Characterization of A390 aluminum alloy produced at different slow shot speeds using vacuum assisted high pressure die casting

The effects of vacuum assistance on the microstructure and mechanical properties of high pressure die cast A390alloy at different slow shot speeds were evaluated.Plate-shaped specimens of hypereutectic A390aluminum alloy were produced on a TOYO BD?350V5cold chamber die casting machine incorporated with a self-improved TOYO vacuum system.According to the results,the vacuum pressure inside the die cavity increased linearly with the increasing slow shot speed at the beginning of mold filling.Meanwhile,tensile properties of vacuum die castings were deteriorated by the porosity content.In addition,the average primary silicon size decreased from23to14μm when the slow shot speed increased from0.05to0.2m/s,which has a binary functional relationship with the slow shot speed.After heat treatment,microstructural morphologies revealed that needle-shaped and thin-flaked eutectic silicon particles became rounded while Al2Cu dissolved intoα(Al)matrix.Furthermore,the fractography revealed that the fracture mechanism has evolved from brittle transgranular fracture to a fracture mode with many dimples after heat treatment.

Process for improving the ladle free- opening rate for high aluminum steel in continuous casting

Steel 20Mn23AlV is a type of high aluminum steel with a very low ladle free-opening rate. The aluminum composition of 20Mn23AlV ranges from 1.6% to 2.45% ,which is significantly higher than other types of steel. According to the real condition of 40 t ladle in steel-making plant of Baosteel Special Steel Company, previous works show that the key factors affecting the ladle free-opening rate of high aluminum steel in continuous casting are：sand material, accessories baking, ladle nozzle cleaning, the process and amount of adding sand, and the rate of argon stirring during refining. Therefore, improving the ladle filler sand quality, baking all of the raw materials, controlling the addition of ladle filler sand, cleaning the ladle nozzle, and optimizing argon stirring during the refining process can resolve the problem of a low ladle free-opening rate of high aluminum steel caused by the long ladle time of liquid steel.

Improving mechanical properties of AZ91D magnesium/A356 aluminum bimetal prepared by compound casting via a high velocity oxygen fuel sprayed Ni coating

In this paper,a Ni coating was deposited on the surface of the A356 aluminum alloy by high velocity oxygen fuel spraying to improve the performance of the AZ91D magnesium/A356 aluminum bimetal prepared by a compound casting.The effects of the Ni coating as well as its thickness on microstructure and mechanical properties of the AZ91D/A356 bimetal were systematically researched for the first time.Results demonstrated that the Ni coating and its thickness had a significant effect on the interfacial phase compositions and mechanical properties of the AZ91D/A356 bimetal.The 10μm’s Ni coating cannot prevent the generation of the Al-Mg intermetallic compounds(IMCs)at the interface zone of the AZ91D/A356 bimetal,while the Ni coating with the thickness of 45μm and 190μm can avoid the formation of the Al-Mg IMCs.When the Ni coating was 45μm,the Ni coating disappeared and transformed into Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles at the interface zone.With a thickness of 190μm’s Ni coating,part of the Ni coating remained and the interface layer was composed of the Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles,Mg_(2)Ni layer,Ni solid solution(SS)layer,Al_(3)Ni_(2) layer,Al_(3)Ni layer and sporadic Al_(3)Ni+Al-Al_(3)Ni eutectic structures from AZ91D side to A356 side in sequence.The interface layer consisting of the Mg-Ni and Al-Ni IMCs obtained with the Ni coating had an obvious lower hardness than the Al-Mg IMCs.The shear strength of the AZ91D/A356 bimetal with a Ni coating of 45μm thickness enhanced 41.4%in comparison with that of the bimetal without Ni coating,and the fracture of the bimetal with 45μm’s Ni coating occurred between the Mg matrix and the interface layer with a mixture of brittle fracture and ductile fracture.

GIGACYCLE FATIGUE BEHAVIOR OF CAST ALUMINUM IN TENSION AND TORSION LOADING

An improved understanding of fatigue behavior of a cast aluminum alloy（2-AS5U3G-Y35）in very high cycle regime is developed through the ultrasonic fatigue test in axial and torsion loading.The new developed torsion fatigue system is presented.The effects of loading condition and frequency on the very high cycle fatigue（VHCF）are investigated.The cyclic loading in axial and torsion at 35 Hz and 20 kHz with stress ratio R=-1 is used respectively to demonstrate the effect of loading condition.S-N curves show that the fatigue failure occurs in the range of 105—1010 cycles in axial or torsion loading and the asymptote of S-N curve is inclined,but no fatigue limit exists under the torsion and axial loading condition.The fatigue fracture surface shows that the fatigue crack initiates from the specimen surface subjected to the cyclic torsion loading.It is different from the fatigue fracture characteristic in axial loading in which fatigue crack initiates from subsurface defect in very high cycle regime.The fatigue initiation is on the maximum shear plane,the overall crack orientation is on a typical spiral 45° to the fracture plane and it is the maximum principle stress plane.The clear shear strip in the torsion fatigue fracture surface shows that the torsion fracture is the shear fracture.

Semi-solid near-net shape rheocasting of heat treatable wrought aluminum alloys

Flexibility of the CSIR-RCS, induction stirring with simultaneous air cooling process, in combination with high pressure die casting is successfully demonstrated by semi-solid rheocasting of plates performed on commercial 2024, 6082 and 7075 wrought aluminum alloys. Tensile properties were measured for the above mentioned rheocast wrought aluminum alloys in the T6 condition. The results showed that tensile properties were close to or even in some cases exceeded the minimum specifications. The yield strength and elongation of rheocast 2024-T6 exceeded the minimum requirements of the wrought alloy in the T6 condition but the ultimate tensile strength achieved only 90% of the specification because the Mg content of the starting alloy was below the commercial alloy specification. The strengths of rheocast 6082-T6 exceeded all of the wrought alloy T6 strength targets but the elongation only managed 36% of the required minimum due to porosity, caused by incipient melting during solution heat treatment, and the presence of fine intermetallie needles in the eutectic. The yield strength of rheocast 7075 exceeded the required one and the ultimate tensile strength also managed 97% of the specification; while the elongation only reached 46% of the minimum requirement also due to incipient melting porosity caused during the solution heat treatment process.

HIGH STRAIN RATE SUPERPLASTICITY IN A SiC_w/2024Al COMPOSITE MADE BY SQUEEZE CASTING

In this paper,the superplastic characteristics of the beta-SiC whisker reinforced 2024aluminum composite, fabricated by squeeze casting and hot-rolling after extrusion were investigated. The compsite had a fine grain size of about 2μm, and exhibited a strain rate sensitivity of about 0.35 and a maximum elongation of 350% at an initial strain rate of 1.1×10-1s-1 at 803K. In addition, the superplastic deformation mechanisme of the composite were also examined.

Microstructure Distribution Characteristics of High-Strength Aluminum Alloy Thin-Walled Tubes during Multi-Passes Hot Power Backward Spinning Process

The microstructure of the thin-walled tubes with high-strength aluminum alloy determines their final forming quality and performance. This type of tube can be manufactured by multi-pass hot power backward spinning process as it can eliminate casting defects, refine microstructure and improve the plasticity of the tube. To analyze the microstructure distribution characteristics of the tube during the spinning process, a 3D coupled thermo-mechanical FE model coupled with the microstructure evolution model of the process was established under the ABAQUS environment. The microstructure evolution characteristics and laws of the tube for the whole spinning process were analyzed. The results show that the dynamic recrystallization is mainly produced in the spinning deformation zone and root area of the tube. In the first pass, the dynamic recrystallization phenomenon is not obvious in the tube. With the pass increasing, the trend of dynamic recrystallization volume percentage gradually increases and extends from the outer surface of the tube to the inner surface. The fine-grained area shows the states of concentration, dispersion, and re-concentration as the pass number increases. .

Effects of temperature on fracture behavior of Al-based in-situ composites reinforced with Mg_2Si and Si particles fabricated by centrifugal casting

An aluminum-based in-situ composites reinforced with Mg2Si and Si particles were produced by centrifugal casting A1-20Si-5Mg alloy. The microstructure of the composites was examined, and the effects of temperature on fracture behavior of the composite were investigated. The results show that the average fraction of primary Si and Mg2Si particles in the composites is as high as 38%, and ultimate tensile strengths （UTS） of the composites first increase then decrease with the increase of test temperature. Microstructures of broken specimens show that both the particle fracture and the interface debonding affect the fracture behavior of the composites, and the interface debonding becomes the dominant fracture mechanism with increasing test temperature. Comparative results indicate that rich particles in the composites and excellent interface strength play great roles in enhancing tensile property by preventing the movement of dislocations.

一体压铸用免热处理铝合金自主研发及应用

为获得性能优异的一体压铸用免热处理铝合金,通过调整合金中各元素的质量分数,设计出3种不同成分比例的Al-Si系免热处理铝合金,采用差示扫描量热仪(DSC)、金相显微镜、扫描电镜、拉伸试验机和电磁共振式疲劳试验机对3种合金的熔化温度区间、组织相构成、断口形貌、拉伸与疲劳性能进行分析,结果表明,2#合金的熔化温度区间为55℃,抗拉强度、屈服强度、断后伸长率分别为303 MPa、153 MPa、11.3%,在1×10^(7)循环周次下的轴向拉压疲劳强度均值为125 MPa,因此,2#合金具有良好的铸造流动性、金相组织、强韧综合性能与铸造工艺性,且疲劳性能优于汽车行业普遍应用的AlSi9Cu3(Fe)压铸合金。

Study of rare earth element effect on microstructures and mechanical properties of an Al-Cu-Mg-Si cast alloy

The improvements of microstructures and properties of a high strength aluminum cast alloy were studied. The effects of rare earth elements on the microstructures and mechanical properties of the high strength cast alloy Al-Cu-Mg-Si were investigated. The result shows that the addition of rare earth elements can change the microstructures in refining the grain size of the alloy and making the needle-like and laminar eutectic Si to a granular Si. With the increase of the rare earth, the tensile strength and elongation of the alloy increase first and then fall down. The mechanical properties of the alloy will reach the highest value when the content of rare earth elements is about 0.7%.

铝合金双辊铸轧工艺进展及发展趋势

双辊铸轧工艺作为铝合金板带材先进的制备方式之一,符合当前“碳达峰、碳中和”的双碳战略要求,对推动我国高端轻质铝合金产业向绿色化、智能化方向发展起到积极的作用。文章通过系统的研究和分析,综述了铝合金双辊铸轧工艺的发展历史及现状,重点介绍了高合金化铝合金铸轧板偏析缺陷的形成机制,系统阐述了电磁外场、数值模拟在铝合金双辊铸轧工艺试验研究方面取得的进展,并对双辊铸轧工艺的发展趋势进行探讨分析,为我国高端轻质铝合金双辊铸轧工艺的发展提供借鉴和参考。

高压铸造参数对汽车用Al-Si-Cu铸造铝合金微观组织的影响

通过试验研究了合金元素含量、铸造温度和喷射压力对压铸铝合金微观组织的影响,对其组织特征和孔隙率进行了评价。对高压铸造零件进行取样与显微组织观察,研究了其微观组织的变化机制。结果表明,较低压力和较低的充型温度使高压铸造Al-Si-Cu合金孔隙率增加,促进粗大富铁金属间化合物的形成,改变α-Al相的形貌,合金元素含量的变化改变了在恒定铸造工艺参数下零件的微观组织。

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 significantly 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℃ 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 coeficient（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.

Sc含量对Al-7Mg合金铸轧板显微组织与性能的影响

主要采用金相显微镜(OM)、扫描电镜(SEM)、差示扫描量热法(DSC)和拉伸试验等检测手段,研究了不同含量的Sc对Al-7Mg合金板材的微观组织和力学性能的影响。试验结果表明:Sc对于减轻由双辊铸轧快速凝固及高镁含量产生的中心偏析带具有显著作用,增加Sc含量后,双辊铸轧板的晶粒尺寸逐渐减小,二次枝晶臂间距最小可减小到9.92μm;各元素的偏析度减小,偏析基本消除;合金中的非平衡共晶相的数量也呈现明显的下降趋势。同时,w(Sc)由0.1%增加到0.2%使得Al-7Mg合金的屈服强度提高了57 MPa,抗拉强度提高了35 MPa,伸长率提高了4.3%。Sc的加入使得凝固过程中的形核率提高,枝晶的生长受到抑制,同时Sc细化晶粒效果显著,并使偏析减轻,明显提高了合金的力学性能。

Strength and ductility optimization of HPDC AlSi8MgCuZn2 alloys by modifying pre-aging treatment

Considering the components produced by high pressure die casting(HPDC)process usually with ultra-large sizes and complex morphologies,high temperature solid solution treatment is not a suitable method to further improve their mechanical properties.In this study,two-stage aging treatment with different pre-aging times was designed and employed to further improve the mechanical properties of HPDC Al8SiMgCuZn alloy.The characteristics of precipitates were evaluated by a transmission electron microscope(TEM),and the precipitation strengthening mechanism was discussed.The results reveal that the strengthening is mainly contributed by the precipitation ofβ″phase after two-stage aging,and the number density and size of the precipitates are significantly depended on the pre-aging time.The number density of precipitates is increased with the pre-aging time prolonged from 0 h to 4 h,and then decreases with the further increase of pre-aging time from 4 h to 6 h.The precipitates with the highest density and smallest size are observed after pre-aging for 4 h.After pre-aged at 100℃for 4 h and then artificial aged at 200℃for 30 min,the yield strength of 207 MPa,ultimate tensile strength of 325 MPa and elongation of 7.6%are achieved.

Sc和Zr的复合添加对高Zn含量7xxx系铝合金组织演变和力学性能的影响

本文采用传统铸造和热加工工艺制备复合添加Sc、Zr的高Zn含量7xxx系铝合金,通过室温拉伸实验、扫描电子显微镜、X射线衍射仪和透射电子显微镜等,研究Sc、Zr的复合添加对高Zn含量7xxx系铝合金显微组织和力学性能的影响。结果表明:设计制备的新型高Zn含量(w(Zn)=10.9%)铝合金的抗拉强度为769 MPa,伸长率为4.7%。合金中高含量的Zn有利于形成高密度的纳米η'相,实现优异的沉淀强化效果。Sc和Zr复合添加形成的初生Al3(Sc,Zr)相有助于细化凝固组织,而时效过程中析出的次生Al3(Sc,Zr)相则可以有效抑制再结晶和阻碍位错运动,二者结合实现了良好的晶界强化作用。

高钛低铝特种焊接用钢浇铸稳定性研究

高钛低铝特种焊接用钢生产难度大,生产过程不稳定。通过对连铸生产过程中出现的结鱼及结瘤物检验及理论分析,查明影响浇铸稳定性的原因主要为钢中氧氮与钛结合形成的钛类夹杂物。通过采取纯化合金、降低精炼渣中SiO_(2)活度、调整钛合金化时间等措施,提高了钢水纯净度,钢中氮质量分数由39×10^(-6)降低至28×10^(-6)、氧质量分数由29×10^(-6)降低至21×10^(-6)、钛回收率由62.5%提高到65.3%,连铸浇铸过程稳定,解决了连铸坯表面夹渣和盘条表面结疤问题。

集成电路用超高纯铝铸造生产实践研究

超高纯铝铸锭是溅射靶材的上游关键材料,本课题根据生产实践中的对比试验,探究不同原料配比对超高纯铝铸锭的不纯物、颗粒物、内部质量的影响,旨在为生产高品质集成电路用超高纯铝铸锭提供参考。生产实践结果表明,重熔料表面进行清理是必要步骤,随着重熔料在原料中占比升高,铝中颗粒物夹杂数量和尺寸有升高和长大的趋势,在生产实践中重熔料在原料中的占比应该控制在30%以下。

乘用车车身压铸铝结构件应用现状及连接技术开发应对

一体化压铸铝合金结构件因其具有高集成、轻量化、刚性好等优点,在乘用车车身上的应用逐渐增多,并且正在向大型化发展。压铸结构件大型化的发展对连接技术提出了更大的挑战。阐述了当前乘用车车身压铸铝合金典型应用部位,分析了大型压铸结构件应用面临的难点、困境以及大型化后连接技术方面的应对策略,展望了未来压铸铝结构件的发展趋势以及对连接技术的新要求。

高强韧铝合金压挤双控铸造工艺及装备开发

介绍了宇部的压挤双控压铸(HFC)设备的构造和铸造成形工艺特点,通过增加加压室、引入氮气加压、局部加压以及热处理工艺优化等措施实施,避免了重力铸造、压铸浇注以及低压铸造液面下降过程中产生氧化物夹杂等缺陷,试制样件微观金相组织和力学性能检测结果完全满足产品高强高韧的技术要求。