Inertia Friction Welding Research Articles

Effect of Post-Welding Aging Treatment on the Microstructure and High-Temperature Properties of Inertia Friction Welded GH4065A Joint.

In this study, post-welding aging treatments were applied to a novel Ni-based superalloy GH4065A inertia friction welding (IFW) joint to improve its high-temperature properties. The effect of aging treatment on the microstructure and creep resistance of the IFW joint was systematically investigated. The results indicated that the original γ' precipitates in the weld zone almost completely dissolved during the welding process, and fine tertiary γ' precipitated during the subsequent cooling process. Aging treatment did not significantly change the characteristics of grain structures and primary γ' in the IFW joint. After aging, the size of tertiary γ' in the weld zone and secondary γ' in the base material increased, but their morphology and volume fraction did not change evidently. After 760 °C, 5 h aging treatment, the tertiary γ' in the weld zone of the joint grew from 12.4 nm to 17.6 nm. Correspondingly, the creep rupture time of the joint at 650 °C and 950 MPa increased from 7.51 h to 147.28 h, which is about 19.61 times higher than that of the as-welded joint. The creep rupture was more likely to occur in the base material instead of the weld zone for the IFW joint. This revealed that the creep resistance of the weld zone was significantly improved after aging due to the growth of tertiary γ'. However, increasing the aging temperature or extending the aging time promoted the growth of secondary γ' in the base material, and meanwhile, M23C6 carbides tended to continuously precipitate at the grain boundaries of the base material. It might decrease the creep resistance of the base material.

Effect of Semi-Aging Heat Treatment on Microstructure and Mechanical Properties of an Inertia Friction Welded Joint of FGH96 Powder Metallurgy Superalloy

Inertia friction welded joints often present different microstructures than the base metal, and subsequent heat treatment processes are always needed to maintain superior performance. This study investigates the effect of semi-aging heat treatment after welding on the microstructure, residual stress, micro-hardness, and tensile properties of inertia friction welded FGH96 powder metallurgy superalloy using optical microscopy, scanning electron microscopy, X-ray diffraction, and hardness and tensile tests. The results show that the semi-aging heat treatment after welding does not affect the grain size or grain morphology of the base metal. However, the recrystallization process can be further promoted in the weld nugget zone and transition zone. Meanwhile, the grain size is refined and the residual stress is significantly reduced in the welded joint after the same heat treatment. Under the synergetic strengthening effect of the γ′ phase, semi-aging heat treatment increased the micro-hardness of the weld nugget zone from 470 HV to 530 HV and improved the average tensile strength at room temperature by 118 MPa. These findings provide a reference for the selection of the heat treatment process after inertia friction welding of nickel-based powder metallurgy superalloys.

Bonding mechanism and fracture behavior of inertia friction welded joint of 2219 aluminum alloy to 304 stainless steel

The 2219 aluminum (Al) alloy bars were welded to 304 stainless steel bars by inertia friction welding. The intermetallic compounds (IMCs) at the friction interface were characterized and analyzed and the bonding mechanism of the welded joint was studied in detail. Characterization of the microstructure at the friction interface revealed that there were two types of IMCs layers, the nanoscale Fe4Al13 layer and the microscale Cu-rich layer. In particular, the Cu-rich layer is bonded to the base material by Al2Cu and two Fe–Al–Cu ternary IMCs. Meanwhile, it was verified both theoretically and experimentally that the Fe4Al13 layer had less misfit with the base material with higher bonding strength at the interface. The formation of the Cu-rich layer increases the lattice mismatch, particularly at the interface of the ternary IMCs layer which becomes a weak area where the crack initiates and propagates easily.

Differences in the Microstructures and Tensile Properties of Each Zone of Inertia Friction Welded Joints of TA19 Titanium Alloy

TA19 titanium alloy is a novel medium-temperature, high-strength titanium alloy widely used in the aerospace industry, and its welding performance is very important for the manufacturing of structural parts. In this study, TA19 titanium alloy was connected by inertial friction welding (IFW). After welding, the microstructural and alloying elements of the IFW joints were investigated; the results showed that the microstructures of each zone of the IFW joint were different, and accumulations of the β-stable element Mo were only observed in the base metal (BM) and the heat-affected zone (HAZ). Tensile tests were performed using specially designed specimens with circular grooves to obtain the axial mechanical properties of different zones of IFW joints. The stress–strain curves and tensile fractures of the different specimens were analyzed; the results showed that the tensile strength of the welded joint increased, but the plasticity decreased from BM to WZ.

Research on Dynamic Characteristics Analysis Method of Spindle-Flywheel Rotor System of Inertia Friction Welding Machine

A rotor is a special vibration system whose mechanical characteristics change with rotating speed. Taking the spindle-flywheel rotor system of inertia friction welding machine as the research object, in order to explore the variation law of critical speed and the unbalanced response of rotor system at different node positions, according to the special form of the spindle-flywheel rotor system, the combined flywheel set is simplified as a node of a lumped mass model, and the Riccati transfer matrix method and finite element method are used to calculate respectively. The error of the Riccati transfer matrix method is less than 4% compared with the finite element method, which proves the rationality of an equivalent flywheel node. Compared with the finite element method, the Riccati transfer matrix method, which simplifies the flywheel model, not only ensures accuracy but also shortens the calculation time. This method is obviously more suitable for calculating the spindle-flywheel rotor system model of an inertial friction welding machine. In addition, this method can also calculate the unbalanced response. When the unbalanced mass distribution is closer to the head end of the spindle, the unbalanced response vibrates more strongly at the second-order natural frequency, and the rotor response during vibration can be predicted.

Effect of Heat Treatment on the Microstructure and Properties of Ti600/TC18 Joints by Inertia Friction Welding

The Ti600/TC18 dissimilar titanium alloy joints were prepared by inertia friction welding (IFW). Then, stress-relief annealing and two-stage annealing were performed to optimize the microstructure and properties of the original joints, the purpose of them is to improve the structure and performance of the joints. Then, the microstructure, phase composition, tensile properties, microhardness, and fracture morphology of the joints after heat treatments were investigated. The results showed that after stress-relief annealing, the microstructure of the joints was almost similar to that of the specimen before annealing; the weld zone (WZ) of the joints was composed of fine recrystallized grains and α', and the more β phases underwent a martensitic transformation. The shapes and sizes of αp phases were increased after two-stage annealing; its percentage content was decreased. The tensile properties and the microhardness values of the joints undergoing stress-relief annealing were relatively higher than that of the joints undergoing two-stage annealing; there was no obvious change in the plasticity of the joints. It was confirmed that the stress-relief annealing microstructure was composed of α' and β phases, which were beneficial to the properties of the joints. However, the αs phases were coarsened after two-stage annealing, and the properties of the joints were reduced.

Investigation of Low Cycle Fatigue Behaviors of Inertia-Friction-Welded Joints of the TC21 Titanium Alloy

As a new highly damage-tolerant structural material, the TC21 titanium alloy has been widely used in aerospace applications. Inertial friction welding (IFW) is a form of pressure welding technology with less welding parameters and high welding joint performance, which is especially suitable for the connection of rotors of aero-compressors and engines. In this paper, inertia friction welding of TC21 titanium alloys was successfully carried out, and the microhardness, tensile properties and low cycle fatigue (LCF) behaviors of IFW joints were studied. Based on the mechanical parametric results of the tensile test, the true stress–strain curves of the IFW joint of TC21 titanium alloys are obtained by further calculation. Based on the LCF test results under different strain amplitudes, life prediction of IFW joints was investigated. The results of the LCF test show that there is no obvious cyclic hardening and cyclic softening of the IFW joints. Moreover, the fracture morphology of LCF samples under high strain amplitude (0.9%) and low strain amplitude (0.6%) was observed. The results show that the fatigue cracks initiate and propagate at multiple points in the LCF samples, and the transient fracture zone is larger under high strain amplitude. However, under low strain amplitude, a fatigue crack nucleates and propagates at a single point, and the crack propagation zone is larger.

Constitutive modeling and dynamic recrystallization mechanism elaboration of FGH96 with severe hot deformation

FGH96 nickel-based superalloy is widely used in manufacturing high-temperature components of aero engine, and welded by inertia friction welding (IFW). The materials welded by IFW suffer high temperature just below melting point and strain rate above 10 s−1. The deformation behavior and microstructures of FGH96 at severe deformation conditions are not sufficiently studied. In this paper, hot compression experiments with temperature of 1273–1473 K and strain rate of 0.01–30 s−1 were carried out to analyze the deformation behavior and dynamic recrystallization (DRX) of FGH96. Different from low strain rate researches, the continuous dynamic recrystallization was found complete and dominant at high strain rate and inferred to be stress driven. Two strain modified viscoplastic constitutive models which cover different DRX mechanisms were established by polynomial fitting or defining strain factor. The flow stresses calculated by both constitutive models were in good agreement with the experimental results. The finite element simulation application showed that the two constitutive models can accurately reflect the deformation behavior, and are suitable for the numerical simulation of IFW.

Effect of thermo-mechanical distribution on the evolution of IMCs layer and mechanical properties of 2219 aluminum alloy/304 stainless steel joints by inertia friction welding

The hybrid structure of 2219 aluminum alloy (Al alloy) and 304 stainless steel is effectively joined by inertia friction welding. There are the Cu-rich layer and the Fe4Al13 layer in the friction interface. The Cu-rich layer is discontinuous and its thickness is not uneven. While the Fe–Al layer is continuous and its thickness is closely related to the thermo-mechanical distribution at the interface. The thickness of the Fe–Al IMCs layer in the 1/2 radius zone is 6 fold of that in the center, while the center zone has unbonding defects due to low temperature and poor plastic flow of Al alloy. However, after changing the shape of the Al alloy end face, especially for the tapering surface joint, the homogeneous layer of Fe–Al IMCs forms in the center and 1/2 radius zones, which makes the tensile strength of different zones of the joint more balanced and improves the integral tensile strength. Meanwhile, the evolution of the two IMCs layers was investigated. It is found that the Cu-rich layer is formed through the precipitation of Al2Cu in the Al alloy. While the Fe–Al layer is formed through atomic interdiffusion and its growth is influenced not only by the thermo-mechanical coupling but also the precipitation of the Al2Cu phase.

Near-Net Shape Manufacture of Ultra-High Strength Maraging Steel Using Flow Forming and Inertia Friction Welding: Experimental and Microstructural Characterization

Abstract Flow forming and inertia friction welding (IFW) have been widely used as manufacturing processes that produce high-value engineering components. Combining these two advanced processes facilitates the fabrication of near-net shape components leading to optimized designs. This study introduces the joining of flow-formed seamless tubes of MLX®19 maraging steel using the IFW process to fabricate a near-net shape component used in landing gears and missile parts. The as-received material was initially provided ≈30% reduction in thickness from the flow forming trials and then welded at four varying weld energies while maintaining constant friction and forge pressures. The mechanical behavior of the weldments was characterized, and the optimized weld parameters were determined. The concomitant microstructural evolution of the optimized weld was also examined to comprehend the underlying deformation mechanisms. The weld strength, axial shortening, and width of dynamic recrystallization (DRX) displayed an increasing trend with an increase in the weld energy. The weld-zone (WZ) and thermomechanical affected zone (TMAZ) showed the presence of martensite, whereas in the HAZ presence of intermetallic precipitates and reverted austenite was confirmed along with tempered martensite. Based on microstructural evidence, it was concluded that the peak temperature attained in the WZ was above Ac3, whereas in the TMAZ it was in-between Ac1 and Ac3. The evolution of crystallographic texture implied that WZ was subjected to pure shear deformation during the welding whereas the TMAZ experienced a combined shear and compressive deformation.

Microstructure Characterization and Mechanical Property of the GH4065A Superalloy Inertia Friction Welded Joints

Structural characteristics and design requirements for the integration of the integral rotor and disc shaft of the engine, the welding quality, and mechanical properties of superalloy weldments have received more and more attention in recent years. Inertia friction welding (IFW) was carried out with the typical fiber structure of the solid solution GH4065A alloy as the research object, the microstructure evolution rules of the plastic deformation zone (PDMZ), the thermally affected zone (TMAZ), and the welding zone (WZ) were studied, and the formation mechanism of metallurgical joints was explored. The size difference of the γ′ phase at the grain boundary and in the fiber structure was revealed. The reason is that the γ′ phase located at the grain boundary has lower diffusion activation energy and higher diffusion rate. The microhardness and tensile properties of the IFW joints were explored, the study found that the microhardness of the TAMZ is the highest, followed by the PDMZ and the WZ. The tensile test results show that with the increase in temperature, the fracture position shifts from the BM to the WZ, the microstructure at the fracture changed significantly, and the yield strength decreased from 1372 to 1085 MPa.

Microstructure and mechanical properties of dissimilar inertia friction welded 316L stainless steel to A516 ferritic steel for potential applications in nuclear reactors

Defect-free welds between A-516 ferritic and 316L austenitic stainless steel were achieved using inertia friction welding (IFW) under varying friction and forge pressures. The microstructural evolution and the associated mechanical properties were characterised across different weld regimes. The welds were free from microcracks and demonstrated higher strength and hardness than the parent metal (PM), indicating enhanced properties. Carbide precipitates were not observed at the weld interface, implying no occurrence of sensitisation in the stainless steel. The presence of refined grains coupled with low grain orientation spread (GOS) values was the indication of continuous dynamic recrystallisation (CDRX) occurring during IFW.

Microstructure Evolution of Inertia Friction Welded Joints of TC21 Titanium Alloy

In this paper, TC21 titanium alloy welded joints were successfully formed through inertial friction welding (IFW) processes. Microstructure evolution of IFW joints was investigated by way of different analysis methods including optical microscope (OM), scanning electron microscope(SEM), Electron Back-Scattered Diffraction(EBSD), X-Ray Diffraction(XRD), and Energy Dispersive Spectrometer(EDS). The results indicate that large-sized equiaxial β grains, original α phases, and basketweave structure existing in the BM have completely disappeared in the WZ. Instead, fine equiaxial grains sized at 20–30 μm and very fine α + β lamellar microstructure are formed in the WZ. However, as transition zones, the microstructures of the TMAZ and HAZ are also in transition state while the microstructures existing in the BM partially remain in the TMAZ and completely remain in the HAZ. In addition, second α phases are precipitated and fine α + β lamellar microstructure are formed on the original β base in the TMAZ and HAZ. XRD and EBSD results reveal that the proportion of β phase in the WZ zone decreases greatly. EDS results show that there are aggregations of stabilizing elements of β phase in the BM, but no element aggregation in the WZ. Dynamic recrystallization during the IFW process and element distribution under the rapid cooling condition after the welding process are believed to be responsible for formation of the microstructure in the weld zone of IFW joints.

Investigation of the Mechanical Properties of Inertia-Friction-Welded Joints of TC21 Titanium Alloy

TC21 titanium alloy is a new high damage-tolerant structural material for aerospace applications; its welding performance is very critical for the manufacturing of structural parts. In this research, the inertia friction welding (IFW) process of TC21 alloy was conducted, and the microstructure and mechanical properties of IFW joints were investigated. In tensile tests, specially designed tensile samples with grooves were utilized to achieve the tensile properties of IFW joints. The results show that the microhardness and tensile strength of IFW joints are higher than that of the base metal, but the plasticity of joints is worse compared with the base metal. The SEM results reveal that the weld zone has a dynamic recrystallization microstructure with uniform fine-needle α phases. The microstructure evolution in the weld is the key factor that results in the change of the mechanical properties of TC21 IFW joints.

The evolution of microstructural parameters and mechanical properties of inertia friction welded GH4151

The mechanical properties and distribution of microstructural parameters of GH4151 superalloy joined by inertia friction welding (IFW) were investigated in this study. Electron backscattering diffraction (EBSD) was used to characterize γ grain size, size and volume fraction of γ′ particles and stored energy across the weld line. The micro-hardness profiles were measured across the weld line. Significant changes in the microstructure were observed within 2 mm from the weld line since the steep temperature gradient and severe plastic deformation during the IFW process. Moreover, the postweld heat treatment (PWHT) could result in obvious changes in the microstructural parameters, such as coarsening of γ′ particles, dissolution and precipitation of carbides and relief of stored deformation energy. Furthermore, the micro-hardness profiles are influenced by the variation of grain size, γ′ particle size, γ′ volume fraction and the deformation energy stored in the material. This study can serve as a guide for the microstructural optimization and improvement of mechanical properties of IFWed GH4151 superalloy.

Interfacial microstructure evolution and mechanical properties of inertia friction welded aluminium alloy/stainless steel joint with preheat treatment

This paper reveals the evolution of interfacial microstructure and its effect on the mechanical properties of Al alloy/stainless steel joint made by inertia friction welding with different surface roughness (as-machined and polished) followed by preheat treatment. At the central interface region, an unbonded area is witnessed for the Al alloy/as-machined steel (AA-MS) joint, while an intimate contact is realised for the Al alloy/polished steel (AA-PS) joint. The 1/2 radius (1/2R) region is characterised by the formation of the Fe–Al reaction layer, and no obvious layer exists at the peripheral region. Further microstructural characterisation indicates the reaction layer consists of a partially nanoscale crystallised layer of Fe2Al5 and a nanoscale amorphous layer in the as-welded joint induced by the severe shear effect. Preheat treatment promotes the growth of the crystallised layer and suppresses the amorphous layer due to the enhanced atom mobility. Preheat treatment improves the local interfacial bonding strength by reducing the unbounded area while maintaining a high bonding quality at the 1/2R region in the AA-MS joint. However, the enlarged brittle peripheral region is responsible for a slightly lowered joint strength in the preheated AA-PS joint.

Microstructure and Mechanical Properties of Aluminum Alloy/Stainless Steel Dissimilar Ring Joint Welded by Inertia Friction Welding

In recent years, studying the weldability of a dissimilar metal hybrid structure, with the potential to make full use of their unique benefits, has been a research hotspot. In this article, inertia friction welding was utilized to join Φ130 forged ring of 2219 aluminum alloy with 304 stainless steel. Optical observation (OM), electron back scattering diffraction (EBSD), and scanning electron microscopy (SEM) were utilized to examine the joint microstructure in depth. Depending on the research, a significant thermal–mechanical coupling effect occurs during welding, resulting in inadequate recrystallization on aluminum-side thermo-mechanically affected zone (TMAZ) and forming zonal features. The crystal orientation and grain size of each TMAZ region reflect distinct differences. On the joint faying surface, the growth of intermetallic compounds (IMCs) is inhibited by a fast cooling rate and metallurgical bonding characteristics were found depending on the discontinuous distribution of IMCs. The average joint tensile strength can reach 161.3 MPa achieving 92.2% of 2219-O; fracture occurs on aluminum-side base metal presenting ductile fracture characteristics.

Effect of Thermo-Mechanical Distribution on the Evolution of Imcs Layer and Mechanical Properties of 2219 Aluminum Alloy/304 Stainless Steel Joints by Inertia Friction Welding

Effect of Thermo-Mechanical Distribution on the Evolution of Imcs Layer and Mechanical Properties of 2219 Aluminum Alloy/304 Stainless Steel Joints by Inertia Friction Welding

Inter-relationship between microstructure evolution and mechanical properties in inertia friction welded 8630 low-alloy steel

The evolution of microstructure and mechanical properties in AISI 8630 low-alloy steel subjected to inertia friction welding (IFW) have been investigated. The effects of three critical process parameters, viz. rotational speed, friction and forge forces, during welding of tubular specimens were explored. The mechanical properties of these weld joints, including tensile and Charpy V-notch impact were studied for determining the optimum welding parameters. The weld joints exhibited higher yield strength, lower hardening capacity and ultimate tensile strength compared to base metal (BM). The maximum strength and ductility combination was achieved for the welds produced under a nominal weld speed of ~ 2900–3100 rpm, the highest friction force of ~ 680–720 kN, and the lowest axial forging load of ~ 560–600 kN. The measured hardness distribution depicted higher values for the weld zone (WZ) compared to the thermo-mechanically affected zone (TMAZ), heat-affected zone (HAZ) and BM, irrespective of the applied welding parameters. The substantial increase in the hardness of the WZ is due to the formation of microstructures that were dominated by martensite. The observed microstructural features, i.e. the fractions of martensite, bainite and ferrite, show that the temperature in the WZ and TMAZ was above Ac3, whereas that of the HAZ was below Ac1 during the IFW. The fracture surface of the tensile and impact-tested specimens exhibited the presence of dimples nucleating from the voids, thus indicating a ductile failure. EBSD maps of the WZ revealed the formation of subgrains inside the prior austenite grains, indicating the occurrence of continuous dynamic recrystallisation during the weld. Analysis of crystallographic texture indicated that the austenite microstructure (i.e. FCC) in both the WZ and TMAZ undergoes simple shear deformation during IFW.

Non-uniformity of intermetallic compounds and properties in inertia friction welded joints of 2A14 Al alloy to 304 stainless steel

Inertia friction welding (IFW) is attracting considerable attention in recent years for dissimilar metals joining such as aluminum (Al) alloy to stainless steel due to its ease to control heat input accurately. As a result of thermo-mechanical conditions, the microstructure at the friction interface, especially the brittle IMCs, is usually considered to be non-uniformly distributed. In the present study, the non-uniformity of IMCs at different interfacial regions in the IFWed joint and the diffusion bonded joint was comparatively studied by annealing experiments with tensile tests conducted accordingly for quantitatively evaluating the influence of IMCs thickness on the bonding properties. Following the heat treatment, unlike diffusion bonded joints, different growth behavior of IMCs at different interfacial positions of the IFWed joint was observed, which deviated with a varying degree from the parabolic diffusion law. The phenomenon indicated a non-uniform distribution of energy storage along friction interface after welding, resulting from the unique thermo-mechanical conditions in the friction welding process. Moreover, the highest bonding strength appeared at the central interface region where no obvious IMCs layer was founded in the as-welded joint, and a negative correlation between IMCs thickness layer and bonding strength was observed. Therefore, for designing a high-performance Al/steel IFWed joint, the distribution and the corresponding thickness of IMCs should be carefully considered.