Pub Date : 2026-02-01Epub Date: 2025-12-22DOI: 10.1016/j.msea.2025.149657
Xi Jiang , Haiping Yu , Haohua Li , Feng Lyu , Xiao Cheng
Interface microstructures of Al/Fe magnetic pulse welded (MPW) joints are known to significantly influence the mechanical properties. However, their impact on joint failure remains unclear. In-situ tensile tests were conducted at room temperature and 300 °C in this study. At room temperature, cracks are deflected by intermetallic compounds (IMCs) towards the Al sheet. However, crack growth can be terminated by hard-oriented grains and grain boundaries (GBs). In contrast, at 300 °C, the sliding of GBs and the weakening of the crack hindering effect of IMCs lead to failure of the Al sheet near the interface. These findings provide insights into the failure mechanisms of MPW joints.
{"title":"In-situ observation of tensile crack evolution of magnetic pulse welded joint","authors":"Xi Jiang , Haiping Yu , Haohua Li , Feng Lyu , Xiao Cheng","doi":"10.1016/j.msea.2025.149657","DOIUrl":"10.1016/j.msea.2025.149657","url":null,"abstract":"<div><div>Interface microstructures of Al/Fe magnetic pulse welded (MPW) joints are known to significantly influence the mechanical properties. However, their impact on joint failure remains unclear. In-situ tensile tests were conducted at room temperature and 300 °C in this study. At room temperature, cracks are deflected by intermetallic compounds (IMCs) towards the Al sheet. However, crack growth can be terminated by hard-oriented grains and grain boundaries (GBs). In contrast, at 300 °C, the sliding of GBs and the weakening of the crack hindering effect of IMCs lead to failure of the Al sheet near the interface. These findings provide insights into the failure mechanisms of MPW joints.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"952 ","pages":"Article 149657"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145838894","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}
To overcome the persistent strength-ductility trade-off in aluminum alloys, this work introduces a synergistic microalloying strategy involving Sc and Cu, integrated with multiscale heterogeneous structures for Al-Cu-Mn-Mg-Ag alloys. This approach achieves a very good strength-ductility balance, with an ultimate tensile strength (UTS) of 531.0 MPa, a yield strength (YS) of 470.1 MPa, and an elongation at fracture of 12.0 %. Quantitative microstructural analysis reveals that bimodal grain formation results from competing mechanisms: particle-stimulated nucleation (PSN) induced by coarse θ-Al2Cu, T-Al20Cu2Mn3, and W-Al8-xCu4+xSc (0<x < 2.6) phases, in contrast to Zener pinning exerted by submicron TMn-Al20Cu2Mn3 dispersoids and nanosized Al3Sc precipitates. The resulting heterogeneous structures generate a hetero-deformation induced (HDI) stress exceeding 300 MPa, which enhances work hardening and promotes uniform deformation throughout the alloy. This study presents a novel pathway to overcome the strength-ductility trade-off in aluminum alloys through the combined control of bimodal grains and multiscale precipitation.
{"title":"Achieving enhanced strength-ductility synergy in heterogeneous Al-Cu-Mn-Mg-Ag alloys by dual strategy: Cu optimization and Sc microalloying","authors":"Han Zhang , Yanqing Xue , Wentao Yu , Haiyan Yang , Yadong Lv , Qitang Hao , Ruirun Chen , Mengqian Zhang","doi":"10.1016/j.msea.2025.149686","DOIUrl":"10.1016/j.msea.2025.149686","url":null,"abstract":"<div><div>To overcome the persistent strength-ductility trade-off in aluminum alloys, this work introduces a synergistic microalloying strategy involving Sc and Cu, integrated with multiscale heterogeneous structures for Al-Cu-Mn-Mg-Ag alloys. This approach achieves a very good strength-ductility balance, with an ultimate tensile strength (UTS) of 531.0 MPa, a yield strength (YS) of 470.1 MPa, and an elongation at fracture of 12.0 %. Quantitative microstructural analysis reveals that bimodal grain formation results from competing mechanisms: particle-stimulated nucleation (PSN) induced by coarse θ-Al<sub>2</sub>Cu, T-Al<sub>20</sub>Cu<sub>2</sub>Mn<sub>3</sub>, and W-Al<sub>8-x</sub>Cu<sub>4+x</sub>Sc (0<x < 2.6) phases, in contrast to Zener pinning exerted by submicron T<sub>Mn</sub>-Al<sub>20</sub>Cu<sub>2</sub>Mn<sub>3</sub> dispersoids and nanosized Al<sub>3</sub>Sc precipitates. The resulting heterogeneous structures generate a hetero-deformation induced (HDI) stress exceeding 300 MPa, which enhances work hardening and promotes uniform deformation throughout the alloy. This study presents a novel pathway to overcome the strength-ductility trade-off in aluminum alloys through the combined control of bimodal grains and multiscale precipitation.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"952 ","pages":"Article 149686"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145838898","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}
Pub Date : 2026-02-01Epub Date: 2026-01-12DOI: 10.1016/j.msea.2026.149779
Tingxiao Yu , Honglong Zhao , Qingdong Qin , Kai Feng , Juan Li , Chuang Yang , Yu Zeng
Achieving a high-quality joint in refractory high-entropy alloys (RHEAs) remains a significant challenge. In the present study, an appropriate filler metal of TiZrCuNi was selected to successfully join TiVNbTa RHEA using vacuum brazing. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and shear tests were used to systematically study the interfacial microstructure and mechanical properties of the joints. The results showed that the brazing seam consists of a diffusion-affected zone (Zone I) and a central brazed zone (Zone II), with a convex structure formed between these two zones. TEM images revealed α-Ti(Zr) nano-precipitates in Zone I. As the brazing temperature increased, the thickness of Zone I gradually increased, while the volume fraction of the blocky α-Ti phase in Zone II significantly decreased. The shear strength of the joints initially increased and then decreased with rising brazing temperature, reaching an optimal value of 179 ± 8 MPa after brazing at 880 °C for 15 min. The enhanced bonding strength of the joint is attributed to the interlocking effect of the convex structure and nano-precipitation strengthening. This study provides valuable insights into the welding challenges of TiVNbTa RHEA, offering guidance for achieving high-quality welding of RHEAs.
{"title":"Enhancing the interfacial strength of TiVNbTa refractory high entropy alloy joint for vacuum brazed via convex structure with nano-precipitates","authors":"Tingxiao Yu , Honglong Zhao , Qingdong Qin , Kai Feng , Juan Li , Chuang Yang , Yu Zeng","doi":"10.1016/j.msea.2026.149779","DOIUrl":"10.1016/j.msea.2026.149779","url":null,"abstract":"<div><div>Achieving a high-quality joint in refractory high-entropy alloys (RHEAs) remains a significant challenge. In the present study, an appropriate filler metal of TiZrCuNi was selected to successfully join TiVNbTa RHEA using vacuum brazing. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and shear tests were used to systematically study the interfacial microstructure and mechanical properties of the joints. The results showed that the brazing seam consists of a diffusion-affected zone (Zone I) and a central brazed zone (Zone II), with a convex structure formed between these two zones. TEM images revealed α-Ti(Zr) nano-precipitates in Zone I. As the brazing temperature increased, the thickness of Zone I gradually increased, while the volume fraction of the blocky α-Ti phase in Zone II significantly decreased. The shear strength of the joints initially increased and then decreased with rising brazing temperature, reaching an optimal value of 179 ± 8 MPa after brazing at 880 °C for 15 min. The enhanced bonding strength of the joint is attributed to the interlocking effect of the convex structure and nano-precipitation strengthening. This study provides valuable insights into the welding challenges of TiVNbTa RHEA, offering guidance for achieving high-quality welding of RHEAs.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149779"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973532","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}
Pub Date : 2026-02-01Epub Date: 2026-01-16DOI: 10.1016/j.msea.2026.149780
Hongding Wang , Binbin Zhao , Yangcong Xiao , Ning Guo , Qian Meng , Jinyuan Ma , Peiqing La
Fe-Al intermetallic compounds exhibit high specific strength and stiffness, excellent resistance to hot corrosion and erosion, and superior high-temperature oxidation resistance. To address the challenge of balancing strength and ductility in Fe-Al intermetallic compounds, the Fe-Al-Ta eutectic alloys with varying Ta contents were designed and synthesized by the Thermite Self-Propagating High-Temperature Synthesis (SHS) method. The findings indicate that changes in Ta content significantly alter the morphology of the second phase in the alloy. Notably, at a Ta content of 20 wt%, fine and uniformly distributed anomalous eutectic particles substantially enhance the alloy's strength and toughness simultaneously. The SHS method, characterized by high reaction temperatures and rapid cooling rates, facilitates the formation of the desired nanocrystalline structure within the Fe3Al(Ta) matrix phase. This nanocrystalline Fe3Al(Ta) structure, combined with micron-sized anomalous eutectic Fe2Ta(Al) particles, forms a micro-nano composite structure. During deformation, the synergistic interaction of this micro-nano structure enables the alloy to achieve high strength while maintaining good plasticity and toughness. The research reveals that the formation of anomalous eutectic Fe2Ta(Al) particles stems from the remelting of regular eutectic lamellae. The favorable strength and toughness are attributed to grain nanocrystallization, multi-level heterogeneous deformation-induced strengthening, and precipitation strengthening provided by the anomalous eutectic particles.
{"title":"Design and synergistic strengthening mechanisms of high strength-toughness Fe-Al-Ta alloy with multi-scale architecture","authors":"Hongding Wang , Binbin Zhao , Yangcong Xiao , Ning Guo , Qian Meng , Jinyuan Ma , Peiqing La","doi":"10.1016/j.msea.2026.149780","DOIUrl":"10.1016/j.msea.2026.149780","url":null,"abstract":"<div><div>Fe-Al intermetallic compounds exhibit high specific strength and stiffness, excellent resistance to hot corrosion and erosion, and superior high-temperature oxidation resistance. To address the challenge of balancing strength and ductility in Fe-Al intermetallic compounds, the Fe-Al-Ta eutectic alloys with varying Ta contents were designed and synthesized by the Thermite Self-Propagating High-Temperature Synthesis (SHS) method. The findings indicate that changes in Ta content significantly alter the morphology of the second phase in the alloy. Notably, at a Ta content of 20 wt%, fine and uniformly distributed anomalous eutectic particles substantially enhance the alloy's strength and toughness simultaneously. The SHS method, characterized by high reaction temperatures and rapid cooling rates, facilitates the formation of the desired nanocrystalline structure within the Fe<sub>3</sub>Al(Ta) matrix phase. This nanocrystalline Fe<sub>3</sub>Al(Ta) structure, combined with micron-sized anomalous eutectic Fe<sub>2</sub>Ta(Al) particles, forms a micro-nano composite structure. During deformation, the synergistic interaction of this micro-nano structure enables the alloy to achieve high strength while maintaining good plasticity and toughness. The research reveals that the formation of anomalous eutectic Fe<sub>2</sub>Ta(Al) particles stems from the remelting of regular eutectic lamellae. The favorable strength and toughness are attributed to grain nanocrystallization, multi-level heterogeneous deformation-induced strengthening, and precipitation strengthening provided by the anomalous eutectic particles.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149780"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973539","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}
Pub Date : 2026-02-01Epub Date: 2026-01-10DOI: 10.1016/j.msea.2026.149770
Donghui Wen , BeiBei Jiang , Tianlong Zhang , Mengqi Gao , Zhaowen Huang , Fengyu Kong , Yuanmin Zhu , Anding Wang , Qing Wang , Chain-Tsuan Liu
BCC-based high/medium-entropy alloys (H/MEAs) possess prominent high-temperature strength, low thermal expansion, and high thermal conductivity, making them a promising candidate for elevated-temperature applications. However, their limited deformability at room temperature (RT) hinders industrial implementation. Here, we report a novel cost-effective (FeCrNi)85(AlTi)15 MEA featuring a multiple-phase microstructure with BCC/L21, L21/BCC, and FCC/L12 coherent interfaces in the as-cast state. The strategic incorporation of L12-strengthened FCC matrix phase within brittle BCC and L21 matrices can activate hetero-deformation-induced (HDI) hardening effect, achieving an attractive compressive plasticity of 35 % at room temperature. The well-controlled L21-Ni2AlTi, BCC, and L12-Ni3(Al, Ti) nanoparticles coherently precipitate in BCC, L21, and FCC matrix phases, respectively, resulting in a super-high yield strength of 1850 MPa, outperforming existing B2/L21-strengthened BCC H/MEAs. The triple-coherent interface system demonstrates exceptional thermal stability, maintaining yield strengths of 850 MPa at 700 °C and 395 MPa at 800 °C. Moreover, this alloy exhibits a dynamic phase transformation-induced hardening effect during long-term aging due to the precipitation of σ-FeCr phase. These results provide a new strategy for overcoming the drawback of inadequate deformability in BCC-based alloys and developing novel advanced as-cast materials for high-temperature applications under compressive loading.
{"title":"Strong and deformable high-Al/Ti medium entropy alloy with good thermal stability via multiple coherent-precipitation","authors":"Donghui Wen , BeiBei Jiang , Tianlong Zhang , Mengqi Gao , Zhaowen Huang , Fengyu Kong , Yuanmin Zhu , Anding Wang , Qing Wang , Chain-Tsuan Liu","doi":"10.1016/j.msea.2026.149770","DOIUrl":"10.1016/j.msea.2026.149770","url":null,"abstract":"<div><div>BCC-based high/medium-entropy alloys (H/MEAs) possess prominent high-temperature strength, low thermal expansion, and high thermal conductivity, making them a promising candidate for elevated-temperature applications. However, their limited deformability at room temperature (RT) hinders industrial implementation. Here, we report a novel cost-effective (FeCrNi)<sub>85</sub>(AlTi)<sub>15</sub> MEA featuring a multiple-phase microstructure with BCC/L2<sub>1</sub>, L2<sub>1</sub>/BCC, and FCC/L1<sub>2</sub> coherent interfaces in the as-cast state. The strategic incorporation of L1<sub>2</sub>-strengthened FCC matrix phase within brittle BCC and L2<sub>1</sub> matrices can activate hetero-deformation-induced (HDI) hardening effect, achieving an attractive compressive plasticity of 35 % at room temperature. The well-controlled L2<sub>1</sub>-Ni<sub>2</sub>AlTi, BCC, and L1<sub>2</sub>-Ni<sub>3</sub>(Al, Ti) nanoparticles coherently precipitate in BCC, L2<sub>1,</sub> and FCC matrix phases, respectively, resulting in a super-high yield strength of 1850 MPa, outperforming existing B2/L2<sub>1</sub>-strengthened BCC H/MEAs. The triple-coherent interface system demonstrates exceptional thermal stability, maintaining yield strengths of 850 MPa at 700 °C and 395 MPa at 800 °C. Moreover, this alloy exhibits a dynamic phase transformation-induced hardening effect during long-term aging due to the precipitation of σ-FeCr phase. These results provide a new strategy for overcoming the drawback of inadequate deformability in BCC-based alloys and developing novel advanced as-cast materials for high-temperature applications under compressive loading.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149770"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973521","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}
Pub Date : 2026-02-01Epub Date: 2026-01-14DOI: 10.1016/j.msea.2026.149775
Xin Bu , Qian Lei , Xiukuang Zhang , Cong Chen , Liang Tian , Yi Luo , Feng Liu
Laser powder bed fusion (L-PBF) can achieve integrated forming of complex structural components, significantly shortening fabrication processes. This work systematically investigated the effects of L-PBF process parameters and heat treatment on the microstructure and properties of a Cu-Ni-Si alloy. Orthogonal experiments obtained the optimal process parameters for fabricating Cu-Ni-Si alloy bulks by L-PBF. The aging treatment parameters were explored, and the heat treatment process was found to improve the properties of the Cu-Ni-Si alloy. The microstructures and properties of the as-built and heat-treated the Cu-Ni-Si samples were analyzed. The Cu-Ni-Si alloy samples can be fabricated with process parameters of a laser power of 450 W, a scanning speed of 500–800 mm/s, a scanning spacing of 45 μm, and a powder layer thickness of 30 μm. After solid-solution treatment at 920 °C for 1h and subsequent aging at 450 °C for 28h, the Cu-Ni-Si alloy samples show an ultimate tensile strength of 788 MPa and an electrical conductivity of 45.0 % IACS. The nanoscale δ-Ni2Si precipitates are distributed diffusely on the matrix, which contributes to Orowan strengthening in the studied Cu-Ni-Si alloy. These findings provide theoretical guidance for the preparation of high-strength, and high-conductivity Cu-Ni-Si alloys via L-PBF.
{"title":"Effect of heat treatment on the microstructure and properties of a Cu-Ni-Si alloy manufactured by laser powder bed fusion","authors":"Xin Bu , Qian Lei , Xiukuang Zhang , Cong Chen , Liang Tian , Yi Luo , Feng Liu","doi":"10.1016/j.msea.2026.149775","DOIUrl":"10.1016/j.msea.2026.149775","url":null,"abstract":"<div><div>Laser powder bed fusion (L-PBF) can achieve integrated forming of complex structural components, significantly shortening fabrication processes. This work systematically investigated the effects of L-PBF process parameters and heat treatment on the microstructure and properties of a Cu-Ni-Si alloy. Orthogonal experiments obtained the optimal process parameters for fabricating Cu-Ni-Si alloy bulks by L-PBF. The aging treatment parameters were explored, and the heat treatment process was found to improve the properties of the Cu-Ni-Si alloy. The microstructures and properties of the as-built and heat-treated the Cu-Ni-Si samples were analyzed. The Cu-Ni-Si alloy samples can be fabricated with process parameters of a laser power of 450 W, a scanning speed of 500–800 mm/s, a scanning spacing of 45 μm, and a powder layer thickness of 30 μm. After solid-solution treatment at 920 °C for 1h and subsequent aging at 450 °C for 28h, the Cu-Ni-Si alloy samples show an ultimate tensile strength of 788 MPa and an electrical conductivity of 45.0 % IACS. The nanoscale δ-Ni<sub>2</sub>Si precipitates are distributed diffusely on the matrix, which contributes to Orowan strengthening in the studied Cu-Ni-Si alloy. These findings provide theoretical guidance for the preparation of high-strength, and high-conductivity Cu-Ni-Si alloys via L-PBF.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149775"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973665","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}
Pub Date : 2026-02-01Epub Date: 2026-01-27DOI: 10.1016/j.msea.2026.149835
Shangkun Wang , Deli Feng , Yongqing Zhang , Yi Luo , Xiangtao Deng
This study systematically examines the austenitization and continuous cooling transformation (CCT) behavior of two 600 MPa grade seismic-resistant rebars, with and without niobium (Nb), to clarify how Nb microalloying governs microstructural evolution and mechanical properties. The results indicate that prior austenite grains (PAGs) in the Nb-bearing steel exhibit two-stage coarsening with increasing austenitization temperature. At lower austenitization temperatures, the two steels show little difference in PAG size. As the austenitization temperature increases, PAGs in the Nb-bearing steel become significantly coarser than those in the Nb-free steel. During cooling, Nb shifts the CCT curves to lower temperatures, delaying ferrite/pearlite transformation and refining the pearlite interlamellar spacing at a given cooling rate. In addition, the Nb-free steel is harder than the Nb-bearing steel under undeformed conditions. After hot deformation, interphase precipitation makes the Nb-bearing steel harder. However, because of competition among microstructural morphologies and phase constituents induced by Nb precipitation, the hardness-cooling rate curves exhibit a crossover. Furthermore, strain-induced precipitation generated by hot deformation and interphase precipitation (IP) bands ahead of migrating phase boundaries pins migrating interfaces and refines the microstructure. Therefore, the combined effects of microstructural refinement and precipitation strengthening increase the yield strength of the Nb-bearing steel from 606 MPa to 665 MPa while maintaining satisfactory ductility.
{"title":"Effect of Nb microalloying on austenitization, continuous cooling transformation behavior and mechanical properties of seismic-resistant rebar","authors":"Shangkun Wang , Deli Feng , Yongqing Zhang , Yi Luo , Xiangtao Deng","doi":"10.1016/j.msea.2026.149835","DOIUrl":"10.1016/j.msea.2026.149835","url":null,"abstract":"<div><div>This study systematically examines the austenitization and continuous cooling transformation (CCT) behavior of two 600 MPa grade seismic-resistant rebars, with and without niobium (Nb), to clarify how Nb microalloying governs microstructural evolution and mechanical properties. The results indicate that prior austenite grains (PAGs) in the Nb-bearing steel exhibit two-stage coarsening with increasing austenitization temperature. At lower austenitization temperatures, the two steels show little difference in PAG size. As the austenitization temperature increases, PAGs in the Nb-bearing steel become significantly coarser than those in the Nb-free steel. During cooling, Nb shifts the CCT curves to lower temperatures, delaying ferrite/pearlite transformation and refining the pearlite interlamellar spacing at a given cooling rate. In addition, the Nb-free steel is harder than the Nb-bearing steel under undeformed conditions. After hot deformation, interphase precipitation makes the Nb-bearing steel harder. However, because of competition among microstructural morphologies and phase constituents induced by Nb precipitation, the hardness-cooling rate curves exhibit a crossover. Furthermore, strain-induced precipitation generated by hot deformation and interphase precipitation (IP) bands ahead of migrating phase boundaries pins migrating interfaces and refines the microstructure. Therefore, the combined effects of microstructural refinement and precipitation strengthening increase the yield strength of the Nb-bearing steel from 606 MPa to 665 MPa while maintaining satisfactory ductility.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"954 ","pages":"Article 149835"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075469","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}
Pub Date : 2026-02-01Epub Date: 2026-01-16DOI: 10.1016/j.msea.2026.149796
Raj Narayan Hajra , Woong Choo , Gargi Roy , Si Mo Yeon , Kyunsuk Choi , Won-Seok Ko , Jeoung Han Kim
This study investigates the phase transformation mechanisms and mechanical behavior of additively manufactured SKD61/17-4 PH graded structure, targeting high-temperature tooling and die applications where thermal stability and strength retention are critical. Using laser powder bed fusion (LPBF), graded structures were fabricated under high- and low-heat-input (HHI and LHI) conditions to examine the effect of processing on solidification and post-annealing response. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and first-principles diffusion analyses revealed that LHI processing promotes δ-ferrite retention through rapid cooling, while HHI favors full austenitization and martensitic transformation. Non-equilibrium solidification induces Ni-C partitioning and Cr solute trapping in austenite, which drive recrystallization and partitioning-assisted γ reversion during annealing at 480 °C. Ni-C enrichment at prior austenite grain boundaries enhances γ nucleation and stress relaxation, whereas Cr-rich δ-ferrite regions foster carbide formation and sensitization upon prolonged exposure. These mechanisms dictate the strength–ductility balance: HHI specimens achieved ultimate tensile strength (UTS) ≈ 1110 MPa and yield strength (YS) ≈ 1000 MPa, while LHI specimens reached UTS ≈ 1250 MPa and YS ≈ 1080 MPa with superior ductility. The findings provide design insights for thermally stable graded steels in demanding industrial environments.
{"title":"Sensitization and mechanical response of additively manufactured SKD61/17-4PH functionally graded steel: Influence of process parameters, post-AM treatment, and insight into reversed austenite formation","authors":"Raj Narayan Hajra , Woong Choo , Gargi Roy , Si Mo Yeon , Kyunsuk Choi , Won-Seok Ko , Jeoung Han Kim","doi":"10.1016/j.msea.2026.149796","DOIUrl":"10.1016/j.msea.2026.149796","url":null,"abstract":"<div><div>This study investigates the phase transformation mechanisms and mechanical behavior of additively manufactured SKD61/17-4 PH graded structure, targeting high-temperature tooling and die applications where thermal stability and strength retention are critical. Using laser powder bed fusion (LPBF), graded structures were fabricated under high- and low-heat-input (HHI and LHI) conditions to examine the effect of processing on solidification and post-annealing response. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and first-principles diffusion analyses revealed that LHI processing promotes δ-ferrite retention through rapid cooling, while HHI favors full austenitization and martensitic transformation. Non-equilibrium solidification induces Ni-C partitioning and Cr solute trapping in austenite, which drive recrystallization and partitioning-assisted γ reversion during annealing at 480 °C. Ni-C enrichment at prior austenite grain boundaries enhances γ nucleation and stress relaxation, whereas Cr-rich δ-ferrite regions foster carbide formation and sensitization upon prolonged exposure. These mechanisms dictate the strength–ductility balance: HHI specimens achieved ultimate tensile strength (UTS) ≈ 1110 MPa and yield strength (YS) ≈ 1000 MPa, while LHI specimens reached UTS ≈ 1250 MPa and YS ≈ 1080 MPa with superior ductility. The findings provide design insights for thermally stable graded steels in demanding industrial environments.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"954 ","pages":"Article 149796"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075510","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}
The microstructural deterioration and hydrogen embrittlement (HE) susceptibility of a Ni-based single crystalline superalloy, which has been subject to long-term thermal exposure (LTE) at 1100 °C (for up to 1000 h), has here been investigated. An LTE-induced microstructural evolution was revealed, including coarsening and rafting of the primary γ′ phase, formation of a dislocation network, and precipitation of the secondary γ′ phase and σ phase. The HE index initially decreased, which was primarily due to hydrogen trapping by new traps. However, it was partially recovered after a prolonged LTE as the σ phase coarsening promoted interfacial H accumulation and decohesion. The H atoms were preferentially trapped in the γ matrix, at the γ/γ′ interface, and in the σ phase. These trapped atoms enhanced the localized plasticity via stacking fault formation in non-aged alloys, while promoting <100> super-dislocations in the LTE samples. The HE mechanism in the superalloys, with and without an LTE treatment, was also elucidated. In addition, the effect of elemental segregation at the γ/γ′ interface on the H-induced damage was also analyzed using first-principles calculations.
{"title":"Effect of microstructural degradation on the hydrogen embrittlement susceptibility and mechanism of a Ni-based single crystalline superalloy","authors":"Guangxian Lu , Zhixun Wen , Tingting Zhao , Yunsong Zhao , Zhufeng Yue","doi":"10.1016/j.msea.2026.149759","DOIUrl":"10.1016/j.msea.2026.149759","url":null,"abstract":"<div><div>The microstructural deterioration and hydrogen embrittlement (HE) susceptibility of a Ni-based single crystalline superalloy, which has been subject to long-term thermal exposure (LTE) at 1100 °C (for up to 1000 h), has here been investigated. An LTE-induced microstructural evolution was revealed, including coarsening and rafting of the primary γ′ phase, formation of a dislocation network, and precipitation of the secondary γ′ phase and σ phase. The HE index initially decreased, which was primarily due to hydrogen trapping by new traps. However, it was partially recovered after a prolonged LTE as the σ phase coarsening promoted interfacial H accumulation and decohesion. The H atoms were preferentially trapped in the γ matrix, at the γ/γ′ interface, and in the σ phase. These trapped atoms enhanced the localized plasticity via stacking fault formation in non-aged alloys, while promoting <100> super-dislocations in the LTE samples. The HE mechanism in the superalloys, with and without an LTE treatment, was also elucidated. In addition, the effect of elemental segregation at the γ/γ′ interface on the H-induced damage was also analyzed using first-principles calculations.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"954 ","pages":"Article 149759"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075975","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}
Pub Date : 2026-02-01Epub Date: 2026-01-23DOI: 10.1016/j.msea.2026.149804
Halil Yilmaz , Cem Örnek , Beste Payam , Daniel Hallmann
This study demonstrates that hydrogen embrittlement in tungsten is dominated by intergranular brittle fracture arising from hydrogen segregation to grain boundaries, rather than by lattice-based decohesion (HEDE) or localised plasticity (HELP). Through an integrated approach of electrochemical hydrogen charging, mechanical testing, and first-principles calculations, we show that hydrogen insertion into the tungsten lattice is thermodynamically unfavourable, whereas segregation to grain boundaries is exothermic and leads to deep trapping. Each trapped hydrogen atom reduces the grain boundary fracture energy by ∼1 J/m2, and high concentrations lead to spontaneous decohesion. Mean-field elasticity modelling indicates that low levels of hydrogen (up to 55 wppm) increase stiffness, while higher concentrations induce elastic softening and instability. Experimentally, hydrogen-charged samples show premature fracture and intergranular cracking, supporting a grain-boundary-controlled fracture mode. Although hydrogen diffusion is rapid in a defect-free lattice (∼10−10 m2/s), it is strongly suppressed in the presence of microstructural traps (∼10−27 m2/s), indicating that transport is governed by defect networks rather than bulk solubility. These findings establish a clear mechanistic pathway for hydrogen embrittlement in tungsten, highlighting grain boundary engineering as a critical design strategy for hydrogen-resilient nuclear materials.
{"title":"Grain boundary decohesion as the mechanistic origin of hydrogen embrittlement in tungsten explored through an experimental–computational framework","authors":"Halil Yilmaz , Cem Örnek , Beste Payam , Daniel Hallmann","doi":"10.1016/j.msea.2026.149804","DOIUrl":"10.1016/j.msea.2026.149804","url":null,"abstract":"<div><div>This study demonstrates that hydrogen embrittlement in tungsten is dominated by intergranular brittle fracture arising from hydrogen segregation to grain boundaries, rather than by lattice-based decohesion (HEDE) or localised plasticity (HELP). Through an integrated approach of electrochemical hydrogen charging, mechanical testing, and first-principles calculations, we show that hydrogen insertion into the tungsten lattice is thermodynamically unfavourable, whereas segregation to grain boundaries is exothermic and leads to deep trapping. Each trapped hydrogen atom reduces the grain boundary fracture energy by ∼1 J/m<sup>2</sup>, and high concentrations lead to spontaneous decohesion. Mean-field elasticity modelling indicates that low levels of hydrogen (up to 55 wppm) increase stiffness, while higher concentrations induce elastic softening and instability. Experimentally, hydrogen-charged samples show premature fracture and intergranular cracking, supporting a grain-boundary-controlled fracture mode. Although hydrogen diffusion is rapid in a defect-free lattice (∼10<sup>−10</sup> m<sup>2</sup>/s), it is strongly suppressed in the presence of microstructural traps (∼10<sup>−27</sup> m<sup>2</sup>/s), indicating that transport is governed by defect networks rather than bulk solubility. These findings establish a clear mechanistic pathway for hydrogen embrittlement in tungsten, highlighting grain boundary engineering as a critical design strategy for hydrogen-resilient nuclear materials.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"954 ","pages":"Article 149804"},"PeriodicalIF":7.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075977","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}
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