Automotive Aluminum Alloys Research Articles

Mechanical properties and corrosion behavior of similar/dissimilar resistance spot welded automotive aluminum alloys

AbstractRecently, usage of high strength aluminum alloys in automotive applications increase. The reasons for that increase are the light‐weight, high strength, good formability, weldability and corrosion resistance of the aluminum alloys to improve fuel economy as well as decreasing carbon dioxide emission. Automotive hybrid structures are commonly manufactured using dissimilar AA5000‐AA6000 joints to improve mechanical requirements and corrosion resistance of the parts. In this study, AA5754 H111‐AA6063 T4 materials were joined both similarly and dissimilarly by resistance spot welding method. Within the study, a mid‐frequency direct current technology was used instead of conventional alternative current technology. The welded zone was investigated by micro hardness measurements and microstructural characterization. Tensile‐shear and cross‐tension tests were performed. The welded zone of all welded specimens was subjected to salt spray corrosion test. A nugget pull‐out fracture mode was observed on the fracture surface of the all welded joints after tensile‐shear and cross‐tension tests. The lowest hardness values were measured from the weld metals for all welded joints. Porosity and inclusion were observed in the weld nugget with minor cracks in heat affected zone by optical microscope investigations.

Synthesis and characterization of (Al,Si)3(Zr,Ti)-D022/D023 intermetallics: Understanding the stability of silicon substitution

(Al,Si)3(Zr,Ti)-D022/D023 are phases that may form in aerospace and automotive aluminium alloys. The substitution of Zr/Ti in these solid solutions is widely reported in the literature; however, it remains relatively unexplored for Si. In this work, in situ precipitation of (Al,Si)3(Zr,Ti)-D022/D023 intermetallics was performed using Al-Si-Zr-Ti alloys. The precipitation, sedimentation and concentration of numerous intermetallic particles were accomplished by filtrating the residual molten aluminium using a temperature/pressure-controlled vessel adapted with a PoDFA filter. A combination of SEM, TEM, XRD and EMP analysis allowed the identification of (Al,Si)3(Zr,Ti)-D022/D023 intermetallics concentrated within α-FCC matrices of non-Si-doped (sample S2) and Si-doped (samples S4 and S6) alloys. EDS analysis confirmed that Zr and Ti substitute each other in the D022 and D023 phases, whereas Si substitutes in Al sites. Acceptance of Si inside the D023 phase was not expected according to FTlite (FactSage) and TCAL7 (Thermo-Calc) databases. Additionally, Si was found to enhance the formation of (Al,Si)3(Zr,Ti)-D022 intermetallics with high Zr-content, contrary to FactSage 7.3 predictions. TEM results showed intermetallic/FCC crystal coherency for samples S2 and S6, implying that these intermetallics acted as nucleation sites for the Al-phase due to their small lattice mismatch. Furthermore, Si site occupancy was calculated for both (Al,Si)3Ti-D022 and (Al,Si)3Zr-D023 phases via DFT, showing that sites 2b and 4e are the most favorable for Si occupation, respectively. Finally, a thermodynamic model is derived to describe Si substitution upon solidification. Experimental and numerical examinations indicate that Si substitution preferentially occurs in the D022 intermetallics compared to the D023 phase.

Quantitative Evaluation of the Ability of Accelerated Tests to Simulate On-Road Corrosion Morphology of Automotive Aluminum Alloys

Three wrought automotive Al-Mg-Si alloys (6xxx-series) were exposed to an on-road service environment and in six standard laboratory-accelerated exposure tests. Optical micrographs of all these exposures were obtained and the resulting corrosion morphology was quantified using fractal dimension analysis and corrosion boundary length-to-area ratios. Additionally, the images were also used to train a convolutional neural network (CNN)-based pattern recognition algorithm, which was then used to quantitatively identify which accelerated test was the closest match to the field exposures. Overall, no single accelerated test could fully capture the on-road results or ubiquitously be the most appropriate test regardless of alloy and temper. However, results from fractal dimension and length-to-area ratio analyses identified that among the tests studied, those with acidified electrolytes are more appropriate for matching on-road corrosion morphology. The CNN algorithm output also agreed with this finding, indicating that the results from tests with acidified electrolytes correlated to field morphology with a confidence >70% for most of the images tested, thus showing the utility of these methods in providing quantitative bases for morphology comparison. Assessed in the context of literature evidence for localized corrosion mechanisms in 6xxx-series alloys, these results also indicated that pH may play an influential role in how corrosion morphology develops in these alloys upon exposure to a complex on-road environment.

Low-cycle fatigue behavior of Silafont®-36 automotive aluminum alloy: Effect of negative strain ratio

The aim of this study was to determine cyclic deformation behavior of a high-pressure die-cast Silafont®-36 automotive alloy with heterogeneous microstructures, focusing on the effect of strain ratio (Rε) ranging from negative infinity (-∞) to +0.5 at a constant strain amplitude of 0.4%. Pronounced cyclic hardening behavior was observed from the stress-strain hysteresis loops at different strain ratios. The degree of cyclic hardening, evaluated via both the traditional method and a newly-proposed slope method, increased with decreasing strain ratio. Fatigue life of the alloy was slightly lower at positive strain ratios, with its peak emerging at zero mean strain (or Rε = −1). In the negative range of strain ratios (Rε<−1), the fatigue life increased slightly with increasing strain ratio, which was mainly related to the plastic strain amplitude. A new power-law based equation was proposed to describe the change of mean stress relaxation at negative strain ratios (Rε<−1), along with a polynomial equation for depicting the situation at zero and positive strain ratios. Strain-energy density analyses corroborated that the intrinsic fatigue toughness was a material constant since it was not affected by strain ratio.

Approach to Analyse Sustainable Manufacturing Performance at the Production Line and Plant level

The next step in the evolution of manufacturing will be the implementation of flexible, scalable systems that produce a product in the most favorable environment using the best available tools, techniques, and resources to achieve significant cost savings, increased productivity, and long-term benefits. Through a review of relevant literature and a series of case studies, this study assessed the efficiency of sustainable manufacturing at the plant and line levels.The study's basis was the influence of economic, social, and environmental aspects on manufacturing sustainability. Discussions on the fundamental approaches for analysing the performance of sustainable manufacturing at various production levels had taken place throughout the research. This study also extensively analysed the approaches currently used to analyse sustainable manufacturing performance, and it explored and examined the challenges encountered. These approaches are addressed in this study through a case study of a recycle-friendly automotive aluminium alloy business and production of carbonated bottled drinks. The framework is then used to suggest a thorough set of approaches for analysing sustainable manufacturing at the plant and production line levels.

Performance of Ti/Zr and silane coating pretreatments on adhesive bonding of an automotive aluminium alloy produced using the Hot Form Quench (HFQ®) process

Surface pretreatments of an automotive aluminium alloy delivered in F temper and subsequently processed using Hot Form Quench (HFQ®), a novel press forming technique combining solution heat treatment, press forming and in-die quenching to produce high-strength aluminium alloys, for adhesive bonding have been explored. The performance of two commercial pretreatments including Ti/Zr and silane coatings, with either acid spray or alkaline immersion cleaning, was investigated. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) were employed to characterize the surface chemistry and topography of the alloy after pretreatments. Adhesively bonded aluminium-aluminium single lap shear joints and double cantilever beam specimens were tested to evaluate the performance of the pretreatments on the bonding strength and fracture resistance, respectively. The FTIR and TEM techniques show that the natural oxides and near-surface deformed layer have been successfully removed, but the surface cleanliness level was sensitive to the cleaning approach adopted. New Ti/Zr oxide layers or silane films have been built upon the aluminium surfaces, which confirms that sound surface conditions for adhesive bonding can be obtained for parts produced using HFQ® from F temper input material.

Analysis of residual plastic deformation of blanked sheets out of automotive aluminium alloys through hardness map

Reducing overall vehicle weight is essential to reduce fuel consumption and pollutant emission and to improve noise, vibration, and harshness (NVH) performances. The substitution with lighter alloys can involve the grand majority of vehicle components, depending on the market sector. In several applications, e.g., chassis, pulleys, and viscodampers, metal sheets are formed in several steps, each of whom work-hardens the material reducing the available residual plasticity. Typically, the process is designed via FEM, whose results are affected by the initial conditions, often neglected, and is performed on pre-processed materials from suppliers. In this regard, correctly simulating the first step of the process is critical. However, the related initial conditions, in terms of residual stress and strain induced by former preliminary operations, are often neglected. This work proposes a quick and economical experimental procedure based on a hardness map to estimate initial conditions and to validate FEM results. The procedure allows evaluating the material’s residual plasticity, which is necessary to process engineers to design following manufacturing steps. The approach is demonstrated on an industrially relevant case study, i.e., the blanking of an AA 5754, in use for water pump pulleys.

Effect of Combined Pre-Straining and Pre-Aging on the Precipitation Behavior and Age Hardening Response for Al-Mg-Si Alloys

Pre-strain (PS) and pre-aging (PA) treatments are often applied during the preparation of Al-Mg-Si automotive aluminum alloy. In this study, the effect of combined PS and PA on the precipitation behavior and age hardening response for Al-Mg-Si alloys was investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile test, Vickers hardness test, and differential scanning calorimetry (DSC). It was found that the dislocations introduced by PS treatment and the cluster (2) formed during PA treatment effectively inhibited the cluster (1), which further strengthened the inhibition of natural aging hardening at room temperature (RT). The strength increment of the alloys was kept below 10.0 MPa during two weeks RT storage. The dislocations provided heterogeneous nucleation for the precipitates forming and the cluster (2) transformed into β″ strengthening phase during bake hardening treatment. With the acceleration response of the dislocations and the cluster (2), the age hardening response of Al-Mg-Si alloys obviously improved with the denser and larger β″ strengthening phase formed.

Research on the Flow Stress of Thermal Compression Deformation of 5052 Aluminum Alloy Based on Computer

The design of 5052 aluminum alloy products is inseparable from the application of hot compression deformation technology, a considerable part of automotive aluminum alloy parts are composed of complex spatial curved surface rheological stress. CATIA thermal compression deformation technology in the design process not only to meet the structural characteristics of the parts, but also to ensure the smoothness, wear resistance of the product, so as to apply 5052 aluminum alloy products in a more comprehensive and effective application, and promote the design of automotive aluminum alloy more perfect, improve the efficiency of automotive aluminum alloy development.

Komparativna analiza fizičkom simulacijom omekšavanja ZUTa tri različite aluminijumske legure za vozila

The development of high strength aluminium alloy has revolutionized the automotive industry with innovative manufacturing and technological process to provide high-performance components, weight reduction and also diversified the application field and design consideration for the automotive parts that work under severe conditions, but the selection of proper production parameters is most challenging task to get excellent results. Growing industrial demand of aluminium alloys led to the development of new welding technologies, processes and studies of various parameters effects for its intended purposes. The microstructural changes lead to loss of hardening and thereby mechanical strength in the HAZ welded joint even though the base materials are heat treatable and precipitation hardened. So, our goal is to analyse HAZ softening and analyse the sub-zones as a function of the parameter. In this paper, the influence of weld heat cycle on the heat-affected zone (HAZ) is physically simulated for Tungsten Inert Gas Welding (TIG) using Gleeble 3500 thermomechanical simulator for three different automotive aluminium alloy (AA5754-H22, AA6082-T6 &amp; AA7075-T6) plate of 1 mm thickness. In order to simulate the sub-zones of the heat-affected zone, samples were heated to four different HAZ peak temperatures (550 °C, 440 °C, 380 °C and 280 °C), two linear heat input (100 J/mm and 200 J/mm) by the application of Rykalin 2D model. A series of experiments were performed to understand the behaviour, which make it possible to measure the objective data on the basis of the obtained image of the aluminium alloys tested with heat-affected zone tests in a Gleeble 3500 physical simulator. The main objective is to achieve the weldability of three different automotive aluminium alloys and their comparison based on the welding parameters like heat input. Further, the investigation of HAZ softening and microstructure of the specimens were tested and analysed using Vicker's hardness test and optical microscope respectively. The paper focuses on HAZ softening analysis of different grades of aluminium alloys for automotive application.

Increased Filiform Corrosion Resistance Utilizing a Zirconium-Based Conversion Coating on an Al-Zn-Mg-Cu (AA7075-T6) Alloy as well as Selected Surface Treatments

This study investigates the effect of surface treatment on the formation of Zr-based conversion coatings on AA7075-T6 automotive aluminum alloys and their resistance to filiform corrosion (FFC). Two different surface treatments were studied: (i) alkaline-cleaning and (ii) alkaline-cleaning with a subsequent acid deoxidation step. A model poly-vinyl butyral primer coating was used as the topcoat and specimens were studied with and without the application of a Zr-based conversion coating. Comparisons were made against a control that had no surface treatment. The FFC filament initiation time and propagation kinetics were of particular interest. Scanning electron microscopy and x-ray photoelectron spectroscopy were used to examine the conversion coating thickness and composition. A bi-layer conversion coating structure is demonstrated and both surface treatments are shown to produce copper enrichment that promotes the formation of the Zr-rich coating. Specimens prepared by alkaline cleaning-only resulted in a substantially thicker oxide layer of which 97% was ZrO2. These specimens provide superior resistance to FFC where the thick Zr-rich oxide is thought to provide a dense blocking layer that prevents electron transfer at the interface. In contrast, the control specimen, exposed only to the copper additions present in the conversion bath, is shown to produce an Al oxide-rich layer with only a 33% ZrO2 contribution in the outer layer. The findings demonstrate that the redistribution of functional copper species, that is shown to occur during surface treatment processes, is crucial for the formation of a robust Zr film.

Comparative investigation on single laser beam and dual laser beam for lap welding of aluminum alloy

Aluminum alloy is considered to be one of the ideal materials for light-weighting on aerospace and new energy automotive. Laser welding without a filler wire is an efficient way for weight reduction. The common defects in laser welding of aluminum alloys are porosities and cracks, resulting in poor mechanical performances and short service life of joints. In order to investigate the methods to suppress defects, 1 mm thick automotive aluminum alloy AA6014 was performed for single and dual-beam laser lap welding in this study. The effects of two welding processes on microstructure, cracks, and mechanical properties were investigated. The results showed that the welding adaptability of dual laser beam lap welding was much better than single laser beam lap welding. Well-formed weld could be obtained in a suitable line energy range by both welding processes. The dual beam with an energy ratio of 1:1 was at an angle along the welding direction, which could increase the molten pool area and stir the weld pool more sufficiently. Thus, dual laser beam lap welding could significantly increase the welding speed and alleviate collapse caused by single laser beam welding. The gaps of lap welding tended to be crack sources and generate cracks, while dual-beam laser welding was advantageous for reducing such cracks. This research is of great significance to improve the laser welding quality of all-aluminum automotive bodies, increase production efficiency, and further reduce the weight of the automotive.

A new approach for dissimilar aluminum-steel impact spot welding using vaporizing foil actuators

Abstract Dissimilar joining of aluminum to steel is an important industrial and academic problem. The present study reports the application of a novel approach in impact welding where a pocket machined on the flyer sheet generates the requisite standoff, enabling joining of commonly used automotive aluminum alloys to high-strength low-alloy (HSLA) steels. The new approach enables impact spot welding of heat treatable AA6111-T4 aluminum (Al) alloy to bare, hot-dip galvanized and e-coated HSLA 340 steel (with local removal of the coating on the faying surface) as well as of high-pressure vacuum die cast Aural 2 Al alloy to hot-dip galvanized HSLA 340 steel. Characterization of the welded samples via lap-shear and coach peel testing demonstrated high joint strengths with button pullout failure modes in all weld pairs. Optical microscopy of the weld cross-sections revealed defect-free joints displaying typical impact welded interface morphology. A significant outcome of the novel impact spot welding approach was the ability to produce joints exhibiting flat external target surfaces with unperturbed coating, a potential enabler for mixed metal joining applications involving pre-treated, e-coated, or painted materials.

Investigation of mechanical properties of AA6082-T6/AA6063-T6 friction stir lap welds

A study is conducted to investigate the microstructure and mechanical properties of lap joints produced by friction stir welding (FSW) between 3.5 mm thick sheets of automotive aluminum alloys AA6082-T6 with AA6063-T6. The FSW tool used in this study includes a set of WiperTM scrolls on the shoulder face and a probe having right hand threads, a set of tapered flats, and a set left hand CounterFlowⓇ grooves. The FSW process parameters are first optimized through the use of Design of Experiments (DOE) methodology. Static lap-shear tests are performed on the DOE coupons to identify the optimized parameters and once an optimized set of process parameters is identified, lap joint coupons are fabricated from sheets of each alloy for further mechanical and metallurgical investigation. The study implemented post-weld material characterization tests alongside a novel real-time feedback signal monitoring method for assessing the properties of friction stir lap welds. The analysis included microstructural examination, microhardness testing, lap shear testing, and an advanced electronic non-destructive evaluation (e-NDE) technique that uses the process feedback forces to detect weld anomalies primarily in the form of voids in real time. The analysis includes microstructural examination, microhardness testing, lap shear testing, and an advanced electronic (signal/frequency analysis) non-destructive evaluation (e-NDE) technique in order to detect weld anomalies primarily in the form of voids. For comparison purposes, the specimens are tested under two different loading scenarios; loading of the advancing side, and loading of the retreating side. During FSW, the plasticized material is dragged by the tool from the retreating side of the weld to the advancing side around the rear of the tool. Each loading scenario is tested for three conditions; as-welded, naturally-aged, and post-weld heat treated. The weld produced by the optimized parameters was fully consolidated and had no volumetric defects; absence of hooking is clearly identified in the microstructural analysis of the dissimilar lap joint along with good material flow and mixing of the alloys. The ‘advancing-side-loading’ is found to perform with higher strength than the ‘retreating-side-loading,’ which is evidence that ‘retreating-side-loading’ is less favorable in the FSW lap joints produced in this study because of weaker weld strength in the retreating side. A finite element modeling procedure is utilized to examine the distribution of stresses and displacements in a shear test of a lap weld sample. This study identifies improved process parameters for friction stir welding of dissimilar aluminum alloys for enhanced performance.

Mechanics study of automotive aluminium alloy materials based on elastohydrodynamic model

To solve the problem of large error in traditional testing methods for automotive aluminium alloy materials, a testing method for mechanical properties of automotive aluminium alloy materials based on elastohydrodynamic model was proposed. Firstly, the elastohydrodynamic model of automobile aluminium alloy material is constructed to obtain the bearing capacity and strength of automobile aluminium alloy material. Secondly, based on the elastohydrodynamic model of automobile aluminium alloy material, the load and yield strength of automobile aluminium alloy material mechanical components are analysed, and the vehicle use is estimated. Parameters of mechanical components of aluminium alloy materials. Finally, the mechanical properties of automotive aluminium alloys were further optimised by the evaluation method of under-actuated two-degree-of-freedom mechanism and the calculation of the coupling eigenfunction of mechanical properties of aluminium alloys and the energy equation of the relationship between friction force and friction coefficient.

Formability Studies of Automotive Aluminium Alloy Sheet series: A Review

The job of aluminium alloys in car and aircraft industries has been extending fundamentally over the most recent 20 years. Because of their low thickness to weight proportion and high explicit quality, aluminium turned into a solid trade for steel especially for car producing. However, to stamp a convoluted board parts from aluminium sheet is very troublesome explicitly at cold working temperatures where as far as possible are very less. To enhance formability breaking points of aluminium alloy sheet a few procedures are joined by numerous specialists like warm shaping, hot forming, superplastic forming, cold die quench (HFQ) forms and so on. This paper displays a basic study of various procedures utilized to enhance aluminium alloy sheet formability and distinguishing advantages and downsides for each procedure

Mechanics study of automotive aluminium alloy materials based on elastohydrodynamic model

Mechanics study of automotive aluminium alloy materials based on elastohydrodynamic model

An Investigation of the Deep Drawing Behavior of Automotive Aluminum Alloys at Very Low Temperatures

Sheet metal aluminum alloys in the 5000 and 6000 series show increased formability if deformed at sub-zero temperatures which is beneficial for processing industries using sheet metals where evermore highly complex-shaped components are produced. In order to evaluate a cryogenic forming process, the temperature-dependent forming limits of the selected materials need to be known. For this determination, a device has been developed which allows deep drawing operations with circular specimens at cryogenic temperatures. The limiting drawing ratio (LDR) of the commercial aluminum alloys EN AW-5182 and EN AW-6016 are investigated in a temperature range from 298 K to 77 K. It is shown that the deep drawing behavior of both materials is generally enhanced at very low temperatures, although the LDR of the EN AW-6016 alloy increases only at temperatures T ≤ 77 K. Furthermore, using mathematical formulations and numerical (finite element) simulations the influence of friction on the punch forces could be predicted. The calculated results and experimental data are compared, and then subsequently discussed.

J-integral based correlation evaluation between microstructure and mechanical strength for FSSW joints made of automotive aluminum alloys

Through using the crack resistance energy evaluated by a fracture parameter of J-integral, a correlation evaluation approach for potential relationships between post-weld microstructure and resultant mechanical properties was proposed. The present article, based on this method, discussed the effects of welded base metal combinations, AA 5052-H32 and 6061-T6 while considering their dissimilar configuration, on microstructure forming and further tensile strength of friction stir spot-welded (FSSW) joints, in the hope of micro-action mechanism. With the developed numerical evaluation model considering the weakened binding capability caused by inherent Hook defect, the cracking process during the initial and Hook propagation was simulated utilizing Virtual Crack Closure Technique (VCCT) to achieve a more accurate prediction of mechanical response. Meanwhile, both J-integral values of main kinked cracks was numerically calculated to study the influence of changes in local microscopic features on the overall performance. Consequently, morphological size of the Hook and amount of precipitated particles (Mg2Si mainly) in the stir zone (SZ) play key roles in determining the shear strength. Additionally, the dissimilar 5052/6061 joints exist a sudden change in Mg and Si concentrations at lap interface, thus making the integrity structure more prone to damage during loading. In terms of the two opposite lap orders while bonding dissimilar alloys, configuring the 5052 with greater plastic fluidity to the upper plate will yield a greater degree of embedding and mixing, accompanied by higher joint strength.

Research on Situation and Application Prospect of Automotive Body Sheets Al-Mg-Si Based (6000series) Alloy

This paper mainly focuses on the situation of materials used for body panels at home and abroad. It is found that 6000 series aluminum alloys are widely used in automotive work due to their high strength, good plasticity and excellent corrosion resistance. At the same time, the main problems of automotive aluminum alloy sheets are also analyzed, and the research direction of developing high-performance AI-Mg-Si-based aluminum alloy sheets is prospected.