半固态AlSi6Mg2铝合金循环剪切变形下的触变行为

在Couette型同轴圆桶流变仪上,采用滞后环工艺研究了半固态AlSi6Mg2铝合金浆料的触变行为.实验结果表明:半固态AlSi6Mg2铝合金浆料在循环剪切变形下,静置时间越长、剪切速率到达最大值所用时间越短、固相分数越大、最大剪切速率越大,则合金浆料τ-γ,滞后环所包围区域面积越大,合金浆料的触变性越强.     

浇注温度对AlSi7Mg合金显微组织的影响

研究了不同的烧注温度对铸造AlSi7Mg合金凝固组织的影响。实验表明：当浇注湿度接近液相线温度时,AlSi7Mg合金中的初生α－Al凝固成球状或粒状,晶粒细小,分布均匀;获得球状或粒状AlSi7Mg合金半固态坯料的最佳浇注温度为615℃;在接近液相线温度下浇注,较快的合金溶体冷却速度、浇注引起的合金溶体流动和大范围的同时凝固促使AlSi7Mg合金形成球状或粒状的初生α－Al组织。     

泡沫铝合金在凝固过程中熔体的孔隙率变化

研究了泡沫纯铝和泡沫AlSi7Mg0.45的凝固方式及其对孔结构的影响,并讨论了熔体泡沫在凝固过程中的体积变化和孔隙率变化。结果表明：在合适的冷却条件下,纯铝熔体泡沫倾向于逐层凝固,在凝固过程中易形成中心缩孔,AlSi7Mg0.45熔体泡沫倾向于同时凝固,易形成热裂纹;纯铝熔体泡沫在凝固过程中,体积减小,孔隙率增加,而相对于纯铝来说,AlSi7Mg0.45熔体泡沫的体积及孔隙率均有所减小。     

Preparation of semisolid AlSi7Mg alloy slurry through weak traveling-wave electromagnetic stirring

The semisolid AlSi7Mg alloy slurry with large capacity was prepared by low superheat pouring and week traveling-wave electromagnetic stirring. The effects of electromagnetic stirring power and frequency on the shape and distribution of primary α-A1 grains in the AlSi7Mg alloy slurry were discussed. The experimental results show that the AlSi7Mg alloy slurry with fine and spherical primary α-A1 grains distributed homogeneously can be obtained. Under the condition of low superheat pouring and week traveling-wave electromagnetic stirring, when the pouring temperature is 630℃, raising the stirring power or frequency appropriately can gain a better shape of primary α-Al grains; but if the stirring power or frequency is increased to a certain value (1.72 kW or 10 Hz), the shape of primary α-A1 grains cannot be obviously improved and spherical primary α-Al grains distributed homogeneously can be still obtained.     

包套轧制粉末冶金法制备泡沫铝三明治板

以空气雾化的A1Si12合金粉、镁粉和氢化钛粉末为原料,采用包套轧制法成功制备出了泡沫铝三明治板材.利用300 dpi扫描仪、扫描电镜(SEM)和显微硬度仪等检测方法系统比较了复合轧制和包套轧制方法对制备前驱体的宏观形貌和界面结合及其泡孔结构的影响,结果表明:包套轧制可以有效阻止面板材料裂纹的扩展,获得完整的和致密度均...     

浇注长度对流变压铸AlSi9Mg组织及性能的影响

采用自制的倾斜流变装置制备半固态合金熔体并直接进行流变压铸,研究了浇注长度对半固态AlSi9Mg组织及性能的影响。结果表明:浇注长度对抗拉强度和伸长率影响较大,对硬度和冲击韧性影响较小。浇注长度为500 mm时,抗拉强度为290 MPa,延伸率为4.1%,硬度为77.9HBS,冲击韧性为0.72 kJ/m2。流变压铸后AlSi9Mg组织晶粒尺寸明显减小,形状明显圆整。浇注长度为500 mm时,流变压铸组织中的初生固相平均尺寸为7.1μm,形状因子为0.73。     

Mechanical properties and friction behaviors of CNT/AlSi10Mg composites produced by spark plasma sintering

The mechanical properties and friction behaviors of CNT/AlSi10Mg composites produced by spark plasma sintering (SPS) were investigated.The results showed that the densities of the sintered composites gradually increased with increasing sintering temperature and that the highest microhardness and compressive strength were achieved in the specimen sintered at 450℃.CNTs dispersed uniformly in the AlSi10Mg matrix when the addition of CNTs was less than 1.5wt％.However,when the addition of CNTs exceeded 1.5wt％,the aggregation of CNTs was clearly observed.Moreover,the mechanical properties (including the densities,compressive strength,and microhardness) of the composites changed with CNT content and reached a maximum value when the CNT content was 1.5wt％.Meanwhile,the minimum average friction coefficient and wear rate of the CNT/AlSi10Mg composites were obtained with 1.0wt％ CNTs.     

La对AlSi10Cu0.2Mg0.2Mn和ZnAl12Cu1(Mg)铸造合金力学性能的影响

利用Al-La中间合金制备了AlSi10Cu0.2Mg0.2Mn-x La和Zn Al12Cu1(Mg)-x La铸造合金,考察了不同的La含量对合金组织和抗拉强度、伸长率、冲击强度等性能的影响.研究结果表明:微量稀土La可以细化合金的晶粒,改变Si相晶粒大小和形状.与未添加La的合金相比,含有微量稀土La的AlSi10Cu0.2Mg0.2Mn-x La合金和Zn Al12Cu1(Mg)-x La合金具有更优良的力学性能.当AlSi10Cu0.2Mg0.2Mn铸造合金中La添加量为0.15%(质量分数)时,铸造合金的伸长率增加2.7倍.含有0.1%(质量分数)La的Zn Al12Cu1(M g)-x La合金抗拉强度和伸长率相比于未添加稀土La的合金,分别增强1.3倍和3.2倍.含有0.3%(质量分数)La时Zn Al12Cu1(Mg)-x La的硬度增强1.8倍,但冲击强度是含有0.15%(质量分数)La时最高.综合考虑Zn Al12Cu1(Mg)-x La铸造合金的机械性能,稀土La的最优添加量为0.1%~0.2%(质量分数).     

充型速度对半固态A1Si9Mg组织及性能的影响

采用倾斜冷却剪切流变法制备半固态A1Si9Mg合金熔体,流变压铸标准力学性能试样并进行了力学性能测定,用定量金相技术对力学性能试样的初生固相微观组织特征参数(固相率、晶粒尺寸和形状因子)进行了分析,研究了充型速度对半固态AlSi9Mg合金组织及性能的影响.研究结果表明:随着充型速度的提高,AlSi9Mg合金组织的初生固...     

Effects of heat treatment on microstructure and mechanical properties of SLMed Sc-modified AlSi10Mg alloy

The influence of heat treatments on the microstructures and mechanical properties of the selective laser melting manufactured AlSi10Mg alloy modified with Sc was systematically investigated. The results showed that the addition of Sc element introduced primary Al₃Sc, which increased the heterogeneous nucleation during the solidification of AlSi10Mg alloy, and then the ultrafine network eutectic structure was obtained, and hence the tensile strength was improved significantly (nearly 23 ​%). During the heat treatment process, the network eutectic structure transformed from continuous to discontinuous, and the grain refinement was weakened with an increasing heating temperature, both of which affected the mechanical properties of the Sc modified AlSi10Mg alloy. The tensile strength decreased from 438 ​± ​10 ​MPa for the Sc-modified alloy to 208 ​± ​6 ​MPa, while the fracture strain significantly increased from 6 ​± ​0.2 ​% to 30.2 ​± ​1.2 ​% when the Sc-modified alloy was heat-treated at 325 ​°C for 12 ​h. It has been found that the desirable microstructure and mechanical properties of SLM Sc-modified AlSi10Mg alloy can be realized by controlling the heat treatment process parameters.     

选区激光熔化成形AlSi10Mg合金力学性能稳定性研究

采用选区激光熔化（selective laser melting，SLM）技术在X、Y、Z 3个成形方向上批量生产了AlSi10Mg合金棒状试样，热处理后对所有试样进行室温拉伸性能测试，并对屈服强度和伸长率等主要拉伸性能指标进行统计分析，研究采用SLM技术在X、Y、Z 3个方向成形的AlSi10Mg合金力学性能稳定性。研究结果表明：不同方向成形的试样经热处理后力学性能差异较小，伸长率和屈服强度均表现出较小的离散；各个方向成形试样的屈服强度和伸长率满足正态分布，并且在正态分布概率密度函数曲线中均表现出以均值为中心的较高程度的集中；采用SLM技术制备的AlSi10Mg合金，成形参数和热处理工艺控制得当时，可以有效地缓解力学性能的各向异性，使X、Y、Z 3个方向成形试样的力学性能具有较高的稳定性。     

Surface tension of molten Al-Si alloy at temperatures ranging from 923 to 1123 K

The surface tension of molten AlSi20 alloy has been measured by using the sessile drop method at 923-1123 K under argon atmosphere in both heating-up and cooling processes. The result shows that the surface tension of this alloy decreases as long as temperature increases. The results of surface tension and contact angles in heating-up process have differences from those obtained in cooling process, because the metal microstructures have some changes at different temperatures based on the metal genetic theory. The surface tension of molten AISi20 alloy and that of molten pure aluminum have been compared as well, and the temperature coefficient of AlSi20 alloy is slightly lower than that of AI. The result has been analyzed by the linear scanning analysis with ESEM. The concentration of silicon in most region of the bulk is lower than that of the surface and the addition of Si to pure AI decreases the surface tension of molten pure Al.     

Preparation of CNT/AlSi10Mg composite powders by high-energy ball milling and their physical properties

This study investigated the effects of carbon nanotube (CNT) concentration on the micro-morphologies and laser absorption properties of CNT/AlSi10Mg composite powders produced by high-energy ball milling. A scanning electron microscope, X-ray diffractometer, laser particle size analyzer, high-temperature synchronous thermal analyzer, and UV/VIS/NIR spectrophotometer were used for the analysis of micrographs, phases, granulometric parameters, thermal properties, and laser absorption properties of the composite powders, respectively. The results showed that the powders gradually changed from flake- to granule-like morphology and the average particle size sharply decreased with increases in milling rotational speed and milling time. Moreover, a uniform dispersion of CNTs in AlSi10Mg powders was achieved only for a CNT content of 1.5wt%. Laser absorption values of the composite powders were also observed to gradually increase with the increase of CNT concentration, and different spectra displayed characteristic absorption peaks at a wavelength of approximately 826 nm.     

铝合金半固态触变充型过程的计算机模拟

分析半固态AlSi7Mg合金触变充型过程中各个阶段浆料的压力和速度变化特征,建立耦合半固态表观粘度的三维流场数学模型,在考虑半固态边界条件和气体阻力方程基础之上,采用SOLAVOF法对铝合金件的触变充型过程进行模拟计算.结果表明, 入流速度大小对半固态浆料充填流态有显著影响.小的入流速度浆料充填流态倾向于采用平稳充型,同时气孔等缺陷产生倾向也小.与刹车泵体轴向注入工艺相比,在一定入流速度下,采用径向注入工艺成形阻力较小,充型中不会出现充不满的铸造缺陷.上述模拟结果与实际相吻合.     

AlSi7MgBe合金半固态坯料制备及其触变成形

采用近液相线半连续铸造技术制备AlSi7MgBe合金半固态坯料,研究制坯工艺以及二次加热温度和保温时间对半固态浆料微观组织的影响,通过组织与性能分析对AlSi7MgBe合金的半固态触变成形性进行了研究.研究结果表明,AlSi7MgBe合金采用近液相线半连续铸造,坯料具有均匀、细小的蔷薇状组织.当二次加热温度为595℃,保温15 min时,能够得到适合于进行半固态触变成形的球化组织.对近液相线半连续铸造AlSi7MgBe合金坯料进行半固态触变成形,可以获得轮廓清晰、组织致密的成形件,成形件的组织与性能得到改善,与液态模锻工艺相比,硬度提高20%.     

AlSi/AlMn双金属复合材料制备试验研究

在自行设计和制造的双金属复合材料连铸设备上,通过工艺参数的合理配置,成功制备出尺寸为150mm×120mm×100mm的AlSi/AlMn双金属复合材料铸坯。分析了复合铸锭的宏观和显微组织、界面附近的元素成分以及界面结合强度和硬度分布。结果表明,复合界面为冶金结合,所制备复合材料的微观组织与化学成分分布及硬度之间有良好的对应关系。     

Mg对碳纤维稳定泡沫铝发泡过程和胞孔结构的影响

利用溶体直接发泡法制备出了不同Mg和碳纤维添加量的闭孔泡沫铝材料,详细研究了Mg的添加对泡沫铝发泡过程和胞孔结构的影响.研究结果表明:Mg元素的加入明显增大了泡沫体的膨胀率,拓宽了孔径分布的范围,并增加泡沫体中小气孔的数量.气泡壁内部和表面的微观形貌观察表明:Mg元素加入后,造成铝液表面张力降低,改善了铝液和氧化物颗粒的润湿性,有助于增加发泡过程中的气体释放,使泡沫体气泡壁平整且变薄,有助于提升气泡壁的稳定性,使获得的泡沫铝的孔隙率达到90%以上.     

铝及铝镁合金的室温电沉积制备

采用氯化铝-氢化铝锂-四氢呋喃-苯的有机体系电沉积铝,并在此基础上,研究n（氯化铝）∶n（氯化镁）=10∶1时电沉积铝镁合金的工艺条件.结果表明,采用该法在室温下能够成功制备铝及铝镁合金,电沉积铝比沉积铝镁合金条件容易控制,沉积效果也优于铝镁合金.当电流密度为0.010A/cm2,苯与四氢呋喃的体积比为8∶7,氢化铝锂的质量为1.27g时,成功获得了灰黑色粉末状的铝镁镀层,但晶粒较大,镀层与铜基体的结合力差.通过SEM和XRD对镀层进行形貌观察和成分检测可知,该铝镁合金成分为Al3Mg2,且随着电沉积时间的加长,镀层厚度随之增加.     

可溶性镁合金的制备及其性能

针对传统可溶性压裂球材质存在的缺点,采用铸造法制备性能优异的可溶性镁合金,系统研究了铝含量对可溶性镁合金组织、溶解性能及力学性能的影响.结果表明:可溶性镁合金组织由α-Mg和β-Mg17 Al12相组成,随着铝含量的增多,组织中β-Mg17 Al12相数量增多,呈连续网状分布于α相晶界处,并且α晶粒也变得粗大.可溶性镁合金在氯化钾(KCl)溶液中可自行溶解,且随KCl浓度的升高,溶解速率变大,在质量分数为3％的KCl中溶解性能最佳.随着铝含量的增加,可溶性镁合金的溶解速率变大,室温下溶解速率最高可达7.42 mg·h-1·cm-2.溶解产物粒度分析结果显示,中值粒径D50为38.691μm,溶解产物物相为Mg17 Al12和Mg(OH)2.可溶性镁合金的抗压强度最高可达430 MPa,变形量为3.0％时试样断裂,随着铝含量的增加,可溶性镁合金的塑性降低.     

Zn和Mg质量比对7055铝合金淬火敏感性的影响

通过测定时效曲线,结合金相显微镜和透射电镜等组织观察以及DSC分析,研究Zn和Mg质量比(4.10和4.67)对7055铝合金淬火敏感性的影响.结果表明:在120℃时效时,合金的淬火敏感性随着时效时间的延长而降低,而Zn和Mg质量比低的合金比Zn和Mg质量比高的合金的淬火敏感性高7％～11％:空气淬火时,Zn和Mg质量比低合金的再结晶晶粒内析出了较多粗大的η(MgZn2)平衡相,因而减少了过饱和固溶体中溶质原子的数量,降低合金的时效强化效果,提高合金的淬火敏感性:然而,Zn和Mg质量比高的合金在空气淬火过程中析出的η相较Zn和Mg质量比低的合金少,且在局部形成了S(A12CuMg)相.