Pub Date : 2026-03-01Epub Date: 2026-01-02DOI: 10.1016/j.mtla.2026.102650
Muhammad Akmal, Jenniffer Bustillos, Mahya Azizi, Atieh Moridi
Additive manufacturing (AM) can enable novel alloy design by merging multiple commercial alloys into a single build, a concept we term alloy amalgamation. Here, we demonstrate how directed energy deposition (DED) of Ti-5553 and Ti-6Al-4V in equal proportions produces a chemically and structurally heterogeneous microstructure comprising both arguably hard (α, α′) and ductile (metastable β, α″) phases, all derived from the high-temperature β phase. Regions associated with metastable β and α″ underwent transformation and twinning under stress, respectively, consequently showing enhanced strain hardening. Phase analysis of samples under tensile testing revealed martensite and nano-domain (O’ and O’’) formation in β regions, followed by twinning and slip in harder phases at higher stresses. These cooperative mechanisms yielded a synergistic strength–ductility balance, with ultimate tensile strength comparable to Ti-6Al-4V and elongation approaching Ti-5553. Such exclusive trait combinations arose from localized compositional gradients and multiphase stabilization enabled by AM
{"title":"Alloy amalgamation via additive manufacturing for phase and deformation engineering in titanium alloys","authors":"Muhammad Akmal, Jenniffer Bustillos, Mahya Azizi, Atieh Moridi","doi":"10.1016/j.mtla.2026.102650","DOIUrl":"10.1016/j.mtla.2026.102650","url":null,"abstract":"<div><div>Additive manufacturing (AM) can enable novel alloy design by merging multiple commercial alloys into a single build, a concept we term alloy amalgamation. Here, we demonstrate how directed energy deposition (DED) of Ti-5553 and Ti-6Al-4V in equal proportions produces a chemically and structurally heterogeneous microstructure comprising both arguably hard (α, α′) and ductile (metastable β, α″) phases, all derived from the high-temperature β phase. Regions associated with metastable β and α″ underwent transformation and twinning under stress, respectively, consequently showing enhanced strain hardening. Phase analysis of samples under tensile testing revealed martensite and nano-domain (O’ and O’’) formation in β regions, followed by twinning and slip in harder phases at higher stresses. These cooperative mechanisms yielded a synergistic strength–ductility balance, with ultimate tensile strength comparable to Ti-6Al-4V and elongation approaching Ti-5553. Such exclusive trait combinations arose from localized compositional gradients and multiphase stabilization enabled by AM</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102650"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145939104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-01-22DOI: 10.1016/j.mtla.2026.102672
Sujit K Nayak, Jugal K Banikya, Devesh K Chouhan, Somjeet Biswas
This work investigates the heterogeneous bending behavior of hot-rolled -Titanium (Ti) after plane-strain bending at ambient temperature via microstructure and texture evolution. The through-thickness deformation heterogeneity in the bend portion could be microstructurally distinguished into three regions: the inner compressive region (ICR), the undeformed neutral region (NR), and the outer tensile region (OTR). The bend thickness of -Ti sheets increased, and the NR shifts towards the OTR (instead of ICR, which usually occurs in the case of Steel, Al, and Cu). This phenomenon could be attributed to the hot-rolled split basal texture normal to the rolling direction (RD). For this texture, -Ti is geometrically hard in tension with higher yield strength (∼275 MPa), lower ductility (∼0.25) and strain hardening exponent (, ∼0.15) than compression (∼240 MPa, ∼0.69, and ∼0.3) along the rolling direction. Thus, larger plasticity was possible in ICR, accompanied with extension twins (ET) evolution. Lesser deformation occurred in OTR with the formation of a few contraction twins (CT). The ETs that developed in ICR followed Schmid's law, while the CTs in OTR didn't. After the springback, compressive residual stresses in both ICR and OTR resulted from balancing the elastic bending moment during unbending.
{"title":"Heterogeneous bending behavior of hot-rolled α-Titanium sheet via microstructure and texture evolution","authors":"Sujit K Nayak, Jugal K Banikya, Devesh K Chouhan, Somjeet Biswas","doi":"10.1016/j.mtla.2026.102672","DOIUrl":"10.1016/j.mtla.2026.102672","url":null,"abstract":"<div><div>This work investigates the heterogeneous bending behavior of hot-rolled <span><math><mi>α</mi></math></span>-Titanium (Ti) after <span><math><mrow><mo>∼</mo><msup><mrow><mn>90</mn></mrow><mo>∘</mo></msup></mrow></math></span> plane-strain bending at ambient temperature via microstructure and texture evolution. The through-thickness deformation heterogeneity in the bend portion could be microstructurally distinguished into three regions: the inner compressive region (ICR), the undeformed neutral region (NR), and the outer tensile region (OTR). The bend thickness of <span><math><mi>α</mi></math></span>-Ti sheets increased, and the NR shifts towards the OTR (instead of ICR, which usually occurs in the case of Steel, Al, and Cu). This phenomenon could be attributed to the hot-rolled split basal texture normal to the rolling direction (RD). For this texture, <span><math><mi>α</mi></math></span>-Ti is geometrically hard in tension with higher yield strength (∼275 MPa), lower ductility (∼0.25) and strain hardening exponent (<span><math><mi>n</mi></math></span>, ∼0.15) than compression (∼240 MPa, ∼0.69, and ∼0.3) along the rolling direction. Thus, larger plasticity was possible in ICR, accompanied with <span><math><mrow><mrow><mo>{</mo><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow><mrow><mo>〈</mo><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn></mrow><mo>〉</mo></mrow></mrow></math></span> extension twins (ET) evolution. Lesser deformation occurred in OTR with the formation of a few <span><math><mrow><mrow><mo>{</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn></mrow><mo>}</mo></mrow><mrow><mo>〈</mo><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mover><mn>3</mn><mo>¯</mo></mover></mrow><mo>〉</mo></mrow></mrow></math></span> contraction twins (CT). The ETs that developed in ICR followed Schmid's law, while the CTs in OTR didn't. After the springback, compressive residual stresses in both ICR and OTR resulted from balancing the elastic bending moment during unbending.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102672"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-02-06DOI: 10.1016/j.mtla.2026.102678
Prabhu Prasad Biswal , Samuel Graf , Martin Luckabauer , Marlene Eichlseder , Fernando Gustavo Warchomicka , Fabio Blaschke , Harald Fitzek , Tatiana Kormilina , Maximilian Fuchs , Eduardo Machado Charry , Birgit Kunert , Eva-Maria Steyskal , Roland Resel , Karin Zojer
Nanoporous copper (np-Cu) is a cost-effective alternative to nanoporous gold and platinum in heterogeneous catalysis provided that np-Cu has a hierarchical pore structure that interconnect small pores for high surface area-to-volume ratio with large pores for efficient mass transport. Dealloying binary Al–Cu alloys is a promising route to provide np-Cu. Using two differently produced precursor alloys of similar composition, it was investigated whether hierarchical np-Cu can be produced with a similar electrochemical dealloying process. The alloys were either cast (Al-46 wt%-Cu) or in-situ alloyed from a 50:50 (wt%) mixture of aluminum and copper powders using laser powder bed fusion. Both alloys consist of 2 and AlCu domains that exhibit distinct, alloy-specific morphologies. Regardless of the precursor alloy, the resulting np-Cu contains less than 0.1% residual Al and is hierarchical with pore sizes in three different diameter ranges, 4-, 40-200 nm, and 2-10 nm. The latter pores are more abundant in np-Cu from the cast alloy. Micro-computed X-ray tomography and scanning electron microscopy reveal domains of different Cu densities being reminiscent in size and shape of the domains in the precursor alloys. Thus, tailoring the phase composition of intermetallic precursor alloys enables simultaneous control of pore sizes between 0.1 and for mass transport and of the local density of np-Cu.
{"title":"Microstructure of hierarchical nanoporous copper from electrochemical dealloying of additively manufactured and cast Al–Cu intermetallics","authors":"Prabhu Prasad Biswal , Samuel Graf , Martin Luckabauer , Marlene Eichlseder , Fernando Gustavo Warchomicka , Fabio Blaschke , Harald Fitzek , Tatiana Kormilina , Maximilian Fuchs , Eduardo Machado Charry , Birgit Kunert , Eva-Maria Steyskal , Roland Resel , Karin Zojer","doi":"10.1016/j.mtla.2026.102678","DOIUrl":"10.1016/j.mtla.2026.102678","url":null,"abstract":"<div><div>Nanoporous copper (np-Cu) is a cost-effective alternative to nanoporous gold and platinum in heterogeneous catalysis provided that np-Cu has a hierarchical pore structure that interconnect small pores for high surface area-to-volume ratio with large pores for efficient mass transport. Dealloying binary Al–Cu alloys is a promising route to provide np-Cu. Using two differently produced precursor alloys of similar composition, it was investigated whether hierarchical np-Cu can be produced with a similar electrochemical dealloying process. The alloys were either cast (Al-46 wt%-Cu) or in-situ alloyed from a 50:50 (wt%) mixture of aluminum and copper powders using laser powder bed fusion. Both alloys consist of <span><math><mi>Al</mi></math></span> <sub>2</sub> <span><math><mi>Cu</mi></math></span> and AlCu domains that exhibit distinct, alloy-specific morphologies. Regardless of the precursor alloy, the resulting np-Cu contains less than 0.1% residual Al and is hierarchical with pore sizes in three different diameter ranges, 4-<span><math><mrow><mn>100</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span>, 40-200 nm, and 2-10 nm. The latter pores are more abundant in np-Cu from the cast alloy. Micro-computed X-ray tomography and scanning electron microscopy reveal domains of different Cu densities being reminiscent in size and shape of the domains in the precursor alloys. Thus, tailoring the phase composition of intermetallic precursor alloys enables simultaneous control of pore sizes between 0.1 and <span><math><mrow><mn>100</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> for mass transport and of the local density of np-Cu.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102678"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146187838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-11-24DOI: 10.1016/j.mtla.2025.102616
Zhao-Sheng Wu, Kai-Chieh Chang, Fei-Yi Hung
This study investigates 17–6 stainless steel processed by Laser Powder Bed Fusion (LPBF), focusing on the microstructure and mechanical properties following direct aging heat treatment. The applicability of horizontal (X) and vertical (Z) build directions was evaluated. Experimental results revealed that the as-printed lath martensitic structure was retained after direct aging, with precipitation hardening contributing to improved tensile properties. The horizontally printed specimens exhibited fewer melting pool defects, which prevent mechanical degradation. Consequently, subsequent analyses focused on the superior-performing horizontal builds. Electron backscatter diffraction (EBSD) phase composition and local strain distribution analyses revealed high body-centered cubic (BCC) phase fractions (∼ 98 %) and sustained ductility due to dislocation recovery. Thermal cycling tests further demonstrated that the mechanical properties and phase composition of the post-cycled material were maintained, suggesting excellent potential for high-temperature and high-strength applications. For strength-critical applications, an aging condition of 495 °C for 3.0 h leads to an ultimate tensile strength (UTS) of 1413 MPa and an elongation (EL) of 19.1 %. For applications requiring improved toughness, direct aging at 560 °C for 3.0 hours results in a toughness of 51 J with an EL of 20.9 %. Unlike commercial 17–4 and 17–7 stainless steels, 17–6 stainless steel does not require solution treatment to reduce the retained austenite. Direct aging enables the use of thin-walled components, minimizing deformation while providing substantial strengthening and achieving energy savings.
{"title":"Direct aging hardening and deformation resistant of additively manufactured 17-6 precipitation-hardened stainless steel: Microstructural evolution and precipitation mechanism","authors":"Zhao-Sheng Wu, Kai-Chieh Chang, Fei-Yi Hung","doi":"10.1016/j.mtla.2025.102616","DOIUrl":"10.1016/j.mtla.2025.102616","url":null,"abstract":"<div><div>This study investigates 17–6 stainless steel processed by Laser Powder Bed Fusion (LPBF), focusing on the microstructure and mechanical properties following direct aging heat treatment. The applicability of horizontal (X) and vertical (Z) build directions was evaluated. Experimental results revealed that the as-printed lath martensitic structure was retained after direct aging, with precipitation hardening contributing to improved tensile properties. The horizontally printed specimens exhibited fewer melting pool defects, which prevent mechanical degradation. Consequently, subsequent analyses focused on the superior-performing horizontal builds. Electron backscatter diffraction (EBSD) phase composition and local strain distribution analyses revealed high body-centered cubic (BCC) phase fractions (∼ 98 %) and sustained ductility due to dislocation recovery. Thermal cycling tests further demonstrated that the mechanical properties and phase composition of the post-cycled material were maintained, suggesting excellent potential for high-temperature and high-strength applications. For strength-critical applications, an aging condition of 495 °C for 3.0 h leads to an ultimate tensile strength (UTS) of 1413 MPa and an elongation (EL) of 19.1 %. For applications requiring improved toughness, direct aging at 560 °C for 3.0 hours results in a toughness of 51 J with an EL of 20.9 %. Unlike commercial 17–4 and 17–7 stainless steels, 17–6 stainless steel does not require solution treatment to reduce the retained austenite. Direct aging enables the use of thin-walled components, minimizing deformation while providing substantial strengthening and achieving energy savings.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102616"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145698133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-08DOI: 10.1016/j.mtla.2025.102627
Subhas Bhunia , Poornachandra Satyampet , M.P. Gururajan , Shubo Wang , Harishchandra Singh , Al Rahemtulla , Prita Pant
In this study, we examine the effect of two different initial microstructures of a medium manganese steel on the kinetics of austenite reversion and elemental partitioning during intercritical annealing, using in-situ synchrotron and ex-situ scanning transmission electron microscopy (STEM)/atom probe tomography (APT) based elemental mapping. These microstructures are tempered-cold-rolled (TCR) and hot-rolled-quenched (HRQ) martensite. The HRQ specimen exhibits faster kinetics of austenite reversion and higher austenite volume fraction than the TCR specimen during intercritical annealing. However, after cooling to room temperature, HRQ specimen had less retained austenite than the TCR specimen. To identify the reasons behind different austenite stability, detailed analysis of elemental partitioning was carried out using synchrotron data for lattice parameters, as well as elemental mapping using STEM and APT. For the HRQ specimen, austenite growth during the first 20 min. occurs by carbon (C) partitioning, with increased manganese (Mn) concentration near the austenite–ferrite interface. In contrast, for the TCR specimen, growth of austenite is accompanied by C and Mn partitioning from the initial stage itself. These observations confirm that for the first 20 min. austenite growth occurs by the negligible partitioning local equilibrium (NPLE) mechanism for HRQ, and subsequently changes to partitioning local equilibrium (PLE), while the growth mode is PLE for TCR sample throughout intercritical annealing. Higher C and Mn enrichment leads to greater thermal stability of austenite in the TCR specimen. Hence the TCR sample has greater volume fraction of retained austenite for various annealing durations.
{"title":"An in-situ synchrotron study of austenite reversion kinetics and elemental partitioning during intercritical annealing","authors":"Subhas Bhunia , Poornachandra Satyampet , M.P. Gururajan , Shubo Wang , Harishchandra Singh , Al Rahemtulla , Prita Pant","doi":"10.1016/j.mtla.2025.102627","DOIUrl":"10.1016/j.mtla.2025.102627","url":null,"abstract":"<div><div>In this study, we examine the effect of two different initial microstructures of a medium manganese steel on the kinetics of austenite reversion and elemental partitioning during intercritical annealing, using in-situ synchrotron and ex-situ scanning transmission electron microscopy (STEM)/atom probe tomography (APT) based elemental mapping. These microstructures are tempered-cold-rolled (TCR) and hot-rolled-quenched (HRQ) martensite. The HRQ specimen exhibits faster kinetics of austenite reversion and higher austenite volume fraction than the TCR specimen during intercritical annealing. However, after cooling to room temperature, HRQ specimen had less retained austenite than the TCR specimen. To identify the reasons behind different austenite stability, detailed analysis of elemental partitioning was carried out using synchrotron data for lattice parameters, as well as elemental mapping using STEM and APT. For the HRQ specimen, austenite growth during the first 20 min. occurs by carbon (C) partitioning, with increased manganese (Mn) concentration near the austenite–ferrite interface. In contrast, for the TCR specimen, growth of austenite is accompanied by C and Mn partitioning from the initial stage itself. These observations confirm that for the first 20 min. austenite growth occurs by the negligible partitioning local equilibrium (NPLE) mechanism for HRQ, and subsequently changes to partitioning local equilibrium (PLE), while the growth mode is PLE for TCR sample throughout intercritical annealing. Higher C and Mn enrichment leads to greater thermal stability of austenite in the TCR specimen. Hence the TCR sample has greater volume fraction of retained austenite for various annealing durations.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102627"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145749327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-17DOI: 10.1016/j.mtla.2025.102644
Xiaoyu Wu, Wei Li, Ziheng Huang, Weitian Wang
High-entropy perovskite oxides (HEPOs) constitute a novel class of functional materials in which configurational entropy contributes to the stabilization of unique structural and functional properties. This study investigates the effect of sintering temperature (1100∼1250 °C) on the structural evolution, dielectric behavior, and impedance characteristics of a newly developed A-site quintuple-cation perovskite ceramic, (Bi0.2La0.2Ba0.2Sr0.2Ca0.2)TiO3. X-ray diffraction analysis confirms the formation of a phase-pure tetragonal structure at temperatures exceeding 1200 °C. Microstructural analysis demonstrates temperature-dependent grain growth kinetics: a rapid increase in grain size below 1200 °C (from 0.53 to 1.39 μm) is followed by entropy-suppressed coarsening, resulting in a maximum grain size of 1.50 μm at 1250 °C. This phenomenon is attributed to lattice strain induced by A-site cationic disorder. X-ray photoelectron spectroscopy verifies the presence of multivalent Ti3+/Ti4+ oxidation states and a significant concentration of oxygen vacancies, which form defect dipoles that influence polarization mechanisms. Dielectric spectroscopy reveals exceptional frequency stability within the 104–106 Hz range, with a maximum relative permittivity (ε′) of 3.05 × 105 and a low dielectric loss (tanδ) of 0.05 observed for the sample sintered at 1250 °C. Impedance spectroscopy confirms thermally activated conduction, with reduced resistance and enhanced carrier mobility at higher sintering temperatures, attributed to decreased grain boundary density and optimized defect chemistry. These findings highlight sintering temperature as a key parameter for entropy-mediated property optimization in HEPOs systems, thereby establishing (Bi0.2La0.2Ba0.2Sr0.2Ca0.2)TiO3 as a favorable combination of dielectric properties worthy of further investigation for potential use in high-stability capacitive applications.
{"title":"Effect of sintering temperature on the dielectric and impedance properties of high-entropy perovskite oxides (Bi0.2La0.2Ba0.2Sr0.2Ca0.2)TiO3","authors":"Xiaoyu Wu, Wei Li, Ziheng Huang, Weitian Wang","doi":"10.1016/j.mtla.2025.102644","DOIUrl":"10.1016/j.mtla.2025.102644","url":null,"abstract":"<div><div>High-entropy perovskite oxides (HEPOs) constitute a novel class of functional materials in which configurational entropy contributes to the stabilization of unique structural and functional properties. This study investigates the effect of sintering temperature (1100∼1250 °C) on the structural evolution, dielectric behavior, and impedance characteristics of a newly developed A-site quintuple-cation perovskite ceramic, (Bi<sub>0.2</sub>La<sub>0.2</sub>Ba<sub>0.2</sub>Sr<sub>0.2</sub>Ca<sub>0.2</sub>)TiO<sub>3</sub>. X-ray diffraction analysis confirms the formation of a phase-pure tetragonal structure at temperatures exceeding 1200 °C. Microstructural analysis demonstrates temperature-dependent grain growth kinetics: a rapid increase in grain size below 1200 °C (from 0.53 to 1.39 μm) is followed by entropy-suppressed coarsening, resulting in a maximum grain size of 1.50 μm at 1250 °C. This phenomenon is attributed to lattice strain induced by A-site cationic disorder. X-ray photoelectron spectroscopy verifies the presence of multivalent Ti<sup>3+</sup>/Ti<sup>4+</sup> oxidation states and a significant concentration of oxygen vacancies, which form defect dipoles that influence polarization mechanisms. Dielectric spectroscopy reveals exceptional frequency stability within the 10<sup>4</sup>–10<sup>6</sup> Hz range, with a maximum relative permittivity (<em>ε</em>′) of 3.05 × 10<sup>5</sup> and a low dielectric loss (tanδ) of 0.05 observed for the sample sintered at 1250 °C. Impedance spectroscopy confirms thermally activated conduction, with reduced resistance and enhanced carrier mobility at higher sintering temperatures, attributed to decreased grain boundary density and optimized defect chemistry. These findings highlight sintering temperature as a key parameter for entropy-mediated property optimization in HEPOs systems, thereby establishing (Bi<sub>0.2</sub>La<sub>0.2</sub>Ba<sub>0.2</sub>Sr<sub>0.2</sub>Ca<sub>0.2</sub>)TiO<sub>3</sub> as a favorable combination of dielectric properties worthy of further investigation for potential use in high-stability capacitive applications.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102644"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145841446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-02-02DOI: 10.1016/j.mtla.2026.102679
Bibo Yao , Jiajin Yu , Jingxuan Ge , Zhenhua Li , Meihong Liu , Zhanliang Liu , Dingbang Wang , Xiaoyan Yang
Powder reuse is critical in selective laser melting (SLM), but changes in powder characteristics after reuse may affect forming quality. In this study, the changes in Ti-6Al-4V powder characteristics after reuse were investigated, and the printing parameters were optimized based on a reuse strategy involving blending of reused and virgin powders at a fixed ratio. The forming quality, microstructural features, and mechanical properties of reused-powder samples fabricated under different combinations of laser power and scanning speed were systematically examined. Results show that reused powder exhibits reduced sphericity, a narrower particle size distribution, and increased oxygen content. These changes render the original processing parameters unsuitable, leading to a decrease in relative density from 99.28 % to 98.43 %, accompanied by increased strength and reduced elongation. Increasing the energy density (EV) to 62.5 J/mm³ helps mitigate the adverse effects of reused powder, restoring the relative density to 99.07 %. Under this EV, different parameter combinations result in distinct thermal histories and forming quality. Specifically, at a laser power of 170 W and a scanning speed of 1133 mm/s, reused-powder Ti-6Al-4V samples exhibit the optimal forming quality and mechanical performance, with a tensile strength of 1298.25 MPa and an elongation of 8.01 %, along a microstructure characterized by refined α′ martensite.
{"title":"Effect of powder reuse on forming characteristics and mechanical properties of SLM formed Ti-6Al-4V","authors":"Bibo Yao , Jiajin Yu , Jingxuan Ge , Zhenhua Li , Meihong Liu , Zhanliang Liu , Dingbang Wang , Xiaoyan Yang","doi":"10.1016/j.mtla.2026.102679","DOIUrl":"10.1016/j.mtla.2026.102679","url":null,"abstract":"<div><div>Powder reuse is critical in selective laser melting (SLM), but changes in powder characteristics after reuse may affect forming quality. In this study, the changes in Ti-6Al-4V powder characteristics after reuse were investigated, and the printing parameters were optimized based on a reuse strategy involving blending of reused and virgin powders at a fixed ratio. The forming quality, microstructural features, and mechanical properties of reused-powder samples fabricated under different combinations of laser power and scanning speed were systematically examined. Results show that reused powder exhibits reduced sphericity, a narrower particle size distribution, and increased oxygen content. These changes render the original processing parameters unsuitable, leading to a decrease in relative density from 99.28 % to 98.43 %, accompanied by increased strength and reduced elongation. Increasing the energy density (<em>E<sub>V</sub></em>) to 62.5 J/mm³ helps mitigate the adverse effects of reused powder, restoring the relative density to 99.07 %. Under this <em>E<sub>V</sub></em>, different parameter combinations result in distinct thermal histories and forming quality. Specifically, at a laser power of 170 W and a scanning speed of 1133 mm/s, reused-powder Ti-6Al-4V samples exhibit the optimal forming quality and mechanical performance, with a tensile strength of 1298.25 MPa and an elongation of 8.01 %, along a microstructure characterized by refined α′ martensite.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102679"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146187832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-06DOI: 10.1016/j.mtla.2025.102625
Jingwen Li , Cai Chen , Qiankun Tan , Xiaoxiao Ma , Jinglian Du , Jianwei Xiao , Zhonghua Du , Chuang Deng
Body-centered cubic (BCC) tungsten (W) exhibits a striking transition in deformation mechanisms under impact loading, yet the underlying criteria governing the competition between dislocation slip and twinning remain unresolved. Here, we combine molecular dynamics (MD) simulations and density functional theory (DFT) calculations to establish a stress-dependent framework for this mechanistic crossover. At low impact velocities (250–500 m/s), plasticity is mediated by dislocation activity, while twinning emerges as the plastic mechanism at velocities above 500 m/s. At 500 m/s impact velocity, twinning nucleation occurs via heterogeneous (dislocation-mediated) mechanisms, while at 2000 m/s, homogeneous nucleation becomes active through local phase transition mediation. DFT and MD reveal that compressive stress stabilizes metastable two-layer near-isosceles twin boundaries (near-isoTBs), reducing the energy barrier for twinning nucleation by altering the generalized stacking fault enthalpy (GSFH) profile. Stress-driven disconnection dissociation further governs twin growth kinetics. These findings quantitatively link intrinsic material properties (GSFH) and extrinsic loading conditions (stress states) to deformation pathways, providing design principles for BCC metals in high-strain-rate applications such as penetrators and impact-resistant structures.
{"title":"Impact-loading-driven dislocation-to-twinning transition in BCC tungsten: A generalized stacking fault enthalpy criterion","authors":"Jingwen Li , Cai Chen , Qiankun Tan , Xiaoxiao Ma , Jinglian Du , Jianwei Xiao , Zhonghua Du , Chuang Deng","doi":"10.1016/j.mtla.2025.102625","DOIUrl":"10.1016/j.mtla.2025.102625","url":null,"abstract":"<div><div>Body-centered cubic (BCC) tungsten (W) exhibits a striking transition in deformation mechanisms under impact loading, yet the underlying criteria governing the competition between dislocation slip and twinning remain unresolved. Here, we combine molecular dynamics (MD) simulations and density functional theory (DFT) calculations to establish a stress-dependent framework for this mechanistic crossover. At low impact velocities (250–500 m/s), plasticity is mediated by dislocation activity, while twinning emerges as the plastic mechanism at velocities above 500 m/s. At 500 m/s impact velocity, twinning nucleation occurs via heterogeneous (dislocation-mediated) mechanisms, while at 2000 m/s, homogeneous nucleation becomes active through local phase transition mediation. DFT and MD reveal that compressive stress stabilizes metastable two-layer near-isosceles twin boundaries (near-isoTBs), reducing the energy barrier for twinning nucleation by altering the generalized stacking fault enthalpy (GSFH) profile. Stress-driven disconnection dissociation further governs twin growth kinetics. These findings quantitatively link intrinsic material properties (GSFH) and extrinsic loading conditions (stress states) to deformation pathways, providing design principles for BCC metals in high-strain-rate applications such as penetrators and impact-resistant structures.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102625"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145749328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-01-14DOI: 10.1016/j.mtla.2026.102664
Gabriel Peinado , Daniela P.M. Fonseca , Naga V.V. Mogili , Carlos Ospina , Antonio J. Ramirez , Carlos A.R.P. Baptista , Julian Avila
Maraging steel with 18 wt.% Ni (Mar18Ni) has attracted growing interest for additive manufacturing (AM), particularly through powder bed fusion with a laser beam (PBF-LB), owing to its high strength and heat-treatability. However, the microstructural characteristics introduced by PBF-LB can significantly influence phase transformation pathways during post-processing. While conventionally processed maraging steels have been extensively studied, the precipitation behavior and austenite reversion kinetics in AM-produced Mar18Ni steel remain insufficiently understood. This study investigates the phase transformations in PBF-LB Mar18Ni steel using in-situ transmission electron microscopy (TEM). Samples were subjected to isothermal aging at 480 °C and austenite reversion heat treatments at 650 and 670 °C. The evolution of intermetallic precipitates and the nucleation and morphological development of austenite were systematically characterized. The first precipitation sequence involved Fe2(Mo,Ti) and Ni3Mo after ∼1 h at 480 °C, followed by Ni3Ti formation after a crystallographic rearrangement between martensite and austenite. Unlike the conventionally processed alloy, Ni3Mo forms prior to Ni3Ti in this PBF-LB steel. During aging, precipitation initially competes with austenite reversion as Fe, Ni, and Ti are consumed from the matrix, reducing austenite stability. With prolonged exposure, however, austenite persists and coarsens. At 650 °C, twinning-mediated reversion begins after ∼12 min, whereas at 670 °C, reversion proceeds entirely via the Kurdjumov-Sachs orientation relationship. Al-Ti-rich nano-oxides act as preferential heterogeneous nucleation sites for austenite, promoting reversion but limiting further precipitation. Overall, the results reveal a thermokinetic balance between precipitation and reversion in PBF-LB Mar18Ni steel, providing mechanistic insight into its microstructural evolution.
{"title":"In-situ observation of precipitation and austenite reversion in additively manufactured 18 wt. % Ni maraging steel","authors":"Gabriel Peinado , Daniela P.M. Fonseca , Naga V.V. Mogili , Carlos Ospina , Antonio J. Ramirez , Carlos A.R.P. Baptista , Julian Avila","doi":"10.1016/j.mtla.2026.102664","DOIUrl":"10.1016/j.mtla.2026.102664","url":null,"abstract":"<div><div>Maraging steel with 18 wt.% Ni (Mar18Ni) has attracted growing interest for additive manufacturing (AM), particularly through powder bed fusion with a laser beam (PBF-LB), owing to its high strength and heat-treatability. However, the microstructural characteristics introduced by PBF-LB can significantly influence phase transformation pathways during post-processing. While conventionally processed maraging steels have been extensively studied, the precipitation behavior and austenite reversion kinetics in AM-produced Mar18Ni steel remain insufficiently understood. This study investigates the phase transformations in PBF-LB Mar18Ni steel using in-situ transmission electron microscopy (TEM). Samples were subjected to isothermal aging at 480 °C and austenite reversion heat treatments at 650 and 670 °C. The evolution of intermetallic precipitates and the nucleation and morphological development of austenite were systematically characterized. The first precipitation sequence involved Fe<sub>2</sub>(Mo,Ti) and Ni<sub>3</sub>Mo after ∼1 h at 480 °C, followed by Ni<sub>3</sub>Ti formation after a crystallographic rearrangement between martensite and austenite. Unlike the conventionally processed alloy, Ni<sub>3</sub>Mo forms prior to Ni<sub>3</sub>Ti in this PBF-LB steel. During aging, precipitation initially competes with austenite reversion as Fe, Ni, and Ti are consumed from the matrix, reducing austenite stability. With prolonged exposure, however, austenite persists and coarsens. At 650 °C, twinning-mediated reversion begins after ∼12 min, whereas at 670 °C, reversion proceeds entirely via the Kurdjumov-Sachs orientation relationship. Al-Ti-rich nano-oxides act as preferential heterogeneous nucleation sites for austenite, promoting reversion but limiting further precipitation. Overall, the results reveal a thermokinetic balance between precipitation and reversion in PBF-LB Mar18Ni steel, providing mechanistic insight into its microstructural evolution.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102664"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146037649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-18DOI: 10.1016/j.mtla.2025.102645
Galina G. Maier, Elena G. Astafurova
We study phase transformations and recrystallization during the high-temperature annealing (500 °C – 800 °C) of three nanostructured austenitic TWIP steels with a high fraction of twinning boundaries. Before annealing, model twin-assisted microstructures were created in the single-crystalline Fe-13Mn-1.3C (Hadfield steel), Fe-13Mn-2.7Al-1.3C, Fe-28Mn-2.7Al-1.3C steels by high-pressure torsion. The highest density of twin boundaries and scalar dislocation density was generated in Fe-13Mn-1.3C (ρtw = 25 × 1013 m-2) and the lowest one in Fe-28Mn-2.7Al-1.3C steel (ρtw = 8 × 1013 m-2). HPT-induced high defect density promotes primary recrystallization in the steels, starting at 500 °C in specimens of Hadfield steel, while twin-assisted nanostructures remain unaffected in two other steels with lower densities of twin boundaries and dislocations. Deformation defects act as primary sites for austenite decomposition γC→α(α′)+M3C or γC→γ+α(α′)+M3C during post-deformation annealing, providing formation of a nanocrystalline heterophase structure (γ+α(α′)+M3C). A direct comparison of two Al-alloyed steels with similar twinning and dislocation densities reveals that the decomposition of austenite in the HPT-deformed microstructure depends on steel composition rather than twin boundaries: it starts at lower annealing temperatures and is more complete in Fe-13Mn-2.7Al-1.3C steel compared to Fe-28Mn-2.7Al-1.3C one. No special role of deformation twins in the migration of grain boundaries or interphase boundaries during annealing at temperatures above 500 °C has been revealed.
{"title":"High-temperature recrystallization behavior and phase transformations in austenitic Fe-Mn-(Al)-C TWIP steels pre-deformed by high-pressure torsion","authors":"Galina G. Maier, Elena G. Astafurova","doi":"10.1016/j.mtla.2025.102645","DOIUrl":"10.1016/j.mtla.2025.102645","url":null,"abstract":"<div><div>We study phase transformations and recrystallization during the high-temperature annealing (500 °C – 800 °C) of three nanostructured austenitic TWIP steels with a high fraction of twinning boundaries. Before annealing, model twin-assisted microstructures were created in the single-crystalline Fe-13Mn-1.3C (Hadfield steel), Fe-13Mn-2.7Al-1.3C, Fe-28Mn-2.7Al-1.3C steels by high-pressure torsion. The highest density of twin boundaries and scalar dislocation density was generated in Fe-13Mn-1.3C (<em>ρ<sub>tw</sub></em> = 25 × 10<sup>13</sup> m<sup>-2</sup>) and the lowest one in Fe-28Mn-2.7Al-1.3C steel (<em>ρ<sub>tw</sub></em> = 8 × 10<sup>13</sup> m<sup>-2</sup>). HPT-induced high defect density promotes primary recrystallization in the steels, starting at 500 °C in specimens of Hadfield steel, while twin-assisted nanostructures remain unaffected in two other steels with lower densities of twin boundaries and dislocations. Deformation defects act as primary sites for austenite decomposition γ<sub>C</sub>→α(α′)+M<sub>3</sub>C or γ<sub>C</sub>→γ+α(α′)+M<sub>3</sub>C during post-deformation annealing, providing formation of a nanocrystalline heterophase structure (γ+α(α′)+M<sub>3</sub>C). A direct comparison of two Al-alloyed steels with similar twinning and dislocation densities reveals that the decomposition of austenite in the HPT-deformed microstructure depends on steel composition rather than twin boundaries: it starts at lower annealing temperatures and is more complete in Fe-13Mn-2.7Al-1.3C steel compared to Fe-28Mn-2.7Al-1.3C one. No special role of deformation twins in the migration of grain boundaries or interphase boundaries during annealing at temperatures above 500 °C has been revealed.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"45 ","pages":"Article 102645"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145939105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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