Preparation of primary Al-Si alloy from bauxite tailings by carbothermal reduction process

Effects of various reaction parameters such as atmospheric pressure, treating temperature, sintering time and bituminite content on the preparation of primary Al-Si alloy by carbothermal reduction of bauxite tailings were investigated by XRD,XRF, infrared absorption carbon-sulfur analysis unit and SEM coupled with EDS. Meanwhile, the mechanism of carbothermal reduction of Al2O3 and SiO2 was discussed. It is found that pressure and temperature are major factors that influence the carbothermal reduction of bauxite tailings. The appropriate conditions for preparation of primary Al-Si alloy are as follows: atmospheric pressure of 0.1 MPa, heating temperature of 1 900 ℃,bituminite content of 95% (mass fraction) of theoretic bituminite content and sintering time of 1 h. Among four mechanisms of carbothermal reduction of Al2O3 and SiO2, the theory of the formation and decomposition of carbides might be the best one to interpret the reaction process.     

镁合金表面激光熔覆Al-Si合金涂层的组织和耐磨性

以Al-Si共晶合金粉末为熔覆材料,在AZ91D镁合金表面进行了激光熔覆试验,利用光学显微镜(OM)、扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)对激光熔覆层的组织、成分和相组成进行了分析,测试了激光熔覆层的显微硬度和磨损性能。结果表明,激光熔覆层由α-Mg过饱和固溶体和Mg17Al12、Mg2Si、Al3Mg2金属间化合物等相组成,且与基材之间形成了良好的冶金结合。由于激光熔覆层中存在金属间化合物析出相强化、细晶强化和固溶强化等多种强化作用,熔覆层的硬度比AZ91D合金提高了3#4倍,磨损量比AZ91D合金降低了72%。     

铸造铝硅合金热处理工艺的优化

通过对铸造铝硅合金热处理工艺参数的研究,优化其热处理参数,得到其优化热处理工艺.     

铝-硅合金砂型铸件改为压铸生产的工艺改进

通过一个铝-硅合金端盖压铸件设计实例,探讨了铝-硅合金砂型铸件改为压铸生产时,要在合金化学成分、熔炼工艺和铸件的工艺性能等方面,根据压铸工艺的特点对铸件整个生产工艺进行改进,以满足压铸生产的特殊要求。压铸铝-硅合金中ω（Fe）可以达到1．0％。ω（Fe）〈0．150%时,ω（Mn）要达到0．5％-0．8％,以防止粘模。对于不太重要的铝合金压铸件可以省略熔炼过程中的变质处理过程,通过合理设置加强筋、减少壁厚、减小拔模斜度等措施,改善压铸件的结构工艺性。     

亚共晶Al-Si合金凝固过程的热分析研究

用热分析技术分析亚共晶Al—Si合金的凝固过程，发现样杯模数、样杯结构是影响其凝固过程特征的主要因素。通过试验确定其参数可准确分析该合金的凝固过程。     

Influencing factors of surface roughness of MAO ceramic coating on AZ91D

To investigate the treating parameters＂ influence on the surface roughness of the MAO ceramic coating on AZ91D, experiments were implemented in the alkaline electrolyte by using a pulse power source with positive and negative pulse, and the surface roughness was measured and analyzed by using a Times roughness-meter and an optical microscope. The machining parameters＇ influencing rule on the coating surface roughness was investigated. The result indicates that the influence of all parameters is interactive, while the positive voltage and the electrolyte concentration, or increasing the frequency and the positive and negative voltage ratio are appropriate, the coating surface roughness will be improved.     

Sr变质对Al-Si合金组织的影响

利用扫描电镜、透射电镜等分析手段,研究了Al-10Sr变质剂对Al-Si合金中共晶Si形貌及尺寸的影响。实验结果表明,Sr变质工艺不仅对共晶Si的组织产生很大的影响,并且影响Si的生长特征。随Sr加入量的增加,共晶硅的形貌由片状变为针片状加纤维状,最后为细小纤维状,而且纤维状共晶硅越来越细小;随加入温度的提高,共晶Si组织逐渐均匀和细化。最佳的Sr变质工艺为:加入量0.03%~0.05%、加入温度740~750℃、变质后保温时间40min。加Sr变质后共晶硅连续生长,成束分布,分枝较多。通常含有高密度孪晶,且常有两个或两个以上孪晶系同时启动,孪晶化晶体分布不均匀。     

Al-Si合金表面激光熔覆铝青铜合金的工艺研究

采用２ｋＷＣＯ２激光器，在无贵重气体保护激光熔池的条件下，开展了Ａｌ－Ｓｉ合金表面激光熔覆Ａｌ青铜合金的研究。探讨了激光工艺参数对熔覆层宏观质量影响的基本规律，获得了完整的工艺操作图；研究了扫描速度对熔覆层宏观形貌和显微硬度的影响；分析了自重式送粉条件下铝合金激光熔覆的作用过程和工艺操作图的成因     

Effects of vibration and grain refiner on microstructure of semisolid slurry of hypoeutectic Al-Si alloy

The effects of vibration and grain refiner on the microstructure of semisolid slurry of hypoeutectic Al-Si alloy were studied. The impact of vibration on the convection of liquid was conducted by using a system of water-particle tracer. The 356 melt at temperature of 630-660 ℃ with or without grain refiner Al-5%Ti-1%B was poured into a metal cup as the vibrating vessel, then it was cooled to 590-610 ℃ in the semisolid zone and kept for some time, subsequently vibration with different frequencies was applied. The results show that the primary a（Al） particles become finer and rounder with the increase of vibration frequency. The slurry with primary a（Al） equivalent particle diameter（EPD） of about 90μm and average shape coefficient（ASC） of about 0.5 can be prepared under vibration of 20 Hz. With the combined action of vibration and grain refiner Al-5Ti-B, even smaller and rounder spheroids with EPD of about 85μm and ASC of about 0.6 are obtained.     

Broad-beam laser cladding of Al-Si alloy coating on AZ91HP magnesium alloy

In the present study, an attempt was made to improve the wear resistance and the corrosion resistance of AZ91HP magnesium alloy by laser cladding Al-Si eutectic alloy. The results showed that the clad layer mainly consisted of Mg₂Si, Mg₁₇Al₁₂ and Mg₂Al₃ phases. The microstructure of the bonding zone changed from columnar grains to equiaxial grains along the direction of heat-flow. The heat-affected zone consisted of α-Mg and α-Mg + β-Mg₁₇Al₁₂ eutectic. The formation of multiple Mg intermetallic compounds allowed the clad layer to exhibit higher hardness, better wear resistance and corrosion resistance.     

Effects of high magnetic field on modification of Al-Si alloy

1INTRODUCTIONAmong Al-Si alloys,the Al-Si eutectic alloyhas the best foundry capability.The mechanicalproperties of Al-Si eutectic and hypoeutectic alloyhighly relates to the shape,size and distribution ofSi phase in eutectic structure.Coarse acicular-likeeutectic Si dissevers Al matrix badly to inducestress concentration and debase the mechanicalproperties,especially the tenacity.Modification isthe process to change the shape and size of eutecticSi,namely to change the shape of eutec…     

过共晶铝硅合金耐磨性能的研究进展

过共晶铝硅合金是一种软基体上分布着硬质点的理想轻质耐磨结构材料.研究表明影响其耐磨性能的主要因素包括微观结构和工况条件,其中硅相的含量、形态、分布有非常大的影响.本文总结了过共晶铝硅合金的磨损机理和提高耐磨性能的工艺方法,并对其以后的研究和发展方向进行了展望.     

Effect of bariun on the refinement of primary aluminum and eutectics in a hypoeutectic Al-Si alloy

The effect of barium on the refinement of primary aluminum and on the modification of eutectics in a hypoeutectic aluminm-silicon alloy was investigated. The results indicate that barium not only modifies the eutectic silicon but also refines the primary aluminum and there is a relationship between the retained barium and the second spacing of primary aluminum. Experiments of barium-treated commercial Al-Si hypoeutectic alloy show that barium is a better modifier than sodium when there is a longer holding time.     

Effect of barium on the refinement of primary aluminum and eutectics in a hypoeutectic Al-Si alloy

The effect of barium on the refinement of primary aluminum and on the modification of eutectics in a hypoeutec-tic aluminum-silicon alloy was investigated. The results indicate that barium not only modifies the eutectic silicon but also refines the primary aluminum and there is a relationship between the retained barium and the second spacing of primary aluminum. Experiments of barium-treated commercial Al-Si hypoeutectic alloy show that barium is a better modifier than sodium when there is a longer holding time.     

过共晶Al-Si合金熔体中初生硅生长特性

利用等温液淬的方法,研究了Al-18%Si过共晶合金熔体中初生硅的生长行为及机制.结果表明:重熔过程中熔体中未溶解的硅相粒子,在凝固过程中可成为初生硅生长核心,并且未熔颗粒与初生硅形状之间存在明显对应关系; 初生硅的生长机制不是惟一的,既可以以孪晶凹角(TPRE)机制生长,还可以以层状机制生长,初生硅最终形状还要取决于溶质传输等动力学环境; 随着熔体过热温度的升高,凝固组织中初生硅形状由多边形向星形及树枝状转变.     

过共晶铝-硅合金处理技术的研究进展

综述了为改善过共晶铝-硅合金的性能,目前所采用的控制合金中初晶硅尺寸、形态和分布的各种处理方法及其机制,它们包括细化变质、合金熔体过热处理、半固态搅拌、快速凝固、电磁场作用、电脉冲孕育处理等方法。从合金中初晶硅尺寸、形态和分布等方面比较了各种处理方法的优缺点。     

Effect of electric current on the cast micro-structure of Al-Si alloy

1. IntroductionRecently,much work has been contributed to study theeffect of electromagnetic field on the properties of castaluminum alloy. Results of CUI indicated that the meltingpoint of aluminum alloys was changed. The melting pointof aluminum alloy, such as Al-Cu alloy, decreased inmagnetostatic field, and increased in alternating magneticfield. Results of BAN showed that the solute content ofalloying element increased as electromagnetic fieldapplied during solidification. Electromagn…     

深冷处理铝硅合金的微观组织与力学性能

对铸态Al-Si合金在?196 ℃进行深冷处理,研究了深冷时间和深冷步数对Al-Si合金的微观组织、布氏硬度和拉伸性能的影响。结果表明：深冷处理可以促进析出细小的Si相;随着深冷时间的增加,导致（200）面衍射峰值先升高后降低;随着深冷时间的增加（0～12 h）,布氏硬度逐渐增大,12 h达到最大值,12～24 h逐渐下降并且24 h后趋于稳定,随着深冷步数的增加,布氏硬度也逐渐增大;深冷处理12 h后Al-Si合金的抗拉强度和伸长率分别达到176 MPa和10％。通过指数拟合法建立了深冷时间与布氏硬度的关系方程。     

Effects of ZnS modification on primary Si in hypereutectic Al-Si alloy

A new modifying agent, ZnS, was used as a refiner to modify primary silicon in hypereutectic AlSi alloy. The factors affecting the modification results, including addition level of ZnS and holding time, were investigated. The results showed that the average size of the most effectively modified primary silicon was 28.5 μm when the ZnS mixed powder addition was 0.15 wt.% with a holding time of 10 min. More important, the average size of primary silicon could remain below 40 μm despite the holding time extending to 120 min, which means ZnS is a promising modifying agent of primarySi in industrial applications.