Conventional Aluminum Alloys Research Articles

Weld Solidification Cracking Behaviour of AA2195 Al–Cu–Li Alloy

In this study, weld solidification cracking behaviour of AA2195 Al–Cu–Li alloy was studied and compared with conventional AA2219 and AA2014 aluminium alloys. Cracking susceptibility was evaluated using varestraint test and Gleeble® hot ductility test and the slope of liquidus temperature as function of liquid fraction was also evaluated. Solidification cracking susceptibility of AA2195, AA2219 and AA2014 alloys was ranked based on the above methods. Consistent trend in cracking susceptibility was observed in all the methods where AA2195 and AA2219 alloys showed highest and lowest cracking susceptibility, respectively.

Experimental Investigation of Second-Harmonic Lamb Wave Generation in Additively Manufactured Aluminum

The correlation between the nonlinear acousto-ultrasonic response and the progressive accumulation of fatigue damage is investigated for an additively manufactured aluminum alloy AlSi7Mg and compared with the behavior of a conventional wrought aluminum alloy 6060-T5. A dual transducer and wedge setup is employed to excite a 30-cycle Hann-windowed tone burst at a center frequency of 500 kHz in plate-like specimens that are 7.2 mm thick. This choice of frequency-thickness is designed to excite the symmetric Lamb mode s1, which, in turn, generates a second-harmonic s2 mode in the presence of distributed material nonlinearity. This s1-s2 mode pair satisfies the conditions for internal resonance, thereby leading to a cumulative build-up of amplitude for the second-harmonic s2 mode with increasing propagation distance. Measurements of a nonlinearity parameter β derived from the second-harmonic amplitude are plotted against propagation distance at various fractions of fatigue life under constant amplitude loading, for three different stress levels corresponding to low-cycle fatigue (LCF), high-cycle fatigue (HCF), and an intermediate case. The results show both qualitative and quantitative differences between LCF and HCF, and between the additively manufactured specimens and the wrought alloy. The potential use of this nonlinearity parameter for monitoring the early stages of fatigue damage accumulation, and hence for predicting the residual fatigue life, is discussed, as well as the potential for quality control of the additive manufacturing (AM) process.

Surface quality characterisation of diamond cut V-groove structures made of rapidly solidified aluminium RSA-905

V-groove structure is the key composing feature of many optical products such as gratings and optical fibre connectors. The quality of the V-groove structure depends on multiple factors of manufacturing routines, process parameters, material properties, etc. among which the machinability of the workpiece materials plays a crucial role in achieving high-quality V-grooves. Due to the superior mechanical and material properties, rapidly solidified aluminium RSA-905 emerges as an ideal alternative for stainless steel and conventional aluminium alloys for optical components. This paper presents a theoretical and experimental investigation on ultra-precision machining of V-groove structures on RSA-905 using single crystal diamond tools, aiming to reveal some new insights into the material removal mechanism of V-grooving process. A model was established to explain chip flow and material removal phenomena, and effects of depth of cut and feed rate on cutting forces, surface quality and form accuracy were quantitatively evaluated. The results showed that less than 1 μm peak-to-valley (PV) form accuracy and 15 nm Ra surface roughness were obtained on V-groove surface under the best machining condition. A high-stress concentration existed in the vicinity of the straight cutting edges along the slope of the V-grooves, resulting in surface and subsurface damages due to the loss of harder particles. Besides, the unremarkable tool wear and smooth chip morphology demonstrated the good machinability of RSA-905.

Investigation on Surface Integrity of Rapidly Solidified Aluminum RSA 905 by Magnetic Field-Assisted Finishing.

RSA 905, a rapidly solidified aluminum alloy, has been widely utilized in optical, automotive, and aerospace industries owing to its superior mechanical properties such as hardness and strength compared to conventional aluminum alloys. However, the surface finishing of RSA 905 to achieve submicron surface roughness is quite challenging and was rarely addressed. This paper presents an experimental and analytical study on magnetic field-assisted finishing (MFAF) of RSA 905 through a systematic investigation on surface integrity in relation to the MFAF process parameters. The effect of abrasive and polishing speed conditions on material removal and surface roughness was quantitatively investigated. The surface and subsurface quality were evaluated by optical microscope and scanning electron microscope (SEM) observations, residual stress measurement, surface microhardness and tribology test. The results show that relatively high material removal and low surface roughness were obtained under conditions using the SiC abrasive with a grit size of 12 µm at polishing speed of 400 rpm or using the Al2O3 abrasive with a grit size of 5 µm at polishing speed of 800 rpm. Heat melt layer caused by wire electrical discharge machining (EDM) during the sample preparation was removed by MFAF without inducing new subsurface damage. The MFAF process also helps release the surface residual stress and improve the tribological performance although the surface microhardness was slightly reduced.

Aluminum metal matrix composites a review of reinforcement; mechanical and tribological behavior

This review aims to explore the fundamental mechanical and tribological behavior Aluminum matrix composites (AMCs) reinforced with different reinforcements. Aluminum matrix composites are considered to be the new emerging class of materials which are having the tailored properties for specific applications. AMCs are the advanced engineering materials having superior properties as comparison to other conventional aluminum alloys. AMCs exhibits attractive properties such as high hardness, better yield strength, strength to weight ratio, high thermal conductivity, low coefficient of thermal expansion, superior wear and corrosion resistance. In recent times, because of these properties they have repealed keen interest for various potential applications in aerospace, automotive and various other structural applications.. Extensive research and development has been made in the Al-based MMCs with every possible alloy and different reinforcements so as to get the material of desired properties. By suitable use of different reinforcements in the Al metal matrix a wide range of properties combination can be obtained. The fundamental mechanical and tribological behavior of different reinforcements under dry and wet lubricated sliding conditions is recently being studied. It is reported that various reinforcement were successfully employed to decrease friction and wear in various applications. A comprehensive review is provided with the aim to analyze such properties of different reinforcements.

Excellent room temperature deformability in high strain rate regimes of magnesium alloy

Magnesium and its alloys have the lowest density among structural metallic materials; thus, this light-weight metal has great potential for reducing the weight, for example, of vehicles and trains. However, due to its crystal structure, deformability is poor; in particular, under compressive stress. In this study, we modified magnesium with bismuth as an alloying element, which has the characteristics of being likely to form precipitates instead of grain boundary segregation. The Mg-Bi binary alloy showed excellent deformability and high absorption of energy in high-strain rate regimes at room temperature via contribution of grain boundary sliding. These properties, which are closely comparable to those of conventional middle-strength aluminum alloys (Al-Mg and Al-Mg-Si series alloys), have never been observed before in magnesium alloys. The development of such properties opens the door for not only academic but also industrial research in magnesium.

Micro-crack initiation and propagation in a high strength aluminum alloy during very high cycle fatigue

The behavior of the new AA2198-T8 high strength aluminum alloy during tensile and very high cycle fatigue (VHCF) tests is studied. The results of the tensile tests show that the alloy in this heat treatment state has excellent mechanical properties compared with the same alloy with other heat treatment conditions and the 2024 and 7075 conventional aluminum alloys. The VHCF tests show a fatigue life plateau with the fatigue life reaching 109 cycles under a stress amplitude of 200MPa, suggesting the existence of an endurance limit. Two different crack initiation modes are observed under scanning electron microscopy (SEM). Cracks tend to initiate from the interior of the specimen when fatigue life is in the VHCF regime. The interior crack initiation mode has a characteristic of a fish-eye, at the center of which is a white rough area (WRA) where the original micro-crack initiates. The thermo-mechanical process during ultrasonic fatigue is also studied. Quantitative analyses on micro-crack initiation and propagation show that the threshold stress intensity factor for stable micro-crack propagation is 1.66MPam1/2, and the threshold stress intensity factor for unstable macro-crack propagation is 3.17MPam1/2. Finally, analyses based on the Paris-Hertzberg law suggest that the micro-crack initiation stage likely consumes most of the fatigue life. The analyses do not apply to fatigue lives less than 106 cycles. The prediction of fatigue life is confirmed by the analyses of the thermo-mechanical process.

Role of Reinforcements on the Mechanical and Tribological Behavior of Aluminum Metal Matrix Composites – A Review

The target of this review is to explore the fundamental mechanical and tribological behaviour of different reinforcements on Aluminium matrix composites (AMCs). Aluminium matrix composites are the new emerging materials of this generation which can be tailored and engineered to obtain specific required properties for special applications. AMCs are recognizably different category of advanced engineering materials having superior properties over other conventional aluminium alloys. AMCs exhibits attractive properties of high hardness, better yield strength, strength to weight ratio, high thermal conductivity, low coefficient of thermal expansion, superior wear and corrosion resistance. Due to this they have repealed keen interest in recent times for various potential applications in aerospace, automotive and various other structural applications. Use of AMCs is constantly growing over the years, because of its better physical, mechanical and tribological properties as compared to other metal matrix composites. Extensive research and development has been made in the Al-based MMCs with every possible alloy and different reinforcements so as to get the material of desired properties. By suitable use of metal matrix and the reinforcement a wide range of properties combination can be obtained. The fundamental mechanical and tribological behavior of different reinforcements under dry and lubricated sliding conditions is recently being studied. It is shown that various reinforcement were used in metal matrix can be successfully employed to decrease friction and wear in tribological applications. A comprehensive review is provided with the aim to analyze such properties of different reinforcements. Moreover, the application of different reinforcements in the field of tribology for reducing friction and wear for better lubrication will be explored.

Role of Fabrication Route on the Mechanical and Tribological Behavior of Aluminum Metal Matrix Composites – A Review

Aluminum matrix composites (AMCs) are the new emerging materials of this generation which can be tailored and engineered to obtain specific required properties for special applications. AMCs are recognizably different category of advanced engineering materials having superior properties over other conventional aluminum alloys. AMCs exhibits attractive properties of high hardness, better yield strength, strength to weight ratio, high thermal conductivity, low coefficient of thermal expansion, superior wear and corrosion resistance. Due to this they have repealing keen interest in recent times for various potential applications in aerospace, automotive and various other structural applications. Use of AMCs is constantly growing over the years, because of its better physical, mechanical and tribological properties as compared to other metal matrix composites. Extensive research and development has been made in the Al-based MMCs with every possible alloy and different reinforcements by using different synthesis techniques so as to get the material of desired properties. By suitable use of metal matrix and the reinforcement a wide range of properties combination can be obtained. This paper attempts to review the role of different types of fabrication routes in the AMCs. In this paper we also briefly discuss the major fabrication-synthesis techniques, properties characterization, applications and the future scope of AMCs.

Solidification and Microstructure of Ni-Containing Al-Si-Cu Alloy

2 wt. % nickel (Ni) addition was introduced into a conventional cast aluminum alloy A380. The influence of transition alloying element nickel on the solidification behavior of cast aluminum alloy A380 was investigated via thermal analyses based on temperature measurements recorded on cooling curves. The corresponding first and second derivatives of the cooling curves were derived to reveal the details of phase changes during solidification. The nucleation of the primary α-Al phase and eutectic phases were analyzed. The microstructure analyses by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) indicate that different types and amount of eutectic phases are present in the tested two alloys. The introduction of Ni forms the complex Ni-containing intermetallic phases with Cu and Al.

Improvement of deep drawability of ultra-fine grained 6000 series aluminum alloy by tailored heat treatment

Among other approaches like alloying, it is possible to increase the strength of aluminum sheet material by the application of processing techniques like Accumulative Roll Bonding. However, the ductility will be reduced, which results in a limited formability in deep drawing operations. In this context, the Tailor Heat Treated Blanks technology is a well-known approach to enhance the forming limits of conventional precipitation hardenable aluminum alloys. The local softening of a blank can be achieved by a short-term heat treatment, which causes a dissolution of the MgSi-clusters in the heat treated zones. In a subsequent deep drawing operation, the material flow can be improved from the softened towards crack-critical areas. Within this investigation, the method of Tailor Heat Treated Blanks is transferred to a multi-layered, ultra-fine grained sheet material of the aluminum alloy AA6014 in order to investigate the effect of a local short-term heat treatment on the forming limits in deep drawing. In a first step, a material characterization in dependency of different heat treatment temperatures is carried out. The strength and ductility, as well as the bond strength of the multi-layered sheets, are investigated. Concluding, the effect on the formability is examined by deep drawing experiments on cylindrical cups in combination with a local heat treatment of the outer flange area prior to the forming step. The results regarding the limiting drawing ratio are compared with a conventional sheet material in the T4 temper condition and a multi-layered sheet material without heat treatment. The investigations indicate that the drawability can be enhanced significantly by the combination of both methods.

Surface modification of aluminum alloys using diffusion process

An applicability of solid diffusion of zinc (Zn) into an aluminum (Al) alloy for surface modification was investigated. A conventional Aluminum (Al) alloy (A5056) containing magnesium (Mg) was used for specimen. Liquefied Zn was plated on the Al alloy surface at a temperature of 450 degree Celsius (deg.) in air atmosphere then was aged for 5 hours was at various temperatures from 300 to 500 deg. As results, the increase in the diffusion distance of Zn from the surface and Al content into the Zn coated layer with the increase in the temperature was found. In addition, segregation of Mg was occurred near the surface and the coated layer was hardened. The tribological properties evaluated with 3 cast iron (FC250) pin in a lubricated condition showed that the difference of the friction coefficient depending on the heat treatment temperature was small and that the wear loss of the disc surface treated at a temperature of 300 deg. decreased. It was estimated that the transfer film containing Zn on the pin surface resulted in the low friction coefficient and the wear loss. Therefore, it is concluded that Zn coating accompanying with a heat treatment is effective means as the surface modification to decrease in the friction coefficient and the wear loss of Al alloy containing Mg.

Microstructure and mechanical properties of hard ceramic particulate reinforced AA7075 alloy composites via liquid metallurgy route

Particulate reinforced aluminium matrix composites (PRAMCs) are extensively substituting the conventional aluminium alloys in several applications and components in aircraft, marine, construction and automobile industries. Research is being carried out across the globe to enrich the mechanical, tribological and physical properties of PRAMCs using novel manufacture techniques and reinforcements. In this article, an attempt is made to analyse the influence of the different weight fraction of aluminum nitride (AlN) particle reinforced composites. Aluminium alloy AA7075 was reinforced with several quantities (0, 5, 10 and 15 wt%) of AlN through stir casting route. The microstructures, as well as mechanical properties of the manufactured composites are analysed. The manufactured composites were inspected by using Optical Microscope. Optical micrographs revealed the nearly uniform dissemination of reinforcement particles in the matrix alloy (AA7075). The hardness, as well as the tensile strength of the composite, has increased with the increase in weight fraction of aluminium nitride particulates in the AA7075 matrix.

Study and comparison of A356-WC composite and A356 alloy for an off-road vehicle chassis

Every vehicle manufactured has a chassis design that corresponds to its body shape, size and material used, to its performance. Aluminium alloys are most commonly used due to its high strength to weight ratio. Recent studies reveal that addition of reinforcements enhance the mechanical and tribological properties of aluminium and its alloys. So in this study, keeping aluminium (A 356) alloy as the matrix, WC particulates were added at 4 wt.% to the matrix using stir casting technique. The composition and microstructure of the cast specimens were studied by using EDS and SEM. The Vickers hardness test was carried out on both as-cast and heat treated specimens. The inference was that the composite had no effect on the heat treatment. A sample design of a roll cage chassis of an off-road vehicle was designed in Solidworks. Computer Aided Engineering (CAE) analysis was carried out on both composite and A 356 alloy chassis. The analysis showed that the composite was a better choice of material selection than the conventional aluminium alloy for its improved impact resistance and high strength to weight ratio and design safety.

Impact and modal analysis for different alloy wheel compositions

Wheels are an important component in the vehicle. The strength of the Alloy wheel rim is an important property of the Alloy wheel, which plays an important part in determining the overall performance of the vehicle, the structural integrity of the rim and the life of the Alloy wheel rim. With the advent of new Alloy wheel materials, new options are available to replace the conventional Aluminium Alloy wheels with new ones. The new Alloy wheel rim material and design need to be tested virtually for optimizing the appropriate design and material and the optimised wheel in virtual mode can be tested experimentally for the performance in real-time conditions before they can be used in the vehicles. The work in this project includes doing the impact and modal analysis for different alloy wheel compositions. From the results obtained, the optimum alloy wheel is suggested, which can be considered with further experimental validation.

Effect of porosities on tensile properties of laser-welded Al-Li alloy: an experimental and modelling study

Aluminium–lithium (Al-Li) alloys are very attractive for aerospace applications due to their outstanding properties, such as high specific strength, high rigidity and good resistance to corrosion and fatigue, compared to conventional aluminium alloys. The butt joints of Al-Li 2A97-T3 alloy sheet produced by fibre laser welding with ER2319 filler wire were investigated in this paper. Uniaxial tensile tests have been performed to determine the nominal mechanical properties of the joints with and without porosities. In addition, a defect zone was defined in the welded specimens to investigate the effects of porosity on the joint tensile behaviour. The post-weld strength prediction (PWSP) model in a previous study has been extended by including the effects of the porosity in the welds to predict the overall response of the butt joints. The experimental and the modelling results show a good agreement, with the yield strength having a deviation lower than 5%. Both the yield strength and the ductility of the tensile specimens were observed to have decreased with the presence of porosities. The porosities aggravated the inhomogeneous deformation in the weld zone. Higher strain rate was found in the defect area than the remaining weld zone during plastic deformation, as the porosity in the specimen caused inhomogeneous deformation. It was found that this accelerated the failure of the specimen and lowered the global ductility significantly.

Eco-efficient lightweight carbon-fiber reinforced polymer for environmentally greener commercial aviation industry

This research aims to perform comparative impact assessment for production of conventional aluminum alloy (AlMg3) used in aircraft fuselage and lighter weight carbon-fiber reinforced polymer (CFRP). The epoxy resin (EP), a thermosetting polymer typically impregnated with carbon fiber (CF) tows is assumed to be replaced by polypropylene (PP) which is a thermoplastic polymer. The assessment framework is demonstrated by postulating a scenario where AlMg3 in Boeing B737-800 fuselage is substituted with CFRP to reduce the fuselage weight by about 4.3 tons. OpenLCA 1.4.2 platform, including Ecoinvent v2.2 life cycle inventory (LCI) database and TRACE 2.1 methodology for life cycle impact assessment (LCIA), is used to quantify and compare mid-point impact categories of the AlMg3-based scenario and the postulated base case scenario using CFRP (53.8 wt% CF). The CF content in CFRP is used as a sensitivity parameter for impact categories calculations. The assessment results showed that AlMg3-based scenario leads to higher impact categories compared to the postulated CFRP (53.8 wt% CF) base case scenario. Additionally, results of the performed scenario analysis show ≈ 42% reduction in energy intensity associated with the high-volume CFRP production (base case scenario) compared to the low-volume production scenario. All calculated impact categories associated with the low-volume production scenario exceed the corresponding impact categories associated with the high-volume production (base case scenario). For example, ozone depletion potential (ODP) for the low-volume production scenario is ≈ 20.7% higher than that of the high-volume production scenario and global warming potential (GWP) for the low-volume production scenario is ≈10.2% higher than that of the high-volume production scenario. This research also compares impact categories associated with recycled CF (rCF) from end-of-life (EOL) CFRP (with PP resin matrix) to those corresponding to rCF from EOL-CFRP (with EP resin matrix). Overall, the results of this research support its alternative hypothesis (H1) which claims that replacing PE with PP in CFRP reduces the energy intensity and LCIA impact categories associated with CFRP production as well as rCF from EOL-CFRP. Finally, replacing fuselage’s AlMg3 with CFRP in Boeing’s new aircraft fleet by 2035 (Boeing Market Outlook 2016–2035) will lead to an estimated global carbon footprint reduction of ≈ 1x106 tons CO2 eq. Future global commercial aircraft could adopt the insights of this contribution to shrink their carbon footprint.

Great room temperature stretch formability of fine-grained Mg-Mn alloy

The effect of grain size and forming speed on room temperature formability was examined using Mg-0.3at%Mn binary alloy with different average grain sizes (2.5 and 18.5µm). Erichsen tests revealed that the limited dome height (LDH) was clearly influenced by these factors. LDHs increased with finer grain sizes and/or lower forming speeds. The highest LDH was obtained to be 8.2, which is superior to that in the conventional aluminum (A5083) alloy (LDH=4.3), in the present Erichsen testing conditions. The results obtained from the tensile tests under strain rate ranges similar to those of the Erichsen tests showed high strain rate sensitivity (m-value, where m=0.06–0.13 for the meso-grained alloy and 0.11–0.22 for the fine-grained alloy, respectively), irrespective of the extrusion direction vs. the tensile direction. Deformed microstructural observations after tensile and Erichsen tests revealed the existence of deformation twinning; however, the area/volume fraction of its microstructural feature was too small to affect the deformation mechanism. Instead of the deformation twinning-related fracture, cavitation due to grain boundary sliding was the origin of fracture during the present Erichsen tests. The further activation of grain boundary sliding was an effective method to improve the room temperature formability of magnesium alloys.

Optimization of Process Parameters in Stir Casting of Hybrid Metal Matrix (LM25/SiC/B4C) Composite Using Taguchi Method

Aluminium based composites exhibit many attractive material properties such as increased stiffness, wear resistance, specific strength and vibration damping and decreased co-efficient of thermal expansion compared with the conventional aluminium alloys. Aluminium Matrix Composites consist of non-metallic reinforcement which offers advantageous properties over base material. Reinforcements like SiC, B4C and Al2O3 are normally preferred to improve the mechanical properties. Here Aluminum LM25 is selected as matrix material while Silicon carbide and Boron carbide are selected as reinforcement material. The fabrication of aluminium matrix was done by stir casting method. In the present study an attempt has been made to investigate the effect of three major stir casting parameters (stir speed, stir duration and preheated temperature of reinforcement material) on stir casting of Aluminium LM25 - SiC - B4C composite. Experiments were conducted based on Taguchi methodology. Taguchi quality design concepts of L9 orthogonal array has been used to determine S/N ratio and through S/N ratio a set of optimum stir casting parameters were obtained. The experimental results confirmed the validity of Taguchi method for enhancing tensile strength of castings.

Origin of unusual fracture in stirred zone for friction stir welded 2198-T8 Al-Li alloy joints

Friction stir welded (FSW) joints of conventional precipitation-hardened aluminum alloys usually fracture in the lowest hardness zone (LHZ) during tension testing. However, all of the FSW joints of a 2198-T8 Al-Li alloy fractured in the stirred zone (SZ) instead of the LHZ with the welding parameters of 800rpm-200mm/min and 1600rpm-200mm/min under the condition that no welding defects existed in the SZ. The experiment results revealed that lazy S was not the dominant factor resulting in the unusual fracture. The SZ consisted of three subzones, i.e., the shoulder-affected zone, the pin-affected zone, and the transition zone between them. While the former two zones were characterized by fine and equiaxed recrystallized grains, incompletely dynamically recrystallized microstructure containing coarse elongated non-recrystallized grains was observed in the transition zone. The transition zone exhibited the lowest average Taylor factor in the SZ, resulting in a region that was crystallographically weak. Furthermore, obvious lithium segregation at grain boundaries was observed in the transition zone via time-of-flight secondary ion mass spectroscopy analysis, but not in the shoulder-affected zone or the pin-affected zone. The combined actions of both the two factors resulted in the appearance of preferential intergranular fracture in the transition zone and eventually caused the failure in the SZ. The lithium segregation at grain boundaries in the transition zone was closely associated with both the segregation in the base material and the partially dynamically recrystallized microstructure resulting from the inhomogeneous plastic deformation in the SZ.