Submerged Friction Stir Processing Research Articles

Submerged friction stir processing of wire arc additively manufactured Al alloy: Microstructure and mechanical properties

Friction stir processing (FSP) significantly improves the microstructure and mechanical properties of wire arc additive manufacturing (WAAM) components. This study pioneers the application of submerged friction stir processing (SFSP) to thin-walled WAAM components fabricated from Al-2319, Al-5087, and Al-6082 alloys. The samples were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, and microindentation. The results demonstrate that SFSP leads to a break of the eutectic network, the uniform distribution of precipitates originating from the Al matrix, a marked reduction in porosity and cracks, and grain refinement attributed to accelerated dynamic recrystallization, enhancing hardness and ductility across all three alloys. The improvement was most notable in the Al-6082 alloy relative to the others. Water cooling delays precipitates formation and encourages the development of fine particles. The uncoarsened θ' phase in Al-2319 and the fine β' phase in Al-5087 both contribute to superior tensile properties.

Effect of multipass submerged friction stir processing on the microstructure, mechanical properties and corrosion resistance of 5383Al alloy

The 5383Al alloy is commonly used as a hull material because of its excellent mechanical properties, corrosion resistance and weldability. Nevertheless, the presence of coarse Al6(Fe, Mn) particles and the aggregation of the β phase at the grain boundaries noticeably diminish the corrosion resistance of 5383Al, even though they improve its mechanical properties somewhat. In the present study, multipass submerged friction stir processing (M-SFSP) was conducted on 5383Al alloy to precisely control the microstructure while maintaining a balance between mechanical performance and corrosion resistance. The effects of M-SFSP on the microstructure, mechanical properties and corrosion resistance of the 5383Al were investigated. The results show that homogenous ultrafine equiaxed grains of around 0.65 μm in size was acquired in the M-SFSPed zone through dynamic recrystallization. In the M-SFSPed zone, the dislocation density decreased and the proportion of high-angle grain boundaries increased. As a result, the M-SFSPed 5383Al alloy exhibited excellent and homogeneous mechanical properties, including an ultimate tensile strength of up to 400 MPa, comparable to that of the base material (BM). In addition, many fine Al6(Fe, Mn) particles were uniformly distributed in the M-SFSPed zone, and no β-Al3Mg2 phase was detected at the grain boundaries in the M-SFSPed zone. The M-SFSPed samples showed considerably lower mass loss to corrosion than the BM (1.8 mg/cm2 vs. 42.8 mg/cm2), indicating that M-SFSP increased the corrosion resistance of the 5383Al alloy through microstructure control. This improvement was attributed to the refinement of the Al6(Fe, Mn) phase and the redissolution of the β-Al3Mg2 phase, which effectively inhibited the spread of corrosion. Thus, M-SFSP is considered as a promising method for the manufacturing of 5383Al with high strength and outstanding corrosion resistance.

Enhanced Strength–Ductility Synergy in Submerged Friction Stir Processing ER2319 Alloy Manufactured by Wire-Arc Additive Manufacturing via Creating Ultrafine Microstructure

Enhanced Strength–Ductility Synergy in Submerged Friction Stir Processing ER2319 Alloy Manufactured by Wire-Arc Additive Manufacturing via Creating Ultrafine Microstructure

Obtaining ultra-fine and uniform two-phase structures: Evolution of morphology and phase redistribution in a dual-phase Mg–Li alloy during submerged friction stir processing

This study analyzed the microstructure and mechanical properties of a dual-phase Mg–Li alloy produced through submerged friction stir processing. The study focused on the recrystallization and grain refinement of distinct α-Mg and β-Li phases. Two methods were identified for refining the grains. The first method involved dynamic recrystallization in large deformed grains, resulting in recrystallized grains that had minimal impact on the two-phase distribution. The second method utilized a phase transition for the growth of new α-Mg and β-Li grains occurred through heterogeneous nucleation in the other phase. The relationship between the α-Mg and β-Li phases after the phase transition was observed to have an orientation of Mg[11–20]//Li[100], Mg(0–110)//Li(011). Maelstrom-affected zones were carefully observed near the advancing side, where severe recrystallization, phase transition, and second phase refinement occurred in this region. Submerged friction stir processing prevented grain growth due to a high density of phase boundaries and rapid heat dissipation. As a result, micro-nano grains were observed in the maelstrom-affected zone. The ductility of the interface was enhanced by the maelstrom-affected zone. Therefore, the maelstrom flow can improve mechanical performance through grain refinement and redistribution for dual-phase Mg–Li alloys during submerged friction stir processing.

Nickel-aluminum bronze (NAB) alloy design under two-steps casting and submerged friction stir processing

This research aimed to investigate the impact of friction stir processing (FSP) as a modifying technique on the microstructure and mechanical properties of Cu–10Al, Cu–10Al–5Ni, and Cu–10Al–5Ni–5Fe nickel-aluminum bronze (NAB) alloys under two different conditions of ambient and underwater submerged conditions concerning the as-cast state of these materials. Adding nickel as an alloying element to the Cu–10Al composition resulted in the formation of NiAl intermetallic compound and a 3 % increase in the volume percentage of secondary phases. Furthermore, incorporating iron into the Cu–10Al–5Ni composition prevented the formation of detrimental γ2 phase and instead created κ intermetallic compounds within the structure, leading to an overall increase of approximately 14 % in the volume percentage of secondary phases compared to the Cu–10Al composition. The initial coarse, rough, and heterogeneous structure of the cast samples was transformed into a fine, equiaxed, and homogeneous structure through the friction stirring modification conducted in both air and underwater environments for all alloy compositions, primarily due to action of dynamic recrystallization (DRX). Notably, a finer structure was achieved when the FSP was performed underwater in the submerged state. Regarding developments in mechanical properties, FSP treatment performed in air demonstrated an average enhancement of 15 % in strength and hardness across all three compounds. In contrast, the flexibility of Cu–10Al, Cu–10Al–5Ni, and Cu–10Al–5Ni–5Fe alloys in terms of elongation to failure was reduced by 70 %, 80 %, and 20 %, respectively, in comparison to the cast samples. Conversely, the underwater submerged FSP led to a notable increase of 55 % in both strength and hardness for all three compounds. However, the ductility of the alloys was reduced by 80 % compared to the cast states.

Correlation between microstructure, tribology and corrosion behaviors of Mg-Al-Zn alloy via creating fine and uniform twins through submerged friction stir processing

Twins and fine microstructure can improve the surface properties of magnesium alloys. However, most of the current grain refinement and twinning technologies are costly or complex. In contrast, submerged friction stir processing (SFSP) is a cost-effective process. In this work, Mg-Al-Zn alloys with a fine and uniform twin structure were prepared by multi-pass SFSP with flowing water as coolant. The macro/micro-structure and properties of the surface layer under different processing conditions were characterized. The correlation between microstructure, tribology and corrosion behaviors was systematically studied. The results display that SFSP led to finer grains and created a large number of ultra-fine tensile twins and high-density dislocations in the processed zones compared with air-cooled FSP (AFSP). This unique microstructure resulted in synergistic enhancement of wear and corrosion resistance of Mg-Al-Zn alloy at room temperature.

Developing Ultrafine Twinned Microstructure Enabled Excellent Strength–Ductility Synergy in Mg–Al–Zn Alloy by Submerged Friction Stir Processing

Developing Ultrafine Twinned Microstructure Enabled Excellent Strength–Ductility Synergy in Mg–Al–Zn Alloy by Submerged Friction Stir Processing

Electrochemical corrosion behavior of 6061 Al alloy under high rotating speed submerged friction stir processing

In this study, we report the high rotating speed submerged friction stir processing (HRS-SFSP) designed to modify 6061 Al alloy to improve its corrosion resistance in saltwater. The effect of this processing technology on the microstructure and corrosion behavior of aluminum alloy was studied. The results show that the grain size of Al alloy after HRS-SFSP was refined from 50.8 µm is refined to 3.21 µm. In addition, compared with the low rotation speed (1800 r/min), a higher proportion of high-angle grain boundaries (77.1 %) formed when the rotation speed was 3600 r/min, which effectively reduced the defect density. At the same time, recrystallization in a large area lowered the energy storage in the grain, which further alleviates the corrosion. In addition, the second phase dominated by Mg2Si was fine and uniformly distributed, which also reduced the galvanic corrosion tendency. Therefore, high corrosion resistance was obtained using HRS-SFSP. On the other hand, continuously increasing the rotation speed coarsened the grains and the second phase,which decreased the corrosion resistance.

Inhomogeneous Microstructure Evolution of 6061 Aluminum Alloyat High Rotating Speed Submerged Friction Stir Processing.

An inhomogeneous microstructure induced by high rotating speed submerged friction stir processing (HRS-SFSP) on 6061 aluminum alloy was researched in detail.The microstructures of the aluminum alloy processing zone were characterized by electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) qualitatively and quantitatively.The results show that the recrystallization proportion in the inhomogeneous structure of the processing zone is 14.3%, 37.8% and 35.9%, respectively. Different degrees of grain deformation can affect the dislocation and lead to the formation of a plastic-elastic interface. At the same time, the second-phase particles in the processing zone were inhomogeneity and relatively, which further promotes the plastic-elastic interface effect. The plastic-elastic interface can significantly improve the strength of aluminum alloy, whileat the same time, rely on recrystallized grains to provide enough plasticity. When the rotation speed was 3600 r/min, the strength and ductility of the aluminum alloy after HRS-SFSP were increased by 48.7% and 10.2% respectively compared with that of BM. In all, the plastic-elastic interface can be formed by using high rotating speed submerged friction stir processing, and the strength-ductility synergy of aluminum alloy can be realized at the plastic-elastic interface.

Effect of processing parameters on the microstructure and tensile properties of a dual-phase Mg–Li alloy during friction stir processing

A dual-phase Mg–Li alloy LA103Z sheet was subjected to single pass submerged friction stir processing (FSP) at various of tool sizes, rotation rates and travel speeds. The relationships between processing parameters, frictional heat generation, microstructure, and the room-temperature tensile properties of LA103Z in the stir zone were systematically investigated. Both the α-Mg phase and the β-Li phase undergo complete dynamic recrystallization, the grains are significant refined and the texture is significantly weakened. The precipitation of the AlLi phase and the Li2MgAl phase are promoted by FSP. With the increase of the tool size and rotation rate, the average grain size of the FSPed LA103Z rises as well as the tensile strength, showing an inverse Hall–Petch relation. This is owing to the solid-solution strengthening effect and the reduction of the α/β phase boundaries caused by the dissolution of the α-Mg phase. After being processed by a 16 mm-diameter-shoulder stirring tool under the rotation rate of 800 rpm and the traverse speed of 100 mm/min, the ultimate tensile strength of the FSPed LA103Z is remarkably improved from 177.92 MPa (base metal, BM) to 268.04 MPa, showing the best mechanical property.

An Investigation into Microstructures and Mechanical Properties of 1060 Pure Aluminum during Submerged Friction Stir Processing at a High Rotating Speed

In this work, 1060 pure aluminum was subjected to high rotating speed submerged friction stir processing (HRS-SFSP). The heat cycle curve of the processing area was measured by K-type thermocouple and temperature recorder. The microstructure, grain size, texture, and tensile fracture of the processing area were analyzed by electron backscattered diffraction and scanning electron microscopy. The results show that the HRS-SFSP caused severe plastic deformation of 1060 aluminum and produced fine recrystallized grains. The minimum average grain size was 0.686 μm at the 2-pass. In addition, the dislocation density in the stirred region was greatly reduced and the high angle grain boundaries (HAGBs) were dominant. The texture strength of pure aluminum increased with the increase in processing passes. The maximum hardness of 66.3 HV and ultimate tensile strength of 95.2 MPa were obtained at 1-pass, which were 86% and 33.9% higher than those of the base material, respectively. The hardness and strength of the stirring zone (SZ) decreased with the increase in the number of processing passes. Therefore, HRS-SFSP pure aluminum can obtain high strength and hardness while maintaining good plasticity.

Excellent High‐Strain‐Rate Superplasticity of Fine‐Grained ZK60 Magnesium Alloy Produced by Submerged Friction Stir Processing

ZK60 magnesium alloy is produced via submerged friction stir processing (SFSP), and its microstructural characteristics and deformation behaviors at elevated temperature are investigated. Due to the severe plastic deformation with enhanced cooling rate, dynamic recrystallization occurs but grain growth is significantly retarded. Therefore, the as‐cast microstructure is greatly refined after SFSP, and an average grain size of 1.84 μm is attained. High‐strain‐rate superplasticity (HSRS) is observed at temperature of 573–723 K. A maximum elongation of 1205% is obtained at 1 × 10−2 s−1 and 673 K. The excellent HSRS is attributed to the uniform fine‐grained structure and the relatively high fraction of high‐angle grain boundaries (71.5%), which facilitate grain boundary sliding. The comparatively high portion of dispersed fine particles/precipitates also enhances the microstructural stability of the SFSP specimens. Grain boundary sliding is the dominated deformation mechanism for superplasticity and the failure of the deformed samples is due to the coalescence of cavities.

Electrochemical Corrosion Behavior of 6061 Aluminum Alloy at High Rotating Speed Submerged Friction Stir Processing

Electrochemical Corrosion Behavior of 6061 Aluminum Alloy at High Rotating Speed Submerged Friction Stir Processing

Fabrication of High Strength-Plastic Synergistic Mg-Al-Zn Alloy by Creating Ultrafine Twinned Microstructures During Multi-Pass Submerged Friction Stir Processing

Fabrication of High Strength-Plastic Synergistic Mg-Al-Zn Alloy by Creating Ultrafine Twinned Microstructures During Multi-Pass Submerged Friction Stir Processing

Inhomogeneous Microstructure Induced Strength-Ductility Synergy by Plastic-Elastic Interface at High Rotating Speed Submerged Friction Stir Processing Aluminum Alloy

Inhomogeneous Microstructure Induced Strength-Ductility Synergy by Plastic-Elastic Interface at High Rotating Speed Submerged Friction Stir Processing Aluminum Alloy

Developing α/β Laminar Composite Structure in CuZn Alloy by Heat Treatment and Submerged Friction Stir Processing

A laminar composite structure was developed in a CuZn alloy plate by non-equilibrium heat treatment and subsequent submerged friction stir processing. For this aim, Cu-37 wt.% Zn alloy was initially heat treated to produce a double phase structure. Then, the double phase plate was friction stir processed in underwater media at room temperature. The microstructure and mechanical properties of the samples were analyzed using optical microscopy and tensile test. During heat treatment, the large α grains containing annealing twins converted to a double phase structure with β grains on the α grain boundaries. Heat treatment caused an increase in ultimate tensile strength from 240 MPa to 275 MPa, and a reduction in elongation from 67 to 49%. After friction stir processing, the ultimate tensile strength and elongation were obtained as 380 MPa and 48%, respectively. This desirable mechanical property was achieved due to the formation of a novel composite structure containing parallel ultra-fine grained β layers between dynamically recrystallized α layers.

Achieving Superior Superplasticity in a Mg–6Al–Zn Plate via Multi-pass Submerged Friction Stir Processing

Achieving Superior Superplasticity in a Mg–6Al–Zn Plate via Multi-pass Submerged Friction Stir Processing

Achieving high strength-ductility in pure copper by cold rolling and submerged friction stir processing (SFSP)

In this research, the combined effect of pre-rolling and submerged friction stir processing (SFSP) on the microstructure, hardness, and tensile behavior of commercially pure copper were evaluated. Several voids and cavities were observed in the stirred zone of 0 %–400, 60 %–400, 60 %–600, and 0 %–800 samples, and the defect-free copper could be achieved under a narrow process window. The microstructures revealed that a significant decrement in grain size occurred in the stirred zone of the SFSP-processed coppers due to the occurrence of dynamic recrystallization (DRX) and water cooling conditions. The pre-rolling led to decreasing the grain size after the SFSP owing to providing more nucleation sites for recrystallization. In the 60 %–800 sample, despite the increase in heat-input by increasing the rotational speed, due to the pre-strain, the average hardness was about 5 HV higher than the 0 %–600 sample (92.2 HV vs. 87.1 HV). In the case of the 0% sample, by conducting the SFSP, the yield and ultimate tensile strengths (YS and UTS) increased to 215 and 277 MPa, respectively, due to the lower grain size of the 0 %–600 sample as compared to the 0% sample (4.5 μm vs 17.9 μm). On the other hand, in the 60 %–800 sample, the YS and UTS reduced to 307 MPa as compared to the 60 % sample owing to the transition of the strengthening mechanism from strain hardening to grain refinement. The fractured surfaces of all samples exhibited a ductile manner. However, after the SFSP, the size and depth of dimples were reduced due to the finer grain size.

Experimental investigation of cooling medium on submerged friction stir processed AZ31 magnesium alloy

Submerged Friction stir processing (SFSP) has become apparent as a technique to modify microstructure. It is used to generate refined grains, modify microstructure, achieve superplasticity, synthesize insitu composite and form intermetallic compounds. In this work, AZ31magnesium alloy is friction stir processed at different rotational and welding speed while submerged underwater, cooling oil and brine solution. The effects of different medium on tensile strength, percentage of elongation, hardness, average size of grains in submerged friction stir processed magnesium alloy samples are discussed and the final results are compared. This investigation produces evidence that submerged friction stir processing under coolant oil results in lower peak temperature. During SFSP, water cooling resulted in lower tensile strength when compared to brine solution and coolant oil.

The Influence of Multiple Pass Submerged Friction Stir Processing on the Microstructure and Mechanical Properties of the FSWed AA6082-AA8011 Joints

The AA6082–AA8011 friction stir-welded joints were subjected to submerged multiple pass friction stir processing to evaluate the microstructure and mechanical properties of the joints. A maximum of four submerged friction stir processed passes were used in this study. All the specimens were extracted from three different joint positions (start, middle and end). The tests conducted included microstructural analysis, tensile tests, hardness and fracture surface morphology of the post-tensile specimens, were performed using a scanning electron microscope (SEM). There was no particular trend in the microstructure and mechanical properties when looking at the specimen positioning in all the passes. The minimum mean grain sizes were refined from 3.54 to 1.49 µm and the standard deviation from 5.43 to 1.87 µm. The ultimate tensile strength was improved from 84.96 to 94.77 MPa. The four-pass SFSPed specimens were found to have more ductile properties compared to the one-pass SFSPed one. The hardness of the stir zones in all the passes was found to be higher compared to the AA8011 base material but lower than the AA6082 one. The maximum stir zone hardness of 75 HV was observed on the one-pass SFSP joints.