Ameliorating mechanical properties and reducing anisotropy of as-extruded Mg-1.0Sn-0.5Ca alloy via Al addition

Effects of Al addition to a Mg–Sn–Ca ternary alloy on its microstructure and tensile properties after extrusion were studied via extrusion of Mg-1.0 Sn-0.5 Ca-x Al(x = 0, 0.8, 2.4 wt%) sheets and analysis of the extruded materials.The results showed that Al addition not only refined the grain size(from 9.8 ± 0.7 μm to 8.3 ± 0.4 μm and7.6 ± 0.5 μm) but also accelerated the generation of more second phase(from 0.98 to 1.72 and 4.32%). Except for the CaMgSn and Mg₂Ca in Mg-1.0Sn-0.5 Ca a...     

超细氧化物颗粒对Sn\|58Bi钎料组织及性能影响

研究了分别添加1%Al2 O3 、Fe2 O3 、SiO2 、TiO2 超细粉末对Sn-58Bi共晶钎料的润湿性、钎焊接头微观组织及力学性能影响.结果表明,氧化物粉末的添加对钎料熔点影响不大,但钎料润湿性及钎焊接头剪切强度明显提高;明显细化钎焊接头基体组织及界面金属间化合物颗粒大小,并且界面金属间化合物层厚度也有一定减薄;另外,可抑制钎焊时焊点表面Bi的氧化,因此焊点表面光亮度也有明显提高.     

微量Nd对Sn-9Zn钎料特性及焊点组织与性能的影响

研究Sn-9Zn中添加微量稀土元素Nd对合金显微组织和铺展性能的影响,对比分析Sn-9Zn-xNd(x=0,0.1,0.5)钎料/Cu焊点界面微观特征及力学性能。结果表明:微量Nd元素在Sn-9Zn合金中能够显著细化组织,但添加量为0.5%时合金中形成了"十字状"NdSn3金属间化合物(IMC)。钎焊温度较低或时间较短时,微量Nd添加能够改善Sn-9Zn合金在Cu基板上的铺展性能;但是在温度较高或时间较长的钎焊工艺条件下,由于Nd元素的严重氧化导致钎料铺展性能明显下降。在Sn-9Zn中添加0.1%Nd,在界面处形成了均匀细密分布的"毛绒状"共晶组织,能够提高焊点结合性能;Nd添加量为0.5%时,成分偏聚引起的组织不均匀导致焊点力学性能下降。     

银合金和锡磷青铜合金复合材料界面结合强度的研究

本文报导了银合金和锡磷青铜合金的复合材料界面结合强度的研究结果:界面的断裂强度不低于银合金的断裂强度,并用Seah的准化学方法计算了复合界面断裂强度,结果表明,界面断裂强度为447.1MN/m~2,略高于银合金的断裂强度,与试验结果一致。     

Effect of micro-alloying Ca on microstructure,texture and mechanical properties of Mg-Zn-Y-Ce alloys

Microstructure,texture and mechanical properties of Mg-5 Zn-0.3 Y-0.2 Ce alloys with the addition of trace xCa(x=0,0.3,0.6 wt%) were systematically investigated in this work.The results revealed that more secondary eutectic phases and smaller grain size of as-cast microstructure could be found with increasing Ca content.After hot extrusion,the Ca-free alloy showed a uniformly recrystallized grain structure,while the Ca-containing alloys possessed a bimodal grain structure composed of fine dynamic recrystallized(DRXed) grains with a size of several microns and un-recrystallized coarse grains.EBSD analysis showed that the three extruded alloys had a fiber texture of(0001) basal plane aligned with the extrusion direction.Texture intensity of the DRXed region was weaker than the deformed region.The extruded alloy with the addition of 0.6 wt% Ca exhibited the highest yield strength of 321 MPa due to the smallest DRXed grain size,the deformed region with strong basal texture and dense nanosized precipitates.     

Influence of Mo and Ta additions on solidification behavior of Ni3Al single crystal alloys

Ni3Al(Ni75Al25) and Ni3Al–2Mo/Ta(Ni73.5Al24.5Mo/Ta2) single crystals were prepared by the Bridgman method under high temperature gradient(~170℃/cm) at the withdrawal rates of 5 and 20 μm/s. The experimental results showed that the addition of Mo decreased the liquidus and solidus temperatures, and the addition of Ta increased the liquidus and solidus temperatures. Meanwhile, both Mo and Ta additions were found to increase the solidi fi cation range of experimental alloy. It has been found that for solidi fi cation of stoichiometric Ni3Al at low withdrawal rate(5 μm/s), β/γ'eutectic first solidi fied from liquid(L→β+γ') and then β phase completely transformed into pure γ'(β→γ') after the completion of solidi fi cation. However, at high withdrawal rate of 20 μm/s, the remaining β phase was found in the as-cast microstructure of Alloy Ni3Al. Different from stoichiometric Ni3Al, the solidi fi cation sequence of Alloy Ni3Al–2Mo was identi fi ed as L→β+γ'+Mo-rich phase(ternary eutectic reaction). In addition, the addition of Ta led to the formation of primary γ'phase and then subsequent intercellular/interdendritic β/γ'eutectic microstructure. Based on above study, a new Ta and Mo containing Ni3Al based single crystal alloy with superior tensile strength at ultra-high temperature(1100℃) was designed.     

液态Cu-Ni合金的超过冷与热力学性质

采用熔融玻璃净化法得到质量分数为 Cu- 2 5 % Ni,Cu- 33% Ni,Cu- 5 0 % Ni,Cu- 75 % Ni等 4种铜镍系合金的过冷度与凝固平台的关系。通过传热学分析指出凝固平台时间长度与过冷度成线性关系。在此基础上得到了这 4种成分合金的超过冷临界温度及其熔点以下液态的平均比热容。实验中 4种合金的过冷度分别达到 :381K,380 K,349K和431K。     

High temperature tensile properties,fracture behaviors and nanoscale precipitate variation of an Al-Zn-Mg-Cu alloy

In order to assess Al-Zn-Mg-Cu alloys as potential high temperature structural materials,the hardness,tensile properties and fracture behaviors of 7085 Al alloy were investigated at various temperatures from room temperature to 175℃.High-resolution transmission electron microscopy was used to investigate the evolutions of precipitates at different temperatures,particularly on the relationship between microstructural evolution and tensile strength.The results reveal that both the microstructure and mechanical properties of the alloy are quite sensitive to the environmental temperature.As the temperature increases,the hardness and strength decrease while the elongation and reduction of area increase.As tensile testing temperature rises,the strain hardening exponent(n) decreases due to the thermal softening effect.The fracture mode of the alloy transforms from mixture of intergranular and transgranular fracture to completely transgranular dimples when tensile testing temperature reaches 150℃.The precipitate sequence during high temperature tests is coincident with that of aging.With the increase of tensile testing temperature,the mean precipitate radius grows larger,and the distribution of grain boundary precipitates transforms from continuous to discontinuous.     

Combined effect of pre-aging and Ag/Cu addition on the natural aging andbake hardening in Al-Mg-Si alloys

The combined effect of pre-aging and Ag/Cu addition on natural aging and bake hardening in Al-Mg-Si alloys were studied by Vickers microhardness measurement, tensile test, atom probe tomography and transmission electron microscopy. The results showed that Ag and/or Cu addition could further enhance the positive effect of pre-aging on bake hardening for Al-Mg-Si alloys. Although the pre-aged alloys with individual Ag/Cu addition had higher paint bake hardness, the hardness in T4 P temper was relatively high due to effectively forming of Cluster(2) during pre-aging. While the pre-aged Ag-Cu-added alloy had low T4 P temper hardness and higher bake hardening response. The strong interaction energies between Ag/Cu atoms and Mg atoms were responsible for the facilitated clustering and precipitation processes. After paint bake treatment, most of Ag atoms accumulated preferentially at β″/α-Al matrix interface, while Cu atoms entered into the interior of β″resulting in disordered structure within the precipitate.     

微波加热法所制Ag/Cu双金属纳米粒子的表征及其抗菌性能分析

以AgNO_3和Cu(CH_3COO)_2·H_2O为前驱体,PVP为分散剂,分别以乙醇和乙二醇为还原剂,采用微波加热法制备Ag/Cu双金属纳米粒子,利用XRD、TEM、XPS等技术对其进行表征,并分析反应温度、n(Ag~+)∶n(Cu~(2+))等因素对Ag/Cu双金属纳米粒子微观形貌及抗菌性能的影响。结果表明,以乙二醇为还原剂,当反应温度为169℃、n(Ag~+)∶n(Cu~(2+))为4∶1时,所制Ag/Cu双金属纳米粒子粒径小且分散均匀,粒子粒径在20~60nm范围内,并呈现出各种多面体结构,其对大肠杆菌具有良好的抗菌效果。     

Effect of trace Zn, P and Mg additions on microstructure and mechanical properties of Nb-Si-Ti alloys

The effects of Zn,P and Mg additions on the microstructure and mechanical properties of Nb-22Ti-3Si alloys were studied. The phases of Nbss and Nb_3Si presented in Nb-22Ti-3Si(AC1),Nb-22Ti-3Si-0.2Zn(AC2) and Nb-22Ti-3Si-0.2Mg alloys(AC3). The Nb-22Ti-3Si-0.2P(AC4) alloy consisted of Nbss,Nb_3Si network and eutectic cell of Nbss/α-Nb_5Si_3.By the addition of Zn,the Nb_3Si network was broken and the volume fraction of Nbss increased from 92%to 96%.The values of fracture toughness of the alloy AC2 at ambien...     

Cu/Ni多层膜的调制波长与力学性能的关系

为研究Cu/Ni多层膜的调制波长与力学性能的关系,采用计算机控制的单槽双脉冲控电位沉积系统,在Cu基体上沉积Cu/Ni多层膜,分别采用扫描电镜和纳米压痕技术对Cu/Ni多层膜的截面和硬度进行了测试.结果表明:电沉积方法制备的Cu/Ni多层膜具有良好的周期结构;在调制波长为37 nm时硬度达到极值;在调制波长小于37 nm时其硬度值明显下降.实验结果符合理论分析中多层膜的硬度随调制波长的变化规律,但临界调制波长大于理论计算结果.     

Ca,Si和RE对AZ91合金的组织和性能的影响

Ca,Si和RE合金化和复合合金化AZ91的研究结果表明：Ca单独加入合金中和Ca,Si或Ca,RE同时加入合金中都能明显改善AZ91合金的铸态组织，Si和RE在合金中以Mg2Si和Al11RE3颗粒相形式存在，而Ca则主要溶解于β-Mg17Al12中，未形成新相，DTA分析表明，Ca溶入Mg17Al12后提高了它的熔点，亦即提高了它的热稳定性，这一点对合金的高温性能十分有益，使合金的蠕变性能得到大幅提高，性能最好的是含0.3%（指质量分数，下同）的Ca和2％的RE的合金，它在200℃/50MPa下的蠕变速率相对于基体合金AZ91降低了一个数量级，单独加入Ca对铸态AZ91合金有脆化作用，但Ca,Si或Ca,RE复合加入则能大幅提高AZ91合金的室温和高温强度，同时保持了与AZ91基体合金相同的或更好的塑性。     

Influence of Cr content on the microstructure and mechanical properties of Cr_xFeNiCu high entropy alloys

The effect of Cr content on the microstructure and mechanical properties of Cr_xFeNiCu high entropy alloys(HEAs) was firstly studied by first-principles calculations.The calculated results show that the hardness of the alloys increased with the expense of its plasticity decrease,if the content of Cr in the alloy increased.In order to verify the calculated results,Cr_xFeNiCu(x=0.8,1,1.5 and 2) high entropy alloys were synthesized by vacuum induction melting in the present study.The results show that as the value of x increased from 0.8 to 2,the crystal structure changed from single phase face centered cubic(FCC) phase to a mixture of FCC and body centered cubic(BCC) phases.For the single phase FCC(x=0.8) structure,both the tensile strength and hardness values were low,which were 491.6 MPa and 322.2 HV respectively,however,the plasticity was high,reaching 33.2%.With the formation and growth of BCC phase(x=2) the tensile strength and hardness of the alloy were significantly improved,which were 872.6 MPa and 808 HV,respectively.     

Tuning microstructure,transformation behavior,mechanical/functional properties of Ti-V-Al shape memory alloy by doping quaternary rare earth Y

The microstructure features, martensitic transformation behavior and mechanical/functional properties of Ti–V–Al alloy were tailored by changing rare element Y content in the present investigation. The results showed that Y doping resulted in the grain refinement and formation of Y-rich phase mainly distributing along grain boundary in Ti–V–Al alloys. The martensitic transformation temperatures of Ti–V–Al alloys slightly increased due to the variation of matrix composition induced by the presenc...     

微量元素La,Sb,Ti和Mn对ZA27合金力学性能的影响

研究了微量元素La，Sb，Ti和Mn对ZA27合金力学性能的影响，四种元素分别单独加入。结果表明：在本实验条件下，四种元素加入适量时，均不同程度细化合金显微组织。La加入量在小于0.1%时，提高ZA27合金的抗拉强度，而对合金的延伸率影响不大，略有降低；Sb显著提高合金的抗拉强度，但降低延伸率；Ti加入后抗拉强度和延伸率均有提高；Mn在加入量为1%时，合金性能较好。     

Cu含量对AZ61镁合金显微组织和力学性能的影响

通过真空感应熔炼技术制备出不同Cu含量的AZ61镁合金,采用光学显微镜(OM)、X射线衍射(XRD)、差热分析(DSC)、扫描电镜(SEM)和能谱分析(EDS)等方法研究了Cu元素对合金组织和力学性能的影响。结果表明:Cu元素以三元AlCuMg相存在于合金中,主要分布在晶界处及枝晶间;添加Cu元素后能够细化合金铸态组织,并使β-Mg17Al12相数量减少、尺寸变细;随着Cu含量增加,挤压态合金强度先上升后下降,而延伸率只有当Cu含量达到1%时才开始显著下降。其中AZ61-1Cu具有最佳的综合力学性能,屈服强度、抗拉强度和延伸率分别为230 MPa、321 MPa和9.7%;当Cu含量为1.5%时,粗大的AlCuMg相割裂了合金基体,使合金力学性能下降。     

Effects of small additions of Zn on the microstructure,mechanical properties and corrosion resistance of WE43B Mg alloys

Zn is a commonly used alloying element for Mg alloys owing to its beneficial effects on mechanical properties. To improve the mechanical and corrosion properties of WE43B Mg alloys, the effects of 0-0.7wt% Zn addition on the microstructure and properties of sample alloys were investigated. Addition of Zn to as-cast WE43B alloy promoted the formation of the Mg₁₂Nd phase; by contrast, after T6 heat treatment, the phase composition of WE43B alloys with and without Zn addition remained mostly the same. A long-period stacking ordered phase was predicted by CALPHAD calculation, but this phase was not observed in either the as-cast or heat-treated Zn-containing WE43B alloys. The optimum temperature and duration of T6 heat treatment were obtained using CALPHAD calculations and hardness measurements. Addition of Zn resulted in a slight reduction in the average grain size of the as-cast and T6 heat-treated WE43B alloys and endowed them with increased corrosion resistance with little effect on their mechanical properties.     

Cu对WC-Fe/Co/Ni合金组织和性能的影响

研究了添加元素Cu及其含量对WC-Fe/Co/Ni合金组织和性能的影响。结果表明,当Cu添加较少时,合金的抗弯强度随Cu含量的增加而提高,当Cu含量增加到0.8％时,合金的抗弯强度出现极大值;继续增加Cu的含量,合金的抗弯强度又下降。并对组织结构进行了分析。     

Ni/Ti原子数比值对NiTiAlHf合金微观组织和力学性能的影响

采用扫描电镜、室温和高温压缩实验等方法研究了Ni/Ti值对Ni42+xTi50-xAl4Hf4(x=0～7)合金的微观组织和力学性能的影响.Ni42+xTi50-xAl4Hf4合金由NiTi基体和Ti2Ni相组成,随着Ni/Ti原子数比值的增加,Ti2Ni相的尺寸和数量急剧减少,析出强化效果减弱.室温时,随着Ni/Ti值的增加,NiTiAlHf合金的压缩屈服强度和显微硬度逐渐降低,塑性提高.高温下,当Ni/Ti<1时,Ti2Ni相的析出强化起主要作用,合金的屈服强度随Ni/Ti值增加而降低;当Ni/Ti>1时,Hf固溶强化作用的影响提高,并且Ti2Ni相趋于均匀弥散分布,使合金的屈服强度随Ni/Ti值增加而升高.在化学计量比(Ni/Ti=1)两侧,合金的屈服强度变化不对称.