Linear Friction Welding Research Articles

Residual stress prediction in Ti17 linear friction welds considering inhomogeneous mechanical properties of joints

Microstructural variations of joints occur in linear friction welding, resulting in inhomogeneous mechanical properties that affect the development of residual stress. The mathematical models for elastic moduli and yield strength of Ti17 were firstly developed to obtain the inhomogeneous mechanical properties of joints. Then, the influence of inhomogeneous mechanical properties on residual stress prediction was investigated. The results show that the finite element model considering inhomogeneous mechanical properties accurately captures the bimodal distribution of residual stress and the location of peak stress in joints. Numerically, the peak values of stress are ∼662 and ∼194 MPa along the direction of oscillation and forging, respectively, which is consistent with the result of the contour method.

Effect of Pressure on the Linear Friction Welding of a Tool Steel and a Low‐Alloy Carbon Steel

This study investigates the effect of pressure (burn‐off and forging) on the mechanical properties of the joint between a wear‐resistant tool steel and a low‐alloy steel using linear friction welding. The authors have previously demonstrated the feasibility of joining these dissimilar materials, but the impact of pressure on the mechanical properties of the bimaterial joint remains unclear. To address this, weld samples are prepared using different pressures and are characterized through microstructural analysis, microhardness, tensile testing, and fractography. The results show that the strength of the joint between the wear‐resistant tool steel and the low‐alloy carbon steel increases as the pressure increases up to a certain point, after which a decrease is observed. The highest joint strength is achieved at a pressure of 360 MPa. The microhardness profile measurement reveals a distinct transition zone at the interface between the two materials, with varying hardness values. The hardness of the low‐alloy carbon steel increases near the interface, while that of the wear‐resistant tool steel decreases. This transition zone is found to be narrower at higher pressures. Microstructural characterization shows that the grain structure near the interface differs from that of the starting base materials.

Residual Stress Analysis in Linear Friction Welded Ti17.

Residual stresses with a complex distribution are generated after linear friction welding, which affects the service performance of the weldment. In this work, a numerical model for linear-friction-welded Ti17 (Ti-5Al-2Sn-2Zr-4Mo-4Cr) was developed to investigate the evolution of residual stresses and the effect of welding parameters on residual stresses. Additionally, a method for predicting internal residual stresses was constructed. The results indicate that the residual stresses near the contact interface are largest in the oscillatory direction, peaking at ~661 MPa at 2 mm away from the contact interface. The evolution of stresses is not only related to the inhomogeneous thermal gradient, but also to the forging force. And the stress distribution essentially stabilizes within the duration of the forging force applied. Increasing the amplitude and frequency results in higher peaks of tensile residual stresses and a more concentrated distribution. Conversely, increasing the forging force only reduces the magnitude of the residual stresses. The developed prediction method, based on the similarity of internal residual stress distributions, facilitates the prediction of internal residual stresses using measured surface residual stresses.

Linear Friction Welding of Similar and Dissimilar Materials: A Review

Linear Friction Welding of Similar and Dissimilar Materials: A Review

Investigating microstructure, mechanical properties, and pitting corrosion resistance of UNS S32760 super duplex stainless steel after linear friction welding

High-performance alloys such as super duplex stainless steels (SDSS) are of interest to the oil and gas industry, especially in deep and ultra-deep reservoirs where high pressures and highly corrosive environments are prevalent. SDSS have high nitrogen contents and pitting resistant equivalent number (PREN) values greater than 40, however, fusion welds of these alloys can exhibit unsuitable microstructures and defects that may result in failure during usage. Solid-state linear friction welding (LFW) offers an alternative for the effective joining of SDSS with a less detrimental effect on microstructure and properties. In this work, four LFW joints in UNS S32760 SDSS were produced and investigated by evaluating the process parameters required to achieve a high-quality joint with the desirable metallurgical, mechanical, and localized corrosion properties. These properties were assessed through metallography (optical microscopy and scanning electron microscopy), tensile and microhardness tests, and corrosion analysis according to the ASTM G48A standard. Results indicated that one specific combination of LFW parameters led to a defect-free joint, and that the mechanical properties of the weld in this case were comparable to those of the base material. Additionally, an adequate balance between ferrite and austenite phases was achieved throughout the microstructural gradients seen in the weld region. Microhardness values were below 350 HV, thus complying with the DNV–OS–F101 standard. Furthermore, no pitting corrosion was observed in this joint under the testing conditions suggested by ASTM G48A.

Effective toughening of dissimilar Ti alloy friction welded joint by combining electropulsing thermal and athermal effects

To address the low toughness issue in titanium alloy friction weld joints, this study employs electropulsing treatment to synergistically control the microstructure of TC11/TC17 linear friction welded (LFWed) joint through thermal and athermal effects, transforming equiaxed grains into a basketweave structure in the weld zone. The toughness of the joint increased from 9.3 J/cm2 to 33.5 J/cm2, while the strength maintained surpasses that of both parent materials.

Dissimilar linear friction welding of AZ31 magnesium alloy and AA5052-H34 aluminum alloy

The intermetallic compound (IMC) layer, tensile properties, and fracture behavior of dissimilar Mg/Al joints and their relationship during linear friction welding (LFW) are investigated to develop a strategy to obtain high-strength Mg/Al dissimilar materials. The thickness of the Mg/Al-based IMC layer decreases as the applied pressure increases and the frequency decreases. The IMC layer is mainly composed of Mg17Al12 and Mg2Al3 at the weld interface. The tensile strength of the joints fabricated at an appropriate frequency of 50 Hz and a high pressure of 200 MPa during LFW is 235 MPa, which is 94 % the tensile strength of AZ31 and is attributed to the effective suppression of the Mg2Al3 IMC layer growth. At a lower frequency, large defects and pores are formed near the weld interface edge on the Mg side owing to the low welding temperature. The joint fabricated at a higher frequency exhibits a thick and brittle Mg2Al3 IMC layer at the weld interface because of the high growth rate; thus, the dissimilar joints fractured primarily at the Mg2Al3 IMC layer. The inhibition of the Mg2Al3 IMC layer growth yields superior tensile properties in Mg/Al dissimilar materials.

Comprehensive investigation on linear friction welding a dissimilar material joint between Ti17(α+β) and Ti17(β): Microstructure evolution, failure mechanisms, with simultaneous optimization of tensile and fatigue properties

In order to advance the use of Ti17 (α+β)-Ti17(β) dissimilar material blisks produced with linear friction welding (LFW) for advanced aeroengines, detailed studies of failure mechanisms and performance enhancements of such joints were conducted. The changes in microstructure including phase transformations and dynamic recrystallization were investigated. Also, the tensile failure mechanism of the joint was investigated by in-situ tensile test using scanning electron microscopy, while the high-cycle fatigue failure mechanism was studied using quasi-in-situ electron back-scattering diffraction observations combined with transmission electron microscopy characterization. A post-weld annealing heat treatment (PWAHT) was applied for optimizing tensile and fatigue strength. Results shows that α dissolution and β continuous dynamic recrystallization (CDRX) are controlling microstructure changes during welding. Tensile loading failure is related to local dislocation slip concentration on the Ti17(β) side of the thermo-mechanically affected zone with limited α strengthening phase and low degree β CDRX; while fracture under high-cycle fatigue loading is related to equiaxed α/metastable β boundary microcracks on the Ti17 (α+β) side of the heat-affected zone, which was produced by unequal deformation between the two phases. Following PWAHT for 630 °C at 3 h, re-precipitation of secondary α occurred, which increased dislocation movement resistance in the weak areas, producing tensile and high-cycle fatigue strengths of 1196.4 MPa and 550.2 MPa, respectively, higher than those of BM-(β). In addition, an adequate plasticity of the joint with elongation of 8.7 % (82.1 % of Ti17(β)) was reached.

High cycle fatigue performance at 650 ℃ and corresponding fracture behaviors of GH4169 joint produced by linear friction welding

GH4169 joints manufactured by Linear Friction Welding (LFW) are subjected to tensile test and stair-case method to evaluate the High Cycle Fatigue (HCF) performance at 650 ℃. The yield and ultimate tensile strengths are 582 MPa and 820 MPa, respectively. The HCF strength of joint reaches 400 MPa, which is slightly lower than that of Base Metal (BM), indicating reliable quality of this type of joint. The microstructure observation results show that all cracks initiate at the inside of specimens and transfer into deeper region with decrease of external stress, and the crack initiation site is related with microhardness of matrix. The Electron Backscattered Diffraction (EBSD) results of the observed regions with different distances to fracture show that plastic deformation plays a key role in HCF, and the Schmid factor of most grains near fracture exceeds 0.4. In addition, the generation of twins plays a vital role in strain concentration release and coordinating plastic deformation among grains.

Design and analysis of face recognition system based on VGGFace-16 with various classifiers

This research presents a face recognition system based on different classifiers that deal with various face positions. The proposed system involves the extraction of features through the VGG-Face-16 deep neural network, which only extracts essential features of input images, leading to an improved recognition step and enhanced algorithm efficiency, while the recognition involves the radial basis function in support vector machine (SVM) classifier and evaluate the performance of the system. Also, the system is designed and implemented later by using other classifiers; they are K-neareste2 neighbour (KNN) classifiers, logistic regression (LR), gradient boosting (XGBoost), decision tree classifier (DT) and Naive Bayes classifier (NB). The proposed algorithm was tested with the four face databases: AT&T, PINs Face, linear friction welding (LFW) and real database. The database was divided into two groups: One contains a percentage of images that are used for training and the second contains a percentage of images (remainder) which was used for testing. The results show that the classification by RBF in SVM has the highest recognition rate in the case of using small, medium and large databases; it was 100% in AT&T and Real database, while its efficiency appears to be lower when using large-size databases whereas it is 96% in PINs database and 60.1% in LFW database.

A review of linear friction welding of Ni-based superalloys

A review of linear friction welding of Ni-based superalloys

Role of oscillation frequency and amplitude on the microstructure and properties of linear friction welded nickel aluminium bronze joints

This study explores the influence of oscillation frequency and amplitude on the quality of linear friction welded joints using as-cast nickel aluminium bronze. Welding was conducted at 30 Hz, 50 Hz, and 70 Hz oscillated frequencies and amplitudes of 1.5 mm, 2 mm, and 3 mm. The joint’s performance was thoroughly investigated through systematic analysis, including macrostructure examination, peak interfacial temperature measurement, microstructure evaluation, strain assessment, cooling rate determination, microhardness testing, and tensile property characterization. The width of the weld zone varied from 183 μm to 297 μm, and the thermomechanical affected zone (TMAZ) area ranged from 4.48 mm2 to 14.79 mm2 across different process parameters. In the parent material, the volume fraction of the β-phase was as low as 20.2%, contrasting with the dominant α-phase at 79.8%. The average grain size of the lamellar and globular α-phase mixture was 26.4 μm. Notably, the weld zone exhibited extremely refined α-phase grains, with diameters less than 5 μm in all cases. The volume fraction of the β‘-phase increased significantly with higher frequencies, from 15.299% at 30 Hz to 26.98% at 50 Hz, peaking at 40.08% at 70 Hz, leading to varying k phases. This variation in microstructure had a substantial impact on mechanical properties. Tensile strength ranged from 503 MPa to 582 MPa, while ductility varied from 13.5% to 21.7%. Additionally, the hardness of the parent material increased from approximately 155 Hv to 260 Hv. This study demonstrates that controlling the oscillation frequency and amplitude in linear friction welding processes can yield consistent, high-quality welds in nickel aluminium bronze.

Linear friction welding of light metals and carbon fiber-reinforced plastics

Linear friction welding of light metals and carbon fiber-reinforced plastics

Advancements and Challenges in Linear Friction Welding of Inconel 718: A Comprehensive Review

This comprehensive review explores the linear friction welding of Inconel 718, a super alloy widely employed in aerospace and other high-temperature applications. Delving into the intricate relationship between process parameters and material properties, the paper examines microstructural transformations and their impact on mechanical integrity. Discussions encompass weldability, common defects, and mitigation strategies, providing valuable insights for practitioners. The review also highlights the evolving landscape of research trends, recent developments, and real-world applications, showcasing the versatility of linear friction welding. Challenges in the process are analyzed, offering a nuanced perspective on current limitations and avenues for improvement. Through a comparative lens with traditional welding techniques, the paper elucidates the unique advantages of linear friction welding in enhancing efficiency and performance. This synthesis of knowledge contributes to a holistic understanding of the state-of-the-art in linear friction welding of Inconel 718, presenting opportunities for future advancements in this critical domain.

Anomalous enhancing effects of electric pulse treatment on strength and ductility of TC17 linear friction welding joints

Mechanical properties of TC17 titanium alloy undergo a significant reduction after linear friction welding (LFW), of which the strength and ductility are hard to be improved simultaneously by traditional aging heat treatment (AHT), seriously limiting the application of LFW in the manufacturing of TC17 titanium alloy blisks. To this end, the present work proposes to use electric pulse treatment (EPT) to enhance the strength and ductility of TC17 LFW joints simultaneously by improving its microstructure. The results show that, in comparison to the uneven distribution of α phases in the welding zone (WZ), heat-affected zone (HAZ), and base metal (BM) zone after AHT, EPT can selectively homogenize the α phase distribution of WZ and HAZ without impacting the BM. The selective effect of EPT is reflected as the synergistic influence of the local Joule heating effect and the electron wind effect, which promotes the diffusion of β phase stabilizing element Mo and leads to a competitive precipitation of β phase and α phase in the α phase transition temperature range. The ratio of α phase to β phase in the WZ and HAZ finally approaches an equilibrium point which is similar to that of BM, leading to a uniform distribution of α phase and realizing the synergy of strength-ductility of LFW joint: the maximum strength increase observed is 12.9 %, accompanied by a corresponding elongation increase of 122 % (by AHT & EPT), and the maximum plasticity improvement is 185 %, accompanied by a corresponding strength increase of 4.3 % (by EPT for 1 h). This study provides essential insights for improving the strength and ductility of LFW TC17 titanium alloy blisks and enhancing the applications of LFW in aeroengine components.

Microstructure analysis of 7050 aluminum alloy joint fabricated by linear friction weld

The microstructure of a linear friction welded joint of 7050 aluminum alloy was investigated through optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The analysis focused on grain boundary types, microstructure, and mechanical properties of the joint. The results reveal that fine equiaxed crystals are generated in the welded zone through dynamic recrystallization. The average grain size is 6.8 μm, with a volume fraction of large angle grain boundaries reaching 69.5%. The microstructure primarily consists of Cube {001}<100> texture, {111}<110> Brass recrystallization texture, and a small amount of copper {112}<111> deformation texture. The thermo-mechanically affected zone (TMAZ) presents a linear structure with an average grain size of 15.8 μm and a volume fraction of 36.1% at large grain boundary, resulting in a deformed Brass {011}<211> texture and a small amount of {236}<385> as well as {111}<110> Brass recrystallization texture. The welded joint exhibits a tensile strength of 492 MPa and a yield strength of 380 MPa, which represents 94.2% and 78.5% of the base material, respectively. Furthermore, the elongation of the joint is 10.2% and 98% of the base material, respectively. The fracture of the tensile sample is observed in the TMAZ, showing good mechanical properties with a mixed fracture mode with some degrees of ductility and brittleness.

The effect of inclusions and pores on creep crack propagation of linear friction welded joints of GH4169 superalloy

Superalloy has become the key material in components of blisks for aero-engines produced by linear friction welding. However, during the long-term service of the blisks, stress rupture occurs on the blisk under long-term creep. In this study, the linear friction welded joints of GH4169 superalloy were studied with experiments and numerical simulation. The Sin-Hyperbolic creep-damage constitutive model was established. Based on the compact tension specimen model, the numerical simulation of crack propagation was carried out, analyzing the effect of defects in linear friction welded joints such as cracks, inclusions, and pores on creep crack propagation. Results show that inclusions have an impact on the deflection and promotion of creep crack propagation. The maximum values of crack propagation rate can be observed when radius is 0.03 mm for circular inclusions and length-to-diameter ratio is 3 for elliptical inclusions, respectively. When the transverse distance between the center of the pore and the crack tip is 0.6 mm, the effect on crack propagation is the most significant, with the crack deflecting and expanding towards the direction of the pore. The effect of elliptical pores on creep crack propagation is more significant than that of circular pores. When the length-to-diameter ratio is 3, cracks have initiated firstly on both sides of elliptical pores. When the angle between the pore and the prefabricated crack is 0°, the elliptical pore has the greatest deflection effect on the creep crack. Overall, the effect of pores on creep crack propagation is stronger than that of inclusions.

APPLICATION OF FRICTION WELDING FOR PUMP DESIGN AND MANUFACTURING: A COMPREHENSIVE REVIEW

The discussion regarding the balance between economical and performance for the pump design and manufacturing has been increasing in recent years. Of many intelligent innovations, the use of less costly materials for pump shaft is an interesting solution for the pump design. This solution can also be achieved by selecting less costly materials made from metal. Then, the less costly metal connected to electrical motor is joined with a more costly metal connected to the pump. Since both metals can be difference ones, an advance welding process to join both metals is then required. The friction welding process is expected to fulfill this requirement. In the friction welding, heat is generated during friction between these two dissimilar metals. The generated heat should achieve particular temperatures so that the two dissimilar metals can be joined. There are three types of friction welding, e.g. the stir friction welding, the linear friction welding and the continuous drive friction welding, which can be selected to join these two dissimilar metals. This paper is based on the authors’ experience and literature review to discuss the application of friction welding for the pump design and manufacturing.

Plastic flow and interfacial bonding behaviors of embedded linear friction welding process: Numerical simulation combined with thermo-physical experiment

In this study, a new linear friction welding (LFW) process, embedded LFW process, was put forward, which was mainly applied to combination manufacturing of long or overlong load-carrying titanium alloy structural components in aircraft. The interfacial plastic flow behavior and bonding mechanism of this process were investigated by a developed coupling Eulerian-Lagrangian numerical model using software ABAQUS and a novel thermo-physical simulation method with designed embedded hot compression specimen. In addition, the formation mechanism and control method of welding defects caused by uneven plastic flow were discussed. The results reveal that the plastic flow along oscillating direction of this process is even and sufficient. In the direction perpendicular to oscillation, thermo-plastic metals mainly flow downward along welding interface under coupling of shear stress and interfacial pressure, resulting in the interfacial plastic zone shown as an inverted “V” shape. The upward plastic flow in this direction is relatively weak, and only a small amount of flash is extruded from top of joint. Moreover, the wedge block and welding components at top of joint are always in un-steady friction stage, leading to non-uniform temperature field distribution and un-welded defects. According to the results of numerical simulation, high oscillating frequency combined with low pressure and small amplitude is considered as appropriate parameter selection scheme to improve the upward interfacial plastic flow at top of joint and suppress the un-welded defects. The results of thermo-physical simulation illustrate that continuous dynamic recrystallization (CDRX) induces the bonding of interface, accompanying by intense dislocation movement and creation of many low-angle grain boundaries. In the interfacial bonding area, grain orientation is random with relatively low texture density (5.0 mud) owing to CDRX.

Residual stresses in linear friction welding of TC17 titanium alloy considering phase fraction

To obtain accurate residual stresses in linear friction welding of TC17 alloy, a numerical relationship between the elastic constants and phase fraction of TC17 alloy was established. The elastic constants with gradient distribution were obtained by combining the phase fraction and introduced into the contour method. The results show that the elastic constants of TC17 alloy are positively correlated with α phase fraction and present a significant gradient distribution in the welding area with a width of about 4 mm. The relative error in calculating the welding residual stresses can be up to 36.06% if the gradient distribution of phase fraction is ignored. The corrected residual stresses in the welding area exhibit a bimodal distribution, with a peak stress of ∼442 MPa located at the edge of the heat-affected zone. The results demonstrate the necessity of considering the phase fraction with gradient distribution.