T6 Condition Research Articles

Influence of Si on the Elevated-Temperature Mechanical and Creep Properties of Al–Cu 224 Cast Alloys during Thermal Exposure

The influence of Si content (0.1–0.8 wt.%) on the development of precipitation microstructures and the resultant mechanical and creep properties during thermal exposure, up to 1000 h at 300 °C, in Al–Cu 224 cast alloys, was systematically investigated. The room and elevated temperature yield strength (YS) increased with increasing Si content under the T7 condition, which was attributed to the fact that the Si promoted the precipitation of fine θ′. However, Si increased the coarsening of θ′ during thermal exposure at 300 °C, and the alloys with low Si exhibited a higher YS and creep resistance at elevated temperatures than high Si alloys. The mechanical strength and creep resistance were mainly controlled by the precipitation strengthening of the predominant θ′ phase. Because of the high mechanical strength and creep resistance of the 0.1Si alloy during long-term thermal exposure, the Si level in Al–Cu alloys should be maintained at a low level of 0.1 wt.% for high-temperature applications. The strengthening mechanisms were quantitatively analyzed, based on the characteristics of the precipitate. The predicted YS values under different exposure conditions agreed well with the experimentally measured values.

Evolution of mechanical properties and microstructure of selective laser melted AlSi10MgMn alloy with different post heat treatments

This study investigated the effects of various post heat treatments on the mechanical properties and microstructure evolution of an AlSi10MgMn alloy containing 0.5 wt% Mn produced by the selective laser melting process for the first time. The microstructures under different conditions were analyzed using optical microscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. In the as-manufactured (F) condition, the alloy exhibited an ultimate tensile strength (UTS) of 486 MPa, a yield strength (YS) of 299 MPa, and an elongation of 10.3 %. After a T5 treatment, the UTS and YS increased to 532 MPa and 386 MPa, respectively, resulting in a remarkable 30 % improvement in YS compared to the F state. The tensile properties achieved by the new alloy were considerably higher than those reported for conventional AlSi10Mg alloys in the F, T5, and T6 conditions. The T5 treatment promoted the precipitation of a large fraction of Si-rich nanoparticles and MgSi-based precipitates without disrupting the Si-rich network. After a T6 treatment, the Si-rich network completely disappeared, and the main strengthening phase was MgSi-based precipitates accompanied by α-Al(Mn,Fe)Si dispersoids induced by the Mn addition. Using microstructure-based constitutive models, the strengthening contributions of various microstructural components to mechanical strength in different processing conditions were analyzed.

Cyclic deformation behavior of an overaged high-pressure die-cast aluminum alloy

The aim of this study is to identify the deformation behavior of a high-pressure die-cast Silafont®-36 aluminum alloy in an overaged T7 condition in relation to the significant microstructural changes caused by the overaging heat treatment. The T7 aluminum alloy exhibited a distinctive composite-like microstructure, consisting of coarser α-Al grains and larger spherical Si particles embedded in the matrix, in contrast to its as-cast and T4 counterparts. The softer α-Al matrix of the T7 alloy as revealed by the nanohardness and microhardness led to improved ductility and longer strain-controlled fatigue life at higher strain amplitudes, despite the lower strength. Cyclic stabilization was observed to be a salient feature of the T7 alloy, stemming from the equilibrium between cyclic hardening and cyclic softening. Strain-energy density-based model, by incorporating a material parameter called ‘intrinsic fatigue toughness’, could be used to predict the fatigue life of the alloy.

Optimizing the Zn and Mg contents of Al–Zn–Mg wrought alloys for high strength and industrial-scale extrudability

High-strength Al alloys of the 7xxx series are promising candidates for further light-weighting of car bodies. However, they are difficult to process by extrusion: complex geometries in particular pose a major challenge due to high extrusion pressures and tool wear. In addition to process optimization, alloy chemistries can be tailored for properties such as good extrudability or high strength. In this work, several experimental alloys based on EN AW 7108A were investigated with respect to the contents of the main alloying elements Zn and Mg, as well as heat treatment (e.g., homogenization), to achieve good extrudability and favourable mechanical properties. The experimental alloys were initially extruded on a small-scale extrusion press and evaluated with regards to their warm formability, microstructure, extrudability, and mechanical properties in T5 temper. Alloy compositions with Mg contents <1.2 wt.-% are optimal and lead to good extrudability as well as high yield strengths well above 350 MPa. The Zn content, on the other hand, has minor influence on the extrudability, but significantly increases strength at higher contents (∼60 MPa). However, the combined Zn + Mg content should not exceed 7 wt.-%. Based on these findings, two optimized alloys were designed, direct chill cast on industrial scale, and extruded on an industrial extrusion press. The alloys showed good extrudability and high strength in the T5 condition. The results also reveal that the limits of the EN AW 7108A alloy are exhausted and higher strengths could only be achieved with the optimized EN AW 7003 alloy.

Revisiting Ag addition in 7xxx aluminum alloys: Insights into its impact on the microstructure and properties of an Al-Zn-Mg-Cu-Zr alloy with a Zn/Mg ratio of 4

In this study, the influence of minor Ag addition on the microstructure, mechanical and corrosion properties of an Al-Zn-Mg-Cu-Zr (7449) alloy with Zn/Mg ratio of 4 was systematically investigated using various materials characterization techniques, Slow Strain Rate Test (SSRT), Potentiodynamic Polarization (PDP) and Intergranular Corrosion (IGC) measurements. Microstructure characterization by Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) showed that Ag partitioning in the eutectic Mg(Zn,Cu,Al)2 phase occurs resulting in an increase in its solvus line. After processing to the T4 condition, Ag was partially in solid solution with the excess forming an Ag-rich AlAgZnMgCu phase. Scanning-Transmission Electron Microscopy (STEM) showed evidence of quench-induced η-Mg(Zn,Cu,Al)2 precipitates at the grain boundaries (GBs) in the T4 condition with ∼3 at.% Ag in the Ag-modified alloy. STEM and Atom Probe Tomography (APT) confirmed that ∼1 at. % Ag was present in both the matrix and GB precipitates in the Ag-modified alloy after T76 aging. Furthermore, the frequently reported decrease in the PFZ width with Ag addition was not observed after T76 aging, with both alloys having a similar PFZ width. Despite higher hardness/strength in the T4 condition with Ag addition, no enhanced age hardening response and alteration of the precipitation kinetics was observed during artificial aging at 121 °C. In fact, Ag addition in a 7xxx alloy with Zn/Mg ratio of 4 was found to be detrimental to mechanical properties, stress corrosion cracking, pitting and IGC resistance after T76 aging, which is attributed to the presence of the Ag-rich AlAgZnMgCu phase.

Optimum heating time for warm forming of AA7075 aluminum alloy in T6 condition

Optimum heating time for warm forming of AA7075 aluminum alloy in T6 condition

Microstructural Modification, Mechanical Properties, and Wear Behaviour of Aged Al-Si-Mg/Si3N4 Composites for Aerospace Applications

The main objective of the present research is to probe how ageing time influences the morphological, mechanical, and wear behaviour of stir cast Al-Si-Mg alloy, reinforced with 10 wt.% Si3N4 particles subsequently heat treated in T6 condition. The findings reveal that the presence of Si3N4 reinforcements, followed by the heat treatment, enhances the mechanical and tribological properties of the composite. The ensuing mechanical properties show significant improvement prior to aging heat treatment (180 °C/4h), reaching a hardness of 120.8 HV (45 % increase) and tensile strength of 275 MPa (50 % increment), respectively compared to as-cast composite. Fractography reveals dimples, transgranular cleavage surfaces, cracks, and micro-ploughing. Among the samples tested, the composite aged for 4 h (180 °C/4h, ASN-4) demonstrates the lowest wear rate. Abrasive and adhesive wear in combination is the primary wear mechanism in these samples. Overall, this research provides insights for research endeavors in manufacturing various components in the aerospace industry.

Enhancing the mechanical properties of wire arc directed energy deposition Al–Zn–Mg–Cu aluminum alloy through cyclic deep cryogenic treatment

In this paper, the effects of cyclic deep cryogenic treatment (CDCT) on the mechanical properties and the precipitated phases evolution of 7B55 aluminum alloy produced by wire arc directed energy deposition (WA-DED) were systematically investigated. The findings revealed that, under both T6 and CDCT conditions, the microstructure of the 7B55 aluminum alloy exhibited fine-equiaxed grains. Under the T6 condition, the precipitated phases within the grains were primarily composed of clustered GP zones and η′ phases. Meanwhile, the η phases were continuously distributed along the grain boundaries. Upon subjecting the material to three cycles of CDCT, a noticeable reduction in the number of GP zones within the grains was observed. Simultaneously, there was a substantial increase in the number of η′ phases, accompanied by the occurrence of dislocation lines. The distribution of η phases along the grain boundary transitioned to an interrupted pattern. Under the CDCT-Cycle 3 (CDCT-C3) condition, the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) achieved 658.6 ± 4.5 MPa, 624.2 ± 5.2 MPa, and 8.42 ± 0.18 %, respectively. However, with the progression to four cycles of CDCT, the GP zones within the grains disappeared and the number of η′ phases started to decrease with the formation of a large number of η phases. The η phase along the grain boundary continuously grew by merging and absorbing solute atoms from the Al matrix near the grain boundaries. This led to the formation of coarsen and interrupted η phases and the Precipitate-Free Zone (PFZ) along the grain boundaries. Subsequently, the mechanical properties experienced a substantial decrease after the CDCT-Cycle 4 (CDCT-C4).

Influence of a Preageing Treatment on the Cluster Formation and the Further Ageing Route in Al–Mg–Si Extrusion Alloys

Herein, the influence of one‐ and two‐step preageing treatments prior to the artificial ageing step to peak age condition for three different 6xxx alloys, from low to high alloy content, is investigated. Analysis of the preaged conditions using atom probe tomography (APT) reveals a broad distribution of Mg and Si clusters, with some instances of Guinier‐Preston I zones present. Additionally, the high alloyed system exhibits a growth of precipitates toward a needle‐like shaped. These clusters formed during the preageing treatment serve as nucleation sites in the subsequent artificial ageing treatment, leading to an increase in hardness. Microstructural analysis conducted using transmission electron microscopy and APT demonstrates a reduction in the average precipitate length and a more narrow size distribution for T6 condition. This indicates that the preageing treatment results in a decreased portion of already overaged precipitates compared to the direct aged condition. Consequently, the more narrow size distribution of the precipitates leads to more effective hardening of the material, as a higher portion of precipitates is at or close to their optimum size. The investigations highlight the significant influence and positive effect of a preageing treatment at lower temperatures on the subsequent artificial ageing treatment.

Achieving high strength-ductility synergy via Guinier-Preston zone formation in a new Mg–Zn–Al–Ca–Mn–Ce sheet alloy

ZAXME11100 (Mg–1Zn–1Al-0.5Ca-0.4Mn-0.2Ce, wt.%) is a recently developed sheet alloy with excellent formability at room temperature. The yield strength of this alloy is significantly improved by a short 1-h aging treatment at 210 °C (T6), from 159 MPa in solution-treated state (T4) to 270 MPa in the T6 condition, with a slight reduction in tensile elongation (from 31 % in T4 to 26 % in T6). In this work, precipitation microstructure was characterized to explain the aging hardening and high strength-ductility synergy of the new alloy. A high density (8 × 1023/m3) of ordered monolayer Guinier-Preston (GP) zones enriched in Al, Ca and Zn uniformly form on the Mg basal planes after T6 treatment. Grain boundary segregation of Al, Ca and Zn is also observed. Deformation microstructure of T4 and T6 samples tested to various strain levels was examined. At small strain levels, basal and non-basal <a> dislocation slip dominates the deformation process, and cross slip of <a> dislocations between basal and non-basal planes is observed in T6 samples. The GP zones are gradually destroyed by plastic deformation. Based on those results, the strengthening contribution of ordered GP zones was modeled to be 116 MPa. Therefore, formation of GP zones is an effective way to achieve high strength-ductility synergy in wrought Mg alloys.

Microstructure inheriting evolution and strength-plasticity collaborative improvement mechanism of multidirectional rotary forged Al7075 sheets during T6 heat treatment

Al7075 sheets are widely used in aerospace industry and their higher strength-plasticity collaborative improvement requirement is urgent. In this study, the microstructure inheriting the evolution and mechanical properties of Al7075 sheets during multidirectional rotary forging (MRF) and T6 heat treatment are analyzed. The results show that the average grain size exhibits near-parabolic evolution with increasing MRF deformation amount. MRF20 %+T6 (20 % MRF deformation amount+T6) condition possesses the largest grain size of 72.6 μm, and its abnormal grain growth mechanism is that the medium deformation energy and high deformation heterogeneity in MRF20 % deformed grains could cause asynchronous recrystallization behavior during T6 heat treatment, and the grains with comparatively higher deformation energy get recrystallized firstly and devour adjacent grains along preferred 〈011〉 or 〈223〉 misorientation axis. MRF70 %+T6 condition possesses the finest grain size of 14.2 μm, and its fine grain inheriting mechanism is that the uniformly high deformation energy in MRF70 % deformed grains causes uniformly rapid recrystallization, and rapidly recrystallized grains effectively suppress grain boundary motion from adjacent grains. With increasing MRF deformation amount, tensile strength and elongation values both exhibit near-antiparabolic evolution. MRF70 %+T6 condition possesses the largest tensile strength (563 MPa) and elongation (17.73 %), which increases by 8.27 % and 80.55 % compared to as-annealed+T6 (MRF0 %+T6) condition (tensile strength is 520 MPa and elongation is 9.82 %), respectively. The strength-plasticity collaborative improvement is mainly because the combination of effectively inherited fine grains, refined inclusion particles, and uniformly distributed fine η’ particles after T6 heat treatment could promote smooth dislocation movement and coordinated slip behavior in most matrix grains, which contributes to the delay of stress localization and strength-plasticity collaborative improvement.

Fretting wear behavior on LPBF processed AlSi10Mg alloy for different heat treatment conditions

To widen the industrial application of additively manufactured (AM) parts, the study of fretting wear behavior is essential, as it ensures the safety and reliability that drive innovation in design and materials. This study explores the fretting wear behavior of the as-built and heat-treated state of AlSi10Mg alloy fabricated, viz., laser powder bed fusion (LPBF). Initially, the as-built and T5, T6, and stress-relieved (SR) heat-treated samples were examined using scanning electron microscopy (SEM) to gain insights into the microstructural changes. The as-built samples exhibited a higher hardness level (135 HV) primarily due to the presence of very fine microstructure of the α-Al cellular matrix with embedded Si. The α-Al cellular structure dissolved with various heat treatments, and Si particles coarsened. The hardness decreased to 85, 79, and 67 HV for the T5, T6, and SR conditions, respectively. Subsequently, fretting tests were conducted on the samples, applying various normal loads of 10, 50, and 100 N. Further, the samples were characterized by the coefficient of friction (COF), worn surface morphology, and wear volume loss. The investigation showed that the as-built material showed less wear volume loss under all loading conditions than the heat-treated conditions. Furthermore, the T5 heat treated sample had a lower wear volume when compared to the T6 and SR heat-treated samples. The heat-treated sample exhibits compressive stress, whereas the LPBF processed, the as-built sample shows tensile stress.

Dry milling of stir-cast and heat-treated EV31A magnesium alloy: An experimental investigation based on the multi-criteria optimization method

The purpose of this study is to examine the impact of various milling parameters and sample preparation methods on the end-milling of EV31A Mg alloy under as-cast, T4, and T6 heat-treated conditions. The test specimens were prepared through stir-casting and heat-treated according to T4 and T6 conditions. The CNC vertical milling machine with the HSS tool was used for the end-milling process based on Taguchi's L9 orthogonal array. Three levels of variation are applied to the process parameters, including spindle speed (S), feed rate (f), depth of cut (d), and test specimen (as-cast, T4, and T6 EV31A). The parameters of surface roughness (Ra, Rz, Sa, Sz), the rate of material removal (MRR), and the cutting force (Fr) were similarly measured. For surface roughness, optical profilometry was used, while the weight loss method and dynamometer were employed, respectively, to assess MRR and Fr. In order to improve the process parameters, TOPSIS (techniques order preferences by similarity to ideal solution) is employed. This method reduces several responses to a single measurable response (the closeness coefficient). S = 1500 rpm, f = 150 mm/min, and aP = 1.5 mm are the ideal process parameters to achieve the maximum closeness coefficient (Ci) of 0. 917129 under as-cast circumstances. Furthermore, analysis of variance (ANOVA) verifies that sample preparation methods of 24.59 % and depth of cut of 38.19 % significantly impact response characteristics.

Experimental estimation and numerical comparison of fatigue strength of A356/SiCP composite in T6 condition

Experimental estimation and numerical comparison of fatigue strength of A356/SiCP composite in T6 condition

Genome-wide transcriptome profiling reveals molecular response pathways of Trichoderma harzianum in response to salt stress.

Trichoderma harzianum exhibits a strong biological control effect on many important plant pathogens, such as Fusarium oxysporum, Botrytis cinerea, and Meloidogyne. However, its biocontrol effectiveness is weakened or reduced under salt stress. The aim of this study was to investigate the molecular response of T. harzianum to salt stress at the whole-genome level. Here, we present a 44.47 Mb near-complete genome assembly of the T. harzianum qt40003 strain for the first time, which was assembled de novo with 7.59 Gb Nanopore sequencing long reads (~170-fold) and 5.2 Gb Illumina short reads (~116-fold). The assembled qt40003 genome contains 12 contigs, with a contig N50 of 4.81 Mb, in which four of the 12 contigs were entirely reconstructed in a single chromosome from telomere to telomere. The qt40003 genome contains 4.27 Mb of repeat sequences and 12,238 protein-coding genes with a BUSCO completeness of 97.5%, indicating the high accuracy and completeness of our gene annotations. Genome-wide transcriptomic analysis was used to investigate gene expression changes related to salt stress in qt40003 at 0, 2% (T2), and 4% (T4) sodium chloride concentrations. A total of 2,937 and 3,527 differentially expressed genes (DEGs) were obtained under T2 and T4 conditions, respectively. GO enrichment analysis showed that the T2-treatment DEGs were highly enriched in detoxification (p < 0.001), while the T4 DEGs were mainly enriched in cell components, mostly in cellular detoxification, cell surface, and cell wall. KEGG metabolic pathway analysis showed that 91 and 173 DEGs were significantly enriched in the T2 and T4 treatments, respectively (p < 0.01), mainly in the glutathione metabolism pathway. We further experimentally analyzed the differentially expressed glutathione transferase genes in the glutathione metabolic pathway, most of which were downregulated (13/15). In addition, we screened 13 genes related to active oxygen clearance, including six upregulated and seven downregulated genes, alongside five fungal hydrophobic proteins, of which two genes were highly expressed. Our study provides high-quality genome information for the use of T. harzianum for biological control and offers significant insights into the molecular responses of T. harzianum under salt-stress conditions.

Mechanical, electrochemical corrosion, and high-temperature oxidation properties of stir-cast and heat-treated AZ80 magnesium alloy

This study aims to produce a stir-cast AZ80 magnesium alloy and to correlate the phases and microstructure of the as-cast, T4, and T6 conditions with the alloy's mechanical, corrosion, and oxidation properties. Microstructure was analysed using Field Emission Scanning Electron Microscopy (FE-SEM) with Energy Dispersive Spectroscopy (EDS), Electron Backscatter Diffraction (EBSD), and High-Resolution Transmission Electron Microscopy (HRTEM), and X-ray diffraction (XRD) technique was employed to examine at the alloy’s phases. A Vickers microhardness, tensile, and impact test specimens were meticulously prepared according to ASTM specifications. The electrochemical corrosion was tested in 0.6 M NaCl and 0.05 H2SO4, simulating the salty seawater and low-sulphur air environments. Based on the eutectic temperature of the Mg-Al alloy system, which is 437 ℃, the high-temperature oxidation test was carried out at 400 ℃, 410 ℃, and 420 ℃. Microstructural study confirms that both T4 and T6 alloys undergo grain coarsening with a grain size of 72.64 µm, and the orientation of the grains shifted from the pyramidal plane (2−1-10) to the basal plane (0001). The TEM investigation helps pinpoint the GP zone's genesis in T4 heat-treated AZ80. T4 AZ80 has a maximum ultimate tensile strength of 306 MPa and a ductility of 29.77% because of the dispersion-strengthening effect. The T6 AZ80, on the other hand, has a minimum corrosion rate of 0.158 mm/year in NaCl solution and an oxidation rate constant of 4.19 mg2.cm−4h−1 at 420 ⁰C. Notably, the T6 AZ80 shows significant peaks of Mg2Al3, and the as-cast shows more peaks of Mg17Al12. Magnesium alloy AZ80 is significantly affected by intermetallic phases like Mg17Al12 and Mg2Al3. The Mg2Al3 phase shows the latter tendency to resist corrosion and oxidation.

Enhancing properties of Al-Zn-Mg-Cu alloy through microalloying and heat treatment

This paper aims to understand the influence of microalloying constituents (Ti, Zr, Sr and Sc), and three heat treatment conditions i.e., T6, retrogression and reaging (RRA) and high temperature aging (HTA) on mechanical and thermal characteristics of modified Al-Zn-Mg-Cu-X alloy using microstructural analyses consist of precipitation characteristics, phase fraction and phase morphology. Addition of 0.25 wt % Sc significantly refines the grain structure, reducing the grain size from 62 μm to 34 μm and increasing Al3Zr, Al3(Zr, Ti), and Al3(Sc, Zr) precipitate fraction. After T6 aging, the alloy exhibits primary precipitates of fine η and T phases, accompanied by secondary intermetallics as well as S phases. RRA treatment led to a slightly larger fraction of coarse Zn and Cu-rich phases, while HTA results in larger η, T, and S phases due to high-temperature aging. The addition of Sc reduces the cooling rate by raising the transition temperature to 532 °C with an enthalpy of 22.1 J/g. T6 treatment shows dissolution of most η phases within the matrix, although RRA and HTA exhibit higher enthalpy due to a greater fraction of η phases. The tensile strength of Al-Zn-Mg-Cu-X alloy follows the following sequence: T6 > RRA > HTA > as-cast condition, regardless of micro-alloy additions. Under T6 conditions, Sc added alloy achieves 30 % higher strength, i.e., 575 MPa, than base alloy due to fine dispersoids. RRA treatment enhances elongation without compromising mechanical properties, resulting in a shift from transgranular brittle fracture to intergranular-dominated mix-mode fracture, with the presence of secondary cracking.

Mechanical properties and rate-sensitive deformation of AA6063 aluminum alloys at 298 K, 78 K, and 4 K

The mechanical properties and rate-sensitive deformation of T4 and T6 AA6063 aluminum alloys have been analyzed at 298 K, 78 K, and 4 K. The strength, ductility, and work hardening capacity of two alloys increase with decreasing deformation temperature. Plastic deformation of AA6063-T4 is accompanied by adiabatic flow stress instabilities at 4 K and the Portevin-Le Chatelier (PLC) effect at 298 K. The alloy shows a better synergy of flow stress and work hardening than the T6 condition, determined by the underlying microstructure. The limited ability of dislocation storage in T6 alloy arises from shearing β″ particles and the enhanced dislocation annihilation occurring in pure Al matrix. The failure of the alloys is promoted by void nucleation at intermetallic particles before the Considére criterion is fulfilled. AA6063-T6 exhibits positive strain rate sensitivity (SRS) at three temperatures. Dislocations-β″ particle interactions determine its SRS and are a rate-controlling process at 298 K. AA6063-T4 shows negative strain rate sensitivity (nSRS) at 298 K controlled by dislocation-solute interactions. Data for SRS and thermodynamic deformation parameters characterizing different mechanisms in T4 and T6 alloys between 4 K and 298 K are discussed. The results indicate that plastic deformation produces vacancies by jogs' dragging at 298 K, but this process does not occur at 78 K and 4 K.

Enhanced Mechanical Strength and Electrical Conductivity of Al–Ni‐Based Conductor Cast Alloys Containing Mg and Si

The electrical conductivity (EC), mechanical strength, hot tearing susceptibility (HTS), and related microstructure of Al–xNi–0.55Mg–0.55Si conductor alloys (x = 1–4 wt%) are investigated. Adding Mg and Si into Al–Ni‐based alloys, numerous β″/β′ precipitate after T5 and T6 treatments, thus significantly improving the EC and mechanical strength. The HTS of the alloys reduces significantly as the Ni content increases, mainly because of an increase in the eutectic Al–Al3Ni and a reduction in the grain size. Under T5 condition, the tensile strengths increase gradually with the Ni content and reach a medium strength level, with yield strength (YS) of 158–205 MPa and EC of 47.1–50.7% IACS. After applying T6, all alloys achieve a high strength, with YS of 246–287 MPa and EC of 47.7–51.1% IACS. However, the strength decreases with increasing Ni content. In general, the Al3Ni–0.55Mg–0.55Si alloy presents a better trade‐off among HTS, YS, and EC among the four alloys investigated. Due to its excellent properties (EC of 49.4% IACS and YS of 178 MPa in T5, and EC of 49.7% IACS and YS of 250 MPa in T6), the Al3Ni–0.55Mg–0.55Si alloy is a promising material for the fabrication of Al conductor cast alloys.

Dry sliding wear behavior of AA7075 alloy produced by thixocasting

Abstract In this study, the wear behavior of AA7075 alloy produced by thixocasting was investigated. The wear behavior of the AA7075 alloy is examined for three cases: extruded with T6 heat treatment, as-thixocast, and thixocast with T6 conditions. The dry sliding wear test was conducted with a tribometer according to ASTM G-99 standard. The microstructures were characterized by optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX). The tensile and hardness tests were performed to evaluate the mechanical properties. The AA7075 alloy was successfully shaped by thixocasting. The as-thixocast sample exhibited typical globular structures with multinary eutectic structures along the grain boundaries. The globular grains transform into a polygonal structure, and the grain size increases from 50 μm to 60 μm in the thixocast + T6 sample. This microstructure exhibited excellent wear resistance under dry sliding conditions in the thixocast + T6 sample. The aging treatment with prolonged solution process improved the mechanical properties two times and the wear rate three times for the thixocast AA7075 alloy. Furthermore, the thixocast + T6 sample exhibited a significant decrease in the coefficient of friction with the lowest wear rate compared to the as-thixocast sample. The dominant wear mechanisms are microdelamination, adhesion, and oxidation in all samples.