Aging precipitation characteristics and tensile properties of Al-Zn-Mg-Cu alloys with different additional Zn contents

The increase in zinc content in Al-Zn-Mg-Cu alloys provides an effective method to enhance the strength.Transmission electron microscopy(TEM)and tensile test were employed to analyze the microstructure and tensile properties,respectively,of Al-9.3 Zn-2.0 Mg-1.8 Cu alloy(9.3 Zn alloy)and Al-9.8 Zn-2.0 Mg-1.8 Cu alloy(9.8 Zn alloy)with single-and double-stage aging states.The results showed that the two alloys possessed a closed strength under single-stage peak-aging treatment.As for double-stage aging treatment,9.8 Zn alloy had a higher strength values than 9.3 Zn alloy under the same aging regimes.With the second step aging time prolonging,the strength gap was extended.The main precipitates for the two alloys with single-stage peak-aging state were GP zones andη’phase,while there were a majority ofη’phases andηphases for the two alloys under typical double-stage over-aging state.Under double-stage overaging state,the proportion of precipitate with large size for9.3 Zn alloy was larger than that for 9.8 Zn alloy.Besides,a more obvious trend was revealed for the double-stage overaging state.The gap of strength between the two alloys was explained by the difference of precipitation characteristics via interaction mechanism between precipitates and dislocations.

Microstructure evolution and mechanical properties of Mg-x%Zn-1%Mn(x=4,5,6,7,8,9) wrought magnesium alloys

The roles of Zn content and thermo-mechanical treatment in affecting microstructures and mechanical properties of Mg-x%Zn-1%Mn（mass fraction,x=4,5,6,7,8,9） wrought Mg alloys were investigated.The microstructure was extremely refined by dynamic recrystallization（DRC） during extrusion.With increasing Zn content,the DRC grains tended to grow up,at the same time,more second phase streamlines would be present,which restricted the further growing.During solution treatment,the DRC grains would rapidly grow up;however,higher Zn content could hinder the grain boundary expanding,which results in finer ultimate grains.MgZn2 dispersoid particles which are coherent with the matrix would precipitate from the supersaturated solid solution during the one-step aging process,and nano-sized GP zones formed during the pre-aging stage of the two-step aging provide a huge amount of effective nuclei for the MgZn2 phases formed in the second stage,which makes the MgZn2 particles much finer and more dispersed.The mechanical properties of as-extruded samples were not so sensitive to the variation of Zn content,the tensile strength fluctuates between 300 and 320 MPa,and the elongation maintains a high value between 11% and 14%.The strength of aged samples rises as a parabolic curve with increasing Zn content,specifically,the tensile strength of one-step aged samples rises from 278 to 374 MPa,and that of two-step aged ones rises from 284 to 378 MPa,yet the elongation of all aged samples is below 8%.When Zn content exceeds its solid solution limit in Mg-Zn system（6.2%,mass fraction）,the strength rises slowly but the elongation deteriorates sharply,so a Mg-Zn-Mn alloy with 6% Zn possesses the best mechanical properties,that is,the tensile strengths after one-and two-step aging are 352 and 366 MPa,respectively,and the corresponding elongations are 7.98% and 5.2%,respectively.

Correlations among stress corrosion cracking,grain-boundary microchemistry,and Zn content in high Zn-containing Al-Zn-Mg-Cu alloys

The correlations among the corrosion behaviour,grain-boundary microchemistry,and Zn content in Al-Zn-Mg-Cu alloys were studied using stress corrosion cracking(SCC)and intergranular corrosion(IGC)tests,combined with scanning electron microscopy(SEM)and high-angle angular dark field scanning transmission electron microscopy(HAADF-STEM)microstructural examinations.The results showed that the tensile strength enhancement of high Zn-containing Al-Zn-Mg-Cu alloys was mainly attributed to the high density nano-scale matrix precipitates.The SCC plateau velocity for the alloy with 11.0 wt.%Zn was about an order of magnitude greater than that of the alloy with 7.9 wt.%Zn,which was mainly associated with Zn enrichment in grain boundary precipitates and wide precipitates-free zones.The SCC mechanisms of different Zn-containing alloys were discussed based on fracture features,grain-boundary microchemistry,and electrochemical properties.

Determining the Zn Content of Cherry in Field Using VNIR Spectroscopy

Visible and near-infrared(VNIR)spectroscopy is an eco-friendly method used for estimating plant nutrient deficiencies.The aim of this study was to investigate the possibility of using VNIR method for estimating Zn content in cherry orchard leaves under field conditions.The study was conducted in 3different locations in Isparta region of Turkey.Fifteen cherry orchards containing normal and Zn deficient plants were chosen,and 60 leaf samples were collected from each location.The reflectance spectra of the leaves were measured with an ASD FieldSpec HandHeld spectroradiometer and a plant probe.The Zn contents of leaf samples were predicted through laboratory analysis.The spectral reflectance measurements were used to estimate the Zn levels using stepwise multiple linear regression analysis method.Prediction models were created using the highest coefficient of determination value.The results show that Zn content of cherry trees can be estimated using the VNIR spectroscopic method(87.5<r2<96.79).Moreover,plant nutrient contents can be estimated without using chemicals.However,further research is necessary to develop a standard method for field conditions.Because spectral reflectance is affected by ecological conditions,agricultural applications and nutrient interactions,more effective models must be developed depending on the geographical location,period and plant type.

Zn content mediated fibrinogen adsorption on biodegradable Mg-Zn alloys surfaces

The protein adsorption has an immense influence on the biocompatibility of biodegradable Mg alloy.In this work,the effect of Zn content on the fibrinogen(Fg)adsorption behavior in Mg-Zn binary alloy was systematically investigated.Experimental results showed that the Fg adsorption amount increased at first and then decreased with the increase of Zn content.The adsorption mechanism was investigated by molecular dynamic and density functional theory simulations.The simulations results showed that Zn with low content existed in the inner layer of Mg alloys due to the lower system energy,which promoted Fg adsorption and the promotion effect was more obvious with the increase of Zn content.When Zn content increased to a higher concentration,parts of Zn atoms started to precipitate in the surface,and the Fg-surface interaction energy started to increase.Moreover,the Zn sites favored the formation of ordered water molecules layers,which inhibit the stable adsorptions of Fg.The inhibition effects of Fg adsorption was enhanced with the Zn content increase.In short,the simulation results explain the experimental phenomena and reveal the microscopic mechanism.This study would provide a significant guidance on the design of biodegradable Mg-Zn alloys.

RESEARCHES ON RELATIONSHIP BETWEEN HEARING LOSS AND CONTENT OF Fe AND Zn IN PERILYMPH，CSF，SERUM，AND HAIRS

Fe and Zn levels in perilymph in guinea pigs injected with gentamicin(GM)were examined in this experlment,and those leves were compared with their correspondents in CSF,serum andhairs.Preventive and therapeutic actions of seabuckthorn oil and injective gastrodini to hearing losswe observed.The results showed:①Fe content in perilymph and hair in GM ototxic guinea Pigswas increased,and was decreased after prevention and treating. There was no obvious change in CSFand serum.②Zn content in perilymph was increased in GM ototoxic guinea pigs,and was furtherincreased after prevention.Zn contents in serum and hairs were significantly decreased.The resultssuggest that GM ototoxic reaction is related to increasing Fe contents,and elevation ot Zn content isrelated to the compensative reaction of the body.The cjamges of chemical elements in perilymph aremore important than those in CSF,serum and hairs for pathologic changes in the cochlea,seabuckthorn oil can prevent GM ototoxic reaction.

Effects of zinc content on strength and wear performance of Al-12Si-3Cu based alloy

The effects of Zn content on strength and wear performance of Al-12Si-3 Cu alloy synthesized by gravity casting were systematically investigated.The microstructure and mechanical properties of the alloys were evaluated using OM,XRD,SEM as well as hardness,tension,compression and Charpy impact tests.Their dry sliding wear tests were carried out with a ball-on-disk tester.Microscopic examinations revealed that the microstructure of the base alloy consisted of theα(Al)dendrites,needle-type and coarse Si particles,and CuAl2(θ)phase.The addition of Zn to this alloy resulted in the formation ofα-solid solution phase and the increase of coarse Si particles.The hardness,yield,tensile and compressive strengths,elongation to fracture and impact toughness of the Al-12Si-3 Cu-Zn alloys increased with increasing Zn content,but tendency in the tensile and compressive strengths and ductility reversed after adding 1.5%-2%Zn.In addition,the friction coefficient and volume loss of the Al-12Si-3 Cu-Zn alloys decreased with increasing Zn content.The study showed that the addition of Zn to Al-12Si-3 Cu alloy can improve its potential applications as tribological material.

Influence of Zn Content on Microstructure and Tensile Properties of Mg–Zn–Y–Nd Alloy

In the present study,the effect of Zn content on the microstructure and deformation behavior of the as-cast Mg-Zn-Y-Nd alloy has been investigated.The results showed that as Zn content increased,the volume fraction of secondary phases increased.Moreover,the phase transformation from W-phase to W-phase and I-phase occurred.In the as-cast state,W-phase exists as eutectic and large block form.When Zn content increases to 6 and 8%（wt%）,small I-phase could precipitate around W-phase particles.Additionally,the effect of Zn content on the tensile properties and deformation behavior varies with the testing temperature.At room temperature,the tensile strength increases with Zn content,whereas the elongation increases initially and then decreases.At 250℃,as Zn content increases,the tensile strength decreases initially and then increases slightly,whereas the elongation decreases.At 350℃,the elongation increases with Zn content,whereas the tensile strength decreases initially and then increases slightly.