Effect of thixoextrusion parameters on mechanical properties of 7003 Aluminum wrought alloy

The processing of high strength Al wrought alloys does lead either to restrictions for geometrical complexity or to high production costs due to low productivity and multiple-step processes.Thixoextrusion process to overcome these difficulties has been under investigation.In the present study, the effect of thixoextrusion parameters was investigated on mechanical properties of 7003 Al wrought alloy.The maximum extrusion pressure of the thixoextrusion process is three times lower than that of the hot extrusion process.The elongated grains which have the axisymmetry with extrusion direction are generally observed during hot extrusion process, while the microstructures of the thixoextruded are isotropic.The tensile and yield strengthes of the thixoextruded bar are lower than those of the hot extruded bar, while the elongation value of the thixoextruded bar is higher than that of the hot extruded bar.     

Rendering wrought aluminium alloys castable by means of minimum composition adjustments

Wrought alloys have low fluidity and are prone to hot tearing, which make them difficult to cast. The presence of eutectic-forming elements in the alloy composition lessens these effects. For this reason, the constituents of casting alloys tend to include a eutectic portion. Typically, silicon is added to aluminium alloys to provide casting ability by forming the aluminium–silicon eutectic. However, the presence of silicon in aluminium alloys is associated with a number of issues that do not allow these alloys to reach their full potential. In this publication we report results of our investigation of three alternative eutectics: Al–6.1Ni, Al–1.8Fe, and Al–1.75Fe–1.25Ni. Our results indicate that these eutectics have satisfactory fluidity and resistance to hot tearing and higher strength than the aluminium–silicon eutectic. We also found that introducing these eutectic compositions into 7075 wrought alloy results in a castable composition with yield strength comparable to that of the wrought alloy.     

冷热循环对颗粒增强铝基复合材料微屈服行为的影响

采用微屈服强度测试、透射电镜和高分辨透射电镜分析,对经过不同冷热循环工艺处理后的颗粒增强铝基复合材料的微屈服行为进行了研究。结果表明,冷热循环次数虽然对颗粒增强铝基复合材料微屈服行为的宏观规律没有本质的影响,但是仍然影响颗粒增强铝基复合材料的微屈服行为。对球形颗粒而言,小应变量下的微屈服强度随冷热循环次数的增加而增高;但对棱形颗粒而言,循环次数的影响较为复杂。研究还表明,冷热循环次数影响颗粒增强铝基复合材料微屈服行为的主要原因是其位错组态和残余应力在不同的循环次数下有明显的不同。     

The effect of casting temperature on the properties of squeeze cast aluminium and zinc alloys

Gravity casting and squeeze casting were carried out on an aluminium alloy with 13.5% silicon and a zinc alloy with 4.6% aluminium with different temperatures, 660, 690 and 720 °C for the former and 440, 460 and 480 °C for the latter. A top-loading crucible furnace was used to melt the alloys. The die-preheat temperatures used were 200–220 °C for the aluminium alloy and 150–165 °C for the zinc alloy. A K-type thermocouples with digital indicator were used to measure the die surface temperature and the molten metal temperature; while a 25 t hydraulic press with a die-set containing a steel mould was used to perform the squeeze casting with a pressure of 62 MPa. Tensile, impact and density tests were carried out on the specimens. It was found that casting temperature had an effect on the mechanical properties of both gravity cast and squeeze cast aluminium and zinc alloys. The best temperatures to gravity cast the aluminium alloy and the zinc alloy were 720 and 460 °C, respectively. For the squeeze casting of the aluminium alloy, the best temperature to use was either 690 or 660 °C; the former would give a better property at the top of the casting while the latter, at the bottom of the casting. However, for the squeeze casting of the zinc alloy, the best temperature was again 460 °C.     

FORMING PROCESS OF HOT-EXTRUDED SiCw/6061Al COMPOSITES(Ⅰ)

１ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｒｅｃｅｎｔｙｅａｒｓ，ｍｏｒｅａｎｄｍｏｒｅｃｏｎｔｉｎｕｏｕｓｌｙｏｒｄｉｓｃｏｎｔｉｎｕｏｕｓｌｙｒｅｉｎｆｏｒｃｅｄｍｅｔａｌｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｓ（ＭＭＣｓ）ｈａｖｅｂｅｅｎｕｓｅｄｔｏｍａｋｅｓｔ...     

Structure and mechanical properties of AZ31 magnesium alloy billets by different hot-top semi-continuous casting technology

AZ31 alloy billets of 200 mm in diameter were produced by three different processes of conventional direct chill(DC) casting,low-frequency electromagnetic casting(LFEC) and low-frequency electromagnetic vibration casting(LFEVC),respectively.The effect of LFEC and LFEVC on the microstructures,macrosegregation and mechanical properties of AZ31 alloy billets was investigated.In conventional DC casting,the AZ31 alloy billets exhibited coarse grains(about 370 μm) and severe segregation of Al and Zn.In the presence of a solo low-frequency alternating magnetic field or a low-frequency electromagnetic vibration field applied during DC casting of φ200 mm AZ31 billets,grains in the AZ31 alloy billets were effectively refined(about 210 μm) and the macrosegregation of Al and Zn in the billets was greatly decreased.Furthermore,the tensile strength,fracture elongation and hardness of the as-cast AZ31 alloy billets were improved by the processes of LFEC and LFEVC relative to that cast by the process of conventional DC casting.     

MICROSTRUCTURE MODIFICATIONS OF WROUGHT AND CAST TiAl ALLOYS

１　ＩＮＴＲＯＤＵＣＴＩＯＮＧａｍｍａＴｉＡｌａｌｌｏｙｓｈａｖｅａｔｔｒａｃｔｅｄａｇｒｅａｔｄｅａｌｏｆｉｎｔｅｒｅｓｔｓｆｒｏｍｔｈｅａｅｒｏｓｐａｃｅａｎｄａｕｔｏｍｏｂｉｌｅｉｎｄｕｓｔｒｉｅｓｉｎＣｈｉｎａｉｎｔｈｅｐａｓｔ５ｙｅａｒｓ．ＡｆｅｗＴｉＡｌｃｏｍｐｏｎｅｎｔｓｈａｖｅｂｅｅｎｆａｂｒｉｃａｔｅｄｂｙｅｉｔｈｅｒｃａｓｔｉｎｇｏｒｈｏｔｗｏｒｋｉｎｇ．Ｈｏｗｅｖｅｒ,ｔｈｅｒｅａｒｅｓｔｉｌｌｍａｎｙｔｅｃｈｎｉｃａｌｉｓｓｕｅｓｗｈｉｃｈｒｅｍａｉｎａｓｂａｒｒｉ…     

喷射成形Zn—27Al—1Cu合金制备滑动轴承

研究了喷射成形Zn-27Al-1Cu合金棒坯的制备技术、热挤压工艺以及Zn-27Al-1Cu合金滑动轴承的制备技术,分析了喷射成形Zn-27Al-1Cu合金的显微组织、力学性能、耐磨性能。实验结果表明：采用喷射成形制备的Zn-27Al-1Cu合金的棒坯经后续热挤压成形后,具有比传统铸造ZA27合金更高的力学性能和耐磨性能。这种由喷成形Zn-27AL-1Cu合金制造的滑动轴承在实际使用过程中,其寿命比传统材料制造的滑动轴承提高150％以上。     

第四届亚洲铸造大会特铸及有色合金部分论文简介

有选择地介绍了第四届亚洲铸造大会部分论文内容，涉及Ａｌ－Ｓｉ合金变质处理、铝合金晶粒细化处理新发现，Ａｌ－Ｓｉ－Ｍｇ合金裂纹源的新观点，铁对铝铸件形成孔洞的新论点，预测壳芯发气量的新技术，挤压铸造工艺新发展及新型阻燃型镁合金材料等。     

Solid-state recycling of aluminium alloy swarf through cold profile extrusion and cold rolling

In this study, the possibility of solid-state recycling of aluminium alloy machining swarf using cold extrusion and a subsequent cold rolling process is investigated. Cast Al-Si alloy swarf was cold compacted into billets and successfully profile-extruded into square bars with a rectangular cross-sectional aspect ratio of 1:1.8 under an extrusion ratio of 4 or more. After annealing, the extruded bars underwent multi-pass cold rolling into 1-mm thick strips with a total rolling reduction of 85%. Optical microscopy demonstrated that in material recycled using only an extrusion process, coarse residual voids existed in regions where insufficient plastic strain was introduced, causing a visible expansion of the material during heat treatment. However, uniaxial tensile tests showed that extrusion-recycled material had a higher mechanical strength than the original aluminium alloy, implying sufficient bonding among the individual pieces of machining swarf. It was also found that the strength and density of material recycled through extrusion and an additional rolling process were superior to material recycled using extrusion only. Moreover, it was observed that the ductility of the recycled materials was inferior to that of the original aluminium alloy.     

Deformation mechanism and forming properties of 6061Al alloys during compression in semi-solid state

The 6061 semi-solid aluminium alloy feedstocks prepared by near-liquidus casting were compressed in semi-solid state by means of Gleeble-3500 thermal-mechanical simulator. The relationship between the true stress and the true strain at different temperatures and strain rates was studied with the deformation degree of 70%. The microstructures during the deformation process were characterized. The deformation mechanism and thixo-forming properties of the semi-solid alloys were analyzed. The results show that the homogeneous and non-dendrite microstructures of semi-solid 6061Al alloy manufactured by near-liquidus casting technology could be transformed into semi-solid state with the microstructure suitable for thixo-forming which are composed of near-spherical grains and liquid phase with eutectic composition through reheating process. The deformation temperature and strain rate affect the peak stress significantly rather than steady flow stress. The resistance to deformation in semi-solid state decreases with the increase of the deformation temperature and decrease of the strain rate. At steady thixotropic deformation stage, the thixotropic property is uniform, and the main deformation mechanism is the rotating or sliding between the solid particles and the plastic deformation of the solid particles.     

Al-Si基铸铝合金阳极氧化

Al-Si合金由于其良好的性能已在工业中得到了广泛的应用.阳极氧化成为铝合金铸件表面处理的一种重要方式,而阳极氧化膜色差直接影响到铸件的表面质量、使用寿命及外观要求.探讨了影响铸铝阳极氧化的因素,研究了铸铝合金的表面预处理和阳极氧化工艺,讨论了铸铝合金的表面预处理和工艺条件对阳极氧化膜性能的影响,据此优化工艺,获得了合适的表面预处理方法和阳极氧化最佳工艺条件.该工艺操作简便,节约能源,生产效率高,易于推广应用.     

常用铝合金及其热处理工艺

对国内外常用铝合金及其牌号对照等相关信息进行了总结，列出了国内外常用铝合金的牌号对照表，并根据铝合金在汽车工业中的应用状况，简述了铸造铝合金A356和锻造铝合金6082的热处理和表面处理，推荐了可行的热处理工艺。     

Influence of Hot Extrusion Temperature on the Microstructure and the Mechanical Properties of (ABOw + WO3p)/Al Hybrid Composites

The (ABOw + WO₃p)/Al hybrid composite was fabricated by squeeze casting and subsequently hot extruded at temperatures that varied from 440°C to 560°C. The microstructures of extruded composites were examined by scanning electron microscopy and transmission electron microscopy techniques. The results show that ABOw aligns along the extrusion direction after the hot extrusion process. The aspect ratio of ABOw in extruded composites is lower than that of as-cast composite. The aspect ratio of ABOw in extruded composites increases with the increase of extrusion temperature. The larger WO₃p particles are broken into smaller particles during the extrusion process. The transmission electron microscopy (TEM) images show that hot deformation leads to high dislocation density at a lower deformation temperature and leads to grain recovery and recrystallization at a higher deformation temperature. The strength of extruded composites increases first and then decreases with the increase of extrusion temperature, and it reaches maximum value at 500°C. The elongation of extruded composites increases with the increase of extrusion temperature.     

Effect of fabrication method on the aging behavior of 6061 Al matrix composites reinforced with SiC whiskers

Age hardening behaviors of SiC whisker reinforced composites with 6061 Al matrix fabricated by P.M. (powder metallurgy) and squeeze casting were investigated to examine the effect of the fabrication method on the aging kinetics. In the squeeze cast composite, numorous triangular particles which is believed to be MgAlp₂O₄ were observed at Al/SiC interfaces whereas no visible interface particles were observed in the P. M. composite. P.M. composite showed faster age hardening and reached the maximum hardness earler than the squeeze cast composites. The decrease of the aging kinetics in squeeze cast 6061 Al matrix composites compared to that in P.M. composites is thought to result from more severe depletion of Mg atoms due to interfacial reactions in squeeze cast composites. The uniformity of whisker distribution is suggested to influence the general aging behavior through its effect on the local dislocation density. Data on the aging kinetics and the interfacial reactions in other Al alloys were also examined to study various factors which can influence the aging kinetics.     

Effect of extrusion on properties of Al-based composite

An aluminium alloy and its composite with dispersed SiC particles made by liquid metallurgy route were extruded under optimized conditions.The properties were characterized in terms of microstructure,hardness and sliding wear behaviour and then compared between the extruded and cast alloys and composites,in order to understand the benefits of composite and extrusion on the alloy.It was observed that composites drastically increased the hardness and the extruded composites further increased this value.The advantage of composites was realized in sliding wear tests.     

Optimization of squeeze cast parameters of LM6 aluminium alloy for surface roughness using Taguchi method

The ability to produce near net shape components with good surface finish is made possible by means of squeeze casting, a hybrid metal forming process combining features of both casting and forging in a single operation. The primary objective of this paper is to analyze the influence of the process parameters on surface roughness in squeeze casting of LM6 aluminium alloy using Taguchi method. In Taguchi method, a three level orthogonal array has been used to determine the S/N ratio. Analysis of variance and the ‘F’-test values are used to determine the most significant process parameters affecting the surface roughness. The results indicated that the squeeze pressure and the die preheating temperature are the recognized parameters to cause appreciable improvement in the surface finish of the squeeze cast components.     

Effects of fabrication methods on deformability and microstructure of Mg–Zn–Zr wrought alloy

The effects of fabrication processing methods on the workability of Mg–Zn–Zr wrought magnesium alloy (ZK60A) were investigated based on the microstructure and inherent internal defects. Three different billets, semi-continuously cast, semi-continuously cast and subsequently extruded, and die-cast, were fabricated and uniaxially compressed at elevated temperatures and two different strain rates to determine the deformation capabilities. The grain structure of the billets was investigated using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The internal defects were inspected by an X-ray scanner. The enhanced deformability was observed in semi-continuously cast billet compared to the one fabricated by conventional die-casting, and the subsequent extrusion further improved the deformability.     

挤压铸造制备半固态AZ61镁合金的组织演变及力学性能(英文)

采用挤压铸造后直接二次重熔的方法制备半固态AZ61镁合金。首先通过挤压铸造预成形铸态AZ61镁合金,以获得细小的枝晶;然后在半固态区间进行二次重熔,细小的枝晶演变成球状晶,完全球化的晶粒被液相均匀包裹。研究结果表明:通过挤压铸造预成形的铸态AZ61镁合金与传统铸造预成形的铸态AZ61镁合金相比,在相同的二次重熔条件下,挤压铸造预成形的铸态AZ61镁合金获得更细小的半固态组织。此外,挤压铸造加上二次重熔触变成形的AZ61镁合金,力学性能优于传统铸造后二次重熔触变成形的AZ61镁合金。     

新型铝硅钛多元合金管材的研究

利用河南铝矿石直接电解的Ａｌ－Ｓｉ－Ｔｉ多元合金,系统研究了添加少量合金元素后的变形铝硅钛多元合金的显微组织、挤压性能和力学性能。结果表明,变形铝硅钛多元合金显微组织细小均匀,偏析小,Ｔｉ元素分布均匀;有较好的挤压性能和力学性能。特别是热处理后可成为综合性能很好的新型应用管材,可广泛用于交通、石油、化工等行业。