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Special Issue "Welding and Processing in Alloy Manufacturing"

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: 20 May 2023 | Viewed by 8429

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Special Issue Editors

Prof. Dr. Xinjie Di

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Guest Editor

School of Materials Science and Engineering, Tianjin University, Tianjin 300350, China
Interests: welding metallurgy; weldability of metals; additive manufacturing; welding consumables; material characterization

Dr. Chengning Li

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Guest Editor

School of Materials Science and Engineering, Tianjin University, Tianjin 300350, China
Interests: nanoprecipitation; welding metallurgy principles; alloy welds; wire arc additive manufacturing; welding consumables; ultra-high strength steel

Special Issue Information

Dear Colleagues,

Welding, also known as materials joining engineering, is an important material processing technology, which is widely used in the petrochemical, electric power, aerospace, marine engineering, nuclear power engineering, microelectronics technology, national defense and military fields, among others. In the past two decades, advanced materials such as advanced metals, high-entropy alloys and ceramic materials have been developed continuously. At the same time, weldability, matching welding materials and welding technology have been explored in the development of new materials. In order to obtain high-quality welded joints with excellent performance and controllability, it is necessary to clarify the weldability of materials, welding metallurgy, design of structures, welding processes, etc. The development of welding science has great importance for the development and application of new materials.

On the other hand, additive manufacturing (AM) is an attractive process providing the possibility to create almost any shape that could be very difficult to machine. Note that the metal AM process has many similarities with the conventional welding process, that is, the feedstock forms a high-temperature molten pool under the action of a high-energy density heat source. The molten metal in both processes undergoes non-equilibrium solidification, and a complex solid state phase transformation occurs with the help of in situ cyclic reheating.

This Special Issue aims to enrich the global exchange of scientific activities in alloy welding and additive manufacturing. Topics that are appropriate for this Special Issue include, but are not limited to, alloy welds, microstructure and mechanical properties of HAZ, weldability of alloys, welding metallurgy principles, welding cracking, constitution of weld metals, development and behavior of filler metals, metallurgy of additive manufactured components and process of welding or additive manufacturing.

Prof. Dr. Xinjie Di
Dr. Chengning Li
Guest Editors

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Keywords

alloy welds
microstructure and mechanical properties of HAZ
weldability of alloys
welding metallurgy principles
welding cracking
welding consumables
constitution of weld metals
development and behavior of filler metals
metallurgy of additive manufactured components
process of welding or additive manufacturing

Published Papers (10 papers)

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Research

Open AccessCommunication

Characterizing Oxide Inclusions in Welded Lean Duplex Stainless Steels and Their Influence on Impact Toughness

Suphitcha Moonngam

Pranpreeya Wangjina

Ekkarut Viyanit

and

Chaiyasit Banjongprasert

Materials 2023, 16(5), 1921; https://doi.org/10.3390/ma16051921 - 25 Feb 2023

Viewed by 389

Abstract

In newly developed 2101 lean duplex stainless steel, oxide inclusions have been detected on welded metal zones after subjecting them to flux-cored arc welding with an E2209T1-1 flux-cored filler metal. These oxide inclusions directly affect mechanical properties of the welded metal. Hence, a correlation requiring validation has been proposed between oxide inclusions and mechanical impact toughness. Accordingly, this study employed scanning electron and high-resolution transmission electron microscopy to assess the correlation between oxide inclusions and mechanical impact toughness. Investigations revealed that the spherical oxide inclusions comprised a mixture of oxides in the ferrite matrix phase and were close to intragranular austenite. The oxide inclusions observed were titanium- and silicon-rich oxides with amorphous structures, MnO with a cubic structure, and TiO₂ with an orthorhombic/tetragonal structure, derived from the deoxidation of the filler metal/consumable electrodes. We also observed that the type of oxide inclusions had no strong effect on absorbed energy and no crack initiation occurred near them. Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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Open AccessArticle

Characterization of Microstructural Evolution in Heat-Affected Zone of Cu-Bearing Ultra-High-Strength Steel with Lamellar Microstructure

and

Materials 2023, 16(2), 550; https://doi.org/10.3390/ma16020550 - 05 Jan 2023

Viewed by 656

Abstract

The advanced lamellar microstructure significantly improves the toughness of Cu-bearing ultra-high strength steel by delamination toughening (yield strength: 1370 MPa, impact toughness at −40 °C: 60 J). The lamellar microstructure affects the microstructure evolution of heat-affected zone (HAZ), resulting in separate distributions of lath martensite and granular bainite in the complete austenitizing zone and the formation of cluster fresh martensite in the partial austenitizing zone. The grain refinement and decrease in dislocation density are predominant features, especially for the complete austenitizing zone, where the grain is refined to 4.33 μm, and dislocation density is decreased by 27%. With the degree of austenitizing increase, the dissolution of Cu-rich precipitates (CRPs) aggravates during welding. A small fraction of CRPs in the complete austenitizing zone implies the onset of reprecipitation of CRPs. The reason for softening in HAZ is attributed to a combined effect of granular bainite forming, dislocation density decreasing, and CRPs dissolving. After PWTH, large numbered reprecipitation of coherent CRPs occurs, contributing to the hardness recovery of HAZ. Meanwhile, due to the high density of dislocation of lamellar microstructure inherited by partial austenitizing zone, coarsening of coherent CRPs is easy to occur, and various incoherent structures are observed. Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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Open AccessArticle

Study on Microstructure of Fiber Laser Welding of CoCrCuFeNi High Entropy Alloy

and

Materials 2022, 15(24), 8777; https://doi.org/10.3390/ma15248777 - 08 Dec 2022

Viewed by 418

Abstract

A CoCrCuFeNi high-entropy alloy was successfully welded in this study using fiber laser welding. The effects of the welding parameters on the microstructure and mechanical properties were studied. Three zones were formed: the fusion zone, partial melting zone, and base metal. The base metal exhibited a typical dendrite structure, and the Cu element segregated in the interdendrite. The fusion zone consisted of fine equiaxed crystals and columnar crystals with the same crystalline structure as the base metal. The fusion zone exhibited minimal compositional microsegregation after laser welding. Electron backscatter diffraction results showed that the low-angle grain boundary fraction in the fusion zone increased. Furthermore, some dislocations and dislocation pile-ups were present in the fusion zone, and the densities of the dislocations and dislocation pile-ups were higher than those of the base metal. The hardness of the fusion zone was considerably higher than that of the base metal, while the ultimate tensile strength and elongation values were lower than those of the base metal for all conditions. The ultimate tensile strength and the elongation increased gradually and then decreased with increasing laser power. The maximum ultimate tensile strength exceeded that of the base metal by 90%. Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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Open AccessArticle

Interlaminar Microstructure and Mechanical Properties of Narrow Gap Laser Welding of 40-mm-Thick Ti-6Al-4V Alloy

and

Materials 2022, 15(21), 7742; https://doi.org/10.3390/ma15217742 - 03 Nov 2022

Viewed by 641

Abstract

Narrow gap laser welding (NGLW) is a common solution for the welding of thick structures. NGLW was carried out on narrow-gap butt joints of 40 mm-thick Ti-6Al-4V alloy plates with a U-shaped groove. The distribution characteristics of the interlaminar microstructure in different height ranges of the joint were investigated, and the evolution behavior and formation mechanism of the interlaminar microstructure of the joint were also revealed. This showed that a large amount of short needle martensite nucleated and grew up near the fusion line and the upper boundary of the remelting zone. The “softening” phenomenon occurred in all welds except the cover layer weld. The microstructure evolution and defect migration, induced by multiple welding thermal cycles in the upper weld forming process, were the main reasons for the “softening” of the lower weld. The tensile strength of each sample changed in the range of 920~990 MPa; the fracture mode of the sample belongs to a transgranular ductile fracture. In addition, compared with the upper part of the joint, the plasticity and toughness of the weld area in the lower part of the joint was improved. Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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Open AccessArticle

Comparison of Fracture Toughness in the Coarse-Grain Heat-Affected Zone of X80 Pipelines Girth-Welded under Conventional and Ultra-Low Heat Input

and

Materials 2022, 15(21), 7701; https://doi.org/10.3390/ma15217701 - 02 Nov 2022

Viewed by 618

Abstract

The coarse-grain heat-affected zones (CGHAZs) of X80 girth-welded steel pipelines are prone to embrittlement, which has an extremely adverse effect on their structural integrity. In the present work, the fracture behavior of the CGHAZs of X80 girth welds under the conditions of conventional and ultra-low heat input was studied. The fracture toughness of CGHAZs was evaluated using the crack tip opening displacement (CTOD) test at −10 °C, and the fracture behavior mechanism of CGHAZs were clarified by analyzing microstructural characteristics at prefabricated fatigue cracks containing fracture cloud image, scanning electron microscopy (SEM), and electron back-scatter diffraction (EBSD) figures. The results illustrate that the average fracture toughness (CTOD) value of the ultra-low heat input CGHAZ is 0.6 mm, and the dispersion of CTOD values is small, while the CTOD value of conventional heat input is only 0.04 mm. The ultra-low heat input makes the high-temperature residence time of the coarse-grained region short, reduces the proportion of prior austenite grain boundaries, and inhibits the formation of strip-like bainite and island-like M-A components. The reduction of these deleterious ductile microstructures increases the plastic reserve and deformation capacity of the CGHAZ. Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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Open AccessArticle

Effect of Post-Weld Heat Treatment on Microstructure and Fracture Toughness of X80 Pipeline Steel Welded Joint

and

Materials 2022, 15(19), 6646; https://doi.org/10.3390/ma15196646 - 25 Sep 2022

Cited by 1 | Viewed by 713

Abstract

In the current study, post-weld heat treatment (PWHT 580 °C) was used for an X80 pipeline steel-welded joint, and the fracture toughness of the welded joint was investigated using a crack tip opening displacement (CTOD) test. The relationship between microstructure evolution and fracture toughness is also discussed in this study. The results showed that the weld center mainly consisted of acicular ferrite (AF). The subcritical heat-affected zone (SCHAZ) consisted of a large amount of fine polygonal ferrite and some AF, and it maintained the rolling state of the base metal. The microstructure of the coarse-grained heat-affected zone (CGHAZ) was composed of granular bainite (GB) and M/A constituents, the latter of which decreased after the PWHT. The CTOD values of the weld center were in the range of 0.18–0.27 mm, while those of the CGHAZ were in the range of 0.02–0.65 mm. A brittle fracture occurred in the CGHAZ for both the as-welded and PWHT samples; the CTOD values were 0.042 mm and 0.026 mm, respectively. The CTOD values of the SCHAZ’s location were in the range of 0.8–0.9 mm. The PWHT did not deteriorate the microstructure of the CGHAZ and had little influence on the fracture toughness of the X80 pipeline steel-welded joint; it ensured the fracture toughness of the welded joints and reduced the welding residual stress. Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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Open AccessArticle

Microstructural Characteristics and Hardness Enhancement of Super Duplex Stainless Steel by Friction Stir Processing

Linlin Pan

Chi Tat Kwok

and

Kin Ho Lo

Materials 2022, 15(18), 6267; https://doi.org/10.3390/ma15186267 - 09 Sep 2022

Viewed by 569

Abstract

In the present study, microstructural evolution and hardness of the friction stir processed (FSPed) SAF 2507 super duplex stainless steel fabricated at a rotational speed of 650 rpm and a traverse speed of 60 mm/min were investigated. A scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) detector was used to study the microstructure of the stir zone. The grain sizes of austenite and ferrite in the FSPed 2507 were found to be smaller (0.75 and 0.96 μm) than those of the substrate (6.6 and 5.6 μm) attributed to the occurrence of continuous dynamic recrystallization (CDRX) in both phases. Higher degree of grain refinement and DRX were obtained at the advancing side of the FSPed specimens due to higher strain and temperature. A non-uniform hardness distribution was observed along the longitudinal direction of the SZ. The maximum hardness was obtained at the bottom (407 HV₁). Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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Open AccessArticle

Effect of H₂S Corrosion on the Fracture Toughness of the X80 Pipeline Steel Welded Joint

and

Materials 2022, 15(13), 4458; https://doi.org/10.3390/ma15134458 - 24 Jun 2022

Cited by 2 | Viewed by 763

Abstract

To analyze the causes and mechanisms affecting the fracture toughness of X80 pipeline steel welded joints against H₂S, the fracture toughness of different zones of X80 pipeline steel welded joints in both air and saturated H₂S solution was investigated. The fracture toughness of welded joints degraded significantly in the saturated H₂S solution, where the crack tip opening displacement (CTOD) characteristic value in the coarse grain heat-affected zone (CGHAZ) and weld metal (WM) was only 8% and 12% of that in air, respectively. However, the sub-critical grain heat-affected zone (SCHAZ) showed better resistance to H₂S corrosion, with the CTOD characteristic value reaching 42% of that in air. The resistance of the welded joint to H₂S corrosion was sensitive to microstructures. The grain boundary ferrite (GBF) presented in WM, and the angle of grain boundary orientation in CGHAZ was not conducive to hindering crack propagation. Moreover, the formation of the resultant hydrogen cracks owing to the H₂S corrosion also reduced the fracture toughness of the welded joint. Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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Open AccessArticle

Pulsed FCAW of Martensitic Stainless Clads onto Mild Steel: Microstructure, Hardness, and Residual Stresses

Joao Sartori Moreno

Fabio Faria Conde

Celso Alves Correa

Luiz Henrique Barbosa

Erenilton Pereira da Silva

Julian Avila

Ricardo Henrique Buzolin

and

Haroldo Cavalcanti Pinto

Materials 2022, 15(8), 2715; https://doi.org/10.3390/ma15082715 - 07 Apr 2022

Cited by 1 | Viewed by 1287

Abstract

The low carbon martensitic stainless AWS 410NiMo steel has in its chemical composition 13% chromium, 4% nickel, and 0.4% molybdenum (wt.%) and is used in turbine recovery, rotors, and high-pressure steam pump housings due to its resistance to impact at low temperatures, as well as to corrosion and cavitation. Those applications of the AWS 410NiMo steel frequently demand repair, which is performed by welding or cladding. Arc welding is a well-established technique for joining materials and presents several parameters that influence the mechanical performance of the weld bead. Although numerous welding processes exist, optimizing welding parameters for specific applications and materials is always challenging. The present work deals with a systematic study to verify the correlation between the pulsed fluxed core arc welding (FCAW) parameters, namely pulse current and frequency, welding speed, and contact tip work distance (CTWD), and the bead morphology, microstructure formation, residual stress, and hardness of the martensitic clad. The substrate used was the AISI 1020 steel, and the AWS 410NiMo steel was the filler metal for clad deposition. From the initial nine (9) samples, three (3) were selected for in-depth characterization. Lower heat input resulted in lower dilution, more elevated hardness, and lower compressive residual stresses. Therefore, the results highlight the need for selecting the proper heat input, even when using a pulsed FCAW procedure, to achieve the desired performance of the clad. In the present case, a higher heat input appears to be more advantageous owing to the lower convexity index, smooth hardness transition between fusion and heat-affected zones in addition to more elevated compressive stresses. Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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Open AccessArticle

Wire + Arc Additive Manufacturing and Heat Treatment of Super Martensitic Stainless Steel with a Refined Microstructure and Excellent Mechanical Properties

and

Materials 2022, 15(7), 2624; https://doi.org/10.3390/ma15072624 - 02 Apr 2022

Cited by 2 | Viewed by 1346

Abstract

Due to the advantages of relatively low cost, increased energy efficiency, increased deposition rate, and the capacity to create medium to large scale components, wire + arc additive manufacturing (WAAM) has gained growing interest. Super martensitic stainless steel (SMSS) combines outstanding strength, ductility, and corrosion resistance, making it a great option for WAAM. In the present work, an SMSS component was successfully produced by WAAM. Additionally, the influence of post-manufactured heat treatment on the microstructural characteristics and mechanical properties of SMSS components was systematically examined. A microstructural analysis of the as-printed and heat-treated samples revealed the formation of typical martensite and a small amount of retained austenite. However, the sample heat-treated by solutionizing at 1050 °C for 1 h followed by aging at 400 °C for 2 h exhibited a finer martensitic structure with an effective grain size of 5.6 μm compared to as-printed sample, leading to an increase in ultimate tensile strength from 1054 ± 6 MPa to 1141 ± 3 MPa with a concomitant increase in elongation from 7.8 ± 0.4% to 12.6 ± 0.2%. Additionally, the fracture morphology of the solution + aging sample demonstrated a more uniform distribution and greater mean size of dimples, indicating better ductility. Full article

(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)

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