6061-T6 Aluminum Alloy Research Articles

Evaluating the Plastic Anisotropic Effect on the Forming Limit Curve of 2024-T3 Aluminum Alloy Sheets Using Marciniak Tests and Digital Image Correlation

This study thoroughly investigates the influence of anisotropy on the formability of 2024-T3 aluminum alloy sheets using advanced techniques such as digital image correlation (DIC) and Marciniak tests. A key finding is the relatively small variation in anisotropy values across different strain paths and orientations, contrasting with more significant variations reported in other studies. Tests were conducted on nine samples with various geometries to induce specific strain paths, including uniaxial, plane, and balanced biaxial strains, oriented in different directions relative to the rolling direction. The study also provides a detailed analysis of microstructural and mechanical characteristics, such as precipitate distribution and anisotropy behavior, which are crucial for understanding the relationship between microstructure and material formability. The results show that while anisotropy impacts deformation capacity, the differences in formability among the directions were minimal, with slightly greater formability observed in the diagonal direction. These findings are compared with forming limit curves (FLCs), offering an integrated view of how relatively uniform anisotropic properties influence formability. These insights are essential for optimizing the processing and application of 2024-T3 alloy in industrial contexts, emphasizing the importance of understanding anisotropy in the design of metal components.

Experimental Investigation of Hardness and Surface Roughness in the Friction Stir Welding of the 6061-T6 Aluminum Alloy

Experimental Investigation of Hardness and Surface Roughness in the Friction Stir Welding of the 6061-T6 Aluminum Alloy

Study on asymmetric forming and performance strengthening mechanisms of 6061-T6 aluminum alloy joints fabricated by oscillating laser based on keyhole characteristics and molten pool dynamic behaviors

The study intends to unravel the processes behind the particular forming and performance improvement of 6061-T6 aluminum alloy joints by getting a thorough understanding of keyhole features and dynamical characteristics of molten pools during the laser welding with circular oscillation (C-OLW) process. The C-OLW experiments were carried out considering the pivotal parameters, including oscillation frequency (f) and amplitude (A), and their impacts on joint formation, microstructure, and performance were analyzed. Increasing f from 200 Hz to 300 Hz results in a more homogeneous and centered laser energy distribution, reducing weld breadth and the maximum depth. Raising A from 1.2 mm to 1.5 mm concentrated energy along the workpiece surface, increasing weld breadth but decreasing the maximum weld depth. A three-dimensional transient numerical model was established and verified. The simulation results reveal that increasing f considerably improves keyhole stability by virtue of the beam's mixing effect on energy, resulting in a more evenly distributed temperature within the molten pool. The velocity of the beam's motion intensifies, leading to elevated local temperature and subsequently causing an escalation in splattering. When A grows, keyhole stability reduces, as does the intensity of molten pool flow. The major effect of increased frequency is refining the grain size while increasing amplitude primarily promotes the columnar-to-equiaxed transition (CET) process. The extracted results of temperature distribution illustrate that an increase in f leads to an increase in the solidification rate (R), and temperature gradient values (G) are similar or higher along the same isotherm. Therefore, the G/R ratio rises, promoting the formation of finer microstructures. Although increasing A diminishes G, the reduced overall temperature and molten pool volume contribute to the rise in R. Consequently, the G/R ratio declines, fostering equiaxed grain growth, in line with experimental observations. A higher G value on the left side corresponds to finer grain structures, corroborating experimental findings via Electron Backscatter Diffraction (EBSD). The keyhole stability and microstructure characteristics explain why increasing f or A can enhance joint performance. The research reveals that strategically augmenting both oscillation frequency and amplitude enables the achievement of enhanced performance in 6061-T6 aluminum alloy joints.

Residual stress tests and predictive model of friction stir welded normal-strength aluminium alloy H-shaped sections

To address the challenges of difficult extrusion for super-large cross-section aluminium alloy members, pairs of T-shaped sections were proposed to be longitudinally friction stir welded (FSW) to form the H-shaped sections widely used in structural engineering. It was significantly different from the previous member forming method that one web plate and two flange plates were welded at the flange-web junctions. To understand the novel FSW-induced residual stress distributions and magnitudes in the H-shaped sections, six specimens made of 6061-T6 and 6013-T6 normal-strength aluminium alloys, including various width-to-thickness ratio and plate thickness, were tested using the sectioning method, leading to over 4000 original readings of compressive and tensile residual stresses. The analysis results showed that great tensile residual stresses were clearly concentrated within the web weld, and then rapidly descended to lower compressive stresses near the weld region, followed by approximately linear regression to zero state from the weld edge to the flange-web junction, while the flange data points were relatively scattered. The compressive and tensile residual stresses in each flange and web plate were observed to be slightly associated with the width-to-thickness ratio and plate thickness. A simplified multi-linear residual stress distribution model, including the magnitudes and ranges of constant and linear variation curves, was proposed for the FSW aluminium alloy H-shaped sections, and good accuracy and consistency were observed between the test and predicted results.

Numerical study on surface treatment of vibration-impact composite electric spark based on ABAQUS

Abstract Through numerical simulation, this study explores the effect of vibration-impact composite electric spark (VIES) surface treatment technology on the temperature and thermal stress fields of 2024-T3 aluminum alloy surfaces. The depth of the molten pool and residual stress are evaluated using orthogonal experiments to score different experimental schemes, resulting in three experimental parameters categorized as good, medium, and poor. The study then examines the temperature and thermal stress fields for these three sets of parameters during the strengthening process. The results indicate that, considering the temperature field, the distance between the heat source and the work piece directly affects the heating efficiency and temperature distribution. An appropriate distance and sufficient dwell time are essential for creating the ideal molten pool thickness. Analysis of the stress field results shows that in the early stage of strengthening, the inertia force of the small spheres is dominant, while in the later stage, the stress field created by the electric current becomes decisively dominant. This indicates that the electric current is the core of the three influencing factors in the orthogonal experiment.

Research on ultrasonic-stationary shoulder assisted friction stir lap welding of thermoplastic polymer and aluminum alloy

Friction stir lap welding (FSLW) has advantages on obtaining dissimilar upper polymer and lower aluminum materials joint (polymer/Al joint), and how to heighten the bearing capacity of polymer/Al joint as much as possible is greatly meaningful for the manufacturing industries. In this study, choosing dissimilar polyamide 6 (PA 6) polymer and 6061-T6 aluminum alloy materials as research object, traditional FSLW, stationary shoulder assisted FSLW (SSFSLW) and ultrasonic-stationary shoulder assisted FSLW (U-SSFSLW) processes were compared to understand the mechanism of ultrasonic enhancement on the polymer/Al joint. Firstly, the surface morphologies were studied. Then the analyses of micro/macro-structures, mechanical properties and fracture features were carried out by optical microscopy, scanning electron microscopy, differential scanning calorimetry, X-ray diffraction and tensile tests. Results showed that the lap shear failure load of polymer/Al joint by U-SSFSLW reached 1502 N from 814 N by traditional FSLW, because the addition of ultrasonic avoided the bulged-nodule structures on top surface and the cavity defect in stir zone (SZ), broke the Al anchor in upper plate, enlarge the width of SZ in lower plate, and made the deeper micro-pits and larger dents at the interface between SZ bottom and lower plate. The U-SSFSLW process provides an effective way to fabricate the high-strength hybrid joint of dissimilar upper polymer and lower Al materials.

Effect of cold expansion on the fatigue life of multi-hole 7075-T6 aluminum alloy structures under the pre-corrosion condition

The multi-hole structures with cold expansion are extensively utilized in the various joint parts of aircraft. However, the synergistic effect of stress concentration and atmospheric corrosion will cause severe deterioration of structural loading capabilities. Thus, it is crucial to investigate the fatigue life degradation mechanism of these structures under pre-corrosion conditions. In this paper, three-hole specimens with cold expansion (CE) and non-cold expansion (NCE) were used to investigate the effect of cold expansion on the fatigue performance of multi-hole structures of 7075-T6 aluminum alloy under pre-corrosion conditions. The life degradation law and damage mechanism of these two types of specimens under pre-corrosion conditions were analyzed. Furthermore, the cold expansion strengthening factor was proposed through the curve-fitting of the fatigue life attenuation ratio of these two types of specimens. Finally, a competition mechanism for the contribution ratio to the final fracture of the specimens in corrosive environments was proposed based on the SEM morphology analysis of the fatigue fracture of the specimens.

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.

An experimental and theoretical investigation on residual stress of 7075-T651 aluminum alloy hole under electromagnetic cold expansion

The electromagnetic cold expansion process (ECE) was adopted in this work. The theoretical plastic radius, hole wall stress, radial stress, circumferential stress and release stress under different expansion rates (ER) were studied based on thick cylinder theory and ECE experiments. The released strain, residual stress (RS) and failure force were measured. The tensile fracture morphology was characterized. The results showed that the theoretical plastic radius (maximum 15.87 mm), internal stress (maximum 982.9 MPa), radial stress (maximum −820.9 MPa) and circumferential stress (maximum −271.4 MPa) increased with the increase of ER. The absolute radial and circumferential stress decreased and increased in negative and positive ranges respectively with distance increased. The release strain (maximum −3033 με, 10−6 microstrain), radial RS (maximum 600.9 MPa) and circumferential RS (maximum 601.1 MPa) also increased with the increase of ER, and the minimum relative error of the plastic zone radius of the theoretical model was 3.78 % proving the reliability of the model. In addition, ECE increased the release stress (the maximum radial and circumferential release stresses were 1402.6 MPa and 747.5 MPa) and decreased the failure force (minimum 44.7kN) with increased ER. The initial crack position tended to transition from the inlet and outlet surfaces to the middle position, and the crack propagation angle and axial crack size gradually decreased with the decreased ER and stress level.

Multi-roller taper burnishing of internal chamfers and its enhancement mechanism on 7050 aluminum alloy

The chamfer surface of the hole entrance is considered a source of crack initiation and propagation caused by surface non-uniformity, which undoubtedly has a significant effect on component performance. The present study proposes a multi-roller taper burnishing (MRTB) process that is able to improve the integrity of the chamfer surface and thereby enhance the fatigue performance of 7050-T7451 aluminum alloy. The influence mechanism of the MRTB process on the topography, roughness, microhardness, fatigue performance, and residual stress of the internal chamfer surface was finally investigated. The results showed that the most significant surface improvement was achieved at the optimal burnishing depth of 0.07 mm. Increasing the burnishing depth to the optimal value increased the fatigue life of the samples due to the improvement of surface roughness and compressive residual stress on the chamfer surface. When the burnishing depth exceeded the optimal value, surface defects appeared, and material flowed into the hole, resulting in reduced fatigue life compared to the optimal value. Therefore, the fatigue life of MRTB-treated samples with the optimum value of burnishing depth (0.07 mm) was improved by 55 % and 36 % for thicknesses of 6 mm and 8 mm, respectively, compared to untreated samples.

Evolution of Precipitates in a Mechanical Vibration-Assisted Metal Inert Gas Welded Joint of 6082-T6 Aluminum Alloy Made with an ER5356 Filler Wire

Evolution of Precipitates in a Mechanical Vibration-Assisted Metal Inert Gas Welded Joint of 6082-T6 Aluminum Alloy Made with an ER5356 Filler Wire

Influence of added La2O3 on the microstructure, mechanical properties, and tribocorrosion resistance of TiB2–Ni plasma-sprayed coatings

To enhance the tribocorrosion resistance of 7075-T6 aluminum alloy in deep sea environments, TiB2–Ni coatings with varying La2O3 content were deposited on 7075-T6 aluminum alloy substrates using plasma spray technology. The effects of different La2O3 contents on the organization, structure, and properties of the coatings were analyzed. The results indicated that La2O3 incorporation suppressed brittle phase formation such as Ni3B; 1.0 wt% La2O3 addition reduced Ni3B by 16.9%. The coating's corrosion resistance significantly improved with La2O3 doping - the self-corrosion current density of the 1.0 wt% La2O3-doped coating decreased from 71.2 nA/cm2 to 30.2 nA/cm2.

The electrochemical corrosion performance of aluminum alloys grade 6082-T6 weld repair

This research investigated the corrosion behavior of standard current metal inert gas weld repair for 6082-T6 aluminum alloy using ER5356 filler metal. The new and repaired (NW and RW) welds were studied. The welds comprised the weld metal (WM), the heat affected zone (HAZ) (solid solution and softened zones), and the base metal (BM). The study focused on investigating electrochemical corrosion using polarization and electrochemical impedance spectroscopy (EIS) methods in 3.5% NaCl solutions, especially in HAZ, including metallurgical and mechanical examinations. The BM containing an α-Al matrix with Al(Fe,Mn)Si and Mg2Si phases exhibited the maximum hardness (70–104 HV0.1). The WM hardness decreased (67–76 HV0.1) with the α-Al, β-Mg3Al2, and Mg2Si phases. Despite having comparable phases to BM, HAZs showed lower hardness (Solid HAZ: 70–82 HV0.1) due to more intermetallic phases. The RW’s softened HAZ revealed the minimum hardness (52–63 HV0.1) compared to that of the NW (55–70 HV0.1). Besides, the tensile strength of the RW (179.7 MPa) was also lower than that of the NW (174.4 MPa) because of the reheating effect. The electrochemical corrosion results indicated that the BM exhibited the maximum corrosion resistance (the lowest corrosion current density (icorr), the highest corrosion potential (Ecorr), and the charge transfer resistance (Rct)), followed by the HAZ and the WM, respectively. The softened HAZ demonstrated better corrosion resistance than the solid solution HAZ. Conversely, the over-aging effect reduced the softened zone’s pitting corrosion resistance (Ep) compared to the solid solution zone. The RW exhibited inferior corrosion resistance compared to the NW due to increased intermetallic phases, which was consistent with the mechanical results. However, the RW’s softened HAZ corrosion characteristics were inconsistent with its mechanical properties; its hardness and tensile strength were the lowest, but its corrosion resistance was not. Pitting corrosion was observed on the weld surfaces using the SEM.

Mechanistic insights into abnormal grain growth suppression in friction stir welded 7075-T651 aluminum alloys through variation in tool rotational speed

Friction stir weld joints of precipitation-hardenable aluminum alloys invariably show abnormal grain growth (AGG) during the post-weld T6 heat treatment. This study investigates the influence of tool rotational speed on AGG in FSW joints and elucidates the underlying mechanisms. Friction stir welding (FSW) of heat-treatable 7075-T651 aluminum alloy was conducted at various tool rotational speeds such as 386 rpm, 664 rpm, 931 rpm, and 1216 rpm with a constant traverse speed of 20 mm/min, followed by T6 heat treatment. Further, metallurgical characterization of FSW joints, such as optical stereotype microscopy and electron backscattered diffraction (EBSD) analysis, was employed. In addition, micro-hardness distribution and transverse tensile test of the FSW joints were studied to understand the effect of AGG on the mechanical performance of the weld joint. Results indicate that higher tool rotational speeds lead to more uniform deformation and a higher strain rate, resulting in the formation of a strong B/B̅ texture and higher geometrical necessary dislocation density (GND) within the nugget zone. The presence of this texture, coupled with a higher fraction of high-angle grain boundaries, proves less susceptible to AGG. Conversely, welds produced at lower tool rotational speed exhibit a strong C texture with relatively lower high-angle grain boundaries and GND formation, rendering them more susceptible to AGG. Microstructural analysis reveals that continuous grain growth dominates in welds developed at higher tool rotational speeds, while discontinuous grain growth prevails in those developed at lower tool rotational speeds. A weld joint with AGG leads to a lower tensile strength of 502 MPa and higher ductility of 14.1 %, and the fracture mechanism was found to change from ductile to quasi-cleavage fracture. However, no significant effect of AGG was found on micro-hardness. This study establishes the critical role of optimized tool rotational speed in controlling AGG during FSW and provides a comprehensive understanding through EBSD analysis. The finding of this study bridges the gap between controlled AGG and a detailed mechanistic comprehension, offering valuable insights for enhancing the reliability and performance of FSW joints in precipitation-hardenable aluminum alloys.

A profound study of damage behavior for Al 2024-T3 alloy worksheet produced by constrained groove pressing in the superior practical condition

Constrained groove pressing (CGP) process is one of the most efficient and novel methods of severe plastic deformation to manufacture ultra-fine sheet metal. The present research work is related to the study of CGP process of 2024-T3 Aluminum alloy sheet. The empirical and numerical simulation of CGPed- specimens have been examined at both room and elevated temperatures. In order to simulate the constrained groove pressing process in Abaqus software, the Johnson–Cook material model has been employed. The geometrical variables of the CGP process include the teeth number, teeth angle, and sheet thickness, and the criterion for the superiority of the numerical test is the maximum reduction of two equivalent strain and equivalent force factors, simultaneously. To determine the weight’s coefficients of the target factors and select the superior test, the Shannon’s Entropy and Simple Additive Weighting (SAW) methods have been used, respectively. After validating the numerical findings, the variation of damage parameter, stress triaxiality and the equivalent plastic strain distribution in the superior practical condition have been evaluated in detail. Based on the Entropy-SAW hybrid technique, the weight’s coefficients of equivalent strain and equivalent force target factors were computed to, in turn, 0.38 and 0.62. Also, the results revealed that the CGP process could not be performed at room temperature based on high damage evolution. But, at elevated temperature, the damage parameter (D) doesn't exceed 0.26. Also, the maximum stress triaxiality and equivalent plastic strain (PEEQ) at this process temperature reached to 0.5 and 0.1, respectively.

Effects of spraying parameters and heat treatment temperature on microstructure and properties of single-pass and single-layer cold-sprayed Cu coatings on Al alloy substrate

Exploring the deposition of single-pass and single-layer pure Cu coatings on Al alloy substrate through high-pressure cold spray technology is a crucial endeavor with significant implications for advancing the utilization of such coatings. Regrettably, research in this specific area remains scarce, highlighting the need for further investigation and understanding. This study examined the characteristics of cold-sprayed Cu coatings deposited on a 6061 T6 aluminum alloy substrate under varying gas temperatures and pressures, and explored the effects of subsequent heat treatment on the microstructure and mechanical properties of the Cu coatings. The morphology, phase composition, surface roughness, thickness, porosity, microstructure, shear strength, and microhardness of the cold-sprayed Cu coatings were systematically analyzed. The findings indicated that the spraying parameters had a substantial impact on the properties of the Cu coatings. Specifically, increased gas pressure led to rougher surfaces and lower porosity, whereas higher gas temperature produced smoother surfaces and also reduced porosity. At 800 °C and 4.0 MPa, the Cu coatings exhibited the lowest surface roughness, measuring 8.03 μm. Conversely, at 800 °C and 5.5 MPa, the Cu coatings demonstrated the lowest porosity, at 0.26 %. Moreover, the microstructure analysis showed evidence of dynamic recrystallization in the deposited Cu particles, contributing to enhanced mechanical properties. Following this, the influence of heat treatment on the microstructure and properties of the cold-sprayed Cu coatings was examined. The results demonstrated that annealing at different temperatures induced changes in the interfacial microstructure, with the formation of intermetallic compounds between the Cu coating and Al alloy substrate. This interdiffusion phenomenon led to improved bonding strength and mechanical properties of the Cu coatings, as evidenced by increased shear strength. After undergoing heat treatment at 400 °C, the Cu coatings exhibited the highest shear strength, measuring 49.89 MPa. However, excessive heat treatment temperatures resulted in the formation of cracks and a decrease in mechanical properties.

Investigating the effect of stress ratio on fatigue crack growth rate behaviour in friction stir welded AA7075-T651 aluminium alloy plates

This study examines the characteristics of Fatigue Crack Growth Rate (FCGR) in AA 7075-T651 Friction Stir Welded (FSW) joints with a thickness of 16 mm. Compact tension (CT) specimens from both the base and the FSW joints were utilized to assess FCGR under various stress ratios (0.2 to 0.5). Additionally, the study involved analyzing the transverse tensile characteristics of both the based and the welded joints. The microstructures of the welds were inspected using optical and transmission electron microscopes. Findings indicate that the FSWjoint critical stress intensity factor range (ΔKcr)is lower than the unwelded base, that can be related to precipitates dissolving in the weld zone when the friction stir welding process. Consequently, in contrast to the unwelded base, the fatigue life of AA 7075-T651 aluminium alloy FSW joints is significantly reduced. A scanning electron microscope carried out microstructural analyses of the fracture surfaces of the FSW and base under various stress ratioconditions. The results showed that, in contrast to the parent material, the FSW joint has ultra-fine grains resulting in intergranular cracks in the propagation zone.

New insights into enhancing the mechanical properties of 6061-T6 aluminum alloy MIG welded joints by constructing bionic heterostructure

The trade-off between strength and toughness is a long-term challenge for engineering metal structural materials. However, natural materials overcome the inverse relationship between strength and toughness through their unique structures. Inspired by plant leaves and dragonfly wings, a ‘soft-hard’ alternating bionic heterostructure is prepared on 6061-T6 Al alloy MIG welded joints by laser surface remelting (LSR) technology. After LSR, the grain size of the laser treated zone is significantly refined, dislocation density is increased, and the formation of fine and stable GP zone and β′′ phase is promoted, enhancing microhardness and tensile properties of the LSRed sample. By adjusting the laser stripe spacing and distribution angle, stress transfer and redistribution can be optimized, effectively improving the tensile properties of the welded joint can be. Compared to as-welded sample, the tensile strength, yield strength and elongation of LSRed sample can be increased by 30.6 %, 13.6 % and 102 %, respectively. In addition, the bionic heterostructure composed of grain size gradient, dislocation gradient and precipitated phases gradient can effectively develop heterogeneous deformation induced (HDI) stress strengthening and HDI strain hardening, enabling synergistic strengthening of strength and toughness.

Assessment of the Thermomechanical Behavior and Microstructure of AA 7075-T6 Aluminum Alloy Lap Joints at Optimal Predicted FSW Process Parameters

The lap joints of AA 7075-T6 aluminum alloy were assembled using the friction stir welding (FSW) technique. Experimental studies were performed to characterize the thermomechanical properties of these welds. The main goal of this research was to comprehensively assess the thermomechanical behavior of AA 7075-T6 aluminum alloy under FSW conditions. Tests were carried out at a tool rotational speed of 1320 rpm and at two advancing speeds of 70 mm/min and 120 mm/min, selected based on a previous study aiming to optimize the heat input during the FSW process. The experimental investigations involved the characterization of temperature profiles during welding, mechanical properties such as microhardness and tensile strength, and microstructure examination at the two advancing speed conditions. This study revealed that the welding speed has an obvious influence on the material thermal behavior during the FSW process. Indeed, the peak temperature obtained with a lower welding speed (70 mm/min) was higher by almost 10% compared to that obtained with a higher speed (120 mm/min). Moreover, by increasing the welding speed, the mechanical characteristics, such as microhardness and tensile strength, were increased by almost 5% for the mean microhardness and 6% for the ultimate tensile strength. Additionally, the microstructure examination demonstrated that, by decreasing the welding speed, more interaction between the tool and the material is observed, resulting in a deeper stir zone due to increased heat dissipation downwards into the material, affecting the thermal profile and influencing the resulting mechanical properties of the welded joint.

Initial and grow-up stages of material transfer on Arc-DLC coating in aluminum forming processes at high temperatures

The mechanisms of material transfer in aluminum forming processes at high temperatures have remained a contentious tribological issue. This study aims to investigate the transfer mechanisms in the initial and grow-up stages of 6082-T6 aluminum alloy against commercial Arc-DLC coating under lubricant-free forming conditions. The warm and hot upsetting sliding test (WHUST) was used as the tribological test. It was conducted with two sliding configurations: the full sliding test to study the evolution of aluminum transfer and the short sliding test with a 2-mm sliding distance to observe the initiation of aluminum transfer. Furthermore, the effect of different sliding speeds, 0.5 and 5.0 mm/s, and initial temperatures of the specimen, 300 °C–500 °C, on the phenomenon of aluminum transfer was examined. Experimental results found that the aluminum transfer on the Arc-DLC coating in the initial stage of all cases was mainly caused by mechanical plowing. However, in the grow-up stage, the aluminum transfer could be dominated by mechanical plowing and/or adhesive bonding, depending on contact conditions. The different transfer mechanisms caused variations in the coefficient of friction and surface characteristics on the friction track. It led to the skewness Ssk could be an indicator to differentiate the transfer mechanisms.