Heat-treatable Aluminum Alloys Research Articles

Effectiveness and efficiency of tool alignment and simultaneity factors on double-sided friction stir welding for joining heat-treatable aluminum alloys: a review

Effectiveness and efficiency of tool alignment and simultaneity factors on double-sided friction stir welding for joining heat-treatable aluminum alloys: a review

An aging processing design scheme derived from precipitation thermo-kinetic synergy of heat-treatable aluminum alloys

An aging processing design scheme derived from precipitation thermo-kinetic synergy of heat-treatable aluminum alloys

Feasibility Study of Solid-State Recycling through Direct Hot Rolling of AA5754 Aluminum Chips for Automotive Applications

Recently, researchers have done a lot of efforts to develop new solid-state recycling processes, both experimentally and developing numerical models. This kind of process is energy-saving and environmentally friendly compared to the conventional aluminum recycling process because avoided the melting step. The purpose of this work is to evaluate the feasibility of an innovative solid-state recycling process through direct hot rolling in a non heat-treatable aluminum alloy for automotive applications. AA5754 chips have been produced by turning a bar without the usage of lubricants and compacted with a 150 kN load; the compacted billets were treated at 400 °C and directly hot rolled in several successive passes. Rolled samples are then analyzed in terms of Vickers microhardness and microstructure in both as-rolled and heat treatment conditions, this last was performed at 185°C simulating the process of paint-bake. The produced samples show an excellent bonding between chips.

A Review on Friction Stir Welding of High-Strength Al-Zn-Mg Alloy: Insights on Second-Phase Particles

The friction stir welding (FSW) process is a unique combination of deformation and high temperature, which provides opportunities to modify microstructures through the adjustment of the processing parameters and is an ideal way to join non-weldable aluminum alloys by avoiding the formation of a molten pool. The 7xxx series heat-treatable aluminum alloys are widely used in the aerospace field as high-performance structural materials. The microstructure evolution and mechanical performance of these alloys are affected by the effects of thermomechanical processing, which provides opportunities to optimize the material properties by controlling microstructural features such as intermetallic constituent particles, dispersoids and nanoscale precipitates. This paper focuses on the basic principles of the thermal and mechanical effects generated during FSW on the evolution of second-phase particles in different zones of the weld.

Dynamics of Portevin-Le Chatelier (PLC) bands and fracture behavior of W-tempered 7075 aluminum alloys with different cooling methods

The relationship between Portevin-Le Chatelier (PLC) band propagation, plastic deformation, and failure mechanisms in solution heat-treated 7075-T6 aluminum alloys cooled by water quenching (7075-WQ) or air cooling (7075-AC) is compared using 5052-H32 alloy as a reference. Miniature tension tests, strain rate jump (SRJ) tests, and digital image correlation reveal that 7075-WQ shows diffused band configurations, 7075-AC exhibits localized patterns, and 5052-H32 has relatively stationary bands. These PLC band dynamics, related to geometry and band densities, are supported by fractography and microstructure analyses. The 7075-WQ and 7075-AC alloys exhibit mixed ductile and quasi-brittle fractures, while 5052-H32 shows ductile fractures with cup-and-cone surfaces. The findings provide new insights into the PLC bands and their formation mechanisms in W-tempered 7075 aluminum alloy concerning different cooling methods, supporting the development of thermal-mechanical processing routes for aluminum components with controllable plastic instability.

Novel Aging Warm-Forming Process of Al-Zn-Mg Aluminum Alloy Sheets and Influence of Precipitate Characteristics on Warm Formability

Concurrently improving the formability and post-formed strength of Al-Zn-Mg alloy sheets is crucial for producing high-strength parts with complex shapes. A novel process of aging warm-forming (AWF) to form solution heat-treated and water-quenched aluminum alloy sheets is proposed in this paper. The as-quenched AA 7075 sheet was first pre-aged and then formed at the desired temperature. The automotive paint–bake process was then utilized as the second aging step to achieve the target strength of the formed part. Additionally, the post-formed strength and warm formability of specimens under the AWF process conditions, as well as the warm-forming of various heat-treated Al-Zn-Mg alloy sheets proposed in previous studies, were compared through tensile and limit dome height tests. Precipitate characteristics of specimens subjected to different warm-forming process conditions were examined to understand their impact on warm formability. The warm formability of Al-Zn-Mg alloy sheets was significantly enhanced, and the post-formed strength achieved was more than 90% of the strength of as-received AA 7075-T6 sheets under the AWF process condition. The results demonstrated the feasibility of this novel AWF process to manufacture Al-Zn-Mg alloy stamped parts for improved spring-back, formability, and good overall post-formed strength. The results also indicate that microstructural characteristics in Al-Zn-Mg alloy sheets under different warm-forming process conditions have a noticeable influence on warm formability and final mechanical properties.

Impact energy in Heat-Treated aluminium alloy 6061 and 7075

Instrumented Charpy impact is one of the promising methods to assess the impact energy; toughness and resilience of a material. The test consists of the Charpy machine and instrumentation equipment which is the strain gauge and the data acquisition system. Impact energy evaluations are important to understand the material behaviour subjected to sudden impact loading. Aluminium 7075 has good strength strength-to-weight ratio than aluminium 6061 and hence the AL 7075 is usually used in the aerospace industry, whilst the AL 6061 is commonly used in the automotive industry. The objective of the study is to observe and analyse the impact response of the Aluminium 6061 and 7075 at different heat- treated conditions; O-anneal and T6 temper. In addition to the impact energy absorbed value, the impact strain signal is recorded too. Theoretical impact energy is calculated as well based on the information given by the Charpy machine software. Aluminium 7075 exhibits a lower value of impact energy absorbed and a smaller area under the curve compared to Aluminium 6061. The energy absorption capacity for each material grade and heat-treated condition are different from one another. O-anneal aluminium has a lesser energy absorbed value and a smaller area under the curve than the T6 temper aluminium. The outcome reveals that the heat treatment process alters the material microstructure and mechanical properties, whereas in this study the impact energy responses are influenced by these circumstances. Moreover, the chemical composition of the aluminium alloy distinguishes these two grades from one another, thus resulting in different impact responses.

Study the mechanical and morphological properties of aluminium alloy 7075 by aging treatments

The goal of the current research project is to determine the specimen’s surface morphology and mechanical characteristics by examining the effects of single and duplex ageing on aluminum 7075 alloy (Al-Zn-Mg-Cu). The age hardening strengthening mechanism is responsible for (Al-Zn-Mg-Cu) alloys. The threesteps of solid solution heating, quenching, and age hardening during theageing process. Five samples are used in the single ageing heat treatment with a dimension of60 mm in length and 25 mm in diameter. The specimens are first heated in a solid solution for one hour at 500 °C, followed by a 30-minute soak of the aluminum alloys in a salt bath. Following that, the specimens are matured for 2, 4, 6, 8, and 12 h at 160 °Ctemperature.. Duplex age-hardening process all five specimens are pre-heat at 160 °C after that double ageing process carried by different time periods same as the single ageing process. After heat-treated aluminum alloy specimens undergo investigation of mechanical properties such as tensile test, hardness test and surface morphology analysis using scanning electron microscopy. The result reveals that the aging process at a temperature of 160 °C for a period of 2 h, both the yield strength and tensile strength of the material experienced an increase of approximately 25 %

Abrasion Wear Resistance of Precipitation-Hardened Al-Zn-Mg Alloy.

The heat treatment of aluminum alloys is very important in industries where low weight in combination with high wear resistance, good strength, and hardness are important. However, depending on their chemical composition, aluminum alloys are subjected to different mechanical and thermal treatments to achieve the most favorable properties. In this study, an Al-Zn-Mg alloy was heat-treated including solution annealing at 490 °C for 1 h with subsequent artificial aging at 130, 160, and 190 °C for 1, 5, and 9 h. The hardness (HV1) and abrasive wear resistance with three different abrasive grain sizes were measured for all samples. The highest hardness was measured for the samples artificially aged at 130 °C/5 h, 227 HV1, while the lowest hardness was measured for the samples aged at 190 °C/9 h. The highest and the lowest wear resistance was also observed for the same state, i.e., artificially aged at 130 °C/5 h and 190 °C/9 h, respectively. The critical abrasive grain size was detected for some samples, where a decrease in wear rate was observed with an increase in the abrasive grain size from the medium value to the largest. The Response Surface Methodology (RSM) was applied to demonstrate the influence of the input parameters on the material wear rate.

Impact of in-process cooling and tool rotation speed on the mechanical and microstructural characteristics of friction stir processed AA2024

Despite significant grain size refinement, friction stir processing (FSP) of heat-treatable aluminum alloys is found to degrade the alloys of strength and hardness qualities. The drop in strength brought on by coarsening or the dissolution of the strengthening precipitate(s) could not be made up for by the improvement in strength brought about by the refinement of grain size following FSP. In order to get around this, the current work looks into a practical method of heat rejection from the FSP zone in addition to grain size refinement during FSP of AA2024 to regulate the precipitate evolution. Under natural cooling, air cooling, and CO2 cooling conditions, friction stir processing (FSP) was used to change the microstructure of Solutionized AA2024 at three distinct rotation speeds of 750, 1180, and 1500 rpm (fixed traverse speed of 50 mm/min). The microstructural evolution (through optical microscopy and SEM) and mechanical properties of FSP samples under different conditions of rotation speed and cooling and their differences were mainly discussed. All the FSP samples have a higher Vickers hardness than the base metal (minimum variation of 16.79% and maximum variation of 41.05%). The maximum hardness, yield strength, tensile strength, and elongation have been obtained under air cooling conditions and a rotation speed of 1180 rpm, which is a result of the simultaneous and effective effect of grain boundary strengthening and precipitation hardening.

Effect of natural aging by multifunction cavitation on plane bending fatigue behaviour of heat-treatable Al-Si7Mg aluminum alloys and its fatigue strength estimation

The effect of natural aging by multifunction cavitation (MFC) on the fatigue behaviour of heat-treatable Al-Si7Mg aluminum alloys was examined. Surface observation and plane bending fatigue tests were conducted for the MFC-treated aluminum alloys at a stress ratio, R, of −1. The hardness of aluminum alloy without T6 treatment was significantly increased by MFC due to both the work hardening and natural aging. MFC treatment improved the fatigue lives and the fatigue strength at N = 107 cycles of aluminum alloys due to the generation of compressive residual stress and increasing the surface hardness; however, surface pits were large enough to easily nucleate an initial fatigue crack. In addition, the fatigue strength at N = 107 cycles of MFC-treated aluminum alloys can be estimated considering the residual stress, pit size and surface hardness.

Investigating the Impact of Friction Stir Processing on the Hydrogen Embrittlement in AA6082-T6 Heat-Treatable Aluminum Alloy

This study investigates the impact of friction stir processing (FSP) on the hydrogen embrittlement (HE) in AA6082-T6 heat-treatable aluminum alloy. The effects of different number of FSP passes and different hydrogen cathodic charging (HCC) conditions on the material’s response to HE are examined through comprehensive mechanical testing, microhardness analysis, and microstructural characterization. The results revealed that FSP leads to a decrease in yield strength, ultimate tensile strength, and microhardness, accompanied by an increase in energy absorption. The introduction of hydrogen through HCC significantly reduces mechanical properties, particularly in non-FSPed specimens. Notably, specimens with 8 FSP passes exhibit an interesting behavior with a slight increase in energy absorption and microhardness values after HCC. Microstructural analysis shows that FSP refines the microstructure, resulting in enhanced resistance to hydrogen-induced blistering effects. These findings contribute to the understanding of hydrogen embrittlement in FSPed aluminum alloys, providing insights for developing surface-modified materials suited for hydrogen-rich applications.Graphical

Влияние гафния на высокомагниевые сплавы, легированные переходными металлами, при термической обработке

The purpose of the work is to study the influence of hafnium additives on the mechanical properties and thermal stability of particles at elevated temperature during heat treatment of aluminum alloys with a high magnesium content. Two modifications of 1570 alloy were chosen for the study: without hafnium content and with its addition of 0.5 % by weight. Both alloys were subjected to homogenizing annealing at a temperature of 440 °C with different exposure modes, which ranged from 2 to 100 h. Microhardness was studied for various heat treatment modes, and the fine microstructure was studied as well using transmission microscopy. As a result, it was possible to identify that during annealing at a short exposure time (2–8 h), the alloy with the hafnium addition has higher microhardness values exceeding those of 1570 alloy by an average of 20 HV units. This is associated with the fact that in 1570 alloy with hafnium additives, during heat treatment, the number of precipitated particles increases while their average size decreases compared to the base alloy. At the same time, in 1570 alloy without hafnium content, when annealed at a temperature of 440 °C, there is no increase in microhardness. This is caused by the fact that in 1570 alloy without hafnium content, when cooled after casting, discontinuous decomposition occurs, which resulted in the fact that most of the scandium precipitates from the supersaturated solid solution in the form of dispersoids. This phenomenon is not observed in the alloy with hafnium additives, which indicates its ability to stop discontinuous decomposition during cooling the ingot after casting.

Investigation on the damage mechanism of micro-cutting surface layer of aluminum alloy 7075 with different heat treatment processes

This paper investigates the machinability and microscopic surface damage mechanisms of aluminum alloy 7075 subjected to different heat treatment processes during micro-cutting. Focusing on T6 and T73 heat-treated aluminum alloy 7075, the study employs a combination of experiments and simulations to analyze micro-cutting surface morphology, cutting forces, microstructure evolution, residual stress, and damage characteristics. The findings reveal that micro-cutting of aluminum alloy 7075 after T6 heat treatment exhibits no apparent speed sensitivity in the primary cutting force, while T73 heat treatment demonstrates noticeable speed sensitivity. The surface microscopic damage during micro-cutting is influenced by both cutting speed and depth, resulting in distinct forms and degrees of damage under varying conditions. An analysis of the residual compressive stress field indicates that the magnitude of residual compressive stress on the micro-cutting surface determines crack initiation, and the maximum depth of residual compressive stress dictates crack propagation. Microscopic damage in T6 heat-treated aluminum alloy 7075 predominantly occurs in the second and third deformation zones, while T73 heat treatment leads to most damage in the third deformation zone. Notably, crack propagation is evident in T6 heat treatment at any cutting speed with a cutting depth of 150 μm, whereas it is inconspicuous in T73 heat treatment at cutting speeds below 540 m/min. Furthermore, at cutting speeds below 540 m/min and a cutting depth of 150 μm, T6 heat-treated micro-cutting is prone to oxidative wear. In contrast, at a cutting speed of 72 m/min and a cutting depth of 150 μm, the predominant wear form in T73 heat-treated micro-cutting is oxidation wear. This study underscores the intricate interplay between heat treatment processes, cutting conditions, and microscopic damage in aluminum alloy 7075 micro-cutting. The nuanced insights provided contribute to a deeper understanding of the machining characteristics of this alloy, paving the way for improved processing methodologies.

Application of New Al-Si Welding Filler with High Concentration of Copper and Magnesium: High-Temperature Strength and Anti-Corrosion Mechanism.

Currently, the primary commercial aluminum alloy fillers used are 4043 and 5356. However, when welded with high-strength work pieces like 6061 and 7075 aluminum alloys, the strength of weld beads significantly lags behind that of the original welded material. Both 4043 and 5356 aluminum alloys cannot be strengthened through heat treatment. The strength difference between the weld bead and base material doubles after heat treatment. In this study, an Al-Si-Cu-Mg alloy (SCM) filler modified using a heat-treatable A319 aluminum alloy was employed to investigate the post-welding microstructural and mechanical properties of specimens under room- and high-temperature conditions and after prolonged exposure in a saltwater environment (3.5 wt.% NaCl). The aim was to demonstrate that commercial aluminum alloy fillers could be substituted with a high-silicon aluminum alloy boasting excellent solidification and mechanical properties. The results revealed that, after heat treatment of the weld bead, dendrites were not eliminated, but the tensile strength increased to 310 MPa, closely matching that of commercial 6061 aluminum alloy. The strength of the weld bead remained higher than 250 MPa in high-temperature (240 °C) and saltwater environments. These findings underscore the potential application of this material.

Dissimilar friction-stir welding of aluminum alloys 2519, 6061, and 7050 using an additively-manufactured tool

This work was undertaken to evaluate the feasibility of the additively-manufactured tool for dissimilar friction-stir welding (FSW) of 2519, 6061, and 7050 heat-treatable aluminum alloys. The tool design included a flat shoulder with an Archimedean spiral groove and a threaded probe with a Triflute profile. It was found that the application of such a tool provided a nearly twofold decrease in Z-force and essentially enhanced the mechanical mixing of dissimilar materials within the stir zone. Nevertheless, despite the enhancement effect, FSW was inefficient for a homogeneous intermixing of dissimilar materials, and a distinct interface boundary was present within the stir zone. It was also found that the mechanical performance of the welded joints was sensitive to the initial temper condition of the welded alloys. Specifically, FSW of the alloys in the solution-annealed condition provided no significant influence on material strength, while that in the precipitation-hardened state led to significant material softening. During the post-weld T6 treatment, extensive nucleation of silicon-rich particles was found to occur at this interface. It was deduced that those promoted cracking during transverse tensile tests, thus giving rise to the decohesion of the dissimilar welds along the interface boundary. Hence, the post-weld T6 treatment was concluded to be unfeasible for dissimilar aluminum welds.

Coaxial Wire Laser-based Additive Manufacturing of AA7075 with TiC Nanoparticles

AA7075 is a heat treatable aluminium alloy widely used in aerospace and automotive applications due to its outstanding high strength-to-weight ratio. However, the implementation of this alloy in Additive Manufacturing (AM) processes has been limited due to its susceptibility to hot cracking. Moreover, selective evaporation of low boiling point elements Zn and Mg can cause gas porosity and diminish the mechanical properties of AM parts. Recent research revealed the effectiveness of nanoparticles additives to change the solidification behaviour of high-strength aluminium alloys and improve their weldability/printability. In this study, AA7075 enhanced with TiC nanoparticles was utilized as wire feedstock to create single and multi-layer samples with coaxial laser-directed energy deposition (L-DED). The response of the samples to precipitation hardening was studied, evaluating the microstructure and the microhardness before and after T6 heat treatment. Specimens were characterized using optical and electron microscopy and electron backscatter diffraction (EBSD). Crack-free and virtually porosity-free samples were fabricated, which exhibit a refined equiaxed grain structure with grain size <10μm. This confirms the ability of TiC nanoparticles to prevent columnar dendritic growth and promote heterogeneous nucleation. Microhardness values increased by 51 HV after T6 heat treatment and were uniform across the sample. Energy Dispersive Spectroscopy (EDS) analysis showed that there are evaporation losses of Zn and Mg. Considering the boiling temperatures of these elements, it is inferred that the molten pool reaches temperatures above 1090°C, and the partially melted zone temperature is between 907°C and 1090°C.

Inter-relationship between residual stresses, microstructural evolutions, and mechanical responses of heat-treatable aluminum alloys during welding: a numerical and experimental study

Inter-relationship between residual stresses, microstructural evolutions, and mechanical responses of heat-treatable aluminum alloys during welding: a numerical and experimental study

Optimization on the mechanical parameters and impact of welding parameters of pulsed TIG welding of Aluminium-Zinc-Magnesium alloy

As a function of pulsed Tungsten Inert Gas (TIG) weld processing factor, authors have studied the relationship between dilution and mechanical qualities including impact toughness, notch tensile strength, hardness in the as-welded condition. Welds made with a pulsed TIG torch have a minimum notch tensile strength and impact toughness than the base metal (BM) because of the grains of the inter-dendritic network formed during the welding process. Weldments made from heat-treatable (Al-Zn-Mg) Aluminium alloys have their process parameters for pulsed TIG welding optimized employing the Taguchi analysis to get the best possible mechanical qualities. Notch tensile strength is shown to be inversely proportional to impact toughness.

Aluminum alloy W-temper cryogenic forming with enhanced formability and strength

Simultaneously obtaining excellent formability and post-form strength in the traditional sheet metal forming of heat-treatable aluminum alloy is challenging, owing to the coexistence of wrinkling and splitting defects during forming and the control problem of microstructure. To solve these problems, W-temper cryogenic forming was proposed based on the cryogenic ‘dual-enhancement effect’ of an as-quenched (W-temper) aluminum alloy. The effects of the cryogenic temperature gradient and blank-holder force on the drawing behaviors were studied by analyzing the forming defects and thickness distribution. Strength distributions were reflected through Vickers hardness measurements under different aging conditions. The related strengthening mechanism was revealed through microstructure characterization. The drawability can be significantly improved at small or large cryogenic temperature gradients. An Al-Cu alloy semispherical shell component was fabricated via W-temper cryogenic forming. The depth of the formed hemispherical specimens increased by more than 106.4%. Uniform thickness can be also obtained at the temperature gradient of 216 °C, with an average thickness deviation rate of 6.5%, benefiting from the cryogenic dual enhancement effect and enlargement of the stress gradient. The hardness in all regions was higher than 146.5 HV of traditional T8-temper because of the enough accelerating precipitation of θʺ and θʹ phases by prior cryogenic deformation. Strain and precipitation strengthening were the main strengthening mechanisms under post-forming and post-aging conditions, respectively. The peak-aging time can be shortened to 6 h, which is one-third that of the traditional process. Enhanced formability and post-form strength can be simultaneously obtained by W-temper cryogenic forming, which has great potential for the fabrication of thin shells made from heat-treatable aluminum alloys.