稀土微合金化对Cu-2Ag合金铸态组织和性能的影响

采用真空感应熔炼法制备了稀土微合金化Cu-2Ag合金铸锭,通过显微组织观察、选区成分分析、维氏硬度和导电性能测试,研究了稀土Y和La微合金化对Cu-2Ag合金铸态组织和性能的影响及其机制。结果表明,在Cu-2Ag合金铸锭中添加稀土Y或La,可以显著细化铸锭晶粒,大幅减少柱状晶比例,增加等轴晶比例,抑制铸锭中富银相在晶界处偏聚,同时促进富银相在晶内、晶界呈球状均匀析出,从而改善铸锭中富银相的形貌和分布状态。与Cu-2Ag合金铸锭相比,Cu-2Ag-0.075Y和Cu-2Ag-0.075La合金铸锭的硬度和导电率分别提高了4.43%和4.72%,同时铸锭的性能分布更加均匀。

Ag掺杂Mo-12Si-8.5B合金在25~600℃的摩擦学行为

本文中采用放电等离子烧结法制备了Mo-12Si-8.5B和Mo-12Si-8.5B-10%Ag这2种合金,通过高温真空摩擦磨损试验仪测试了2种合金与Al_(2)O_(3)摩擦副在25~600℃间的干摩擦学性能.结果表明:与Mo-12Si-8.5B合金相比,在25~600℃区间Mo-12Si-8.5B-10%Ag合金表现出更低的摩擦系数和磨损率.在600℃时,Mo-12Si-8.5B-10%Ag合金的摩擦系数和磨损率均可达到最小值,其值分别为0.41和1.14×10^(-5)mm^(3)/(N·m),此时Mo-12Si-8.5B-10%Ag合金的干摩擦性能表现最佳,这与Mo-12Si-8.5B-10%Ag合金磨损表面的MoO_(3)、SiO_(2)和Ag_(2)MoO_(4)等润滑相的存在及Ag在25~600℃范围内起到的润滑效果有关.此外,在25~200℃区间,Mo-12Si-8.5B-10%Ag合金的磨损机制主要为黏着磨损和剥层磨损,在400~600℃范围内,则以黏着磨损和氧化磨损为主.

Effects of stabilizing heat treatment on microstructures and creep behavior of Zn-10Al-2Cu-0.02Ti alloy

The microstructures of as-extruded and stabilizing heat-treated Zn-10Al-2Cu-0.02Ti alloys were observed by scanning electron microscopy,transmission electron microscopy,electron probe microanalysis and X-ray diffraction analysis techniques.The change in structure after heat treatment and its effects on room temperature creep behavior were investigated by creep experiments at constant stress and slow strain rate tensile tests.The results show that after stabilizing heat treatment（（350℃,30 min,water-cooling）＋（100℃,12 h,air-cooling））,the amount of α＋η lamellar structure decreases,while the amount of cellular and granular structure increases.The heat-treated Zn-10Al-2Cu-0.02Ti alloy exhibits better creep resistance than the as-extruded alloy,and the rate of steady state creep decreases by 96.9% after stabilizing heat treatment.

Influence of Li addition on mechanical property and aging precipitation behavior of A1-3.5Cu-1.5Mg alloy

The influence of Li addition on mechanical property and aging precipitation behavior of Al-3.5Cu-1.5Mg alloy was investigated by tensile test,scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and high resolution transmission electron microscopy（HRTEM）.The results show that the tensile strength can be significantly improved with the slightly decreased ductility and the form of fracture morphology is converted from ductile fracture into ductile/britde mixed fracture by adding 1.0%Li.Besides,the peak aging time at 185 ℃ is delayed from 12 to 24 h and the main precipitation phase S（Al2CuMg） is converted into S＇（Al2CuMg）＋δ（Al3Li）,while the formation of S＇（Al2CuMg） is delayed.

稀土钇微合金化对Cu-2Ag合金铸锭成分和热加工性能的影响

采用电感耦合等离子体原子发射光谱仪(ICP-AES)、氧分析仪、扫描电子显微镜(SEM)、差示扫描量热分析(DSC)和热锻试验,研究稀土钇微合金化对Cu-2Ag合金铸锭成分和热加工性能的影响。结果表明:与Cu-2Ag合金铸坯相比,Cu-2Ag-0.075Y铸坯中O、S、P和Zn等杂质元素含量明显降低,Bi、As和Sb的含量也有不同程度的降低;稀土钇微合金化可以显著提升Cu-2Ag合金铸锭成分的洁净度;受稀土钇微合金化的影响,Cu-2Ag-0.075Y合金铸坯在850℃温度以上时,热加工性能发生显著变化,表现为塑性差、呈热脆性,锻后开裂,甚至碎成渣。

Age-hardening behavior and microstructure of Cu-15Ni-8Sn-0.3Nb alloy prepared by powder metallurgy and hot extrusion

Cu-15Ni-8Sn-0.3Nb alloy rods were prepared by means of powder metallurgy followed by hot extrusion.Element maps obtained by electron probe micro analyzer(EPMA)showed that Nb-rich phases were formed and distributed within grains and at grain boundaries of the Cu-15Ni-8Sn-0.3Nb alloy.Transmission electron microscope(TEM)results indicated that there was no obvious orientation relationship between these phases and the matrix.Spinodal decomposition and ordering transformation appeared at early stages of aging at400°C and caused significant strengthening.Cu-15Ni-8Sn-0.3Nb alloy exhibited both higher strength(ultimate tensile strength>1030MPa)and higher tensile ductility(elongation>9.1%)than Cu-15Ni-8Sn alloy after aging treatment.The improvement was caused by Nb-rich phases at grain boundaries which led o the refinement of grain size and postponed the growth of discontinuous precipitates during aging.

Effect of non-isothermal retrogression and re-ageing on through-thickness homogeneity of microstructure and properties of Al-8Zn-2Mg-2Cu alloy thick plate

In order to improve the through-thickness homogeneity and properties of aviation aluminum alloy thick plate.The effect of heating-cooling retrogression and re-ageing on the performance of Al-8Zn-2Mg-2Cu alloy thick plate was investigated by hardness tests, electrical conductivity tests and transmission electron microscopy(TEM) observation.Results revealed that, during retrogression heating, the fine pre-precipitates in surface layer dissolve more and the undissolved η′ or η phases are more coarsened than that of center layer. During slow cooling after retrogression,precipitates continue coarsening but with a lower rate and the secondary precipitation occurs in both layers. Finer precipitates resulting from the secondary precipitation are more in surface. However, the coarsening and secondary precipitation behaviors are restrained in both layers under quick cooling condition. The electrical conductivity and through-thickness homogeneity of precipitates increases while the hardness decreases with cooling rate decreasing. After the optimized non-isothermal retrogression and re-ageing(NRRA) including air-cooling retrogression, the throughthickness homogeneity which is evaluated by integrated retrogression effects has been improved to 94%. The tensile strength, fracture toughness and exfoliation corrosion grade of Al-8Zn-2Mg-2Cu alloy plate is 619 MPa, 24.7 MPa·m^(1/2)and EB, respectively, which indicates that the non-isothermal retrogression and re-aging(NRRA) could improve the mechanical properties and corrosion resistance with higher through-thickness homogeneity.

Effect of ageing temperature on precipitation of A1-Cu-Li-Mn-Zr alloy

The precipitation behaviors of an A1-Cu-Li-Mn-Zr alloy at different ageing temperatures （120, 160 and 200 ~C） were investigated using Vickers hardness measurements and transmission electron microscopy （TEM） characterization. Age hardening curves show an increase in precipitation kinetics with increasing ageing temperature. The results of TEM show that for the samples peak aged at 120 ~C, the amount of g＇ （A13Li）, GP zones/0＇ （A12Cu） and Z （A15Cu6Li2） phases is obviously higher than that of T1 （A12CuLi） precipitates; while the samples peak aged at 160 and 200 ~C are usually dominated by T1 phase with a minor fraction of GP zones/0＇ and g＇, and the Z phase almost does not form. In addition, quantitative analysis on the T1 platelets demonstrates that the samples peak aged at 200 ~C have larger plate diameter and smaller area fraction of T1, as compared to the samples peak aged at 160 ~C. Correspondingly, the possible reasons for such phenomena are discussed.

Ageing behavior of Cu-15Ni-8Sn alloy prepared by mechanical alloying

The ageing behavior of the mechanically alloyed Cu-15Ni-8Sn alloy has been studied. Compared with the alloys prepared by casting and rapid solidification, the modulation structure developed during ageing process of those prepared by mechanical alloying is finer and much more uniform, which leads to a higher peak hardness. However, their spinodal decomposition temperature are almost the same. Cold deformation prior to ageing not only accelerates the ageing process but also increases the peak hardness of the alloy.

Optimal Selection and Control for Precipitation of α_2 Phase in Near α High Temperature Ti Alloys during Aging Treatment

The characteristic of the precipitation and growth of α2 ordered phase during aging treatment in near α Ti alloys have been investigated in terms of the influences of aging temperature, aging time and aging manner. The results exhibit that aging temperatures influence the distribution of α2 phase precipitated and cause the changes in growth speed of α2 phase. For various aging temperatures, the time to finish precipitation of α2 phase is different. The facts that various distribution characteristics and growth speed of α2 ordered phase are caused by changed aging condition imply optimal selection and control for precipitation of α2 ordered phase reachable. Some discussions on adoptable aging steps are presented.

Finite element analysis of stress-strain localization and distribution in Al-4.5Cu-2Mg alloy

Finite element analysis has been carried out to understand the effect of various processing routes and condition on the microscale deformation behavior of Al–4.5 Cu–2 Mg alloy. The alloy has been developed through four different routes and condition, i.e. conventional gravity casting with and without refiner, rheocasting and SIMA process. The optical microstructures of the alloy have been used to develop representative volume elements（RVEs）. Two different boundary conditions have been employed to simulate the deformation behavior of the alloy under uniaxial loading. Finally, the simulated stress-strain behavior of the alloy is compared with the experimental result. It is found that the microstructural morphology has a significant impact on stress and strain distribution and load carrying capacity. The eutectic phase always carries a higher load than the α（Al） phase. The globular α（Al） grains with thinner and uniformly distributed eutectic network provide a better stress and strain distribution. Owing to this, SIMA processed alloy has better stress and strain distribution than other processes. Finally, the simulated yield strength of the alloy is verified by experiment and they have great agreement.

MICROSTRUCTURE OF MARTENSITE IN Cu-14Al-4Ni ALLOY AGED FOR A PROLONGED TIME AT ROOM TEMPERATURE

The microstrueture in shape memory alloy Cu—14Al—4Ni aged for two years at room temper- ature has been studied,and the substructure slow change has been observed.The domains of highly ordered phase and the transition regions appear at grain boundaries,the twin bounda- ries damage.Furthermore,the microstructure also gives the appearance and growth of antiphase domains like rectangular network.The long period antiphuse boundary structures and the antiphase domains have bee.observed first at the single diffracted vector .The con- centration gradient of solute atom Al has heen found from the matrixes to the grain bounda- ries,the matrixe is poor in Al and the grain boundaries are rich in Al.

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.

Influence of surface finish and annealing treatment on oxidation behavior of Ti-48Al-8Cr-2Ag alloy

The effect of surface finish and annealing treatment on the oxidation behavior of Ti-48Al-8Cr-2Ag (molar fraction, %) alloy was investigated at 900 and 1 000 ℃, respectively in air. Thermal gravimetric analysis (TGA) was conducted for the characterization of oxidation kinetics. The microstructures of oxide scales were studied by scanning electron microscopy (SEM) and transmission election microscopy (TEM) techniques. Unfavorable effect of the annealing treatment on the oxidation behavior of the coating was also investigated. The results indicate that the oxidation behavior of the alloy is influenced by surface finish and annealing treatment. The oxidation rate of ground sample is lower than that of the polished alloy at 1 000 ℃ in air. The former forms a scale of merely Al2O3, and the latter forms a scale of the mixture of Al2O3 and TiO2. Annealing can improve the formation of TiO2.

Effect of age condition on fatigue properties of 2E12 aluminum alloy

The fatigue behaviors of 2E12 aluminum alloy in T3 and T6 conditions at room temperature in air were investigated.The microstructures and fatigue fracture surfaces of the alloy were examined by transmission electron microscopy(TEM) and scanning electron microscopy(SEM).The results show that the alloy exhibits higher fatigue crack propagation(FCP) resistance in T3 condition than in T6 condition,the fatigue life is increased by 54% and the fatigue crack growth rate(FCGR) decreases significantly.The fatigue fractures of the alloy in T3 and T6 conditions are transgranular.But in T3 condition,secondary cracks occur and fatigue striations are not clear.In T6 condition,ductile fatigue striations are observed.The effect of aging conditions on fatigue behaviors is explained in terms of the slip planarity of dislocations and the cyclic slip reversibility.

固溶-时效过程中微量Er和Zr添加对6082铝合金力学性能的影响

微量Er和Zr添加是提升6系铝合金力学性能的有效途径,然而微量Er和Zr添加后固溶时效工艺对力学性能的影响机制研究仍不充分。本文研究通过硬度和拉伸性能测试等方法,综合分析固溶-时效过程中添加微量Er和Zr(0、0.1Er+0.1Zr(%)和0.2Er+0.2Zr(%))对6082铝合金力学性能的影响。结果表明,添加Er和Zr对不同固溶温度(530、540、550、560℃)下6082铝合金硬度变化趋势影响较小,较优固溶工艺为540℃×0.5 h。在170℃时效过程中(0~12 h),添加Er和Zr后的Er+Zr/6082铝合金布氏硬度均在8 h时达到峰值,相比于6082铝合金峰时效时间提前2 h。Er和Zr添加降低Mg2Si相的热力学形核能,加快了时效期间Mg2Si相生长和演变过程。

Microstructure and mechanical properties of Mg_(94)Zn_2Y_4 extruded alloy with long-period stacking ordered structure

The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO structure and α-Mg phase are observed in cast Mg94Zn2Y4 alloy. After extrusion, the LPSO structures are delaminated and Mg-slices with width of 50-200 nm are generated. By ageing at 498 K for 36 h, the ageing peak is attained andβ′phase is precipitated. Due to this novel precipitation, the microhardness ofα-Mg matrix increases apparently from HV108.9 to HV129.7. While the microhardness for LPSO structure is stabilized at about HV145. TEM observations and SAED patterns indicate that the β′ phase has unique orientation relationships betweenα-Mg and LPSO structures, the direction in the close-packed planes ofβ′precipitates perpendicular to that ofα-Mg and LPSO structures. The ultimate tensile strength for the peak-aged alloy achieves 410.7 MPa and the significant strength originates from the coexistence ofβ′precipitates and 18R-LPSO structures.

合金元素对Ag/SnO_(2)材料制备初期组织演变的影响

Ag/SnO_(2)电接触材料具有良好的耐电弧侵蚀和抗材料转移性能,广泛应用于低压断路器和继电器中。然而,其制备初期组织和物理性能对产品铆钉的电性能有着最直接和极为重要的影响。采用X射线衍射分析仪(XRD)、场发射扫描电镜(SEM)和电子探针显微分析仪(EPMA)等手段,分析合金元素Sb、La和In对Ag/SnO_(2)材料制备初期组织演变和物理性能的影响。结果表明:添加Sb、La和In的Ag/SnO_(2)烧结坯中除了含Ag和SnO_(2)相外,还分别含有AgSbO3、La2Sn2O7和2In2O3∙3SnO_(2)相。添加Sb的Ag/SnO_(2)烧结坯中氧化物主要在粉末边界上呈网络状分布;添加La的Ag/SnO_(2)烧结坯中氧化物颗粒细小,且均匀弥散分布;添加In的Ag/SnO_(2)烧结坯中氧化物呈块状分布,且存在纯银层。添加In的Ag/SnO_(2)材料的电导率和硬度最高,添加Sb的Ag/SnO_(2)材料的相对密度最大。

多酸/Ag-Cu合金纳米粒子/TiO_(2)三元复合膜电极的制备及光电性能的研究

本文将Ag-Cu合金纳米粒子、Dawson型结构多酸K_(6)[P_(2)W_(18)O_(62)]·14H_(2)O(简写为P_(2)W_(18))同时引入到TiO_(2)薄膜体系中,采用交替沉积自组装法成功制备了P_(2)W_(18)/Ag-Cu/TiO_(2)三元复合膜电极,并通过光电流-时间曲线和光电流-光电压曲线等测试考察了复合膜电极的光电性能。实验结果表明,P_(2)W_(18)/Ag-Cu/TiO_(2)复合膜电极相较于TiO_(2)电极、Ag-Cu/TiO_(2)电极和P_(2)W_(18)/TiO_(2)电极具有更高的光电流响应和光电转换效率。同时,P_(2)W_(18)/Ag-Cu/TiO_(2)三元复合膜电极还展现出更好的对生物小分子乳酸的光电催化活性。

Effects of RRA Treatments on Microstructures and Properties of a New High-strength Aluminum-Lithium Alloy-2A97

A new high strength 2A97 Al-Cu-Li-X alloy was subjected to triple-aging of retrogression and re-aging treatments （RRA）. Transmission electron microscopy （TEM）, differential scanning calorimetry （DSC）, and tensile tests were used to investigate the effects of RRA treatment on the microstructures and properties. DSC test reveals the reversion temperature range of the strengthening δ＇ （Al3Li） phase. The results show that the microstructure consists of δ＇ （Al3Li） phase, T1 （Al2CuLi） phase and θ″/θ′（Al2Cu） phase for 2A97 alloy treated by a triple-aging of a retrogression and re-aging treatment in the following order： （1） at 165℃×30 min, （2） at 220 ℃ or 240℃ × 15 min, （3） at 165℃×24 h. The plastic deformation, incorporated into the treatment after secondary high temperature aging, promotes the T1 precipitation during final re-aging. The tensile properties of the alloy treated by the retrogression and re-aging treatment reach the peak level of alloy single-aged at 165℃ in T6 temper.