Microstructure and Corrosion Resistance of CrN and CrN/TiN Coated Heat-Resistant Steels in Molten Aluminum Alloy

The components of the equipment for processing the Al melts into the molded parts can be markedly corroded by the molten Al. In this study, a 4 μm CrN coating or CrN/TiN multilayer coating for providing the physical and chemical barriers between the molten reactive Al and the steel substrate were deposited by Cathodic Arc Evaporation onto 10 mm-thick heat-resistant steel plates. The dipping tests were conducted in a 700℃ A356 melt for 1 to 21 h at intervals of 3 h. The damage of the coated steel was eva...

Heat Resisting Mechanism of Heat-Resisting Aluminum Alloy Conductor and Its Application in Transmission Line

In this paper the heat withstanding mechanism of heat-resisting aluminum alloy conductor is discussed, the types and performance of the conductor and its application on transmission lines are analyzed and introduced, and suggestions on accelerating exploitation and application of the conductor are put forward.

Characteristic of laser-MIG hybrid welding with filling additional cold wire for aluminum alloy

The weld appearance, deposition rate, welding efficiency, stability of arc, laser keyhole characteristic, and weld property were studied by using a novel laser-MIG hybrid welding process with filling wire of aluminum alloy. The results were also compared with those by conventional laser-MIG hybrid welding process. It was found that with the suitable process parameters this novel welding process for aluminum alloy was stable and final weld bead had fine appearance. Compared to conventional laser-MIG hybrid welding process, during this novel welding process the stability of arc, the laser keyhole characteristic and the weld property were similar, while the keyhole cycle frequency and keyhole opening area had differences of 1.23% and 15.34%, respectively, and the welding efficiency increased by about 31% without increasing heat input.

E2EM’s prediction of LaB_(6) as nucleation substrate for primary Mn-rich phase in Al-Si-Cu-Mn heat-resistant alloy and its refining effect

Edge-to-edge matching(E2EM)model was used to predict the potency of LaB_(6) as the heterogeneous nucleation substrate for primary Al_(13)Mn_(4)Si_(8) phase formed during the solidification of Al−Si−Cu−Mn heat-resistant alloy.There are five pairs of orientation relationships(ORs)between LaB_(6) and Al_(13)Mn_(4)Si_(8) phases which meet the criteria of E2EM model.One pair of plane ORs((110)LaB_(6)//(110)Al_(13)Mn_(4)Si_(8))are demonstrated by TEM observation.This strongly indicates that the LaB_(6) phase can act as the heterogeneous nucleation substrate for the primary Al_(13)Mn_(4)Si_(8) phase.1.0 wt.%of Al−2La−1B master alloy was also added into Al−12Si−4Cu−2Mn alloy to evaluate the refining effect by microstructure observation and tensile test.Experimental results show that addition of Al−2La−1B master alloy can significantly refine the primary Al_(13)Mn_(4)Si_(8) phase,supporting the prediction accuracy of E2EM model.However,such refinement of primary Al_(13)Mn_(4)Si_(8) phase does not lead to an improvement in strength.This is due to the larger difference in elastic modulus between the finally formed Al_(13)Mn_(4)Si_(8) phase and aluminum matrix than that of Al_(15)Mn_(3)Si_(2) phase.

Corrosion resistance of aluminum alloy AA7022 wire fabricated by friction stir extrusion

Friction stir extrusion(FSE)is known as an innovative manufacturing technology that makes it possible to directly produce wire via consolidation and extrusion of metal chips or solid billets.In this study,wire samples were produced using aluminum alloy AA7022 machining chips by the use of the FSE.To this end,the microstructures and mechanical properties of the base material(BM)and the extruded samples were investigated.The corrosion resistance of the given samples was also determined using potentiodynamic polarization technique.The results showed that the samples manufactured at higher rotational speeds possessed good surface quality,the process temperature and the grain size similarly increased following the rise in rotational speed,and the mechanical properties consequently decreased.Using the FSE led to crystallite refinement,increase in volume fraction of grain boundaries,as well as re-distribution of precipitates affecting corrosion resistance.Furthermore,the findings of the corrosion tests revealed that the produced samples by the FSE had adequate corrosion resistance and the growth in die rotation rate augmented current density and subsequently reduced corrosion resistance.

Wire and arc additive manufacturing of 4043 Al alloy using a cold metal transfer method

Cold metal transfer plus pulse(C+P)arc was applied in the additive manufacturing of 4043 Al alloy parts.Parameters in the manufacturing of the parts were investigated.The properties and microstructure of the parts were also characterized.Experimental results showed that welding at a speed of 8 mm/s and a wire feeding speed of 4.0 m/min was suitable to manufacture thin-walled parts,and the reciprocating scanning method could be adopted to manufacture thick-walled parts.The thin-walled parts of the C+P mode had fewer pores than those of the cold metal transfer(CMT)mode.The thin-and thick-walled parts of the C+P mode showed maximum tensile strengths of 172 and 178 MPa,respectively.Hardness decreased at the interface and in the coarse dendrite and increased in the refined grain area.

METAL INERT GAS WELDING OF 2519-T87 HIGH STRENGTH ALUMINUM ALLOY

20 mm thick plates of 2519-T87 high strength aluminum alloy have been welded.The effects of the compositions of filler wires,the heat input and the compositions of shielding gas on the mechanical properties and microstructure of the welded joint have been investigated.The results indicate that finer microstructure,better mechanical properties and higher value of hardness of HAZ can be obtained by using lower heat input.The use of Ar/He mixed shielding gas has several advantages over pure Ar shielding gas.With the increase of the proportion of He in the mixed shielding gas, the grain size of the weld metal as well as porosity susceptibility decreases.When the volume ratio of He to Ar reaches 7：3,the porosity and the grain size of weld metal reach the minimum,and the porosity can be further reduced by filling some CO2.

Joint performance in laser welding Al alloy with filler wire

CO2 laser welding aluminum alloy with filler wire was studied. The results indicate that the problems in CO2 laser welding of Al alloy, such as bad appearance of weld, easily excessive penetration and low strength, can be improved effectively by using laser welding with filler wire, and the maximum tensile strength of weld can reach 94% for the base metal. It also can be found that, the linear energy have great influence on the microstructure and mechanical properties of the joint. As the heat input increases, the cellular fir-tree crystals in the weld zone become sparse and the form of tensile fracture transforms from gliding fracture to brittle fracture.

Microstructure and Mechanical Properties of Wire + Arc Additively Manufactured 2050 Al–Li Alloy Wall Deposits

Aluminum–Lithium(Al–Li) alloy is a topic of great interest owing to its high strength and light weight, but there are only a few applications of Al–Li alloy in wire ss, a special AA2050 Al–Li alloy + arc additive manufacturing(WAAM) process. To identify its feasibility in WAAM procewire was produced and employed in the production of straight-walled components, using a WAAM system based on variable polarity gas tungsten arc welding(VP-GTAW) process. The influence of post-deposited heat treatment on the microstructure and property of the deposit was investigated using optical micrographs(OM), scanning electron microscopy(SEM), X-ray diffraction(XRD), hardness and tensile properties tests. Results revealed that the microstructures of AA2050 aluminum deposits varied with their location layers. The upper layers consisted of fine equiaxed grains, while the bottom layer exhibited a coarse columnar structure. Mechanical properties witnessed a significant improvement after post-deposited heat treatment, with the average micro-hardness reaching 141 HV and the ultimate tensile strength exceeding 400 MPa. Fracture morphology exhibited a typical ductile fracture.

TIG welding-brazing joint of aluminum to stainless steel with hot wire

TIG welding-brazing process with high frequency induction hot wire technology was presented to create joints between 5A06 aluminum alloy and SUS32! stainless steel using ER1100 filler wire with different temperature. The joints were evaluated by mechanical test and microstructural analyses. The welding procedure using hot fiUer wire （400 ℃ ） significantly increases strength stability by 71% and average value of tensile strength by 30. 8 % of the joints, compared with cold wire. The research of microstructures in interfaces and welded seams reveals that using 400 ℃ hot filler wire can decrease the thickness of intermetallic compounds （ IMCs ） from 6 to 3.5 txm approximately, which is the main reason of mechanical property improvement.

高强铝合金电弧增材制造的研究进展

高强铝合金因具有高强度、低密度、优异的延展性和抗腐蚀性,成为了航空航天和汽车应用零件最常用的金属材料之一。电弧增材制造技术具有快速原位成形制造复杂结构零部件的能力,非常适用于中型或大型高强铝合金铝部件的制造。本文综合分析了高强铝合金电弧增材制造工艺和设备研发现状、高强铝合金电弧增材的固有属性和缺陷以及主要的性能优化手段,讨论了组织和性能的固有特征和复合增材制造技术对组织和性能的影响。针对电弧增材制造高强铝合金不可忽略的本质冶金缺陷、特征性能需求和多种优化工艺的优劣等问题,提出了电弧增材制造高强铝合金综合评价体系、成分设计和丝材开发、专用热处理制度和复合增材制造技术的协同性等发展方向,以期为电弧增材制造高强铝合金的性能提升和应用推广提供重要参考。

2219铝合金CMT电弧增材熔滴过渡行为

在冷金属过渡(cold metal transfer,CMT)电弧增材制造过程中,熔池的流动行为极易受到电弧和熔滴的影响,从而严重影响堆积层的稳定性和成形件质量.该文利用高速摄影结果及电信号参数波形图,引入热输入量计算公式,从特征电信号、熔滴过渡特征量、热输入量等方面定量分析了CMT+P模式下送丝速度及脉冲修正系数对熔滴过渡过程及单道成形形貌的影响,同时分析了脉冲变极性冷金属过渡(Advanced CMT,CMT+PA)模式下送丝速度及控制面板上的EP/EN修正系数η对熔滴过渡过程及单道成形形貌的影响,为后续工艺优化提供参考和指导.

沉积策略对电弧增材制造5356铝合金显微组织、缺陷和力学性能的影响

基于电弧增材制造技术(WAAM)研究往复扫描(RS)、振荡扫描(OS)和垂直扫描(VS)3种沉积策略对5356铝合金(AA5356)构件的影响,探讨5356铝合金构件的显微组织、缺陷和力学性能。结果表明:相比于RS和OS策略,VS策略使得构件的热量分布均匀。VS策略的显微组织主要由等轴晶组成,使得显微硬度最高值达到HV 77.25。VS策略使得构件的气孔率和微孔尺寸分别下降了45.52%和19.81%,从而改善了拉伸性能。因此,VS策略为获得显微组织均匀、力学性能优异的AA5356构件提供了一种新的解决方案。

电弧增材镍铝青铜的组织与性能

镍铝青铜合金由于其在海水中的高耐腐蚀性能、抗生物污染性能和良好的抗空化冲击性能,被广泛运用于船舶螺旋桨的制造,但传统的铸造镍铝青铜由于材料成本过高,并且性能已不再适用于现今越来越高的要求.为了获得性能优异的镍铝青铜构件,采用了电弧增材制造技术成功制造了镍铝青铜合金构件,研究了铸造镍铝青铜和电弧增材的镍铝青铜的微观组织和力学性能的差异.结果表明,与铸态镍铝青铜合金相比,电弧增材制造的镍铝青铜合金有更细小的微观组织,κⅠ相的析出被抑制,绝大多数的β′相转变为α+κⅢ的共析组织,元素分布更均匀.与铸态镍铝青铜相比(545 MPa,20%),电弧增材制造的镍铝青铜构件展现了更加优异的力学性能,极限抗拉强度达到700 MPa,断后伸长率达到38%.

电弧增材制造2219铝合金热变形组织演变及本构方程

采用热压缩方法研究了电弧增材制造2219铝合金的热变形行为,变形温度为360~510℃,应变速率为0.01~10 s^(-1)。分析了温度和应变速率对流变应力和微观组织的影响,采用Zener-Hollomon参数的双曲正弦函数建立了电弧增材制造2219铝合金热变形本构方程。结果表明,电弧增材制造2219铝合金热压缩峰值应力随温度的升高和应变速率的降低而逐渐降低。电弧增材合金在420℃及以下温度仅发生滑移变形,450℃及以上发生动态再结晶,480℃为最佳锻造温度,发生完全动态再结晶,可有效细化增材晶粒。本构方程以动态再结晶温度(450℃)为临界点分为两段,动态再结晶温度以下变形激活能为212.53 kJ·mol^(-1),动态再结晶温度以上为163.37 kJ·mol^(-1)。沿晶界分布的共晶θ相在热压缩过程中发生破碎和固溶,变形温度越高或应变速率越小,固溶程度越高。

电弧增材制造铝合金的“控形”和“控性”技术研究现状

电弧增材制造铝合金具有沉积速度快、设备成本低、材料利用率高等优点,受到工业界和学术界的极大关注。但电弧增材制造固有的熔化和凝固特性决定最终材料存在“控形”“控性”的难题。本文从“控形”“控性”两方面对电弧增材制造铝合金的国内外进展进行分析,重点阐述了工艺参数优化、在线处理方式如基板预热、冷轧、熔池在线监测、微铸锻、搅拌摩擦焊等,以及后处理方式,讨论了不同技术的发展现状及趋势,并提出电弧增材制造铝合金“控形”“控性”的发展方向。

铝合金耐火电缆在民用建筑工程中的应用研究

简要介绍铝合金耐火电缆的分类、生产工艺及电缆构造,通过分析铝合金耐火电缆耐火性能试验报告、检测依据,对比铝合金耐火电缆与铜芯耐火电缆的性能,对铝合金耐火电缆在民用建筑工程中应用的可行性进行探讨和研究。

四种铝合金焊丝电弧增材制造构件的成形质量和组织性能对比研究

为了比较不同铝合金焊丝对电弧增材制造过程的适应性,选用ER1070、ER2A12、ER4043和ER5356四种典型铝合金焊丝,采用脉冲MIG电弧熔丝增材制造方法,在同等热输入条件下电弧增材制造直壁构件。通过热分析、表面波纹度计算、微观组织观察、硬度和力学性能测试,研究了四种焊丝在电弧增材成形、组织结构及力学性能方面的差异。结果表明,ER5356焊丝在电弧沉积过程中产生的飞溅最少,相应的直壁构件Al5356成形质量最好,表面波纹度值最小。四种铝合金直壁构件的微观组织差异明显,其中Al1070组织最粗大,孔隙缺陷最多;Al2A12组织为细小的等轴晶,Al4043的组织为发达Al-Si共晶,Al5356的基体最致密。力学性能测试显示,四种铝合金直壁构件在X向的抗拉强度高于Z向,Al1070和Al4043在X向和Z向上的延伸率差异比Al2A12和Al5356的大。Al1070的平均硬度和抗拉强度最低,但延伸率最高;Al2A12的平均硬度和抗拉强度最高,但延伸率不足10%,组织内存在的微裂纹限制了其力学性能的进一步提升;Al5356的平均抗拉强度略低于Al2A12,平均延伸率超过20%,表现出较好的综合力学性能。综上所述,ER5356焊丝更适合电弧增材制造铝合金构件,Al5356构件具有最佳的综合性能。

冷拉变形对7050铝合金丝材组织与性能的影响

对7050铝合金丝材经冷拉变形后过时效态以及冷加工变形态的组织与性能进行了研究。结果表明,随着冷变形量的增加,晶粒拉长,屈服强度、抗拉强度和剪切强度增大。与冷拉态相比较,过时效态丝材的这些指标增加不明显;晶粒越均匀细小,合金丝材冷镦时越不易发生开裂。

5183高端铝合金焊材生产技术开发

通过研究5183高端铝合金焊材生产工艺,确定合金成分、开发熔体深度净化工艺和退火工艺,同时还开发出直接用电解铝液连续铸造-热连轧-冷连轧的短流程、低能耗的5183铝合金焊材生产技术,建成国内首套电解铝液连续铸造-热连轧-冷连轧铝合金焊丝线坯生产线,焊丝线坯最小尺寸达到直径2 mm。