Journal of Materials Processing Technology最新文献

{"title":"Experimental and numerical investigation of process-induced recoil force in keyhole laser welding: Insights for validating multi-physics process simulations and modelling assumptions","authors":"Andreas Andersson Lassila,&nbsp;Erik Lundell,&nbsp;Tobias Andersson,&nbsp;Dan Lönn,&nbsp;Kent Salomonsson,&nbsp;Rohollah Ghasemi","doi":"10.1016/j.jmatprotec.2025.118895","DOIUrl":"10.1016/j.jmatprotec.2025.118895","url":null,"abstract":"<div><div>Among the various driving forces involved in the molten pool during keyhole laser welding, the vaporization-induced recoil pressure is the dominant one. This study experimentally measured the process-induced recoil force during laser welding of aluminium and copper. A customized measurement setup was used to measure the specimen displacement caused by the recoil force, which was then determined by means of a finite element (FE) analysis. Furthermore, multi-physics computational fluid dynamics (CFD) models of the laser welding process were developed. After calibration, these models were used to predict the recoil force and its dependence on various process parameters. When only the recoil pressure acting on regions where vaporization occurs was considered, excluding the gaseous phases in the model, the total recoil force was underestimated. To account for that the formed gas contributes to the total recoil force as it rises and exits the keyhole, the total recoil force was calculated based on the predicted net mass flow due to vaporization and condensation. This simplified model showed good agreement between predicted and experimentally measured recoil forces, demonstrating that the observed consistent recoil force with increasing laser power may be due to a corresponding increase in the condensation rate. This highlights the importance of understanding the behaviour of the vaporized gas phase to determine appropriate simplifications and assumptions in laser welding process modelling. The findings of this study support the development and validation of multi-physics process models, further advancing knowledge of relevant modelling approximations.</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118895"},"PeriodicalIF":6.7,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144146728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metamaterial acoustic lens-enabled noncontact real-time monitoring of mechanical properties of metal structures manufactured by additive friction stir deposition","authors":"Teng Yang ,&nbsp;Yuqi Jin ,&nbsp;Zexi Lu ,&nbsp;Tingkun Liu ,&nbsp;Tianhao Wang ,&nbsp;Shelden Dowden ,&nbsp;Narendra B. Dahotre ,&nbsp;Arup Neogi","doi":"10.1016/j.jmatprotec.2025.118913","DOIUrl":"10.1016/j.jmatprotec.2025.118913","url":null,"abstract":"<div><div>Achieving high fidelity in solid-state additive manufacturing requires a precise understanding of transient material behaviors and defect formation mechanisms. This study introduces a pioneering noncontact, in-situ ultrasonic monitoring system enabled by a metamaterial acoustic lens for additive friction stir deposition (AFSD). The metamaterial lens facilitates super far-field detection at a working distance of 120 mm, ensuring thermal resilience and enhanced spatial resolution, enabling minute crack detection with subwavelength resolution (∼0.8<span><math><mi>λ</mi></math></span>). Numerical simulations of stress-induced variations in bulk modulus and acoustic wave propagation were validated experimentally, revealing a strong correlation between transient acoustic behaviors and material properties. Unlike conventional machine feedback or ex-situ inspections, this method uncovers subtle inconsistencies and asymmetries—such as localized thermal softening, tensile stress gradients, and feeding irregularities—during real-time deposition. Four common manufacturing flaws (over-tensile stress, lack of heat, insufficient deposition, thermal anomalies, and inconsistent feeding) were systematically analyzed, demonstrating the system's sensitivity and multifunctionality. This innovative approach bridges the gap between in-situ diagnostics and ex-situ nondestructive testing, paving the way for advanced quality control in solid-state manufacturing processes. The presented methodology is extendable to other friction-stir and solid-state metal fabrication techniques by enhancing sensitivity and integrating process control, offering transformative potential for industrial and research applications</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118913"},"PeriodicalIF":6.7,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144139690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chemical-assisted magnetorheological finishing of additively manufactured Inconel 718 alloy","authors":"Himanshu Sharma ,&nbsp;Sachin Jha ,&nbsp;Mayank Kumar ,&nbsp;Gourhari Ghosh","doi":"10.1016/j.jmatprotec.2025.118910","DOIUrl":"10.1016/j.jmatprotec.2025.118910","url":null,"abstract":"<div><div>Additively manufactured Inconel 718 is extensively engaged for the developments of various high temperature components owing to its favourable mechanical and tribological properties. In most of the cases, precision surface finishing is required for better functional performance of those components. In the present study, a multi-step finishing strategy is employed that comprises standard magnetorheological finishing (MRF) and chemical-assisted magnetorheological finishing (CAMRF) processes to achieve nano-scale surface finish of Inconel 718 coating fabricated via laser direct energy deposition (LDED) technique. At first, standard MRF is conducted over the ground surface and a surface roughness (Sa) of 210 nm is achieved. The performance of standard MRF process is restricted owing to the considerably higher hardness of Inconel 718 and limited effectiveness of MRF process and that finally leads to the non-uniform polishing of coating. To further improve the surface finish of coated surface, CAMRF is introduced with the employment of two distinct chemical etchants of IN 718, i.e., etchant 1 (i.e., glyceregia reagent) and etchant 2 (i.e., hydrofluoric acid (HF) based). The optimized vol% of both chemical etchants in MR fluids is found to be 8 %. During CAMRF process, the etchant present in CAMR fluid ribbon interacts with the surface peaks and the surface gets oxidized owing to the oxidizing nature of the chemical etchant. As a consequence, the oxides of major constituents of Inconel 718 (i.e., NiO, Cr₂O₃, etc.) are formed (i.e., passivation film). This hypothesis of oxide formation is confirmed by X-ray photoelectron spectroscopy (XPS) analysis. This passivation film makes the surface asperities/peaks weak and less resistant to removal. As a results, those passivated and weak asperities get sheared off easily by the abrasion action of the abrasive particles present in the CAMRF tool. Due to these integrated effects of chemical etching and mechanical abrasion, the effectiveness of CAMRF process is higher than the standard MRF process. The surface roughness (Sa) associated with CAMRF with etchant 1 and etchant 2 is found to be 145 nm and 100 nm, respectively. The improved surface finish in CAMRF with etchant 2 is attributed to the formation stable oxide film owing to the high reactivity of HF. The friction coefficient and specific wear rate of finished coating are reduced by almost 44 % and 49 % than the ground coating, respectively and this indicates a significant improvement in tribological performance of the finished coating.</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118910"},"PeriodicalIF":6.7,"publicationDate":"2025-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144124204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microstructural evolution and bonding mechanisms during multi-pass cold welding of high-strength precipitation-hardened alloys","authors":"Yong Pang ,&nbsp;Haonan Yu ,&nbsp;Chengdong Xia ,&nbsp;Chengyuan Ni ,&nbsp;Chang Chen ,&nbsp;Sufen Wang ,&nbsp;Yanlin Jia ,&nbsp;Zhu Xiao ,&nbsp;Jiang Yi","doi":"10.1016/j.jmatprotec.2025.118905","DOIUrl":"10.1016/j.jmatprotec.2025.118905","url":null,"abstract":"<div><div>Joining high-strength precipitation-hardened alloys without degrading their properties poses a significant challenge. This study investigates multi-pass butt cold welding as a heat-free joining solution, using a high-strength (nearly 600 MPa) Cu-Cr-Zr alloy as a model system to explore the underlying microstructural evolution and bonding mechanisms, aiming to provide insights of generic value. High-integrity joints were achieved after three or more welding passes, exhibiting exceptional tensile strength (average 573 MPa, about 96 % of base material) while retaining high electrical conductivity (about 80 percent International Annealed Copper Standard, %IACS). Systematic analysis reveals that severe localized plastic deformation during welding drives significant microstructural changes: the initial about 10 μm fibrous grains refine into nanocrystalline (sub-micron) equiaxed grains at the joint center. Crucially, this severe deformation also induces partial mechano-chemical dissolution of the strengthening Cr precipitates even at room temperature, highlighting a key aspect of phase stability under severe plastic deformation (SPD). The study demonstrates that the substantial strengthening from nanocrystallization effectively compensates for the softening caused by precipitate dissolution, enabling high joint efficiency. The bonding mechanism is shown to be dynamic, initiating via surface film rupture, followed by extensive plastic flow that expels contaminants and consolidates the interface over multiple passes. These findings provide fundamental insights into the interplay between extreme strain, grain refinement, and phase stability in precipitation-hardened alloys under cold welding conditions, highlighting the process's potential for joining advanced materials where thermal effects are detrimental.</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118905"},"PeriodicalIF":6.7,"publicationDate":"2025-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144131317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of aluminum addition on the microstructure and mechanical properties of high-strength steel T-joints in flux bands constricting arc welding","authors":"Wang Lei ,&nbsp;Li Jiandong ,&nbsp;Liu Yongtao ,&nbsp;Qiao Jisen","doi":"10.1016/j.jmatprotec.2025.118908","DOIUrl":"10.1016/j.jmatprotec.2025.118908","url":null,"abstract":"<div><div>In the context of lightweight manufacturing, High-Strength Low-Alloy (HSLA) steel T-joints have been widely adopted in critical components of advanced equipment. The precise control of alloying elements to synergistically enhance the strength and toughness of HSLA joints remains a pivotal challenge for expanding their applications. Aluminum (Al), recognized as one of the most influential alloying elements affecting the microstructural characteristics of HSLA steels, demonstrates significant metallurgical regulation effects dependent on its content and introduction method. However, conventional welding processes suffer from inherent limitations in Al regulation, including insufficient spatiotemporal control over elemental distribution and restricted process efficiency, while quantitative studies on the complex \"process-composition-property\" relationships of Al in HSLA joints remain scarce. To address these challenges, this study proposes an innovative in-situ dynamic Al regulation approach via Flux Bands Constricting Arc (FBCA) welding. The effects of Al content (0–0.92 wt%) in flux bands on the microstructural evolution and mechanical properties of HSLA joints including heat-affected zone (HAZ) and welding zone (WZ) were systematically investigated. Results demonstrate that Al addition achieves remarkable synergistic regulation on Q960 steel T-joints: average grain sizes in the welding zone and heat-affected zone were refined by 17 % and 21 %, respectively. With increasing Al content, the average hardness of welding zone and heat-affected zone increased by 35 %. Tensile strength reached 955.7 MPa (0.18 wt% Al) and 1044 MPa (0.92 wt% Al), representing a maximum enhancement of 23.5 %. While welding zone impact toughness slightly improved, heat-affected zone toughness decreased from 94.13 J to 65.77 J. Comprehensive microstructural characterization (Optical Microscope, Energy Dispersive Spectrometer, Electron Back Scatter Diffraction) revealed distinct Al-regulated mechanisms: In the welding zone, fine Al₂O₃ particles (&lt;1 μm) induced acicular ferrite formation, enhancing strength without compromising toughness. In contrast, heat-affected zone refinement originated from arc constriction-induced temperature gradient modulation, which promoted low-angle grain boundary accumulation and increased dislocation density, ultimately reducing toughness through elevated strain energy storage. This work provides novel insights into in-situ elemental regulation during welding and elucidates the synergistic mechanisms of Al on HSLA joint performance, offering theoretical foundations for quantitative studies on complex multi-element interactions in HSLA joints.</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118908"},"PeriodicalIF":6.7,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144107964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electrochemical machining mechanism with bipolar pulses and auxiliary electrode elucidated by analyzing behavior of electric double layer","authors":"Qingrong Zhang ,&nbsp;Hongping Luo ,&nbsp;Wataru Natsu","doi":"10.1016/j.jmatprotec.2025.118907","DOIUrl":"10.1016/j.jmatprotec.2025.118907","url":null,"abstract":"<div><div>Electrochemical machining (ECM) has become one of the most promising technologies in non-conventional machining due to its high quality in surface finish, no tool wear, and no residual stress. To achieve high-precision machining with highly-localized material dissolution in ECM, effective measures need to be taken to overcome stray corrosion, which is the critical issue hindering ECM accuracy. Previous work has shown that electrochemical machining with bipolar pulses and auxiliary electrode (BPAE-ECM) can greatly improve machining accuracy and efficiency. However, the underlying mechanism of the proposed method is still unclear, especially the role of the behavior of the electric double layer (EDL). This study clarifies the mechanism through analyzing the behavior of the EDL based on signal processing of the electrochemical system. Briefly, the mechanism involves a neutralizing effect, in which the reverse charges provided by the negative-pulse are utilized to counteract the positive-pulse charges in the EDL of the non-machining area, which effectively reduces the Faradaic current to improve machining accuracy. The mechanism was verified by simulations and experiments. In contrast to conventional ECM with unipolar pulse (UP-ECM), the signals from the simulated equivalent circuit show that the EDL overpotential and Faradaic current of the non-machining area can be reduced greatly by BPAE-ECM. Corresponding experimental results show that stray corrosion is significantly reduced. Furthermore, structures with high shape accuracy are machined to demonstrate the capability of BPAE-ECM.</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118907"},"PeriodicalIF":6.7,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144108048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bi-directional scanning strategies for residual stress management by tailoring microstructural evolution in directed energy deposition of 9Cr-1Mo steel","authors":"Amritesh Kumar ,&nbsp;Swarup Bag ,&nbsp;V.C. Srivastava","doi":"10.1016/j.jmatprotec.2025.118906","DOIUrl":"10.1016/j.jmatprotec.2025.118906","url":null,"abstract":"<div><div>The transient heating and cooling cycles in arc-based directed energy deposition (DED) processes play the critical role in defining the microstructure and mechanical performance of nuclear-grade steel (9Cr-1Mo) deposition. The current study establishes a comprehensive framework that advances the underlining physics of thermal gradients, phase transformations, and residual stress evolution during the DED process. By combining finite element (FE) simulation and microstructural analysis, the study demonstrates a ∼17 % reduction in tensile residual stress along the build direction following optimized bi-directional scanning strategies. Thermodynamic modeling using the Scheil-Gulliver approach elucidates the formation of key phases, such as δ-ferrite, martensite, and precipitates (M₂₃C₆ and MX), under non-equilibrium conditions inherent to DED process. These findings reveal that non-equilibrium cooling suppresses δ-phase formation, promotes a martensitic matrix, and tailors cellular or dendritic morphologies decisive for mechanical performance. Transmission electron microscopy (TEM) analysis highlights that bi-directional scanning refines martensitic laths, reduces dislocation tangles, and promotes uniform carbide precipitation, significantly enhance microstructural stability and material performance. The current work not only shows the ways of mitigating Type IV cracking through stress reduction and microstructural control but also provides a transferable framework for tailoring deposition strategies in ferritic/martensitic steels and other high-performance materials suitable for industrial applications.</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118906"},"PeriodicalIF":6.7,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144108053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-resolution copper micropatterning on flexible substrates via laser-assisted surface activation","authors":"Zhaoyan Li ,&nbsp;Yuhang Luo ,&nbsp;Xiaozhu Xie ,&nbsp;Jiageng Yang ,&nbsp;Huanhuan Zhuang ,&nbsp;Yajun Huang","doi":"10.1016/j.jmatprotec.2025.118901","DOIUrl":"10.1016/j.jmatprotec.2025.118901","url":null,"abstract":"<div><div>High-performance conductive metal circuits are essential in the modern electronics industry. Additive manufacturing techniques offer significant advantages over traditional photolithography (subtractive methods) in terms of simplicity, cost-effectiveness, and scalability. While various printing techniques have been explored, most are limited by minimum feature sizes in the tens of microns and require high-temperature post-processing to enhance the performance of functional materials. Here, a facile, efficient, and versatile additive manufacturing strategy is proposed for creating high-resolution copper patterns via laser-assisted selective metal deposition. This technique employs an ultrafast UV laser to selectively irradiate areas where copper patterns will be formed, inducing photochemical modifications. The irradiated regions are then seeded and subjected to ECP, resulting in a metal layer deposited on catalytic seed crystals. The copper coating achieved exhibits excellent conductivity (1.77 μΩ·cm) and adhesion (5B, ASTM), comparable to bulk copper. This approach enables the fabrication of high-precision miniature circuits with copper patterns as narrow as 4 μm on various untreated rigid and flexible substrates, accommodating diverse and complex design requirements. The approach is demonstrated for patterning metal interconnects in flexible electronics, including touch screens and thermal heaters, advancing the next generation of printed electronics.</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118901"},"PeriodicalIF":6.7,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144139691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal history-tailored microstructure, microhardness, and tensile properties in heterogeneous double-wire arc directed energy deposited martensitic stainless steel","authors":"Weiyao Tian ,&nbsp;Haoyu Kong ,&nbsp;Qi Sun ,&nbsp;Yibo Liu ,&nbsp;Chunyu Wang ,&nbsp;Qingjie Sun","doi":"10.1016/j.jmatprotec.2025.118904","DOIUrl":"10.1016/j.jmatprotec.2025.118904","url":null,"abstract":"<div><div>Martensitic stainless steel (MSS) is renowned for its exceptional performance. However, current researches on the additive manufacturing of MSS rely on pre-alloyed materials with fixed compositions, limiting the flexibility. This study utilized a heterogeneous double-wire arc directed energy deposition (DED) technique to in situ fabricate MSS wall structures, employing a hybrid feedstock of 55 % ER2209 (duplex stainless steel) and 45 % ER70-G (low-alloy steel). Two distinct inter-layer cooling strategies were implemented. Under shortened inter-layer cooling intervals, pronounced thermal accumulation elevated inter-layer temperatures above the martensite start transformation (M_s) temperature, delaying phase transformation until post-deposition cooling. This regime produced coarser lath martensite with retained δ-ferrite, resulting in higher strength and hardness but poorer plasticity. Conversely, prolonged cooling durations allowed inter-layer temperatures to approach room temperature, facilitating thermal cycling-induced microstructure-property transformation. This transitioned initial lath martensite/δ-ferrite to a tempered martensite-austenite dual-phase architecture and promoted microstructural refinement. Consequently, improvement in elongation was achieved despite moderate reductions in strength and hardness. Furthermore, this investigation elucidated the intrinsic correlation between thermal history and phase transformation mechanisms through a synergistic combination of experiment and simulation, reproducing the evolution of microstructure during each deposition. This work demonstrates the feasibility of fabricating MSS using common heterogeneous welding wires and clarifies the regulation mechanism of thermal history on the in situ fabricated MSS. This study establishes a transferable theoretical framework applicable to diverse material systems in DED research.</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118904"},"PeriodicalIF":6.7,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144124203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Eliminating bottom defects in medium-thickness titanium alloy joints by improving material flow via a new dynamic rotation supporting friction stir welding method","authors":"S. Cong ,&nbsp;L.H. Wu ,&nbsp;Z.W. Wang ,&nbsp;N. Li ,&nbsp;F.F. Wang ,&nbsp;X. Zhang ,&nbsp;X.C. Du ,&nbsp;P. Xue ,&nbsp;F.C. Liu ,&nbsp;D.R. Ni ,&nbsp;B.L. Xiao ,&nbsp;Z.Y. Ma","doi":"10.1016/j.jmatprotec.2025.118900","DOIUrl":"10.1016/j.jmatprotec.2025.118900","url":null,"abstract":"<div><div>It is generally difficult to eliminate bottom defects during friction stir welding (FSW) of medium-thick/thick Ti alloy plates, since there still lacks of deep understanding of the material flow mechanism influencing the formation of bottom defects. In this study, different variant FSW methods were conducted to 7 mm Ti-6Al-4V alloy plates, and the oxide tracking method was utilized to study the material flow mechanism. During conventional dynamic supporting FSW, the main reason for bottom defects was related to cavities formed in the bottom at the initial stage and not filling in time during welding. A new dynamic rotation supporting FSW (DRSFSW) method with a movable bottom rotating shoulder instead of the traditional backing plate was first time proposed to eliminate bottom defects in Ti alloy joints. The essential cause of eliminating bottom defects was associated with the fact that the bottom rotating shoulder added an extra reverse material flow pattern to avoid initial defects, following by fuller material flow and faster material filling rates during the welding. The high-temperature phase reconstruction method showed that colonies with high orientation consistency was largely promoted to form by more sufficient deformation, fully dynamic recrystallisation and fewer nucleation sites after adding the extra reverse material flow pattern during DRSFSW. The joint strength reached 971 MPa, with a joint strength coefficient of 96.8 %. This study uncovers the material flow pattern for FSW with different bottom states and provides a new method to enlarge the welding window and improve the quality of FSW Ti alloy joints.</div></div>","PeriodicalId":367,"journal":{"name":"Journal of Materials Processing Technology","volume":"341 ","pages":"Article 118900"},"PeriodicalIF":6.7,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144089203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}