铝及其合金熔体的增黏及泡沫化特性

研究了纯铝、普通铝硅合金和新型多组元铝合金的增黏和泡沫化特性．这三者加入Ca增黏后的物相组成和发泡后的气泡壁微观组织以及三者熔体的表面张力．结果表明：Ca加入后，经过搅拌形成的大量弥散分布的细小Al-Ca中间化合物颗粒快速增加了纯铝以及新型多组元铝合金熔体的黏度，而Ca加入普通铝硅合金中与Si等元素形成较大的颗粒，因而增黏效果不如前两者；Ca的加入也显著降低新型多组元铝合金和纯铝熔体的表面张力，普通铝硅合金降低不多；在相同的表观黏度下，表面张力的差异是引起纯铝．普通铝硅合金、新型多组元铝合金等三种熔体泡沫化特性差异的主要原因．     

铝合金熔体泡沫化过程中粘度的变化

用新型旋转扭矩探测仪对铝合金熔体增粘过程中的粘度进行了实时检测和控制,研究了熔体粘度的变化规律以及粘度对孔结构的影响规律.结果表明,在铝合金的增粘过程中粘度的变化与生长曲线类似;熔体的粘度过高使胞孔小、数量多;而粘度过低则相反.铝合金熔体泡沫化过程的最佳粘度值为27～28 mN·m,可以获得孔结构高度均匀、高比强的泡沫铝合金.     

球形孔通孔和闭孔泡沫铝合金的超声衰减性能

研究了球形孔通孔和闭孔泡沫铝合金在1 MHz～10 MHz的超声衰减性能.结果表明:泡沫铝合金的超声衰减性能决定于其孔结构;通孔泡沫铝合金的超声衰减系数α随着孔径d的减小、孔隙率Ps减小和比表面积Sv的增加而增大;闭孔泡沫铝合金的超声衰减系数α随孔径d的减小、孔隙率Ps的增加和比表面积Sv的增加而增大;当孔径d、孔隙率Ps相近时,闭孔泡沫铝合金的超声衰减性能优于通孔泡沫铝合金;在1 MHz～10 MHz二者是具有良好阻尼性能的轻质材料.其衰减机制为在弹性范围内超声应力波在具有大量孔隙界面的泡沫铝合金中的衰减.     

胞状铝(合金)的准静态压缩性能

测量了新型轻质(0.14ρ0 ~0.09ρ0,ρ0 为纯铝的密度)高强度胞状铝合金(ZL111)和胞状纯铝的压缩应力(σ) 应变(ε)曲线。胞状铝合金的压缩屈服强度σs比胞状纯铝高40%以上,其σε曲线呈锯齿状,平台斜度(dσdε)比后者小。提出了确定泡沫金属材料致密化起始点εD 的方法,为实际应用和科学研究提供了依据。     

ZrTi-V-Mn-Ni系贮氢合金的相结构与电化学性能研究*

优化合金组成,设计六种锆基AB2型贮氢合金材料。XRD分析表明,当0≤x≤0.5时,Zr1-xTix(NiCoMnV)2.1贮氢合金的主相都是Laves C15,但随Ti含量的增加,Laves C14相含量增多;当用V-Fe(85.6%)合金代替Zr0.6Ti0.4(NiCoMn-VFeCr)1.7中的V时,贮氢合金中Laves C14相的含量几乎可与Laves C15相当。电化学测试表明：Zr0.9Ti0.1(NiCoMnV)2.1贮氢电极的放电容量可达340mAh/g左右,但是随着Ti含量的逐渐增加,合金电极的放电容量降低很快。以适量的（V－Fe)合金取代Zr0.6Ti0.4(NiCoMnVFeCr)1.7合金中的V和Fe,发现合金电极的第一次放电容量就能达到200mAh/g左右,并且其容量稍高于含纯V的合金电极,容量可达315mAh/g左右。     

Influence of deformation process on microstructure and properties of 2014 aluminium alloy

The comparisons of forging-extrusion multistage hot deformation, forging and extrusion hot deformation processes on microstructure, mechanical property and impact toughness of 2014 Al alloy have been investigated. Results showed that the strength and impact toughness of the samples under forging-low extrusion multistage deformation process were significantly improved compared with that under forging deformation process due to the formation of smaller insoluble particles, finer grains and higher density of matrix precipitates. However, the strength and impact toughness of the samples under forging-extrusion multistage hot deformation process are lower than that under extrusion hot deformation process. The strengthening and fracture mechanisms with different deformation process have been discussed in detailed.     

泡沫铝合金异型件形成过程中的冶金结合

采用多块均匀分布过剩TiH2的球形孔泡沫铝合金作为坯料置于异型件模具中,用二次泡沫化方法制备出具有均匀孔结构的高孔隙率泡沫铝合金合金异型件,用光学显微镜和层析X射线成像仪(X-CT)观察异型件的冶金结合界面结构,并对异型件冶金结合界面的拉伸性能进行了实验研究,结果表明,采用二次发泡方法在发泡温度700-900℃、发泡时间250-800s条件下,可以实现泡沫铝合金的有效冶金结合;形成的异型件结合界面连接机制分为界面机械连接与界面扩散连接;泡沫铝合金异型件冶金结合面的抗拉强度随着孔隙率的升高而降低,泡沫铝合金异型件的孔隙率为74.9%时,结合界面处抗拉强度与泡沫铝合金的本体强度相当.     

TC18钛合金的组织和性能与热处理制度的关系

通过三因素三水平正交设计方法研究了两阶段退火热处理制度的三个温度阶段对TC18钛合金性能、组织的影响,定量分析了合金热处理温度变化对总体性能的影响,结果表明,在本文试验条件下可通过提高中温温度、降低低温温度来提高合金的强度,降低高温温度、提高低温温度可改善合金的塑性,通过降低高温温度或中温温度可提高合金的冲击韧性,显微组织分析表明,TC18钛合金的强度主要受未转变β组织及在其上产生的次生αs相的总的含量、次生αs相的含量、形状的控制;合金的塑性受初生αp相形状及次生αs相的数量、形状控制;合金的冲击韧性受初生αp相的含量及形状控制.     

The effect of different methods to add nitrogen to titanium alloys on the properties of titanium nitride clad layers

In this investigation, titanium nitride (TiN) reinforcements are synthesized in situ on the surface of Ti–6Al–4V substrates with gas tungsten arc welding (GTAW) process by different methods to add nitrogen, nitrogen gas or TiN powder, to titanium alloys. The results showed that if nitrogen gas was added to titanium alloys, the TiN phase would be formed. But if TiN powder was added to titanium alloys, TiN + TiN_x dual phases would be presented. The results of the dry sliding wear test revealed that the wear performance of the Ti–6Al–4V alloy specimen coated with TiN or TiN + TiN_x clad layers were much better than that of the pure Ti–6Al–4V alloy specimen. Furthermore, the evolution of the microstructure during cooling was elucidated and the relationship among the wear behavior of the clad layer, microstructures, and microhardness was determined.     

Effects of rare earth additions during surface boriding on microstructure and properties of titanium alloy TC21

Abstract

In the present paper, the effects of rare earth (RE) additions to the solid state boriding of titanium alloy TC21 have been studied. The microstructural evolution and phase transformations of the borided layers were examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. Moreover, the microhardness for the borided layer was also determined by Vickers hardness test. The results showed that the addition of a small amount of RE elements in the boriding process can lead to an increased boron concentration in the surface layer coupled with the improved surface hardness and coating layer thickness. Furthermore, the presence of trace quantities of RE oxide (Ce₂O₃) in boride layers indicated that the RE elements as catalysts could not only influence but also accelerate boriding process.     

金刚石/Al(或AlSi合金)复合材料性能衰退及抑制

采用气体压力浸渗法制备了金刚石/Al、金刚石/AlSi7和金刚石/AlSi9复合材料,对比研究了其暴露在空气中的性能衰退行为。研究表明,界面反应产物Al₄C₃会潮解生成Al（OH）₃,增大界面热阻,导致金刚石/Al复合材料性能衰退。Al基体中添加Si元素可以显著降低其性能衰退速率,其机制为:金刚石中C元素在Al液中溶解度的降低和Si在金刚石颗粒表面的优先析出,抑制了Al₄C₃的生成量;此外,金刚石/AlSi复合材料致密度的提高,对Al₄C₃与水汽的接触起到阻碍作用。讨论了抑制金刚石/Al复合材料性能衰退的几种可行方法,有望进一步提高其在潮湿环境中的使用寿命。      

TC8合金转子叶片锻造工艺研究

为研制一项TC8合金转子叶片,并达到提高锻造生产效率、降低生产成本的目的,进行了锻造工艺性试验、工艺参数试验,研究了TC8合金锻造工艺适应性以及加热温度、变形程度对低倍组织、显微组织及力学性能的影响.结果表明,TC8合金十分适合锻造工艺,采用较低的锻造加热温度能够获得初生α相含量更高的等轴组织,变形程度在40%以内所获得的组织均匀性较好.在此基础上,依据TC8合金转子叶片单榫头、小尺寸的结构特点,采用了高效的挤压制坯+终锻成形工艺,通过叶片锻造成形试验,试制出了具有均匀且状态理想的金相组织、良好表面质量的TC8合金转子叶片锻件,表明了所制定的叶片成形工艺及工艺参数合理可行.     

Effects of carbon and titanium on the solidification structure and propertiesof ferrite heat-resistant alloy

In order to design a low-cost high temperature ferrite alloy, the effects of carbon, and titanium on its solidification structure and properties have been studied. When the carbon content is increased from 0.07 to 0.35 wt%, the alloy grains becomes finer, and the grain boundaries become wider and more zigzag. The alloy oxidation weight-gain rate at 1300°C keeps increasing clearly, however, that at 1350°C decreases at first then increases. When the carbon content is above 0.15 wt% the alloy strength at 1300°C decreases acutely. When the titanium content increased from 0.30 to 0.60 wt%, the alloy grains became fine, and both the alloy strength and oxidation resistance improved remarkably.     

The effect of thermal history on the color of oxide layers in titanium 6242 alloy

A study was done to examine the effects of thermal history and surface pretreatment on the color of oxide layers in Titanium 6242 alloy. Coupons of the alloy underwent three different pretreatment options prior to thermal exposure to temperatures from 371 to 760 °C with periods from 6 min up to 100 h. After exposure it was found that there was not a simple correlation between color and thermal history. Also, it was not evident after exposure that the hardness could be traced to the thermal history. However, it was clear that color did rely on pretreatment options. The abrasive treatment resulted in shades of gold with a polished look while the milder treatments produced matte hues of blue. All coupons after exposure were found to have an oxide layer thickness of no more than 400 nm.     

Effect of rolling temperature on microstructure and mechanical properties of 6063 Al alloy

Aluminium alloy (6063) was severely rolled upto 92% thickness reduction at liquid nitrogen temperature and room temperature to study the effect of rolling temperature on its mechanical properties and microstructural characteristics by using tensile tests and SEM/electron back scattered diffraction (EBSD), transmission electron microscope (TEM), DSC, X-ray diffraction (XRD) as compared to room temperature rolled (RTR) material with the same deformation strain. An improved strength (257 MPa) of cryorolled 6063 Al alloy was observed as compared to the room temperature rolled alloy (232 MPa). The improved strength of cryorolled alloy is due to the accumulation of higher dislocation density than the room temperature rolled material. The tensile properties of cryorolled alloy and the alloy subjected to different annealing treatments were measured. The cryorolled alloy subjected to annealing treatment at 300 °C for 5 min exhibits an ultrafine-grained (UFG) microstructure with improved tensile strength and ductility.     

钛板圆孔翻边成形极限与形状非轴对称化研究

为确定钛板圆孔翻边成形性能,揭示各向异性对制件形状和尺寸精度的影响,在室温和600℃用TC1MS1.5 mm钛合金坯料分别进行了圆孔翻边成形试验.结果表明:与室温冷翻边相比,热翻边可有效提高成形极限、消除冷翻边制件形状翘曲以及唇口部位椭圆化现象,在唇口边沿完好与破裂状态之间存在集中颈缩形式,而冷翻边则在底孔尺寸小于极限值时会直接发生破裂;冷、热圆孔翻边变形程度越大,则形状非轴对称化程度越严重.     

等径道角挤压对Mg-6Al合金性能的影响

为了优化铸态Mg-6Al合金等径道角挤压的工艺参数,通过等径道角挤压实验研究了工艺参数对其性能的影响.研究表明:等径道角挤压可大幅度提高Mg-6Al合金坯料的力学性能.当Mg-6Al合金挤压1道次至4道次后,其力学性能提高较大,微观组织明显细化.随挤压温度从260℃升高至300℃,被挤压坯料的力学性能先提高后降低.当挤压路径为路径B,挤压道次为4道次,挤压温度为300℃时,Mg-6Al合金的力学性能最高,其抗拉强度为308.2 MPa,延伸率达到30.6%.     

Rapidly modifying microstructure and mechanical properties of AA7150 Al alloy processed with electropulsing treatment

Studies show that the proper solid solution treatment (SST) is a key step in the precipitation strength-ening of AA7150 Al alloy.Despite the superior characteristics of the fully dissolved phase,it has major drawbacks,including high consumption of energy and low efficiency.Recently,electropulsing treatment(EPT) has been proposed to study dissolved precipitations and modify microstructures of AA7150 Al alloy faster than conventional SST.Experiments have been conducted in the present article,and the obtained results show that EPT can promote the rapid dissolution of the rl'phase at relatively low temperatures in only 20 s.Meanwhile,the strength and ductility of electropulsed samples decrease drastically.Compared with conventional SST,EPT accelerates recrystallization and obtains relatively fine grains after 20 and 50 s electric pulses.Moreover,as the EPT time increases,the corresponding non-uniform local heating and the electron force promote dislocation generation and annihilation.     

Structure and mechanical properties of the annealed TZAV-30 alloy

The Ti–30Zr–5Al–3V (wt.%, TZAV-30) alloy having good mechanical properties is a potential structural material to apply in the aerospace industry. The microstructure and mechanical properties of ZTAV-30 alloy underwent various annealing heat treatments were investigated. The specimens annealed from 500 to 800 °C are composed of α and β two phases. No compound is detected in specimens annealed in that temperature range. The microstructure of annealed specimens is characterized as a typical basketweave microstructure. Three microstructural parameters, thickness of plate α phase, relative fraction of β phase and aspect ratio of α grains, were measured in those annealed specimens. As the alloy annealed in the range from 500 to 800 °C, the average thickness of plate α grains increases with the increasing annealing temperature from 500 to 700 °C but decreases while annealed at 800 °C. The fraction of retained β phase increases with annealing temperature. And the aspect ratio of plate α grains decreases firstly but increases while the annealing temperature is higher than 700 °C. As the variation of those three microstructural parameters, the strength of examined alloy varies from 1269 to 1355 MPa for tensile strength and from 1101 to 1190 MPa for yield strength, inversely, the elongation changes in the range from 12.7% to 8.4%. The strengthening and toughening mechanism of the TZAV-30 alloy with basketweave microstructure is also discussed in this paper.     

工艺参数对真空吸铸TiAl基合金连杆铸造过程的影响

本文利用底漏式真空吸铸方法制备TiAl合金汽车发动机连杆铸件,并研究了吸铸工艺参数对铸造过程的影响.分别采用了金属型芯金属模具、陶瓷芯金属模具以及陶瓷型壳进行性吸铸实验,研究了不同的吸铸参数对连杆铸件的成形性影响.得到了TiAl合金底漏式真空吸铸的优化工艺参数,初步获得了形状完整的连杆件.