Compound Layer Research Articles

Thermal Fatigue Failure of Micro-Solder Joints in Electronic Packaging Devices: A Review

In electronic packaging products in the service process, the solder joints experience thermal fatigue due to temperature cycles, which have a significant influence on the performance of electronic products and the reliability of solder joints. In this paper, the thermal fatigue failure mechanism of solder joints in microelectronic packages, the microstructure changes of the thermal fatigue process, the influence factors on the joint fatigue life, and the simulation analysis and forecasting of thermal fatigue life are reviewed. The results show that the solder joints are heterogeneously coarsened, and this leads to fatigue cracks occurring under the elevated high-temperature phase of alternating temperature cycles. However, the thickness of the solder and the hold time in the high-temperature phase do not significantly influence the thermal fatigue. The coarsened region and the IMC layer thicken with the number of cycles, and the cracks initiate and propagate along the interface between the intermetallic compound (IMC) layer and coarsened region, eventually leading to solder joint failure. For lead-containing and lead-free solders, the lead-containing solder shows a faster fatigue crack growth rate and propagates by transgranular mode. Temperature and frequency affect the thermal fatigue life of solder joints to different degrees, and the fatigue lifetime of solder joints can be predicted through a variety of methods and simulated crack trajectories, but also through the use of a unified constitutive model and finite element analysis for prediction.

Synthesis and Physical Properties of the Misfit Layered Compound (EuS)1.13(NbSe2)2.

A new misfit layered compound with the stoichiometry (EuS)1+δ(NbSe2)2 (δ ≈ 0.13) has been successfully synthesized. High-resolution transmission electron microscopy and powder X-ray diffraction confirm the misfit structure with (EuS)-(EuS) spacing of 18.30(1) Å. Magnetization, electrical resistivity, heat capacity, and thermal transport measurements show that the material is a heavily doped semiconductor or poor metal with a low thermal conductivity of ∼1 W/m K and an antiferromagnetic ordering transition at TN = 4.7 K. In contrast to the parent materials, the misfit is neither ferromagnetic nor superconducting down to T = 0.4 K. We find evidence of a field-driven transition to a ferromagnetic state due to reorientation of ferromagnetic EuS layers at μoH = 0.5 T at T = 2 K.

Exploring microstructural evolution, nitrogen depth profile, and dry wear performance in 31CrMoV9 steel through combined severe shot peening and plasma nitriding

The present study investigates the influence of severe shot peening (SSP) on the plasma nitriding behavior and sliding wear performance of 31CrMoV9 steel. Initially, the steel was austenitized at 880 °C, followed by oil quenching, and tempering at 520 °C for one hour. These samples were shot peened using high-carbon steel shots, resulting in an enhancement in surface hardness up to 447 HV, gradually converging to the initial martensitic hardness after 140 µm depth. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) scrutinized the initial and surface treated martensitic samples. Afterward, the plasma nitriding treatments were carried out at temperatures of 400 °C, 450 °C, and 500 °C for 8 hours in a 30% N2 + 70% H2 atmosphere and 300 Pa pressure. Microhardness testing, SEM, XRD, and glow-discharge optical emission spectroscopy (GDOES) evaluated both plasma nitrided (PN) and severe shot peened/plasma nitrided (SSP-PN) samples. Cross-sectional SEM observations revealed compound layer thicknesses of approximately 2.8 µm, 5.0 µm, and 6.3 µm for PN samples at 400 °C, 450 °C, and 500 °C, respectively. SSP-PN samples exhibited a substantial increase — roughly 71%, 44%, and 33% increase, respectively, compared to PN samples. GDOES analysis supported this trend and indicated enhanced nitrogen diffusion depth, particularly evident in SSP-PN samples at consistent temperatures. The XRD results showed the stability of Fe4N, Fe2–3N, and CrN phases at all three nitriding temperatures. Furthermore, the intensity of these phases increases with temperature and is augmented by the application of the SSP. Microhardness measurements indicated hardness escalation: from 775 HV to 980 HV at 400 °C, 932 HV to 1096 HV at 450 °C, and 1011 HV to 1205 HV at 500 °C due to SSP. Finally, the wear performance was investigated between the non-nitrided, SSP, PN, SSP-PN, samples. Initially, SSP led to decreased wear performance up to 500 m, followed by improved behavior up to 1500 m. At 400 °C, the SSP-PN sample exhibited a 12% lower wear rate than PN. At 450 °C and 1500 m, the SSP-PN sample displayed a 24% reduction, while at 500 °C, it showed a 27% reduction compared to PN. SEM observations indicated abrasion as the primary wear mechanism across all samples. The overall results indicated a significant similarity in the nitrogen depth profile, hardness depth, and wear performance between the SSP-PN sample at 450 °C and the PN sample at 500 °C. The fact suggested a potential reduction of approximately 50 °C in the typical plasma nitriding temperature for 31CrMoV9 steel as a result of the SSP process.

Improved financial forecasting via quantum machine learning

Quantum algorithms have the potential to enhance machine learning across a variety of domains and applications. In this work, we show how quantum machine learning can be used to improve financial forecasting. First, we use classical and quantum Determinantal Point Processes to enhance Random Forest models for churn prediction, improving precision by almost 6%. Second, we design quantum neural network architectures with orthogonal and compound layers for credit risk assessment, which match classical performance with significantly fewer parameters. Our results demonstrate that leveraging quantum ideas can effectively enhance the performance of machine learning, both today as quantum-inspired classical ML solutions, and even more in the future, with the advent of better quantum hardware.

Effect of Multi-pass friction stir processing and Rolling on microstructure of interface structure and mechanical properties of 2024Al/AZ31B composites

Al/Mg laminated composites were successfully prepared by multi-pass friction stir processing(M-FSP) and rolling, and the effects of interface structure on their microstructure and properties were studied by Scanning Electron Microscopy (SEM) and Backscattering Diffraction (BSD). The results showed that there were two layers of intermetallic compounds (IMCs) at the interface of the composites after M-FSP, and the average grain size on 2024Al and AZ31B layers decreased from the initial 12.79μm and 15.06μm to 3.59μm and 6.36μm, respectively. For M-FSP+ Rolling(F+R) samples, after rolling process, the initially straight IMCs layers were fragmented and embedded on the two matrix layers to increase the interface bonding, while the average grain size on the 2024Al and AZ31B sides were further refined to 2.16μm and 4.26μm. The ultimate tensile strength of the F+R sample was increased to 20.6%, with an average value of 322 MPa, compared with the M-FSP samples. This research using M-FSP + Rolling can improve the interface bonding and refine the microstructure, thereby improving the mechanical properties of the composites.

Microstructure homogeneity and its role in the mechanical properties of the magnetic pulse welded steel/Al tubular joint

The steel and aluminum alloy tubes were successfully joined by magnetic pulse welding (MPW). Part of the joints fractured at the interface, yet part of them fractured at the base metal (BM) of aluminum alloy. The tensile test results revealed a fluctuation of the mechanical properties of the steel/Al MPW joints, demonstrating the microstructure inhomogeneity of the MPW joints. The typical wavy interfacial morphology could be observed at the interface of the MPW joints. The element transition zone composed of elements Fe and Al were detected while no obvious intermetallic compound (IMC) layer could be traced. The good mechanical properties of steel/Al MPW joints could be attributed to the longer effective bonding length and larger element transition area. Besides, the grain refinement was observed at the interface of the MPW joint, which explained its microhardness increase.

Scalable NH4V4O10 clusters as functional network nodes on toughened porous carbon nanofibers for hybrid capacitive deionization

Layered vanadium-based compound (e.g., NH4V4O10) is acknowledged as an outstanding candidate for intercalation pseudocapacitance electrode of capacitive deionization (CDI) cells. However, the directed production of high-efficiency NH4V4O10-based self-supporting CDI electrodes and their structure–activity connection warrant more in-depth study. Herein, the delicate design and controllable construction of NH4V4O10 clusters on the freestanding porous carbon nanofiber (PCNF) scaffolds (the composite PCNFs/NH4V4O10 is defined as CNVO) using a new organic reducing agent of citric acid is proposed, where NH4V4O10 clusters as functional network nodes can improve the mechanical toughness, electrochemical capacitive performance, and desalination capability of the CNVO hybrid. The Na+ adsorption mechanism on CNVO is confirmed by ex-situ experimental characterizations and density functional theory (DFT) calculations. The hybrid CDI (HCDI) cell composed of the optimized CNVO cathode and PCNFs anode shows a desirable desalination capacity (45.07 mg g−1), a superior salt removal rate (16.4 mg g−1 min−1), an excellent energy utilization, and an acceptable cyclic regeneration ability in 500 mg L-1 NaCl solution. More importantly, the assembled HCDI system is promising for the desalination of reclaimed water from the printing and dyeing enterprise. This work highlights a scalable strategy that is experimentally and theoretically feasible to design and fabricate high-efficiency CDI electrodes.

Microstructures and properties of 7075 aluminum alloy and CP780 steel resistance spot welded joint assisted by magnetic field

Joining steel and aluminum is vital for lightweight automobile but still challenging due to their different physical properties. Herein, resistance spot welding tests were performed on CP780 high-strength steel (thickness 1 mm) and 7075 aluminum alloy (thickness 1.5 mm) dissimilar metals under steady-state magnetic field. The influences of magnetic field (B = 40 mT) on the structure of welded joints, the phase composition/content of intermetallic compounds, and tensile properties of welded joints were analyzed under different welding current conditions (I = 9 kA,10 kA, 11 kA, and 12 kA). At the same welding current, the Lorentz force generated by the additional magnetic field promoted the outward circumferential movement of the molten metal in the weld along the horizontal surface , as well as increased the diameter of the Fe/Al contact interface in the weld nugget along the horizontal direction, conducive to the effective utilization of heat of the resistance spot welding. Except under (11 kA-0 mT) and (11 kA-40 mT), welded joints under other welding parameters displayed a few welding defects, such as incomplete fusion and shrinkage cavity formed at the cross-section of the welded joints. Therefore, the synergism between the magnetic field and appropriate welding current held important roles in the formation of welded joints without obvious welding defects. The intermetallic compounds of all the welds were mainly composed of (Fe, Si)Al2 and (Fe, Si)Al5. Meanwhile, the thickness and content of the intermetallic compounds layer reduced under a magnetic field at the same welding current, significantly improving the tensile properties of the welded joints. The comprehensive properties of welded joints were the best under 11 kA-40 mT, with an average shear force increase from 3.02 kN to 3.49 kN (15.56%) and an average displacement increase from 1.01 mm to 1.22 mm (20.79%). Overall, the proposed dissimilar aluminum/steel resistance spot welded joint assisted by magnetic field looks promising for lightweight automobile use.

Microstructure and properties of 316 L lattice/Al composites by additive manufacturing and infiltration with different temperature

Interface between lattice reinforcement and matrix played a key factor on properties of the lattice reinforced aluminum matrix composites. However, the effect of interface composed of intermetallic compounds on the properties of 316L lattice/Al composites was still unclear. In this study, 316L lattice reinforced aluminum composite with continuous interface were prepared by combining laser powder bed fusion (LPBF) and vacuum infiltration, and effect of infiltration temperature on interface evolution and properties of the composite was investigated. Results indicated that a continuous dual-phase interfacial layer consisting of hard intermetallic compounds η-Fe2Al5 and θ-FeAl3 was formed between the reinforcement and matrix due to diffusion and reaction of iron and aluminum atoms, and the size of needle-type FeAl3 phase in the interfacial zone increased when infiltration temperature was up from 800 °C to 900 °C. It also confirmed that reinforced by 316L lattice and hard intermetallic compounds layer, the composite showed excellent mechanical and wear resistant properties, with compressive strength of 657 ± 32MPa and specific wear rate of 0.20 × 10−3 (mm3/N·m) for the sample prepared at 800 °C, which were over 10 times and one fifth of that of the aluminum matrix individually. This study provides a new strategy for developing 316L lattice/Al composites with excellent properties.

Disordered Layers and Dimerization in the Crystal Structure of TaOCl2

Understanding the properties of transition metal materials requires consideration of the competition between the various types of electrons that comprise the system, whether they be delocalized and metallic, localized and magnetic, or localized and bonded. Here we report the refined crystal structure determination and physical properties of the two-dimensional layered compound TaOCl2. Within each layer we find a strong in-plane dimerization of Ta atoms perpendicular to the Ta-O-Ta chains, with significant disorder in the positioning of dimers in adjacent layers, suggesting that the free electron of each Ta localizes in Ta-Ta bonds. This is supported by resistivity measurements (ρ300K = 4.4*108 Ω-cm) as well as featureless, temperature-independent magnetic susceptibility up to T = 750 K. Analysis of the phonon contribution to specific heat shows the presence of a localized Einstein mode with TE = 175 K, attributed to the localized vibrations of the Ta-Ta dimers. Density functional theory calculations show that the magnitude of the Ta displacements (0.24 Å) has a dramatic effect on the electronic structure, changing from a metal with a bandwidth of 3.2 eV to an insulator with a flat band just below EF. Our results show how direct exchange interactions between Ta atoms that are relatively far from each other can still play a central role in the behavior of 5d transition metal compounds, taking advantage of the extended 5d atomic orbitals, and produce localized dimers with a bond distance of approximately 2.84 Å.

Disentangling the Unusual Magnetic Anisotropy of the Near‐Room‐Temperature Ferromagnet Fe4GeTe2

AbstractIn the quest for 2D conducting materials with high ferromagnetic ordering temperature the new family of the layered FenGeTe2 compounds, especially the near‐room‐temperature ferromagnet Fe4GeTe2, receives a significant attention. Fe4GeTe2 features a peculiar spin reorientation transition at TSR ≈ 110 K suggesting a non‐trivial temperature evolution of the magnetic anisotropy (MA)—one of the main contributors to the stabilization of the magnetic order in the low‐dimensional systems. An electron spin resonance (ESR) spectroscopic study reported here provides quantitative insights into the unusual magnetic anisotropy of Fe4GeTe2. At high temperatures the total MA is mostly given by the demagnetization effect with a small contribution of the counteracting intrinsic magnetic anisotropy of an easy‐axis type, whose growth below a characteristic temperature Tshape ≈ 150 K renders the sample seemingly isotropic at TSR. Below one further temperature Td ≈ 50 K the intrinsic MA becomes even more complex. Importantly, all the characteristic temperatures found in the ESR experiment match those observed in transport measurements, suggesting an inherent coupling between magnetic and electronic degrees of freedom in Fe4GeTe2. This finding together with the observed signatures of the intrinsic two‐dimensionality should facilitate optimization routes for the use of Fe4GeTe2 in the magneto‐electronic devices, potentially even in the monolayer limit.

Synergetic effects of micro-shot peening and gas nitriding on the fatigue performance of AISI 4140 steel

Gas-nitriding was performed to enhance the surface hardness and fatigue performance of 4140 steel pre-treated with micro-shot peening (MSP). The 4140 steel was solutionized and tempered at 200 °C/1 h, named as the base metal (BM) with the hardness of 500 HV0.05. Some BM samples were subjected to MSP (i.e., SPBM), and subsequently gas-nitrided at 520 °C/6 h (i.e., NBM). A compound layer of about 10 μm thickness formed on the surface of the NBM sample consisted of nano-grained Fe3N and Fe4N. The NBM sample showed a decline in hardness from the nitrided surface (750 HV0.05) to the matrix (300 HV0.05). In the as-peened condition, the peak residual compressive stress (RCS) was close to −500 MPa, and a very shallow stress field was obtained. After gas-nitriding, the peak RCS decreased to less than −400 MPa, while the affected depth expended to 300 μm. Defects in the compound layer did not deteriorate the fatigue strength/life of the nitrided 4140 steel. The RCS field effectively suppressed fatigue crack initiation and propagation at the surface of the NBM and SPBM samples. By contrast, surface cracks resulted in the fatigue failure of the BM sample.

Formation and Evolution of Interfacial Structure in Al–Si–Mg/Stainless Steel Bimetals during Hot-Dipping Process

Understanding trends in the formation of the intermetallic compound (IMC) layer in Al/Fe bimetallic composites can aid in significantly improving their mechanical properties. However, it is currently challenging to predict IMC layer formation during hot-dip aluminizing. Furthermore, the results from previous studies are difficult to compare owing to the variation in the process parameters used. Therefore, to understand how temperatures and holding times affect the thickness and hardness properties of IMC layers, we investigated the interfacial properties of aluminized stainless steel in molten Al-Si-Mg. AISI 420 stainless steel was hot-dip aluminized in an Al–Si–Mg alloy melt for 10–120 min at four different temperatures: 700, 750, 800, and 850 °C. Morphology, type, and element distribution of the phases formed in the reaction layer and the reduction rate of the aluminizing process were studied. Notably, while the reaction layer thickness increased with increasing aluminizing temperature when the holding time was low, long-term reaction caused the reaction layer to become thicker at lower temperatures. The mechanism of this morphological transformation is discussed. The results demonstrated effective trends in controlling the morphology of the intermetallic compound layer with respect to various hot-dip Al plating process parameters.

Influence of compound layer on the corrosion resistance of low alloy steel in a 3.5% NaCl solution

Samples of AISI 4140 low alloy steel were nitrided at different conditions by using plasma nitriding. The optical microscopy observation and x-ray diffraction analysis showed that a 3 ∼ 12 μm thick compound layer composed of ε-Fe2–3N and γ′-Fe4N was formed on the surface after nitriding treatments. The corrosion behavior was evaluated by measuring the anodic polarization curves in a 3.5% NaCl solution along with the observation of corroded surfaces and cross-sectional morphologies using optical and scanning electron microscope. The results indicated that the corrosion resistance of low alloy steel was significantly enhanced through the formation of compound layer. The thickness of compound layer was one important factor in determining its corrosion resistance.

Constructing a interfacial electric field for efficient reduction of nitrogen to ammonia

Electrochemical nitrogen reduction (eNRR) is a cost-effective and environmentally sustainable approach for ammonia production. MoS2, as a typical layered transition metal compound, holds significant potential as an electrocatalyst for the eNRR. Nevertheless, it suffers from a limited number of active sites and low electron transfer efficiency. In this study, we constructed a heterostructure by depositing SnO2 (an n-type semiconductor) nanoparticles on MoS2 (a p-type semiconductor). This unique interfacial structure not only generates abundant interfacial contacts but also facilitates the transfer of electrons from SnO2 to MoS2, leading to the formation of an interfacial electric field. Theoretical calculations demonstrate that this electric field increases the number of active electrons, facilitating N2 adsorption and NN bond activation. Moreover, it increases the degree of orbital overlap between N2 and SnO2/MoS2, effectively reducing the energy barrier of the rate-determining step. Benefiting from the interfacial electric field effect, the SnO2/MoS2 catalyst exhibits significant catalytic activity and selectivity towards eNRR, with an ammonia yield of 47.1 µg h−1 mg−1 and a Faraday efficiency of 19.3 %, surpassing those reported for the majority of MoS2- and SnO2-based catalysts.

Friction, wear, and corrosion behavior of nitrocarburized HT250 gray cast iron

This study employed friction and wear experiments on nitrocarburized HT250 gray cast iron, utilizing GCr15 cemented carbide balls as the friction pair, to investigate the friction behavior and wear mechanism of the compound layer, diffusion layer, and matrix. The findings indicate that the diffusion layer exhibits the highest wear resistance, followed by the compound layer, while the matrix shows the lowest wear resistance. At lower loads, the wear form of the compound layer is characterized by minor flaking wear, the diffusion layer exhibits minor flaking and abrasive wear, and the matrix displays minor adhesive wear accompanied by abrasive wear. With increasing loads, the wear form of the compound layer transitions to flaking and abrasive wear, the diffusion layer shows fatigue flaking wear, and the matrix demonstrates severe adhesive wear, fatigue flaking wear, and abrasive wear. Electrochemical impedance spectroscopy and potentiodynamic polarization were employed to study the corrosion behavior of the compound layer, diffusion layer, and matrix in a 3.5 wt% NaCl solution. The results indicate a 27.7 % decrease in the corrosion current density of the compound layer compared to the matrix, with the diffusion layer exhibiting a corrosion current density two orders of magnitude lower than both the matrix and compound layer. In electrochemical impedance spectroscopy, the diffusion layer shows the highest impedance modulus, largest phase angle amplitude, and circular arc radius. It shows that the corrosion resistance of HT250 gray cast iron is improved after nitrocarburizing, especially the diffusion layer.

Microstructure Characterization and Mechanical Properties of the NiTif‐Reinforced Ti/Al‐Laminated Composites Using Vacuum Hot Pressing with Ultrasonic Consolidation Assisted

A novel method of preparing continuous NiTif‐reinforced Ti/Al‐laminated composites is proposed via ultrasonic consolidation (UC) and vacuum hot pressing. The microstructure of the composites is characterized by X‐ray diffraction, scanning electron microscopy, and electron backscattering diffraction. The tensile properties of the composites are measured by a universal testing machine. Results indicate that the composite exhibits multilayer structure consisting of residual NiTi fiber, intermetallic compounds (IMCs) layer, reaction layer, Ti layer, and Al layer. The intermetallic layer is composed of Al3Ti and Al3Ni, and some Ni‐rich precipitates are dispersed in the matrix. And with the introduction of UC assisted, grain refinement occurs at the IMC/Al interface, texture variation emerges at the NiTi fiber/IMCs interface, and a weakening of texture strength is observed at both interfaces. Compared to NiTif‐reinforced Ti/Al‐laminated composites without UC assisted, both the tensile strength (from 872.4 to 826.5 MPa) and failure strain (from 17.5% to 20.4%) of NiTif‐reinforced Ti/Al‐laminated composites with UC assisted increase due to the contribution of UC assisted. The reinforcing and fracture mechanisms of the UC assisted are also discussed.

High-Temperature Oxidation of the 304/6061 Welding–Brazing Joint and Its Effects on Corrosion Characteristics

Laser–MIG hybrid welding–brazing was used to weld 304 stainless steel and 6061-T6 aluminum alloy with a thickness of 2 mm. The microstructure, morphology, chemical composition and corrosion behavior of the samples after high-temperature oxidation were investigated. The results reveal that the 304/6061 dissimilar joint had a thicker intermetallic compound layer (7–8 μm) during high-temperature oxidation (HTO) treatment than the sample without HTO treatment (2–3 μm). The oxide film thickness of the 6061 side of the weld joint treated by HTO (2401 nm) increased compared to the samples (181.1 nm) without HTO treatment. Unlike other metals treated by high-temperature oxidation, the high-temperature treatment process in this paper can reduce the corrosion resistance of the base metal and dissimilar joints, and the sequence of the corrosion current density was weld (HTO) >weld>6061 (HTO) >6061>304 (HTO) >304.

EFFECT OF A MAGNETIC FIELD ON THE MICROSTRUCTURE AND PROPERTIES OF RESISTANCE SPOT WELDED JOINTS OF 444 FERRITIC STAINLESS STEEL/6082 ALUMINUM ALLOY

To improve the welding quality of resistance spot welding joints of steel/aluminum lightweight structures, the steady magnetic field-assisted resistance spot welding method was used to weld 444 ferritic stainless steel and 6082 aluminum alloy, both with a thickness of 1 mm. Under the same welding parameters, the effect of a magnetic field on the microstructure and mechanical properties of the joint was analyzed. It was found that the Lorentz force generated by the addition of a magnetic field promoted the circumferential movement of the molten metal in the nugget zone, increased the size of the Fe/Al contact interface in the joint along the horizontal direction, and made an effective use of the heat generated during resistance spot welding. Although the intermetallic compounds in the intermediate transition layer of the two welded materials were mainly composed of (Fe, Cr, Si)Al2 and (Fe, Cr, Si)Al3, relatively low contents of (Fe, Cr, Si)Al2 and (Fe, Cr, Si)Al3 were found and a there was a significant decrease in the thickness of the intermetallic compound layer when the magnetic field was applied. Compared with the welded joint devoid of a magnetic field, the tensile strength and ductility of the joint were effectively improved, and the dimples in the fracture surface became relatively deep and numerous. In essence, resistance spot welding joints of steel/aluminum obtain better comprehensive mechanical properties when a magnetic field is applied.

Effect of Alloying Elements in Steels on the Interfacial Structure and Mechanical Properties of Mg to Steel by Laser-GTAW Hybrid Direct Lap Welding.

Mg alloy AZ31B was directly bonded to SK7 with a low alloy content, DP980 with a high Mn content, 316L with a high Cr and high Ni content by laser-gas tungsten arc welding (GTAW) and hybrid direct lap welding. The results showed that the tensile loads of AZ31B/SK7 and AZ31B/DP980 joints were 283 N/mm and 285 N/mm respectively, while the tensile load of AZ31B/316L joint was only 115 N/mm. The fracture and interface microstructures were observed using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and identified through X-ray diffractometry (XRD). For AZ31B/SK7 and AZ31B/DP980, the interface of the front reaction area and the keyhole reaction area was mainly composed of an Fe-Al phase and an Al-Mn phase. However, for AZ31B/316L, the interface of the keyhole reaction area was mainly composed of an Fe-Al phase and an Al-Mn phase, but a multi-layer composite structure consisting of the Mg17Al12 compound layer and eutectic layer was formed in the front reaction area, which led to a deterioration in the joint property. The influencing mechanism of Mn, Cr and Ni elements in steel on the properties and interface structure of the laser-GTAW lap joint between the Mg alloy and the steel was systematically analyzed.