Weld Zone Research Articles

Interpretation of mechanical properties gradient in laser-welded joints: Experiments and grain morphology-dependent crystal plasticity modeling

The grain size and morphology of laser welds show a gradient distribution, leading to variations in mechanical properties. This study proposes a microscopic crystal plasticity constitutive (CPC) model to examine the effect of ER4047 welding wire on the mechanical properties of laser-welded aluminum alloy joints. A finite element model updating strategy was used to fully invert the morphological mechanical parameters, marking a significant advancement. This study combines mesoscale electron backscatter diffraction (EBSD) observations with macroscopic uniaxial tensile tests to obtain crystal plasticity finite element analysis and strain field data from digital image correlation. The mechanical property gradient of the welded joints was systematically analyzed from a crystal perspective. The CPC parameters were inverted for different grain sizes and morphologies. The study found that using ER4047 welding wire significantly enhanced the mechanical properties of the welded joints, especially in the welding zone. As grain size increased, the yield strength of the material decreased, while the hardening modulus increased. Additionally, the cast characteristics of columnar crystal morphology reduced both yield strength and hardening modulus.

Deep learning coupled Bayesian inference method for measuring the elastoplastic properties of SS400 steel welds by nanoindentation experiment

Nanoindentation experiment has shown broad application prospects due to its ability to measure the mechanical properties of various materials at multiple scales. In this paper, a deep learning coupled Bayesian inverse approach is proposed for measuring the elastoplastic parameters of SS400 steel welds by nanoindentation experiment. The nanoindentation experiments were performed on the SS400 steel welds, including base metal (BM), weld zone (WZ), and heat affected zone (HAZ), and the experiment load–displacement (P-h) curves were obtained. The hyper-parameters tunable artificial neural network (ANN) was established to correlate elastoplastic parameters with indentation P-h curves. Based on Bayesian inference theory, the posterior density function for estimating the unknown material parameters was established. Transitional Markov chain Monte Carlo was used for sampling from the posterior density function, and the elastoplastic properties in different regions of SS400 steel welds were identified. The advantage of the established measuring method is that the hyper-parameters optimized ANN model can provide the very accurate forward relationship between material properties and indentation P-h curves. Besides, the inverse Bayesian framework can quantify the potential uncertainty of the identified elastoplastic parameters. The measured elastoplastic properties of the base metal of SS400 steel show good agreement with tensile experiment data, of which the maximum measuring error is less than 12%. The measured elastoplastic properties in WZ and HAZ are also proved to be effective. The uncertainty of the identified elastoplastic parameters of SS400 steel welds can be quantified by posterior marginal distribution, using Mean and Variance values. The results proved that the proposed inverse measuring method is reliable and effective.

Optimizing weld strength and microstructure in CP-titanium and 304 stainless steel friction welds with chromium interlayer

This study investigates the effect of a Cr-interlayer on the hardness and friction-welded joint strength between CP-titanium and 304 stainless steel. Rotary friction welding, with its adjustable parameters such as upset pressure, is the preferred method for this dissimilar joint. Due to the difference between these two base metals, a metallic interlayer like chromium, is crucial for controlling the formation of intermetallic compounds (IMCs). Welding was conducted at three different upset pressures, both with and without the Cr-interlayer. Tensile and microhardness tests were performed, complemented by phase analysis and microstructural characterization using XRD and SEM. Our findings reveal that employing a chromium layer and higher upset pressures enhances strength while reducing the presence of brittle IMCs in the welds. At the CP-titanium side, dynamic recrystallization occurs due to increased heat generation at the interface and strain occurred by materials flow, facilitating IMC formation, especially evident at 250 MPa upset pressure. Interestingly, relatively higher strength at 150 MPa is attributed to the absence of IMCs. Conversely, higher strength results at 350 MPa due to from the flow of softened material, effectively purging IMCs from the weld zone. Notably, both β-titanium and chromium-based IMCs form in the presence of the chromium interlayer, resulting in decreased joint hardness and increased overall ductility. In conclusion, our study's findings contribute to bridging the gap between theoretical strength and practical application, significantly advancing joint performance.

Mechanical performance of dissimilar Al6082 aluminum and AZ91 magnesium alloy joints produced by friction stir welding

Abstract The current research work aims to produce a defect free joint of Al6082 aluminum and AZ91 magnesium alloy sheets by friction stir welding (FSW) at various tool rotational and travel speeds with an objective to obtain the best combination of welding parameters to produce quality joint. The weld joint that was produced at the combination of 1400 rpm tool rotational speed and 30 mm min−1 feed exhibited defect free stir zone. Microstructural studies carried out in the weld joint demonstrated mechanical mixing of base materials from both the alloys in the stir zone. The mixing of Al6082 and AZ91 alloys was clearly appeared in the weld zone. It can be observed that the x-ray diffraction studies clearly demonstrated the development of intermetallics in the weld region. Higher hardness was observed for the joints that can be ascertained to the presence of more mixed regions in the stir zone that contains hard and brittle intermetallics. From the tensile test data, lower strength (175.71 ± 4.24 MPa) was observed for the weld joint compared with Al6082 (242. 6 ± 11.4 MPa) and AZ91 (205.27 ± 6.39 MPa) base materials. Furthermore, the ductility of the weld joint was measured as marginally higher than the AZ91 Mg alloy and lower than the Al6082 alloy. It can be concluded that the defect free weld joints of Al6082-AZ91 alloys can be successfully produced by FSW for structural applications targeted for dry environment.

Characterization of physical metallurgy of quenching and partitioning steel in pulsed resistance spot welding: A simulation-aided study

This study mainly focuses on the microstructure evolution of QP980 steel during resistance spot welding and its influence on the mechanical performance of resistance spot welds which is a critical influencing factor on the quality of body-in-white at the service condition. It is observed that the thermomechanically engineered microstructure of QP980 steel changes to form metastable phases such as martensite in the fusion zone and the heat affected zone due to rapid cooling induced by the thermal cycle of the welding. A finite element modeling of the welding process was used to predict the weldment heat distribution, thermal history and microstructure evolution in different welding zones. The modeled thermal history of the weldments shows that the peak temperature in the four-pulse resistance spot welding is delayed because of pulsed welding conditions and holding times between the welding pulses. This heat management approach in pulsed welding prevents void formation. The modeled thermal history and rapid heating, and cooling conditions are discussed here to predict the microstructure evolution and transformation in the fusion and reheated zones. The modeled results were helpful in the prediction of the microstructure at different weld zones. Then the strategic links between the microstructure and mechanical performance of the welded alloy are discussed thoroughly. The microhardness profile of the weld is discussed from a microstructural point of view to disclose the physical metallurgy of the welds. Softening phenomena were not observed in the sub-critical heat affected zone.

Study of the effect of SMAW welding speed on the microstructure and crystal stability of X70 steel using X-ray diffraction

This study investigates the impact of manual electric arc welding (SMAW) speed on the microstructure of X70 steel. Welding was performed at two distinct speeds: S1 = 20 mm/min and S2 = 35 mm/min, at the COSIDER BISKRA workshop in Algeria. X-ray diffraction (XRD) analysis was conducted on the welded zones to examine crystal orientation, size, dislocation density, and structural stability across different welding areas, including the base metal (MB), heat-affected zones (HAZ1 and HAZ2), and weld zones (WZ1 and WZ2). The XRD results revealed that key crystal peaks, such as {110} and {200}, retained their positions at both welding speeds, though variations in {110} peak intensity were noted. The lower welding speed (S1) resulted in a higher heat input, which enhanced crystal stability, increased crystal size, and reduced dislocation density. On the other hand, the higher speed (S2) produced lower heat input, leading to smaller crystal sizes, increased residual stresses, and a greater number of defects due to rapid cooling. These findings underscore the critical influence of welding speed on heat input, cooling rates, and their consequent effects on microstructure. The study highlights the importance of optimizing welding parameters to balance microstructural integrity, mechanical performance, and production efficiency.

FEM-driven machine learning approach for characterizing stress magnitude, peak temperature and weld zone deformation in ultrasonic welding of metallic multilayers: application to battery cells

Abstract This study investigates the innovative application of machine learning (ML) models to predict critical parameters—stress magnitude (SM), peak temperature (PT), and plastic strain (PS)—in ultrasonic welding of metallic multilayers. Extensive numerical simulations were employed to develop and evaluate three ML models: Radial Basis Function (RBF), Random Forest (RF), and Kernel Ridge Regression (KRR). According to the results, the KRR model demonstrated superior performance, achieving the lowest RMSE and highest R 2 values of 0.068 (R 2 = 0.941) for SM, 0.075 (R 2 = 0.929) for PT, and 0.071 (R 2 = 0.946) for PS, with fewer data samples required. KRR also exhibited low squared bias and variance values, ranging from 1 × 10 − 4 − 3.2 × 10 − 4 for bias and 2.2 × 10 − 4 − 3.6 × 10 − 4 for variance, indicating its precision in predicting the output targets. Moreover, the systematic categorization of input features, including material properties, geometrical factors, and welding parameters, highlighted their significant influence on predictive accuracy, particularly the crucial role of welding parameters at higher output values. Finally, a case study on ultrasonic welding of copper multilayers underscores the model’s effectiveness in unraveling complex relationships, providing a robust tool for optimizing and advancing ultrasonic welding processes.

Microstructure and mechanical properties of thin-walled TA1 titanium pipes fabricated by high-frequency induction welding

High frequency induction welding (HFIW) was effectively employed for the high-speed fabrication of thin-walled TA1 titanium pipes (TWTPs) with a nominal wall thickness of ∼0.6 mm. The microstructure and mechanical properties of TWTPs manufactured under varying welding parameters were investigated. The weld zone (WZ) exhibits a waist shape measuring ∼622 μm in width, and the width of the heat-affected zone (HAZ) spans between 763 and 864 μm. Both the WZ and HAZ are composed of a mixture of coarse serrated α grains with fine acicular and twins, while the BM retains equiaxed grains. This unique microstructure was resulted from the thermal cycling during HFIW, contributing to a notable increase in microhardness within the WZ compared to both the HAZ and the BM. Optimal manufacturing conditions were identified at a welding power of 14.4 kW, a welding speed of 60 m/min, an opening angle of 6°, and a squeeze displacement of 0.2 mm, yielding the TWIP with a tensile strength of ∼307 MPa and tensile elongation of ∼27%. Tensile fracture analysis revealed that failure predominantly occurred within the BM, underlining a ductile fracture mode characterized by pronounced dimple formations. The enhanced mechanical performance of the weld joints can be attributed to the heterogenous microstructure in the WZ, where the presence of large serrated α-grains enhances ductility, and the fine martensite and twins contribute to the high strength.

Effect of water quenching into strength, hardness and microstructure of the welded AA 6061 plates

Purpose The purpose of this study is to find the effect of heat treatment on the mechanical proeprties of aluminum. Aluminum exhibits a good response to heat treatment, especially quenching, according to the mechanical property improvement. The presence and orientation of secondary phases (Al-Fe-Mn-Si) are greatly affected by the quenching process. Design/methodology/approach The present work deals with the effect of water quenching on the mechanical properties of welded AA 6061 plates which were joined by using metal inert gas (MIG) welding, tungsten inert gas welding and friction stir welding (FSW). Three tests like tensile, bending and hardness were considered. The microstructural variation was analyzed by optical microscopy and elemental mapping through field emission scanning electron microscope. Findings A significant enhancement in the tensile strength and hardness was achieved on postquenched specimens. This improvement in mechanical properties is caused by the distribution of fine alloying elements throughout the metal solution rather than precipitation at the grain boundaries. In comparison to the “untreated specimens,” an improvement of 76.7%, 25.32% and 56.81% in the tensile strength of quenched TIGW, MIGW and FSW specimens, respectively, was observed. Originality/value The quenching process has increased the strength of the MIG welded joint over the base metal. The MIG welded joint has a larger flexural modulus than the other two welded plates, according to the results of the bending test. Furthermore, a uniform distribution of hardness was observed in postquenched welded specimens. It was found that welded zone was harder than heat-affected zone. Out of all the specimens, the base metal zone has the lowest hardness.

Novel approach for in-line process monitoring during ultrasonic metal welding of dissimilar wire/terminal joints based on the thermoelectric effect

AbstractUltrasonic metal welding (USMW) is a manufacturing technique widely employed in the automotive and aerospace industries due to its efficiency in joining similar as well as dissimilar metals. Despite its prevalence, the lack of effective in-line process monitoring methods has resulted in high scrap rates, product recalls due to unrecognized scrap or financial losses due to pseudo-scrap, limiting its application in more sensitive industries. This paper presents a novel thermoelectric effect-based method for in-line process monitoring of USMW processes. This approach utilizes the thermoelectric properties, that manifest at the junctions of dissimilar metals during welding to accurately measure the temperature of the weld zone without the need of additional thermocouples, pyrometers or infrared cameras. An experimental setup was developed to validate the thermoelectric-based temperature measurement methodology. Key to this approach is the detection of thermoelectric voltage developed due to thermo diffusion when dissimilar materials are joined. The experiments showed a strong correlation between the thermoelectric voltage and the mechanical strength of the welds, suggesting that this parameter can effectively predict the quality of the weld. In the trials, a series of welded samples was created under controlled conditions to measure the generated thermoelectric voltage and correlate it with ultimate tensile strength tests. The data were analyzed using Spearman’s correlation coefficients to determine the correlation of the thermoelectric signals and joint strength. Results indicate that the thermoelectric voltage measurements correlate highly with the joint strength, with a Spearman’s correlation coefficient of over 0.94, thereby providing a promising predictive metric for assessing weld quality.

Development of the interlayer alloy using for TLP diffusion bonding of GH3230 superalloy based on the CALPHAD method

The hot-end components of aero-engines and gas turbines not only require high-temperature alloys capable of withstanding extreme temperatures, but also demand welds with high-temperature-resistant properties. In this study, the CALPHAD method was employed, utilizing the thermodynamic theory of phase diagrams with Thermo-Calc software and the corresponding database, to design the interlayer composition for superalloy TLP diffusion connections. The optimization aimed to determine the interlayer material's solidus-liquidus and compound phase content, resulting in the selection of a new nickel-based interlayer material containing B as MPD, with Co and W as strengthening elements. Using GH3230 alloy as the research subject, TLP diffusion bonding experiments were conducted at a welding temperature of 1200 °C with a holding time of 4 h. The weld zone exhibited no defects, and the microstructure was identical to that of the GH3230 base metal, consisting entirely of a solid solution. High-temperature tensile tests revealed that fractures consistently occurred in the GH3230 base metal, indicating that the weld's strength significantly exceeded that of the base metal. The average tensile strength of GH3230 high-temperature alloy bar tensile simulated specimens is 899 MPa at room temperature and 213 MPa at high temperature. In addition, the 90° three-point bend test showed no cracking in the weld area, indicating adequate plasticity.

Process optimization of refill friction spot stir of AA6061-T6 aluminum alloy for thick plate

To investigate the process parameters of refillable friction stir spot welding for AA6061-T6 aluminum alloy with a 3 mm plate thickness, and to extend the applicability of this technology, experiments were conducted using custom-made tools under varying rotational and penetration speeds. This study aimed to produce well-formed welds and analyze the metallurgical structure, tensile shear strength, and microhardness of the welded joints. The experiments were performed at rotational speeds of 1000, 1200, 1400, and 1600 rpm and penetration speeds of 20, 30, 40, and 50 mm/min. These conditions were found to facilitate effective refillable friction stir spot welding. The results indicated that at lower rotational speeds, the joints failed at the interface, while at higher speeds, failure occurred through the plug. Optimal tensile shear strength was achieved at a rotational speed of 1400 rpm and a penetration speed of 30 mm/min, with a peak force of 9.27 kN and a joint surface fracture mode. Microstructural examination revealed a significant refinement of grains in the weld zone compared to the base metal. Microhardness measurements showed a concentric ring pattern on the upper surface with higher hardness at the center, decreasing toward the edges. The cross-sectional hardness demonstrated a vertical gradient, being higher at the top and decreasing toward the bottom. Notably, the welded area exhibited signs of annealing with a reduced hardness compared to the base metal, where the maximum value was recorded as HV79.

Numerical simulation and modeling of the trielectrode-coupled corrosion mechanism at the laser-welded interface of N80 steel

Laser welding, a prevalent technique in automotive structure manufacturing, can introduce compositional disparities and stresses within the weld zone, exacerbating corrosion complexity at the weld interface. This paper develops a triple galvanic corrosion model for N80 steel welds under stress conditions, leveraging the COMSOL software for simulations. The findings demonstrate that, within the elastic stress range, an elevation in stress intensifies the overall electrode surface potential, ultimately transitioning into plastic stress and fostering a more negative potential. This, in turn, amplifies the cathode-anode potential difference, rendering the material more susceptible to corrosion. The deeper the depression between the weld zone and the heat-affected zone, the higher this potential difference becomes, exacerbating the corrosion risk. Under stress, the corrosion rate markedly surpasses that observed in unstressed conditions. During the 160 day corrosion period, the weld seam and heat affected zone undergo a transition from plastic strain to elastic strain, while the base metal zone experiences both plastic strain and elastic strain simultaneously. This dynamic strain evolution leads to temporal variations in the stress-induced cathode-anode potential differences. In comparison to stress-free corrosion scenarios, the impact of stress on the cathode-anode potential difference initially intensifies, yet this effect tapers off over time.

Influence of friction stir welding on the localised corrosion behaviour of AA2060 T8E30 and AA2099 T83 Al-Li alloys

The effect of friction stir welding (FSW) on the microstructure and localised corrosion behaviour of the dissimilar weld of AA2099 T83 and AA2060 T8E30 alloys is investigated. FSW results in a drastic change in the microstructure thus altering their corrosion behaviour. The heat-affected region exhibits similar attack morphology to their respective base metal but is the most protected region. The stir zone (SZ) is the most susceptible to attack. During immersion of the entire weld, attack initiation occurs from the AA2060 SZ due to galvanic activity within the region caused by the overlap of the grains in the weld zone.

Flux-bound TIG welding on UNS S32760 super duplex stainless steel using activating fluxes

In this article, the effect of activating flux powders viz., Silicon Dioxide (SiO2), Chromic Oxide (Cr2O3), Titanium Dioxide (TiO2) and Vanadium Pentoxide (V2O5) on Flux-Bound TIG (FB-TIG) welding of UNS S32760 Super Duplex Stainless Steel (SDSS) is investigated. Also, conventional TIG welding is done for a comparative study with the FB-TIG welds. The macrographs of the welds are obtained to analyze the depth, width and aspect ratio. The depths obtained with all the fluxes are found to be superior relative to the conventional TIG welds. The highest penetration of 6 mm is obtained for V2O5 welds. Then the microstructure and composition of the welds are analyzed using Optical Microscopy and Area-Mapping analysis. The authors observed the presence of three forms of austenite viz., Grain Boundary Austenite, Intragranular Austenite and Widmanstatten Austenite in the weldment zones. The micro-hardness profiles of the welds are also analyzed, and the profiles obtained with all the FB-TIG welds are found to be relatively smoother without any abrupt variations. Through this investigation, it is delineated that FB-TIG welding can increase the overall productivity in the welding of SDSS, as the penetration obtained is up to thrice relative to the conventional TIG welding.

Diminishing residual stress and distortion by in-situ rolling tensioning to increase fatigue performance of friction stir welded AA2024-T3 joints

In this research, local mechanical tensioning treatment in the form of in-situ rolling tensioning (ISRT) was applied during friction stir welding of AA2024-T3 sheets. Two types of roller configurations were used. First, a single roller located at the rear of the tool which passed over the weld region and secondly, two rollers were located next to the weld zone symmetrically. Subsequently, several experiments comprising residual stress, distortion and fatigue crack growth (FCG) measurements were carried out combined with microstructure, texture, hardness and tensile tests. Results demonstrated that a single roller ISRT effectively diminished residual stress in the nugget zone (NZ) from + 11.7 MPa to −45.3 MPa accompanied by better weld FCG resistance. Apart from residual stress reduction, the improved weld fatigue performance was likely correlated with the modifications of weld microstructure and texture due to rolling tensioning.

Structure-property correlation for friction stir welded joints of 2219Al alloys microalloyed with Cd

Present study aimed at experimental investigation of microstructural evolution, microhardness profile, tensile and impact properties of friction stir welded (FSW) joints of 2219Al alloys microalloyed with varying (up to 0.1 wt%) Cd contents. FSW was performed on the cast and homogenized alloys. Microstructural analysis from weld line up to base metal, identified three sequential heat affected weld zones having separate grain morphologies, namely Weld Nugget Zone (WNZ), Thermo-Mechanical Affected Zone (TMAZ) and Heat Affected Zone (HAZ). Vickers microhardness value increased from weld line towards the WNZ, then decreased towards the TMAZ, and finally increased through HAZ towards the base metal, which exhibited higher hardness compared to all the heat affected weld zones. Microhardness, yield and tensile strengths of the FSW joint of 2219Al alloy increased, due to microalloying with 0.06 wt% of Cd contents, which was attributed to continuous grain refinement. While tensile ductility and toughness, and impact toughness of the welded joint reduced, resulting from trace additions of Cd. Investigated alloys retained significant mechanical strength, ductility and toughness, on the respective joints, following to the FSW operation. Cd was observed to be a potential microalloying element to control the microstructure, refine grain size and improve mechanical strength and hardness of the welded joint of 2219Al alloy. Present experimental results established a structure-property correlation, in order to validate potential application of FSW technique on investigated 2219Al alloys with trace additions of Cd, to attain desirable weld-quality avoiding welding imperfections.

Effect of paint baking treatment on microstructure and properties of 6082 aluminum alloy CMT welded joints filled with AlSi10Cu2Mg0.7Zn1 wire

Aluminium alloy 6082-T6 is known for its high strength and cost effectiveness, making it a popular choice for thin sheet structures such as automotive body panels. However, the welding-induced softening of the heat affected zone (HAZ) and the insufficient strength of the filler metal are the primary factors limiting its broader application. In this study, the lower heat input cold metal transfer welding method is employed, utilizing heat-treatable reinforced AlSi10Cu2Mg0.7Zn1 wire to weld 6082-T6 plates. Additionally, the impact of the baking paint process within the automotive manufacturing workflow on the evolution of microstructural characteristics of the HAZ and Weld Zone (WZ), as well as the mechanical properties of the joints, is investigated in detail. The findings indicate that the AlSi10Cu2Mg0.7Zn1 filled WZ contains a small quantity of θ, Q, and β phases, alongside a significant amount of reticulated eutectic Si distributed among the Al dendrites. Notably, the strength of the WZ is enhanced compared to that of conventional Al–Si and Al–Mg wires. During the baking process, the WZ exhibits the precipitation of a small amount of fine β’’ and β′ precipitates, which elevates the tensile strength of the WZ to 272 MPa and the yield strength to 179 MPa. Furthermore, the baking treatment promotes the further growth of β′ in the HAZ of the joints, while fine β’’ phases are reprecipitated within the Al matrix. The combined influence of these two precipitated phases results in an increase in the tensile strength of the HAZ by 29 MPa.

Experimental investigation of FSW induced property changes in welded dissimilar Mg–Al–Zn alloys

Intense plastic deformation and intermixing during friction stir welding of dissimilar alloys may suppress the properties in welded zone. To suitably control these changes, careful study is required. Present research investigates microstructure, mechanical performance and corrosion behaviour at different rotational speeds in friction stir welded dissimilar AZ31–AZ91 Mg alloys. Very small cracks were present in welded zone due to formation of magnesium oxide (MgO). The EBSD analysis suggest more concentrated fibre texture at 1000 rpm tool rotational speed as compared to 700 rpm tool rotational speed in welded zone and the texture maximum intensity was 39.447 times of random distribution at tool rotational speed of 1000 rpm. The obtained maximum microhardness was 82 Hv at tool rotational speed of 700 rpm. The maximum values of tensile strength (234.86 ± 7.77 MPa) and flexural strength (350.89 ± 17.67 MPa) of welded samples were decreased as compared to base materials. The corrosion rate of welded samples was increased and corroded surface have some pits and corroded rings. The highest corrosion rate (2.1596 mm / year ) was obtained at 700 rpm. This experimental work suggests that in overall, sample welded at 1000 rpm tool rotational speed has better weld property.

Research on the microstructure, mechanical and fatigue performance of 7075/6061 dissimilar aluminum alloy fusion welding joint treated by nanoparticle and post-weld heat treatment

The microstructure and mechanical properties of 7075/6061 high-strength dissimilar aluminum alloy fusion welds, after TiC nanoparticle-assisted welding and heat treatment, were discussed, and their fatigue performance was analyzed. The results indicate that the significant increase in hardness at the weld zone with T6 treatment compared to T5 is due to the solution treatment providing supersaturated solid solution for subsequent aging precipitation. T5 treatment causes the precipitation in the heat affected zones, thereby increasing the hardness of these regions. The joints exhibit excellent yield strength and tensile strength after heat treatment, with the elongation performance being optimal in T6 state. The fatigue performance of dissimilar aluminum alloy joints treated with nanoparticle and heat treatment is superior to the joints with single riveting. Porosity defects and microcracks generated during welding are prone to stress concentration, with interconnected pores and easily propagating cracks forming fatigue sources for pores and cracks. The crack propagation behavior is influenced by the pinning effect of TiC nanoparticles at the grain boundaries, and the second phase particles hinder crack propagation along the grain boundaries, forcing cracks to extend towards the 6061 side or the HAZ of the lower strength 6061 matrix. It demonstrates that the method of combining nanoparticle-assisted melt inert-gas welding and T6 heat treatment improves the fatigue life of 7075/6061 dissimilar aluminum alloy joints.