α ＋ η） and nonequilibrium eutectic phases （α ＋ η ＋ ε）. After annealing at 250℃ for lh, the e phase disappears due to dissolution into the matrix, and the spacing between the flakes of eutectoid increases. The further increase in the annealing time has little effect on the spacing. The damping mechanism of the alloy was discussed considering the thermoelastic damping and defect damping. The value of thermoelastic damping accounts only for 7%-8% in the overall damping in cantilever beam damping measurements and the damping capacity of the ZA27 alloy came mainly from defect damping.

Effect of small tensile deformation on damping capacities of Mg-1%Al alloy

Tensile tests with small deformation amounts of 0.5%,1%,3%and 5%were performed at room temperature on as cast Mg-1%Al alloy.Microstructures of the Mg-1%Al alloys before and after deformation were observed by optical microscopy(OM) and transmission electron microscopy(TEM).The strain amplitude dependent and temperature dependent damping capacities of the as-cast and deformed Mg-1%Al alloys were investigated by dynamic mechanical analysis(DMA).The mechanism of deformation on damping capacity of Mg-1%Al alloy was discussed.The results show that the as-cast Mg-1%Al alloy has high damping value at high strain.When the tensile elongation is higher than 3%,the damping values of this alloy in high strain region are significantly decreased at room temperature.But the large amount of dislocations produced by tensile deformation are activated by heat,and then increase the damping value at high temperature.

INFLUENCE OF EXTRUSION ON DAMPING CAPACITIES OF AS-SPRAY DEPOSITED HIGH SILICON ALLOY ZA27 MODIFIED BY CERIUM

The effects of cerium modification and extrusion on the resultant damping behavior and mechanical properties of the as-sprayed high silicon alloy ZA27 were investigated in an thort to develop a new functional material possessing high damping capacity and good mechanical properties. The damping capacity, as well as the rslative dynamic modulus, was tneasured at frequencies of 1 and 4 Hertz over the 30 to 200℃runge. At below 80℃ the as-sprayed materials appear to be approximately Asquency independent. Above 80℃, the,naterials becotne temperature sensitive, exhibiting the highest damping for the lowest hequency. The extruded, as-sprayed high silicon alloy ZA27 modified by cerium has the highest damping capacity and elongation values among them. The micro8tructure of the as-sprayed high silicon alloy ZA27 modified by 0. 5 wt% cerium was made up of fine lamellar eutectoid, porositg, a light dot-like phase and a polygonal silicon-rich phase. Finally, the opemtive damping tnechanisms were discussed in light of the data obtained hem characterization of microstructure and damping capacity. The high damping capacity was attributed primarily to phase interface thermoelastic damping between the lamellar phases with various substrvctures,except for the grain refinement.

Solidification microstructure evolution and its correlations with mechanical properties and damping capacities of Mg-Al-based alloy fabricated using wire and arc additive manufacturing

Magnesium(Mg)alloys,as the lightest metal structural material with good damping capacities,have im-portant application prospects in realizing structural lightweight and vibration reduction.However,their engineering application is greatly limited by poor plastic formability.Wire and arc additive manufactur-ing(WAAM)provides a potential approach for fabricating large-scale Mg alloy components with high manufacturing flexibility.In this study,the evolution of the solidification microstructure of a WAAM-processed Mg-Al-based alloy was quantitatively analyzed based on the analytical models;then,the cor-relations between the solidification microstructure and mechanical properties/damping capacities were investigated.The results revealed that the WAAM-processed Mg-Al-based alloy with an equiaxed-grain-dominated microstructure displayed a simultaneous enhancement in mechanical properties and damping capacities compared to those of the cast Mg-Al-based alloy.The good combination of mechanical prop-erties and damping capacities are mainly attributed to the weakened basal texture with a relatively high Schmid factor for basalslip,the twinning-induced plasticity(TWIP)effect associated with the profuse{10-12}tensile twinning,and the relatively high dislocation density caused by the thermal stress during the WAAM process.

Enhanced Damping Capacities of Mg–Ce Alloy by the Special Microstructure with Parallel Second Phase

Microstructure evolution and damping capacities of Mg–Ce binary alloys with three different Ce contents（0.5, 1, or 2 wt%） have been systematically investigated in this work. Numerous fine parallel second phases in Mg–2Ce alloy are obtained, as well as a large number of dislocations around them, but few dislocations appear around the reticular second phase in the Mg–1Ce alloy. Among the three alloys, two internal friction peaks（P;and P;） are detected at about 78 and 167?C in both the Mg–0.5Ce and Mg–1Ce alloys.In addition, the alloy with special parallel second phase structure exhibits excellent damping capacity in both strain amplitude and temperature-dependent regions. These results may be ascribed to the stress concentration and the formation of abundant parallel and uniform dislocation configurations in the ?-Mg matrix without the influence of crystal orientation. The obtained results may provide a novel idea to prepare high-damping magnesium alloys by tailoring their microstructure.

Effects of Semi-solid Isothermal Heat Treatment on Microstructures and Damping Capacities of Fly Ash Cenosphere/AZ91D Composites

The fly ash cenosphere/AZ91D composites were successfully prepared and isothermally heat-treated at different tem- peratures for different time. The effects of semi-solid isothermal heat treatment on the microstructures and damping capacities of fly ash cenosphere/AZ91D composites were investigated. With the increase in isothermal temperature or holding time, the small liquid droplets within grains increased in size but decreased in quantity. The average size and shape factor of Mg2Si particles increased with the rise of isothermal temperature. The damping capacities of the composites were improved by isothermal heat treatment. At room temperature, the composites after heat treatment at 520 and 550 ℃ had a higher damping capacity due to interface damping when the strain amplitude was lower than about 8.8 × 10^-5, and the composite after heat treatment at 580 ℃ had a better damping capacity because of the dislocation damping under the condition of high strain amplitude. The damping capacities of the composites increased with the rise of the test temper- ature, and the damping mechanisms varied depending on different test temperatures. The interface damping played an important role when the test temperature was below about 100 ℃, and the dislocation damping and grain boundary damping took effect with the rise of test temperature.

Prediction of Damping Capacity Demand in Seismic Base Isolators via Machine Learning

Base isolators used in buildings provide both a good acceleration reduction and structural vibration control structures.The base isolators may lose their damping capacity over time due to environmental or dynamic effects.This deterioration of them requires the determination of the maintenance and repair needs and is important for the long-termisolator life.In this study,an artificial intelligence prediction model has been developed to determine the damage and maintenance-repair requirements of isolators as a result of environmental effects and dynamic factors over time.With the developed model,the required damping capacity of the isolator structure was estimated and compared with the previously placed isolator capacity,and the decrease in the damping property was tried to be determined.For this purpose,a data set was created by collecting the behavior of structures with single degrees of freedom(SDOF),different stiffness,damping ratio and natural period isolated from the foundation under far fault earthquakes.The data is divided into 5 different damping classes varying between 10%and 50%.Machine learning model was trained in damping classes with the data on the structure’s response to random seismic vibrations.As a result of the isolator behavior under randomly selected earthquakes,the recorded motion and structural acceleration of the structure against any seismic vibration were examined,and the decrease in the damping capacity was estimated on a class basis.The performance loss of the isolators,which are separated according to their damping properties,has been tried to be determined,and the reductions in the amounts to be taken into account have been determined by class.In the developed prediction model,using various supervised machine learning classification algorithms,the classification algorithm providing the highest precision for the model has been decided.When the results are examined,it has been determined that the damping of the isolator structure with the machine learning method is predicted successfully at a level exceeding 96%,and it is an effective method in deciding whether there is a decrease in the damping capacity.

Optimization of mechanical and damping properties of Mg-0.6Zr alloy by different extrusion processing

In this study,the optimization of mechanical and damping capacities of Mg-0.6 wt.%Zr alloys by controlling the recrystallized(DRXed)grain size under varying extrusion processing parameters including extrusion temperature T and strain rate was investigated.The relationship between the DRXed grain size and damping properties of the studied alloy was also discussed.The DRXed grain size of the as-extruded Mg-Zr alloys decreased as the extrusion temperature T decreased and the strain rateεincreased.As the DRXed grain size decreased,the strength and elongation of the as-extruded alloys exhibited improved performance through the grain refinement mechanism,while the damping properties deteriorated.The extrusion temperature of the Mg-Zr alloy had relatively greater effects on the mechanical and damping properties than the strain rate.The results of the present work indicate that alloys with appropriate mechanical and damping properties may be obtained from controlling the DRXed grain size by careful tailoring of the extrusion process parameters.

Effect of ball-milling parameter on mechanical and damping properties of sintered Mg-Zr alloy

Effects of ball-milling parameter on structures and properties of sintered Mg-l.5Zr （mass fraction, %） alloy were researched by metallographic analysis, mechanical properties tests and DMA technology. The results indicate that with 310 r/min rotation speed, the microstructure of the sintered alloy is greatly refined, and Zr-phase distributes uniformly. The micro-hardness, bending strength and damping capacities are the greatest under 310 r/min rotation speed. The damping peak of sintered Mg-l.5Zr alloy increases with increasing frequency under the testing conditions. The relaxation time meets the Arrhenius relationship, and shows the characteristics of relaxation damping.

Damping capacity of high strength-damping aluminum alloys prepared by rapid solidification and powder metallurgy process

Two kinds of high strength-damping aluminum alloys （LZ7） were fabricated by rapid solidification and powder metallurgy （RS-PM） process. One material was extruded to profile aluminum directly and the other was extruded to bar and then rolled to sheet. The damping capacity over a temperature range of 25-300 ℃was studied with damping mechanical thermal analyzer （DMTA） and the microstructures were investigated by optical microscopy （OM）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results show that the damping capacity increases with the test temperature elevating. Internal friction value of rolled sheet aluminum is up to 11.5×10^-2 and that of profile aluminum is as high as 6.0×10^-2 and 7.5×10^-2 at 300 ℃, respectively. Microstructure analysis shows the shape of precipitation phase of rolled alloy is more regular and the distribution is more homogeneous than that of profile alloy. Meanwhile, the interface between particulate and matrix of rolled sheet alloy is looser than that of profile alloy. Maybe the differences at interface can explain why damping capacity of rolled sheet alloy is higher than that of profile alloys at high temperature （above 120 ℃）.

Effects of Y and Zn on mechanical properties and damping capacity of Mg-Cu-Mn alloy

Optical microscope,X-ray diffractometer,scanning electron microscope,tensile tester and dynamic mechanical analyzer(DMA) were applied to investigate the effects of Y and Zn additions on microstructure,mechanical properties and damping capacity of Mg-3Cu-1Mn(CM31) alloy.The results show that with the increase of Y and Zn contents,the secondary dendrite arm spacing of alloys is reduced;meanwhile,the yield strength is increased.In low strain amplitude,the damping capacity of alloys with Y and Zn addition is lower than that of CM31 alloy.However,in strain amplitude over 5×10-3,the damping capacity of alloy with a trace of Y and Zn addition(1%Y and 2%Zn,mass fraction) increases abnormally with the increase of strain amplitude and is near to that of pure Mg,probably due to the increase of dislocation density caused by the precipitation of secondary phase.The temperature dependence of damping capacity of above alloy was also tested and discussed.

Design optimization of cast Cu-Al-Be-B alloys for high damping capacity

This paper investigated high-damping Cu-Al-Be-B cast alloys using metallographic analysis, X-ray diffraction (XRD) and electrical resistance measurements for transformation temperatures. The results showed that beryllium can stabilize β phase, resulting in a thermo-elastic martensite microstructure leading to high-damping capacity in cast Cu-Al-Be-B alloys. Trace additions of boron to Cu-Al-Be alloys can significantly refine the grains, providing high strength and ductility to the alloys. A factorial design of experiment method was used to optimize the composition and properties of cast Cu-Al-Be-B alloys. The optimal microstructure for thermo-elastic martensite can be obtained by adjusting the amounts of aluminum and beryllium to eutectoid or pseudo-eutectoid compositions. An optimized cast Cu-Al-Be-B alloy was developed to provide excellent mechanical properties, tensile strength σ_b=767MPa, elongation δ=7.62%, and damping capacity S. D. C=18.70%.

Effects of Y content and temperature on the damping capacity of extruded Mg-Y sheets

The damping behavior of extruded Mg-xY(x=0.5,1.0,3.0 wt.%)sheets were investigated in detail concerning the effects of Y addition and temperature,and the relationship between damping capacity and yield strength was discussed.At room temperature(RT),with Y content increasing from 0.5%to 3.0%,the damping capacity(Q-1)significantly decreased from 0.037 to 0.015.For all the studied sheets,the relationship between strain amplitude and Q-1 fitted well with the Granato and Liicke(G-L)dislocation damping model.With temperature increased,the G-L plots deviated from linearity indicating that the dislocation damping was not the only dominate mechanism,and the grain boundary sliding(GBS)could contribute to damping capacity.Consequently,the Q-1 increased remarkably above the critical temperature,and the critical temperature increased significantly from 50℃ to 290℃ with increasing Y contents from 0 to 3.0wt.%.This result implied that the segregation of Y solutes at grain boundary could depress the GBS,which was consistent with the recent finding of segregation tendency for rare-earth solutes.The extruded Mg-IY sheet exhibited slightly higher yield strength(Rp0.2)and Q-1 comparing with high-damping Mg-0.6Zr at RT.At an elevated temperature of 325℃,the Mg-IY sheet had similar Q-1 but over 3 times larger Rp0.2 than that of the pure Mg.The present study indicated that the extruded Mg-Y based alloys exhibited promising potential for developing high-performance damping alloys,especially for the elevated-temperature application.

Influence of RE Content on Damping Capacity of Alloy ZA27

The modification mechanism and damping capacity(Q-1) of conventional ascast ZA27 alloy modified by Al10%RE were investigated. Cantilever beam technique was used to measure the damping capacity. The experimental results show that the addition of RE to the ZA27 alloy can refine microstructure and improve the damping capacity, the best modification effect and the highest damping capacity can be obtained at 03%RE content. It is believed that the damping mechanism of ZA27 alloy is associated with the viscous sliding or slipping of grain boundaries and interfaces, and the more the grain boundaries and interfaces, the higher the damping capacity of ZA27 alloy can be obtained.

Solid solution strengthening and damping capacity of Mg-Ga binary alloys

The mechanical behaviors and damping capacities of the binary Mg−Ga alloys with the Ga content ranging from 1 to 5 wt.%were investigated by means of optical microscope(OM),scanning electron microscope(SEM),X-ray diffraction(XRD),hardness test,tensile test and dynamic mechanical analyzer(DMA).The hardness(HV_(0.5))increases with the increase of Ga content,which can be described as HV_(0.5)=41.61+10.35c,and the solid solution strengthening effect∆σ_(s)of the alloy has a linear relationship with c^(n),where c is the molar fraction of solute atoms and n=1/2 or 2/3.Ga exhibits a stronger solid solution strengthening effect than Al,Zn or Sn due to the large atomic radius difference and the modulus mismatch between Ga and Mg atoms.The addition of Ga makes the Mg−Ga alloys have better damping capacity,and this phenomenon can be explained by the Granato−Lücke dislocation model.The lattice distortion and the modulus mismatch generated because of the addition of Ga increase the resistance to motion of the dislocation in the process of swinging or moving,and thus the better damping capacity is acquired.

A Novel TiNi/AlSi Composite with High Strength and High Damping Capacity

A novel TiNi/AlSi composite with high compressive strength and high damping capacity was obtained by infiltrating Al-12%Si alloy into porous TiNi alloy.It had been found that the high compressive strength (440 MPa) of TiNi/AlSi composite is due to the increase of effective carrying area after infiltrating Al-12%Si alloy,while the high damping capacity is contributed to TiNi carcass,Al-12%Si filling material and micro- slipping at the interface.