多孔铝合金的铸造工艺研究

采用加压铸造工艺，制备出了多孔铝合金。系统地研究了预制块的制备工艺过程及影响因素。利用所制备的预制块，研究了多孔铝合金的加压铸造工艺。研究表明，预制块孔隙大小及其初始温度、金属液浇注温度、外加压力等影响了金属液在预制块中的充型长度。采用合理的工艺，就可以获得大尺寸的多孔制品。     

Massive Si Phase and Its Growth Mechanism in Al-Si Casting Alloy

Optical microscope and scanning electron microscope were used to observe the microstructure of the AI-11.6%Si and AI-11.6%Si-0.4%Mg alloys and the morphology of the massive silicon particles. It is found that the massive silicon phase, observed in the unfully modified alloys with 0.010%Sr, disappears completely in the alloys fully modified with 0.020%Sr. The serrations and reentrant edges shown in the massive silicon particles with the conventional casting indicate that the TPRE mechanism plays an important role in the growth of the massive silicon phase. The ripples and steps suggest that the "lateral microscopic growth" may be another operating mechanism.     

铝硅合金变质的研究进展

综述了当前国内外铝硅合金变质处理及其变质机理的研究进展.变质元素Na、Sr、Sb、Ba、Te、Bi、P、S、Ca、As、稀土等已取得了良好的变质效果,通过对比分析其变质机理以及绿色无污染、经济长效等方面的优缺点,比较了这些变质元素单一变质、二元变质和多元变质的优势与局限性,并展望了铝硅合金变质方法的发展趋势.     

铝硅合金超塑性研究

本文对 Al—13Si 共晶合金在超塑性变形时产生早期断裂的原因进行了研究。对影响Al—Si 共晶合金断裂的因素——第二相 Si 粒子形状、Si 粒子长大以及 Si 相与α相高温硬度差进行了详细分析。文章揭示出 Al—13Si 共晶合金的超塑性拉伸断裂是外部无颈缩的空洞型断裂。Si 粒子周围产生空洞是由于晶内位错堆积在 Si 粒子周围,造成应力集中,以及 Si 相与α相高温硬度相差悬殊,不能协调变形引起的。第二相 Si 粒子为带有尖角的短棒状,使得空洞沿尖角指向不均匀扩展,导致该合金发生早期断裂。     

固体雾化铝硅合金的粉末特性

固体雾化是一种新型的制粉方法 ,通过改变雾化介质来改善雾化效果。本文利用固体雾化方法制备了共晶铝硅合金 ,并与在相同条件下的普通气体雾化的同种粉末作了比较 ,发现采用固体雾化法制备的粉末细 ,粒度分布窄 ,冷却速度高     

Deep Penetration of Aluminum Alloy with High-Power-Density Electron Beam

High-power-density electron beam with single pulse was performed on the LD11R aluminum alloy. Variation of penetration depth and cavity width with focus position and duration time was studied by using the “rapid fixing” method. The influence of focus position on deep penetration was investigated as well. An electron beam deep penetration mechanism is proposed. The results indicate that the electron fusion range rate was the main factor of the deep penetration.     

A1-Si过共晶合金拉伸断裂过程的研究

以铸造Al-Si过共晶合金为研究对象,采用现场金相显微镜对Al-Si过共晶合金的断裂过程进行观察,探讨了两相合金的断裂机理。试验发现:Al-Si过共晶合金的断裂首先发生在先析Si相的凹角处,随着外力的增加,裂纹向先析Si相内部进行扩展,达到相界处时改变方向,沿着Al-Si两相的相界进行扩展。分析认为:Al-Si两相合金中,相界的结合强度最弱,裂纹的扩展是择弱进行的。     

Tensile Properties and Deformation Behaviors of a New Aluminum Alloy for High Pressure Die Casting

Effects of natural aging and test temperature on the tensile behaviors have been studied for a highperformance cast aluminum alloy Al–10Si–1.2Cu–0.7Mn. Based on self-strengthening mechanism and spheroidization microstructures, the alloy tested at room temperature(RT) exhibits higher 0.2% proof stress(YS) of 206 MPa, ultimate tensile strength(UTS) of 331 MPa and elongation of 10%. Increasing aging time improves the YS and UTS and reduces the ductility of the alloy. Further increasing aging time beyond72 h does not signi?cantly increase the tensile strengths. Increasing test temperature signi?cantly decreases the tensile strengths and increases the ductility of the alloy. The UTS of the alloy can be estimated by using the hardness. The Portevin–Le Chatelier effect occurs at RT due to the interactions between solid solution atoms and dislocations. Similar behaviors occurring at 250 °C are attributed to dynamic strain aging mechanism. Increasing aging time leads to decrease in the strain-hardening exponent(n) value and increase in the strain-hardening coe?cient(k) value. Increasing test temperature apparently decreases the n and k values. Eutectic phase particles cracking and debonding determine the fracture mechanism of the alloy. Final failure of the alloy mainly depends on the global instability(high temperature, necking) and local instability(RT, shearing). Different tensile behaviors of the alloy are mainly attributed to different matrix strengths, phase particle strengths and damage rate.     

Al-Si合金熔体变质效果评估判据

综述了评价铝硅合金变质效果的一般方法,主要有断口观察法、电导率法、金相法和热分析法.重点分析了热分析技术的各个判据,指出了目前热分析判据研究的两种动向,并指出人工神经网络技术结合成熟的热分析技术将有广阔的应用前景.     

石膏型渗流法制备低密度开孔泡沫铝工艺研究

研究用可溶石膏型预制块制备低密度开孔泡沫铝的工艺。采用不同孔径的聚氨酯网状海绵为母体材料,用石膏粉、硫酸镁、铝矾土和水为配方制备石膏型预制块,并分析了硫酸镁和铝矾土的加入量对石膏型预制块可溶性和抗压强度的影响。通过加压渗流的方法制备出低密度的开孔泡沫铝,并对渗流参数的选择做出总结。结果表明:利用石膏型渗流法制得的开孔泡沫铝相对密度在0.1以下。     

工艺因素对Al-Si合金熔体粘度的影响

采用旋转柱体法系统地对纯铝及铝硅合金在液相线以上不同温度的粘度进行了研究。实验结果表明:随着温度的升高,熔体的粘度都呈减小的趋势;且当Si含量增至5%时,熔体的粘度在720～790℃之间存在着异常变化,可能是熔体结构发生了改变;在较大过热度(ΔT=100℃或135℃)时,Si含量在不超过7%条件下,Si含量对Al-Si合金熔体粘度的影响较小;而当Si含量达到9%或11%以上时,Si含量对熔体粘度的影响变大。     

Correlation between Porosity and Fracture Mechanism in High Pressure Die Casting of AM60B Alloy

X-ray tomography was used to characterize the porosity in high pressure die casting of AM60B alloy. In situ tensile deformation was performed to observe the change of porosities and their influences on crack initiation,propagation and subsequent fracture of specimen. Results showed that four types of porosities,including gas-shrinkage pore,gas pore,net-shrinkage and island-shrinkage,could be identified according to the formation mechanism and morphology characterization. During tensile deformation,it was shown that the gas-shrinkage pore and net-shrinkage,rather than gas pore or island-shrinkage,were the main sources for crack initiation. In addition,the crack propagated by interconnecting the porosities at the cross section with minimum efficient force bearing area. At these locations where externally solidified crystals(ESCs) were present,the crack would propagate along the ESC boundaries in an intergranular mode,while at these locations without ESCs,the crack would propagate roughly along the direction perpendicular to the tensile stress in a combination of trans-granular and inter-granular modes.     

铈在铸造铝硅合金熔炼过程中的去向

用放射性强度计数法和自射线照相法研究了铈在炼熔过程中的去向。结果表明,铈在铝硅合金熔炼过程中主要分布于合金液中铈与石墨坩埚作用不明显,在铝液中挥发甚微。主要损耗形式是铅液保护膜被破坏时的氧化烧损,铈加入量较多时,形成稀土夹杂物。     

超声制备SiCp增强铝硅合金复合材料的磨损性能研究

研究使用功率超声制备SiCp颗粒增强铝基复合材料的新方法,并对所制得不同粒度SiCp的复合材料进行了组织分析和磨损性能的测试。实验结果表明,利用功率超声可以制备出颗粒在基体中均匀分布的复合材料,可增加SiCp的复合量,使SiCp与基体间润湿性良好。小粒度的SiCp颗粒增强复合材料较大尺寸的复合材料的耐磨性要好。     

Electromagnetic Filtration of Primary Fe-Rich Phases from Al-Si Alloy Melt

Electromagnetic filtration of primary Fe-rich phases(complex compound of AIFeSiMn)from Al-Si alloy melt containing 1.2 wt pct Fe have been studied by theoretical analysis and on a selfdesigned electromagnetic filtration equipment. The principle of the electromagnetic filtration is that the EMF(electromagnetic force)scarcely acts on the primary Fe-rich phases having low electric conductivity, which are then moved in the direction opposite to that of the EMF.Experimental results show that the primary Fe-rich phases are separated from Al-Si alloy melt and are collected in the filter while the melt is in horizontal flow.The removal efficiency of the primary iron-phases(η)calculated is less as the greatest flow velocity of the melt(uM)and the height of the filter (2h) are larger,while it becomes larger as EMF, operating distance of electromagnetic force (x) and particle size (dp) become larger. lt has been confirmed that the primary iron-phases larger than 20 μm can be removed efficiently by theoretical analysis and experiments. This new technique is high efficient and available for continuously flowing melts as compared with natural settling and filtration methods, which offer a possibility for recycling high quality aluminum alloys.     

真空增压铸造对Mg-Y-Nd-Gd-Zn-Zr合金工艺性能和力学性能的影响

目的通过真空增压工艺改善Mg-Y-Nd-Gd-Zn-Zr合金的铸造性能和力学性能。方法采用螺旋法、热裂环法、线收缩率测试方法,分别测试了不同真空度、浇注温度、凝固压力下合金的流动性、热裂倾向和收缩率。采用万能拉伸机测试合金的力学性能,采用金相显微镜观察合金的显微组织,采用截线法测量平均晶粒尺寸。结果重力下Mg-Y-Nd-Gd-Zn-Zr合金的螺旋长度为240~270 mm,裂环宽度为10~15 mm;真空下的螺旋长度为245~330 mm,裂环宽度为7.5~12.5 mm;凝固压力从0.2 MPa提升至0.8 MPa,合金的抗拉强度从320 MPa提升至335 MPa,断后伸长率从4.5%提升至6.0%。结论提高真空度、浇注温度,可显著提升合金的充型能力;提高凝固压力、降低浇注温度,可明显降低合金的热裂倾向;凝固压力越高、真空压力转换时间越短,合金的组织越致密,力学性能越高。     

Microstructure and Mechanical Properties of Hyper-eutectic Al-Si Alloys Fabricated by Spray Casting

Microstructure and mechanical properties of hyper-eutectic Al-Si alloy fabricated by spray casting were in- vestigated and then these results were compared with those by squeeze cast.The spray-cast specimen was found to have finer Si particles （～5μm） compared to the squeeze-cast specimen （10-25μm）.The tensile strength and elongation of the spray-cast specimen are also higher than those of the squeeze cast one.It was considered that the increased mechanical properties of the spray-cast specimen were mainly due to finer size of the Si particles distributed in Al matrix.     

Ti321钛合金轴箱铸件石墨型铸造工艺研究

目的 研究钛合金高铁轴箱铸件采用石墨铸型工艺时,铸件尺寸、成形及内部质量控制技术。方法 通过对高铁轴箱铸件的结构特点进行分析,针对铸件结构复杂、尺寸比较大、铸件成形比较困难、容易变形的特点,开展了铸型结构设计、铸件尺寸控制技术和铸件成形工艺等方面研究。采用多活块组合的石墨铸型,设计底注开放式浇注系统,利用Procast软件对高铁轴箱铸件的浇注方案进行了模拟分析。选用Ti321合金,设定合理的浇注参数,利用真空自耗电极凝壳炉对铸件进行浇注。结果 铸件成形良好,经过热等静压和后精整后的铸件,铸件内外部冶金质量和性能指标,满足客户标准要求,验证了方案的合理性。结论 铸件的计算机模拟对铸件工艺的设计提供了技术支撑,高铁轴箱铸件采用的石墨型浇注工艺比较合理。     

旋转直管浇注法制备A356铝合金半固态浆料

采用旋转直管浇注法制备A356铝合金半固态浆料,在不同浇注温度和转速下进行了系列试验,并与直管法进行了对比分析。结果表明,在不同转速条件下,浇注温度越低,得到的浆料凝固组织晶粒尺寸就越小,颗粒球化程度越高。与直管法相比,同一工艺参数下,旋转直管法制备的坯料的晶粒更为细小和圆整,并且随着旋转速度的增加,可得到理想浆料组织的浇铸温度区间也随之增大。本实验条件下,当转速为300r/mim时,浇注温度为670℃也能得到较理想的半固态凝固组织。