Effect of alloying elements on magnesium alloy damping capacities at room temperature

Alloying is a good approach to increasing its strength but leads to a reduction of damping to pure magnesium.Classifying the alloying characteristics of various alloying elements in magnesium alloys and their combined effects on the damping and mechanical properties of magnesium alloys is important.In this paper,the properties of the Mg-0.6wt%X binary alloys were analyzed through strength measurements and dynamic mechanical analysis.The effects of foreign atoms on solid-solution strengthening and dislocation damping were studied comprehensively.The effect of solid solubility on damping capacity can be considered from two perspectives:the effect of single solid-solution atoms on the damping capacities of the alloy,and the effect of solubility on the damping capacities of the alloy.The results provide significant information that is useful in developing high-strength,high-damping magnesium alloys.This study will provide scientific guidance regarding the development of new types of damping magnesium alloys.

Aging kinetics of 14H-LPSO precipitates in Mg-Zn-Y alloy

Alloys with long-period stacking ordered structures(LPSO)have good properties and are highly regarded.Mg-Zn-Y alloy containing LPSO phase was prepared by the traditional casting method,and the aging heat treatment was performed at different temperatures and times.The microstructure and phase constitutions of the alloy were observed by means of optical microscopy and scanning electron microscopy methods.Results show the microstructure of as-cast Mg95.5Zn1.5Y3 mainly consists ofα-Mg,W phases and LPSO phases.During the aging treatment,fine lamellar-shaped 14H-LPSO phase is formed at the grain boundaries and precipitates from the supersaturated magnesium matrix,and the volume fraction increases as the aging time increases.By controlling the aging time,Mg-Zn-Y alloys with different volume fractions of 14H-LPSO phase were prepared.The aging kinetics equation of the 14H-LPSO phase is summarized,that is f=1-exp(-0.2705 t 0.6368).The phase transformation mechanism of 14H-LPSO in Mg95.5Zn1.5Y3 alloy can be described as the change of dislocation energy.

Effects of Pb on microstructure, mechanical properties and corrosion resistance of as-cast Mg97Zn1Y2 alloys

In this present work, Pb was applied in the Mg97Zn1Y2 alloy to improve its microstructure and properties, using conventional casting methods. The microstructure and properties of the Mg97 Zn1 Y2 alloy and Mg97Zn1Y2-x Pb(x=0.6 wt.%, 1.2 wt.% and 1.8 wt.%) alloys were observed by optical microscopy, scanning electron microscopy method and analyzed by X-ray diffraction, hardness and strength measurement and electrochemical testing. After adding Pb to the Mg97Zn1Y2 alloy, a new particle phase Mg_2 Pb was identified along the grain boundaries, and dendrites were refined. In addtion, the hardness of Mg97Zn1Y2-xPb(x=0.6 wt.%, 1.2 wt.% and 1.8 wt.%) alloys was higher than that of the Mg97 Zn1Y2 alloy; with the increase of Pb content, the hardness of the alloy increased first and then decreased, followed by a final slight increase, and reached a maximum of 89.1 HV when the Pb content was 0.6 wt.%. The strength of the alloy increased first and then decreased as the Pb content increased. Moreover, adding a small amount of Pb to the alloy can effectively inhibit corrosion, and Mg97Zn1Y2-0.6 wt.%Pb exhibits the best corrosion resistance ability.

Strain amplitude-dependent internal friction of as-cast high damping magnesium alloy during cyclic vibration

An investigation on strain amplitude-dependent internal friction （IF） of an as-cast high damping Mg-7 wt% Ni alloy was carried out. In the range of our tested strain amplitudes, whether the strain amplitude is increasing or decreasing, the strain amplitude-dependent IF curve can be divided into two stages： one is the strain amplitude weakly dependent part and the other is the strain amplitude strongly dependent part. However, after several cyclic vibrations, the IF values measured during the strain amplitude increasing are smaller than those obtained during the strain amplitude decreasing. The phenomenon is also observed at 100 C. Partial dislocations generate a short-range slip under the cyclic stress to be responsible for it.

Corrosion and chemical behavior of Mg_(97)Zn_(1)Y_(2)-1wt.%SiC under different corrosion solutions

To explore the corrosion properties of magnesium alloys, the chemical behavior of a high strength Mg_(97)Zn_(1)Y_(2)-1 wt.%Si C alloy in different corrosion environments was studied. Three solutions of 0.2 mol·L^(-1) NaCl, Na_(2)SO_(4) and NaNO_(3) were selected as corrosion solutions. The microstructures, corrosion rate, corrosion potential, and mechanism were investigated qualitatively and quantitatively by optical microscopy(OM), scanning electron microscopy(SEM), immersion testing experiment, and electrochemical test. Microstructure observation shows that the Mg_(97) Zn_(1)Y_(2)-1 wt.%Si C alloy is composed of α-Mg matrix, LPSO(Mg_(12) ZnY) phase and Si C phase. The hydrogen evolution and electrochemical test results reflect that the Mg_(97)Zn_(1)Y_(2)-1 wt.%SiC in 0.2 mol·L^(-1) Na Cl solution has the fastest corrosion rate, followed by Na_(2)SO_(4) and NaNO_(3) solutions, and that the charge-transfer resistance presents the contrary trend and decreases in turn.

Single and double aging treatments on Mg97Zn1Y2 alloy

The development of magnesium alloys was limited due to the low absolute strength and poor corrosion resistance. It was found that the optimal performance could not be achieved in some alloys by a single quenching and aging treatment, but could be achieved after a graded aging or multiple-stage aging heat treatment. The Mg97Zn1Y2 alloy was prepared and subjected to single and double aging treatments. Single aging was carried out at 250 ℃ for 6 to 15 h. For double aging, the first step was performed the same as the single aging. The second step was performed at 350 ℃ for 12 h. The microstructure and properties of the alloy with single and double aging were analyzed by means of hardness measurement, optical microscopy, scanning electron microscopy, X-ray diffraction, and polarization curve measurements. Results show that the precipitated nanoscale phases are formed during aging, and evenly distributed in the matrix. Compared with the single aging treatment, the hardness and corrosion resistance of the alloy are further improved due to the double aging treatment.

Quasicrystal dissolution and performance of isothermally heat-treated Mg–Zn–Y alloy

Conventional casting method was employed to prepare Mg–Zn–Y alloy only with a-Mg+I-phase; however, the grain size of quasicrystal is quite large in the ascast state.Therefore, isothermal treatment was applied to refine the quasicrystal phase.The result shows that after the Mg–Zn–Y alloy was isothermally treated at 500 °C for several hours, the coarse quasicrystal can be gradually dissolved and thus refined.Generally, the dissolving processes of quasicrystal are slow first and then accelerate;after isothermally treated with 8 h at 500 °C, the quasicrystal is almost completely dissolved into the matrix only with 1–5 lm tiny quasicrystals remained.Refinement of quasicrystal can markedly reduce the wear resistance, but increase the corrosion resistance.

Stirred casting Al–Pb monotectic alloys with high damping capacity

In this study, the stirred casting with various processing parameters, such as stirring temperature and stirring speeds, was carried out on the Al–Pb monotectic alloys in order to make Pb particles distribute much more uniformly. More importantly, their damping capacities were systematically studied. The results show tha mechanical stirring can not only make Pb in the aluminum matrix uniformly distribute but also dynamically influence the damping capacity of this alloy system. The Al–Pb alloy was prepared under a slow speed at solid–liquid temperature region, wherein high volume fraction of Pb in alloy could be obtained. The high volume fraction of Pb gives high overall damping capacity. The dislocation damping and interface damping theories are mainly dominated to the alloys.

Phase selection and performance of Mg–Cu–Y amorphous composite with different Mg/Cu ratios

In this article, Mg-Cu-Y alloys with two dif- ferent Mg/Cu ratios （in at%） were prepared using a water- cooled copper mold. Scanning electron microscopy and X-ray diffraction were applied to analyze the microstructure and phase composition. Moreover, corrosion resistance and wear resistance were studied systematically. The results show that both Mg65Cu25Ylo and Mg60Cu30Ylo alloys could form a composition of crystalline and amorphous phases. Although the microstructure of Mg65Cu25Ylo con- sists of an amorphous phase and ：t-Mg, Mg2Cu, and Cu2Y crystalline phases, the microstructure of Mg60Cu30Ylo alloy mainly consists of the amorphous phase and ：t-Mg, Mg2Cu. With reducing Mg/Cu ratio, the alloys have better corrosion resistance and wear resistance. The mechanism has also been discussed in detail.