Microstructure and mechanical properties of stationary shoulder friction stir welding joint of 2A14-T62 aluminum alloy

2A14-T62 butt joint was successfully welded by stationary shoulder friction stir welding(SSFSW)method.The results showed that using a pin with small shoulder could broaden the process window,and under a rotation speed of 2000 r/min and welding speed of 30 mm/min,joint with smooth surface,small reduction in thickness and little inner defects was obtained.The weld nugget zone was approx-imately circular,which was a unique morphology for SSFSW.The heat-affected zone(HAZ)and thermo-mechanically affected zone(TMAZ)were both quite narrow due to the lower heat input and slight mechanical action of the stationary shoulder.The fraction of high angle grain boundaries(HAGBs)exhibited a“W”shape along horizontal direction(from advancing side to retreating side),and the minim-um value located at HAZ.The average ultimate tensile strength and elongation of the joint were 325 MPa and 4.5%,respectively,with the joint efficiency of 68.3%.The joint was ductile fractured and the fracture surface contained two types of dimples morphology in different re-gions of the joint.Microhardness distribution in the joint exhibited a“W”shape,and the difference along the thickness direction was negli-gible.The joint had strong stress corrosion cracking susceptibility,and the slow stain rate tensile strength was 139 MPa.Microcrack and Al2O3 particulates were observed at the fracture surface.

Influence of Non-Natural Ageing Temperature on the Microstructural Characteristics and Mechanical Properties of Cast Aluminum 6063 Alloy

This research considered the effect of non-natural aging on the microstructural characteristics and mechanical properties of as-cast aluminum 6063 alloys. The samples were developed through a sand casting process and machined into tensile and impact test samples before carrying out solution heat treatment at 550?C (0.83 Tm) on two parts of the samples while retaining one part as the control. The two parts were further divided into sets denoted A and B and were aged at 180?C (0.27 Tm) and 160?C (0.24 Tm), respectively, for 12 hours. The results showed that sample A has the optimal yield strength and ultimate tensile strength of 192 and 206 MPa, respectively. Likewise, the sample gave the highest impact strength value of about 9.63 J/mm2. The observed results were supported by the optical micrograph, which revealed that the sample has evenly dispersed precipitates in its microstructure. This is deemed responsible for the observed increase in strength of the sample.

High corrosion and wear resistant electroless Ni–P gradient coatings on aviation aluminum alloy parts

A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.

Review on laser directed energy deposited aluminum alloys

Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstream AM technique,laser-directed energy deposition(LDED)shows good scalability to meet the requirements for large-format component manufacturing and repair.However,LDED Al alloys are highly challenging due to their inherent poor printability(e.g.low laser absorption,high oxidation sensitivity and cracking tendency).To further promote the development of LDED high-performance Al alloys,this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys.The porosity,cracking,distortion,inclusions,element evaporation and resultant inferior mechanical properties(worse than laser powder bed fusion)are the key challenges in LDED Al alloys.Processing parameter optimizations,in-situ alloy design,reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys.The underlying correlations between processes,alloy innovation,characteristic microstructures,and achievable performances in LDED Al alloys are discussed.The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized.This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys.Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.

Simulation of Dynamic Recrystallization in 7075 Aluminum Alloy Using Cellular Automaton

The evolution of microstructure during hot deformation is key to achieving good mechanical properties in aluminum alloys.We have developed a cellular automaton(CA) based model to simulate the microstructural evolution in 7075 aluminum alloy during hot deformation.Isothermal compression tests were conducted to obtain material parameters for 7075 aluminum alloy,leading to the establishment of models for dislocation density,nucleation of recrystallized grains,and grain growth.Integrating these aspects with grain topological deformation,our CA model effectively predicts flow stress,dynamic recrystallization(DRX) volume fraction,and average grain size under diverse deformation conditions.A systematic comparison was made between electron back scattered diffraction(EBSD) maps and CA model simulated under different deformation temperatures(573 to 723 K),strain rates(0.001 to 1 s^(-1)),and strain amounts(30% to 70%).These analyses indicate that large strain,high temperature,and low strain rate facilitate dynamic recrystallization and grain refinement.The results from the CA model show good accuracy and predictive capability,with experimental error within 10%.

Effect of Sc on Al_(3)Fe phase and mechanical properties of as-cast AA5052 aluminum alloy

The AA5052 aluminum alloy is widely used in automobile and aerospace manufacturing,and with the development of light-weight alloys,it is required that these materials exhibit better mechanical properties.Previous studies have demonstrated that the addition of Sc to aluminum alloys can improve both the microstructure and properties of the alloys.In this study,the effect of Sc on the Fe-rich phase and properties of the AA5052 aluminum alloy was studied by adding 0%,0.05%,0.2%,and 0.3%Sc.The results show that with the increase of Sc,the coarse needle-like Fe-rich phase gradually transforms into Chinese-script and then nearly spherical particles,reduce the size of Fe-rich phase,and refine the grain with increase of high angle grain boundaries(HAGBs).These microstructure changes enhance the strength of the AA5052 alloy through Sc addition.The ductility of the alloy is obviously improved because the addition of a lower amount of Sc changes the morphology of Fe-rich phase from needle-like into a Chinese-script,and it is subsequently reduced as a result of significant increase in HAGBs with increasing Sc content.

Electrochemical Hydrogen Charging on Corrosion Behavior of Ti-6Al-4V Alloy in Artificial Seawater

This study employs advanced electrochemical and surface characterization techniques to investigate the impact of electrochemical hydrogen charging on the corrosion behavior and surface film of the Ti-6Al-4V alloy.The findings revealed the formation ofγ-TiH andδ-TiH_(2) hydrides in the alloy after hydrogen charging.Prolonging hydrogen charging resulted in more significant degradation of the alloy microstructure,leading to deteriorated protectiveness of the surface film.This trend was further confirmed by the electrochemical measurements,which showed that the corrosion resistance of the alloy progressively worsened as the hydrogen charging time was increased.Consequently,this work provides valuable insights into the mechanisms underlying the corrosion of Ti-6Al-4V alloy under hydrogen charging conditions.

Effect of process parameters on the morphology of aluminum/copper alloy lap joints by red and blue hybrid laser welding

In order to overcome the problems of many pores,large deformation and unstable weld quality of traditional laser welded aluminumcopper alloy joints,a red-blue dual-beam laser source and a swinging laser were introduced for welding.T2 copper and 6063 aluminum thin plates were lap welded by coaxial dual-beam laser welding.The morphology of weld cross section was compared to explore the influence of process parameters on the formation of lap joints.The microstructure characteristics of the weld zone were observed and compared by optical microscope.The results show that the addition of laser beam swing can eliminate the internal pores of the weld.With the increase of the swing width,the weld depth decreases,and the weld width increases first and then decreases.The influence of welding speed on the weld cross section morphology is similar to that of swing width.With the increase of welding speed,the weld width increases first and then decreases,while the weld depth decreases all the time.This is because that the red laser is used as the main heat source to melt the base metals,with the increase of red laser power,the weld depth increases.As an auxiliary laser source,blue laser reduces the total energy consumption,consequently,the effective heat input increases and the spatter is restrained effectively.As a result,the increase of red laser power has an enhancement effect on the weld width and weld depth.When the swing width is 1.2 mm,the red laser power is 550 W,the blue laser power is 500 W,and the welding speed is 35 mm/s,the weld forming is the best.The lap joint of T2 copper and 6063 aluminum alloy thin plate can be connected stably with the hybrid of blue laser.The effect rules of laser beam swing on the weld formation were obtained,which improved the quality of the joints.

Effect of Thermal-cold Cycling Treatment on Mechanical Properties and Microstructure of 6061 Aluminum Alloy

The influence of thermal-cold cycling treatment on mechanical properties and microstructure of 6061 aluminum alloy was investigated by means of tensile test, optical microscopy(OM), X-ray diffraction(XRD) and transmission electron microscopy(TEM). The cryogenic treatment mechanism of the alloys was discussed. The results show that thermal-cold cycling treatment is beneficial since it produces a large number of dislocations and accelerates the ageing process of the alloy and yields the finer dispersed β" precipitates in the matrix. This variation of microstructural changes leads to more favorable mechanical properties than the other investigated states, while grain boundary precipitation is coarse and distributed discontinuously along grain boundaries, with a lower precipitation free zone(PEZ) on the both sides of precipitated phase. As a result, the tensile strength, elongation and conductivity of 6061 aluminum alloy after thermal-cold cycling treatment are 373.37 MPa, 17.2% and 28.2 MS/m, respectively. Compared with conventional T6 temper, the mechanical properties are improved significantly.

Effects of Spinning Process on Intergranular Corrosion Behavior of 5A06 Aluminum Alloy

Aluminum alloy tubes were prepared by tube spinning.The intergranular and electrochemical corrosion tests were used to investigate the intergranular corrosion behavior of the 5A06 aluminum alloy blank sample and the spinning sample.Results showed that the intergranular corrosion resistance of the spinning sample was higher than that of the blank sample.In addition,the electrochemical corrosion resistance of the spinning sample was higher than that of the blank sample.The EDS maps indicated a uniform element distribution pattern of aluminum and magnesium.Moreover,the phase composition and lattice constant of the samples were obtained by XRD analysis.The differences in microstructure between the aluminum alloy subjected to the spinning process and the untreated aluminum alloy were determined by EBSD.The differences were mainly attributed to the complex interactions among grain size,dislocations and grain boundaries.

Influence of Production Sequence of Aluminum Alloy Hot Rolling on Strip Surface Quality

With the intensification of market competition in the aluminum alloy strip processing industry,it is dif-ficult to control the mass production of the same specifications,which is bound to affect the hot rolling production.This paper studied the effect of the hot rolling order of aluminum alloy on the surface quality of strip,such as roll printing,color difference,anodic oxidation,etc.,reasonable discharge sequence and corresponding optimization measures were formulated.

Effectiveness of Sodium Silicate on the Corrosion Protection of AA7075-T6 Aluminium Alloy in Sodium Chloride Solution

The influence of sodium silicate on the corrosion behaviour of aluminium alloy 7075-T6 in 0.1 M sodium chloride solution was studied by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy (SEM) was used to characterize the AA7075-T6 surface. Silicate can significantly reduce corrosion deterioration and the inhibition efficiency increases with the concentration of Na2SiO3. The corrosion inhibition mechanism involves the formation of a protective film over the alloy surface by adsorption of aluminosilicate anions from solution, as has also been suggested by others in literature.

阴极电流密度对6061铝合金在含Na_(2)WO_(4)电解液中微弧氧化膜结构和耐磨性能的影响

目的 研究恒流模式下阴极电流密度对6061铝合金在含Na2WO4的电解液中制备的微弧氧化膜厚度、形貌、相组成及耐磨性能的影响。方法 固定阳极电流密度为5.0 A/dm^(2),阴极电流密度分别为0、1.25、2.5、3.75、5.0 A/dm2,对6061铝合金进行微弧氧化40 min。用涡流测厚仪测量了氧化膜的厚度,用扫描电镜观察了微弧氧化膜的表面形貌和截面形貌,用能谱分析仪分析了氧化膜的表面成分,用X射线衍射分析仪分析了微弧氧化膜的相组成,用往复式摩擦磨损试验机测试了氧化膜的耐磨性能。结果 随着阴极电流密度的增加,氧化膜内的W含量逐渐减少,氧化膜颜色逐渐变浅,氧化膜厚度逐渐增加。微弧氧化膜的主要组成相为α-Al2O3和γ-Al2O3。当阴极电流密度从0 A/dm2增加到3.75 A/dm2时,氧化膜内孔洞的数量和尺寸逐渐减少,孔洞到氧化膜/基体界面的距离逐渐增加,氧化膜的耐磨性能逐渐提升。当阴极电流密度为3.75 A/dm2时,氧化膜的磨损率最低,仅为1.07×10-4mm3/(N·m)。但阴极电流密度增加到5.0 A/dm2时,氧化膜表层出现孔洞和剥落,耐磨性能下降。结论 阴极电流的加入有助于增加6061铝合金微弧氧化膜的厚度,提高氧化膜的致密性和耐磨性能,但过高的阴极电流会导致氧化膜表层出现孔洞,降低耐磨性能。

热轧变形对含0.5%B的6063铝合金导电率和组织性能的影响

借助导电率测试仪、电子万能材料试验机、场发射扫描电镜(SEM)和金相显微镜(OM),研究轧制变形量对含0.5%B的6063铝合金的导电性能、力学性能和显微结构的影响。结果表明:随着轧制变形量的增加,晶粒越来越细小。在增强合金拉伸强度、硬度的同时,合金的导电率并没有降低,轧制状态下的合金导电率高于铸态和均匀化的合金,其中导电率最高的为50%轧制变形量的合金,达到57.11%IACS,此时合金的抗拉强度达到128 MPa,伸长率为15.9%。当合金的最高轧制变形为75%时,抗拉强度为162 MPa,伸长率为10.35%,导电率为56.58%IACS。

热轧变形量对含0.5%B的6063铝合金晶粒取向、织构及再结晶的影响

借助SEM、EBSD、EDS等测试手段,研究了轧制变形量对含0.5%B的6063铝合金的晶粒取向、形变织构以及再结晶的影响。结果表明:随着轧制变形量的增加,晶粒越来越细小,越来越扁平,晶粒取向趋于一致,小角度晶界密度增加。轧制变形可以明显改变铝合金内部织构占比,合金随着压下量的增加,S织构和Brass织构占比变少,Cube织构和Goss织构的占比变多。均匀化热处理会使样品的再结晶晶粒增加至87.4%,轧制会使再结晶晶粒数量急剧下降,但是随着变形量的增加,再结晶晶粒数量会缓慢增加至1.18%。

激光熔覆Stellite 6合金涂层的耐磨耐蚀性能研究

为提高阀杆用SUS630不锈钢的耐磨耐蚀性能,利用激光熔覆技术在其表面制备Stellite 6钴基合金涂层,随后对比研究了Stellite 6合金涂层和SUS630不锈钢基体的显微硬度、摩擦磨损性能和腐蚀性能。结果表明:相对于SUS630不锈钢,Stellite 6合金涂层的硬度提高了25%,磨损体积减少了50%,说明Stellite 6合金涂层的耐磨性能优于SUS630不锈钢基体;此外,在3.5%NaCl溶液中,Stellite 6合金涂层的腐蚀电位(-0.18 V)和钝化膜的阻抗值(367 kΩcm^(2))均高于SUS630不锈钢基体的腐蚀电位(-0.35 V)和钝化膜的阻抗值(129 kΩcm^(2)),而其钝化电流密度(10^(-7)-10^(-6)A/cm^(2))小于SUS630不锈钢基体的钝化电流密度(10^(-6)-10^(-5)A/cm^(2)),说明Stellite 6合金涂层的耐腐蚀性能优于SUS630不锈钢基体。因此,激光熔覆Stellite 6合金涂层可提高SUS630不锈钢的耐磨耐蚀性能。

膜层厚度对6061铝合金黑色微弧氧化陶瓷膜层结构与性能的影响

为了明确膜层厚度对铝合金黑色微弧氧化陶瓷膜层的黑度、耐蚀性和硬度的影响规律,促进其实际应用,在硅酸盐-钒酸盐复合溶液体系中对6061铝合金进行微弧氧化处理,通过控制微弧氧化时间获得具有不同膜层厚度的铝合金黑色陶瓷膜层。利用测厚仪、粗糙度测量仪、SEM和EDS对黑色陶瓷膜层的表面结构、膜层成分和粗糙度等进行表征,并借助色差仪、维氏硬度计和电化学工作站等研究了膜层厚度对陶瓷膜层的黑度、显微硬度和耐蚀性的影响。结果表明:膜层厚度对黑色陶瓷膜层的表面形貌、粗糙度、显色特性、硬度和耐蚀性有较大影响。随着微弧氧化时间延长,膜层厚度增加,膜层表面更为粗糙,表层放电微孔数量减少,放电微孔孔径增大;当膜厚达到30.786μm时,陶瓷膜层的放电微孔显著增大,孔径达到10μm。随着膜层厚度增加,陶瓷膜层的黑度增加,显微硬度提高,但耐蚀性先增强后降低。当膜层厚度为20.781μm时,陶瓷膜层的黑度和硬度较高,耐蚀性最好,其在3.5%NaCl溶液中的自腐蚀电流密度为1.093×10^(-6) A/cm^(2)。

6061铝合金超声辅助搅拌摩擦焊温度场分析

为了分析超声振动对6061铝合金超声辅助搅拌摩擦焊接过程温度场的影响,采用解析建模和数值模拟的方法,建立了超声辅助搅拌摩擦焊过程中接触界面摩擦系数模型和热力耦合有限元分析模型,开展了6061铝合金超声辅助搅拌摩擦焊温度测量试验,结合有限元与试验结果进行对比分析.结果表明,仿真得到的工件表面温度分布曲线及取样点温度都与试验结果基本吻合,验证了建立模型的准确性;超声振动可以改变摩擦状态,降低焊接摩擦产热,减少峰值温度及高温区域的面积,振幅对焊接峰值温度影响的显著性高于频率.

6061铝合金FSW接头组织与耐蚀性能的研究

对4 mm厚的6061-T6铝合金板进行了搅拌摩擦焊接,通过浸泡腐蚀试验和电化学腐蚀试验研究焊缝腐蚀性能,采用金相显微镜、透射电镜等观察接头的微观组织。结果表明:6061铝合金FSW焊核区晶粒显著细化,晶界第二相较少;焊核区的耐剥落腐蚀和晶间腐蚀性能优于热影响区的;焊核区比热影响区的腐蚀电位较高,腐蚀电流密度较小,焊核区表现出更好的耐腐蚀性能。

6063铝合金中性无铬转化膜制备及膜层性能分析

目的提高铝合金微小器件的耐蚀性,开发一种条件温和可控的转化膜成膜工艺。方法采用中性无铬转化工艺,在6063铝合金表面制备转化膜。通过研究NaF、NH_(4)HF_(2)、KMnO_(4)、十二烷基硫酸钠(SDS)和没食子酸等几种添加剂对转化膜外观与耐蚀性的影响,确定NH_(4)HF_(2)为最佳添加剂。采用电化学方法分析膜层的耐蚀性,用SEM和EDS分析表面形貌及元素组成,并采用XRD和XPS表征膜层晶态结构和化合物组成。基于检测结果,简要分析转化膜的成膜过程。结果最终得到了中性转化处理的最佳成膜工艺为EDTA-2Na8.0g/L,单宁酸1.0g/L,Na_(2)WO_(4)6.0g/L,H_(2)ZrF_(6)4.0g/L,NH_(4)HF_(2)3.0g/L,pH6.6,成膜温度为30℃,成膜时间为15 min。该工艺所制备的转化膜外观致密均匀,颜色为浅黄色。电化学测试结果表明,转化膜具有良好耐蚀性,自腐蚀电流密度由基体铝合金的16.22µA/cm^(2)下降为转化处理后的0.87µA/cm^(2)。EDS能谱分析结果表明,膜层主要由Al、C、F、O、Na、Zr和W元素组成。XRD结果显示,膜层中含有Na_(3)AlF_(6)晶体。XPS分析结果表明,膜层中还含有Al_(2)O_(3)、AlF_(3)、WO_(3)、ZrF_(4)以及金属有机络合物。结论采用中性转化处理工艺,可以在6063铝合金表面制备有色均匀、耐蚀性良好的转化膜,膜层主要由Al的难溶化合物组成。