Pub Date : 2025-11-07DOI: 10.1016/j.mtla.2025.102599
E.C. Galliopoulou , S. He , G.T. Martinez , H. Shang , C. Jones , M. Zimina , J. Siefert , J.D. Parker , G.M. Hughes , A. Cocks , T.L. Martin
Creep cavity formation in Grade 91 steel components is a serious challenge that energy applications face, as cavities grow, coalesce, form propagating cracks and eventually lead to failure. This study investigates the microstructural parameters associated with creep cavity nucleation in ex-service martensitic P91 material. Three uniaxial and one double-notched creep tested samples were investigated, interrupted at 0.5 % and 1 % and failed at 3.7 % strain fractions, in order to inspect the evolution of damage in early and late stages of the creep life. A correlative SEM-EBSD technique was employed, revealing that most cavities nucleated along the parent austenite grain boundary (PAGB) structure, with grain boundary junctions exhibiting increased susceptibility to damage. Although PAGBs with misorientation angles of 15–35° and 60° were not the predominant boundary type in the parent microstructure, they exhibited high cavitation ratios. Manganese sulfide (MnS) inclusions were found to be highly prone to cavity nucleation, while smaller precipitates, such as M23C6 carbides, Laves phase and MX-type nitrides, facilitated cavity formation at the MnS/martensite matrix interface. Since the vast majority of grains were soft, no clear correlation between the Schmid Factor and cavitation could be established.
{"title":"Microstructural parameters associated with cavity nucleation in martensitic Grade 91 steel under creep conditions","authors":"E.C. Galliopoulou , S. He , G.T. Martinez , H. Shang , C. Jones , M. Zimina , J. Siefert , J.D. Parker , G.M. Hughes , A. Cocks , T.L. Martin","doi":"10.1016/j.mtla.2025.102599","DOIUrl":"10.1016/j.mtla.2025.102599","url":null,"abstract":"<div><div>Creep cavity formation in Grade 91 steel components is a serious challenge that energy applications face, as cavities grow, coalesce, form propagating cracks and eventually lead to failure. This study investigates the microstructural parameters associated with creep cavity nucleation in ex-service martensitic P91 material. Three uniaxial and one double-notched creep tested samples were investigated, interrupted at 0.5 % and 1 % and failed at 3.7 % strain fractions, in order to inspect the evolution of damage in early and late stages of the creep life. A correlative SEM-EBSD technique was employed, revealing that most cavities nucleated along the parent austenite grain boundary (PAGB) structure, with grain boundary junctions exhibiting increased susceptibility to damage. Although PAGBs with misorientation angles of 15–35° and 60° were not the predominant boundary type in the parent microstructure, they exhibited high cavitation ratios. Manganese sulfide (MnS) inclusions were found to be highly prone to cavity nucleation, while smaller precipitates, such as M<sub>23</sub>C<sub>6</sub> carbides, Laves phase and MX-type nitrides, facilitated cavity formation at the MnS/martensite matrix interface. Since the vast majority of grains were soft, no clear correlation between the Schmid Factor and cavitation could be established.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102599"},"PeriodicalIF":2.9,"publicationDate":"2025-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145525453","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 : 2025-11-07DOI: 10.1016/j.mtla.2025.102602
Chen Cai , Gabriel Spartacus , Amlan Das , Katherine S. Shanks , Wangzhong Mu , Peter Hedström
The parent austenite grain size (PAGS) plays a critical role in governing the austenite to martensite transformation in steels, as it directly influences the stability of the austenite phase. Therefore, a thorough understanding of the PAGS effect is essential for the design of advanced steels with optimized performance. In this study, we investigate the influence of PAGS on both athermal and deformation-induced martensitic transformation (AMT and DIMT) in an Fe-18Cr-12Ni (wt.%) alloy. In situ and ex situ high-energy synchrotron X-ray diffraction (HEXRD) measurements were conducted during tensile loading and after cooling, respectively. These measurements were complemented by electron microscopy to elucidate the underlying mechanisms governing the PAGS effect on martensitic transformation. The results reveal PAGS exerts opposite effects on AMT and DIMT. Grain refinement increases the barrier for martensitic transformation onset, and in the case of AMT, this leads to a lower martensite start temperature (Ms) and suppressed transformation. Conversely, although grain refinement delays DIMT and raises the critical stress required for its initiation, the associated Hall-Petch strengthening enhances the flow stress, thereby promoting DIMT at higher strain levels. These findings offer valuable insights for the microstructural design of austenitic steels and contribute to the modeling of martensitic transformation behavior under varying mechanical and thermal conditions.
{"title":"On the contrasting effects of parent austenite grain size on athermal and deformation-induced martensitic transformation in an Fe-18Cr-12Ni (wt.%) alloy","authors":"Chen Cai , Gabriel Spartacus , Amlan Das , Katherine S. Shanks , Wangzhong Mu , Peter Hedström","doi":"10.1016/j.mtla.2025.102602","DOIUrl":"10.1016/j.mtla.2025.102602","url":null,"abstract":"<div><div>The parent austenite grain size (PAGS) plays a critical role in governing the austenite to martensite transformation in steels, as it directly influences the stability of the austenite phase. Therefore, a thorough understanding of the PAGS effect is essential for the design of advanced steels with optimized performance. In this study, we investigate the influence of PAGS on both athermal and deformation-induced martensitic transformation (AMT and DIMT) in an Fe-18Cr-12Ni (wt.%) alloy. In situ and <em>ex situ</em> high-energy synchrotron X-ray diffraction (HEXRD) measurements were conducted during tensile loading and after cooling, respectively. These measurements were complemented by electron microscopy to elucidate the underlying mechanisms governing the PAGS effect on martensitic transformation. The results reveal PAGS exerts opposite effects on AMT and DIMT. Grain refinement increases the barrier for martensitic transformation onset, and in the case of AMT, this leads to a lower martensite start temperature (Ms) and suppressed transformation. Conversely, although grain refinement delays DIMT and raises the critical stress required for its initiation, the associated Hall-Petch strengthening enhances the flow stress, thereby promoting DIMT at higher strain levels. These findings offer valuable insights for the microstructural design of austenitic steels and contribute to the modeling of martensitic transformation behavior under varying mechanical and thermal conditions.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102602"},"PeriodicalIF":2.9,"publicationDate":"2025-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145525454","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 : 2025-11-05DOI: 10.1016/j.mtla.2025.102598
Jun Utsumi, Ryo Takakura, Ryo Takigawa
The microstructures and electrical properties of Cu–Cu film direct-bonding interfaces prepared via room-temperature surface-activated bonding were evaluated before and after annealing. Transmission electron microscopy (TEM) images taken before annealing revealed a zigzag morphology without a clearly distinguishable bonding interface. In contrast, after annealing at 350 °C for 1 h in N₂ atmosphere, the bonding interface was no longer visible and the grain boundaries disappeared. The bonding strength of the specimens exceeded 8 MPa both before and after annealing, with no fractures observed at the bonding interface during tensile testing. The electrical resistance of the Cu–Cu bonded films was approximately 17 mΩ before annealing and 7 mΩ after annealing. These findings demonstrate the feasibility of employing low- or room-temperature bonding methods for three-dimensional integration technologies.
{"title":"Direct Cu films bonding via surface-activated bonding method at room temperature","authors":"Jun Utsumi, Ryo Takakura, Ryo Takigawa","doi":"10.1016/j.mtla.2025.102598","DOIUrl":"10.1016/j.mtla.2025.102598","url":null,"abstract":"<div><div>The microstructures and electrical properties of Cu–Cu film direct-bonding interfaces prepared via room-temperature surface-activated bonding were evaluated before and after annealing. Transmission electron microscopy (TEM) images taken before annealing revealed a zigzag morphology without a clearly distinguishable bonding interface. In contrast, after annealing at 350 °C for 1 h in N₂ atmosphere, the bonding interface was no longer visible and the grain boundaries disappeared. The bonding strength of the specimens exceeded 8 MPa both before and after annealing, with no fractures observed at the bonding interface during tensile testing. The electrical resistance of the Cu–Cu bonded films was approximately 17 mΩ before annealing and 7 mΩ after annealing. These findings demonstrate the feasibility of employing low- or room-temperature bonding methods for three-dimensional integration technologies.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102598"},"PeriodicalIF":2.9,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145578545","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}
<div><div>Deformation twins are often observed in ordered B2 crystals, but existing explanations of their formation based on a single simple shear invoke processes, such as interatomic bond shortening and atom shuffling, with unusually high energy barriers. We propose a new mechanism for the formation of <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> twins in ordered B2 crystals that avoids these energetically unfavorable steps. Specifically, a B2-ordered <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> twin can be produced by two consecutive shear twinning events in {1<span><math><mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>2</mn><mo>}</mo><mo><</mo></mrow><mover><mn>1</mn><mo>¯</mo></mover><mn>11</mn><mo>></mo></mrow></math></span> and <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>12</mn><mo>}</mo></mrow><mo><</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> systems, oriented 109.47° apart. The first shear generates a {1<span><math><mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>2</mn><mo>}</mo><mo><</mo></mrow><mover><mn>1</mn><mo>¯</mo></mover><mn>11</mn><mo>></mo></mrow></math></span> pseudo-twin, and the second shear, along <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>12</mn><mo>}</mo></mrow><mo><</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span>, restores the B2 order, giving a B2-ordered <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> rotational twin. Both shear steps occur with modest shear magnitude (<em>s</em> = 1/√2) and avoid unphysically short interatomic distances, atom shuffling, and excessive shear displacements. The resulting <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> twin corresponds to a 38.94° crystal rotation about 〈110〉 and is associated with low-energy (Σ9) coincidence site lattice boundary. This shuffle-free mechanism helps explain the frequent experimental observation and relative energetic stability of <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></
{"title":"Shuffle-free deformation twinning in ordered body centered cubic crystals","authors":"O.N. Senkov, D.B. Miracle, J.P. Simmons, B.W.J. McArthur","doi":"10.1016/j.mtla.2025.102597","DOIUrl":"10.1016/j.mtla.2025.102597","url":null,"abstract":"<div><div>Deformation twins are often observed in ordered B2 crystals, but existing explanations of their formation based on a single simple shear invoke processes, such as interatomic bond shortening and atom shuffling, with unusually high energy barriers. We propose a new mechanism for the formation of <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> twins in ordered B2 crystals that avoids these energetically unfavorable steps. Specifically, a B2-ordered <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> twin can be produced by two consecutive shear twinning events in {1<span><math><mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>2</mn><mo>}</mo><mo><</mo></mrow><mover><mn>1</mn><mo>¯</mo></mover><mn>11</mn><mo>></mo></mrow></math></span> and <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>12</mn><mo>}</mo></mrow><mo><</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> systems, oriented 109.47° apart. The first shear generates a {1<span><math><mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>2</mn><mo>}</mo><mo><</mo></mrow><mover><mn>1</mn><mo>¯</mo></mover><mn>11</mn><mo>></mo></mrow></math></span> pseudo-twin, and the second shear, along <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>12</mn><mo>}</mo></mrow><mo><</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span>, restores the B2 order, giving a B2-ordered <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> rotational twin. Both shear steps occur with modest shear magnitude (<em>s</em> = 1/√2) and avoid unphysically short interatomic distances, atom shuffling, and excessive shear displacements. The resulting <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></mrow></math></span> twin corresponds to a 38.94° crystal rotation about 〈110〉 and is associated with low-energy (Σ9) coincidence site lattice boundary. This shuffle-free mechanism helps explain the frequent experimental observation and relative energetic stability of <span><math><mrow><mrow><mo>{</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>14</mn><mo>}</mo></mrow><mo><</mo><mover><mn>2</mn><mo>¯</mo></mover><mn>2</mn><mover><mn>1</mn><mo>¯</mo></mover><mo>></mo></","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102597"},"PeriodicalIF":2.9,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145525452","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 : 2025-11-04DOI: 10.1016/j.mtla.2025.102594
Renze Ouyang , Yinghua Lin , Jinhai Lin , Longsheng Peng , Xinlin Wang
Fe-Cr-Mo alloy coatings fabricated by laser cladding often suffer from microstructural inhomogeneity and poor hardness uniformity. To address this, the study proposes integrating an 8-shaped oscillating laser with conventional laser cladding. Comparative studies on non-oscillating laser cladding (LC) and oscillating laser cladding (O-LC) evaluated their effects on the coating’s microstructure, hardness uniformity, and wear resistance. Results show that 8-shaped oscillation induces molten pool stirring, suppresses columnar grain formation, and promotes additional nucleation sites to facilitate equiaxed grain growth, which transforms the microstructure from a mixed columnar/equiaxed grain structure (in LC mode) to a predominantly equiaxed grain-based network-like structure. It modifies the temperature gradient and solidification rate during solidification, refining average cross-sectional grain size to 5.45 μm (19.26 % lower than LC) with more uniform grain size distribution (consistent in longitudinal sections and horizontal surfaces). O-LC alleviates segregation of constituent elements (Fe, Cr, Mo, etc.), with Mo showing the most significant improvement (segregation ratio k decreased by 40.91 % to 2.34). Enhanced uniformity in grain morphology and elemental distribution provides a favorable microstructural foundation for improved hardness uniformity and wear resistance. O-LC coatings exhibit hardness inhomogeneity factors (IF) of 2.08, 2.05, and 2.23 across all examined planes, with reductions of 42.06 %, 50.12 %, and 58.70 %, respectively, confirming significantly better overall hardness uniformity. The friction coefficient and wear mass of O-LC coatings are 0.55 and 0.17 mg, respectively, with reductions of 12.70 % and 81.72 %, indicating enhanced wear resistance. At room temperature, both coatings exhibit a wear mechanism dominated by abrasive wear and adhesive wear.
{"title":"Microstructure, hardness homogeneity, and wear resistance of Fe-Cr-Mo alloy coating by 8-shaped oscillating laser cladding","authors":"Renze Ouyang , Yinghua Lin , Jinhai Lin , Longsheng Peng , Xinlin Wang","doi":"10.1016/j.mtla.2025.102594","DOIUrl":"10.1016/j.mtla.2025.102594","url":null,"abstract":"<div><div>Fe-Cr-Mo alloy coatings fabricated by laser cladding often suffer from microstructural inhomogeneity and poor hardness uniformity. To address this, the study proposes integrating an 8-shaped oscillating laser with conventional laser cladding. Comparative studies on non-oscillating laser cladding (LC) and oscillating laser cladding (O-LC) evaluated their effects on the coating’s microstructure, hardness uniformity, and wear resistance. Results show that 8-shaped oscillation induces molten pool stirring, suppresses columnar grain formation, and promotes additional nucleation sites to facilitate equiaxed grain growth, which transforms the microstructure from a mixed columnar/equiaxed grain structure (in LC mode) to a predominantly equiaxed grain-based network-like structure. It modifies the temperature gradient and solidification rate during solidification, refining average cross-sectional grain size to 5.45 μm (19.26 % lower than LC) with more uniform grain size distribution (consistent in longitudinal sections and horizontal surfaces). O-LC alleviates segregation of constituent elements (Fe, Cr, Mo, etc.), with Mo showing the most significant improvement (segregation ratio <em>k</em> decreased by 40.91 % to 2.34). Enhanced uniformity in grain morphology and elemental distribution provides a favorable microstructural foundation for improved hardness uniformity and wear resistance. O-LC coatings exhibit hardness inhomogeneity factors (<em>IF</em>) of 2.08, 2.05, and 2.23 across all examined planes, with reductions of 42.06 %, 50.12 %, and 58.70 %, respectively, confirming significantly better overall hardness uniformity. The friction coefficient and wear mass of O-LC coatings are 0.55 and 0.17 mg, respectively, with reductions of 12.70 % and 81.72 %, indicating enhanced wear resistance. At room temperature, both coatings exhibit a wear mechanism dominated by abrasive wear and adhesive wear.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102594"},"PeriodicalIF":2.9,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474087","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 : 2025-11-04DOI: 10.1016/j.mtla.2025.102595
Sayed Ehsan Saghaian , Ahmad Salaimeh , Soheil Saedi , Sayed M. Saghaian , Haluk E. Karaca
This study presents a comparative experimental investigation of the elastocaloric (EC) behavior of a quaternary NiTiHfPd shape memory alloy (SMA) and a conventional binary NiTi under uniaxial compressive loading. Near-adiabatic temperature changes (ΔT) arising from stress-induced martensitic transformations were measured using high-speed, non-contact infrared thermography across a systematic range of applied strain levels (up to 7 %) and strain rates (0.0007–0.30 s−1). Binary NiTi exhibited a more uniform temperature distribution and achieved a slightly higher average ΔT, while NiTiHfPd demonstrated superior peak cooling performance, attaining a maximum ΔT of −16.80 °C at 7 % strain and a strain rate of 0.30 s⁻¹, with lower energy dissipation (ΔW). The influence of applied strain and strain rate on ΔT, hysteresis loss (ΔW), and the coefficient of performance (COP) was systematically evaluated and quantitatively compared between the two alloys. Results indicate that NiTiHfPd’s reduced hysteresis and strong peak cooling performance offer distinct advantages for applications requiring high stress tolerance and rapid, localized cooling.
{"title":"Elastocaloric behavior of NiTi and NiTiHfPd shape memory alloys","authors":"Sayed Ehsan Saghaian , Ahmad Salaimeh , Soheil Saedi , Sayed M. Saghaian , Haluk E. Karaca","doi":"10.1016/j.mtla.2025.102595","DOIUrl":"10.1016/j.mtla.2025.102595","url":null,"abstract":"<div><div>This study presents a comparative experimental investigation of the elastocaloric (EC) behavior of a quaternary NiTiHfPd shape memory alloy (SMA) and a conventional binary NiTi under uniaxial compressive loading. Near-adiabatic temperature changes (ΔT) arising from stress-induced martensitic transformations were measured using high-speed, non-contact infrared thermography across a systematic range of applied strain levels (up to 7 %) and strain rates (0.0007–0.30 s<sup>−1</sup>). Binary NiTi exhibited a more uniform temperature distribution and achieved a slightly higher average ΔT, while NiTiHfPd demonstrated superior peak cooling performance, attaining a maximum ΔT of −16.80 °C at 7 % strain and a strain rate of 0.30 s⁻¹, with lower energy dissipation (ΔW). The influence of applied strain and strain rate on ΔT, hysteresis loss (ΔW), and the coefficient of performance (COP) was systematically evaluated and quantitatively compared between the two alloys. Results indicate that NiTiHfPd’s reduced hysteresis and strong peak cooling performance offer distinct advantages for applications requiring high stress tolerance and rapid, localized cooling.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102595"},"PeriodicalIF":2.9,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474175","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 : 2025-11-03DOI: 10.1016/j.mtla.2025.102596
Yongliang Mu , Yaopeng Duan , Weiyuan Liu
In the present study, a cost-effective aluminum matrix syntactic foam (AMSF) was prepared by embedding fly ash ceneosphere (FAC) into aluminum alloy matrix through vacuum-assisted infiltration method. The introduction of FAC has significantly contributed to the lightweight and multifunctional properties of composite materials, reducing the density of AMSF to 1.53g/cm3, while the volume fraction of FAC in the aluminum alloy reaches up to 58 %. The interfacial bonding between the aluminum matrix and FAC was characterized. The presence of magnesium in the matrix significantly enhances the interfacial bonding, while the interfacial reaction renders the originally non-heat-treatable matrix alloy amenable to heat treatment. The peak stress of AMSF increased by over 30 %, while its energy absorption capacity improved by >40 % after heat treatment. During the intermittent cyclic compression tests, distinct hysteresis loops were observed throughout the compression process. The specific damping capacity of the aged AMSF increased with strain, demonstrating excellent damping energy dissipation even during the later stages of compression. This behavior is attributed to the accumulation of damage due to FAC rupture and compressive friction during the deformation process.
{"title":"Experimental investigation of compression and energy absorption characteristics of Al/fly ash cenospheres syntactic foam","authors":"Yongliang Mu , Yaopeng Duan , Weiyuan Liu","doi":"10.1016/j.mtla.2025.102596","DOIUrl":"10.1016/j.mtla.2025.102596","url":null,"abstract":"<div><div>In the present study, a cost-effective aluminum matrix syntactic foam (AMSF) was prepared by embedding fly ash ceneosphere (FAC) into aluminum alloy matrix through vacuum-assisted infiltration method. The introduction of FAC has significantly contributed to the lightweight and multifunctional properties of composite materials, reducing the density of AMSF to 1.53<em>g</em>/cm<sup>3</sup>, while the volume fraction of FAC in the aluminum alloy reaches up to 58 %. The interfacial bonding between the aluminum matrix and FAC was characterized. The presence of magnesium in the matrix significantly enhances the interfacial bonding, while the interfacial reaction renders the originally non-heat-treatable matrix alloy amenable to heat treatment. The peak stress of AMSF increased by over 30 %, while its energy absorption capacity improved by >40 % after heat treatment. During the intermittent cyclic compression tests, distinct hysteresis loops were observed throughout the compression process. The specific damping capacity of the aged AMSF increased with strain, demonstrating excellent damping energy dissipation even during the later stages of compression. This behavior is attributed to the accumulation of damage due to FAC rupture and compressive friction during the deformation process.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102596"},"PeriodicalIF":2.9,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474174","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 : 2025-10-31DOI: 10.1016/j.mtla.2025.102593
Panpan Xu, Wentao Hao, Xiaole Qiu, Ensi Cao, Bing Sun
Bi-doped (In,Nb)TiO2 ceramics with nominal composition (Bi0.1In0.4Nb0.5)0.1Ti0.9O2 were synthesized to mitigate the high low-frequency dielectric losses present in undoped counterparts. The incorporation of Bi2O3 as a sintering aid significantly enhanced densification and effectively reduced the sintering temperature. Bi doping resulted in grain size refinement to 4.18–8.38 μm, increased the grain boundary area density, and facilitated the formation of insulating Bi2Ti2O7 secondary phases at the grain boundaries. These structural modifications decreased the low-frequency dielectric loss from over 0.1 to below 0.05, with a minimum of 0.042 at 300 Hz, while preserving the colossal permittivity. A novel dielectric relaxation phenomenon near 100 kHz was observed, which is explicitly attributed to Maxwell-Wagner interfacial polarization at the boundaries between semiconducting grains and insulating Bi2Ti2O7 secondary phases. Complex impedance analysis revealed that the enhanced grain boundary resistance was the primary factor responsible for the reduction in dielectric loss. XPS confirmed the coexistence of Ti3+/Ti4+ oxidation states and oxygen vacancies, indicating that the colossal permittivity originated from a combination of electron-pinned defect dipole behavior and internal barrier layer capacitor mechanisms.
{"title":"Synergistic grain boundary engineering and insulating phase formation for low-loss colossal permittivity in Bi-doped (In,Nb)TiO2 ceramics","authors":"Panpan Xu, Wentao Hao, Xiaole Qiu, Ensi Cao, Bing Sun","doi":"10.1016/j.mtla.2025.102593","DOIUrl":"10.1016/j.mtla.2025.102593","url":null,"abstract":"<div><div>Bi-doped (In,Nb)TiO<sub>2</sub> ceramics with nominal composition (Bi<sub>0.1</sub>In<sub>0.4</sub>Nb<sub>0.5</sub>)<sub>0.1</sub>Ti<sub>0.9</sub>O<sub>2</sub> were synthesized to mitigate the high low-frequency dielectric losses present in undoped counterparts. The incorporation of Bi<sub>2</sub>O<sub>3</sub> as a sintering aid significantly enhanced densification and effectively reduced the sintering temperature. Bi doping resulted in grain size refinement to 4.18–8.38 μm, increased the grain boundary area density, and facilitated the formation of insulating Bi<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> secondary phases at the grain boundaries. These structural modifications decreased the low-frequency dielectric loss from over 0.1 to below 0.05, with a minimum of 0.042 at 300 Hz, while preserving the colossal permittivity. A novel dielectric relaxation phenomenon near 100 kHz was observed, which is explicitly attributed to Maxwell-Wagner interfacial polarization at the boundaries between semiconducting grains and insulating Bi<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> secondary phases. Complex impedance analysis revealed that the enhanced grain boundary resistance was the primary factor responsible for the reduction in dielectric loss. XPS confirmed the coexistence of Ti<sup>3+</sup>/Ti<sup>4+</sup> oxidation states and oxygen vacancies, indicating that the colossal permittivity originated from a combination of electron-pinned defect dipole behavior and internal barrier layer capacitor mechanisms.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102593"},"PeriodicalIF":2.9,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474176","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 : 2025-10-30DOI: 10.1016/j.mtla.2025.102591
Melika Mansouri Moghaddam , Rana Imani , Elaheh Jooybar , Martin Ehrbar
The treatment of significant bone defects often involves invasive surgeries and autologous bone grafting, highlighting the need for less invasive and more efficient alternatives. Existing injectable carriers often fail to provide both optimal mechanical support and a biologically favorable environment for mesenchymal stem cell (MSC) survival and osteogenic differentiation. Minimally invasive delivery of stem cells using engineered microcarriers represents a promising strategy to overcome these limitations. This study explores the potential of injectable hyaluronic acid (HA) and gelatin (Ge) microgels, chemically modified with tyramine (TA), for delivering human bone marrow-derived MSCs (hBM-MSCs) in bone regeneration. Microgels were fabricated via enzymatic crosslinking using horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂), and their physicochemical properties were systematically characterized. The average microgel sizes were 114.2 ± 42.2 µm (Ge-TA), 114.3 ± 31.6 µm (HA/Ge-TA), and 114.8 ± 30.0 µm (HA-TA). Surface analysis showed higher porosity in Ge-containing microgels, while enzymatic degradation revealed that HA incorporation improved structural stability. HA/Ge-TA microgels exhibited higher enzymatic stability than Ge-TA after 20 h of hyaluronidase and trypsin treatment, with average relative stability values of 1.53 and 1.22, respectively. Atomic force microscopy (AFM) measured stiffness as 1.83 ± 0.71 kPa (Ge-TA), 4.41 ± 0.68 kPa (HA/Ge-TA), and 11.79 ± 3.45 kPa (HA-TA). MTT assays demonstrated higher optical density (OD) in Ge-containing microgels at day 7 (Ge-TA: 0.328 ± 0.038; HA/Ge-TA: 0.299 ± 0.011; HA-TA: 0.143 ± 0.017). Osteogenic differentiation was significantly enhanced in HA/Ge-TA microgels, with alkaline phosphatase (ALP) activity at day 14 showing a 1.81-fold increase relative to TCP (1.807 ± 0.139), compared to 1.61 ± 0.072 for Ge-TA and 1.52 ± 0.284 for HA-TA. Alizarin Red S staining confirmed greater mineral deposition in HA/Ge-TA microgels (1.65 ± 0.08-fold increase relative to TCP). These findings suggest that HA/Ge-TA microgels offer an optimal balance of mechanical stability, cell viability, and osteoinductive capacity, representing a scalable, minimally invasive platform with significant potential for clinical translation in bone tissue engineering.
{"title":"Evaluation of osteogenic differentiation of stem cells on hyaluronic acid/gelatin microgels as 3D microcarriers for bone regeneration","authors":"Melika Mansouri Moghaddam , Rana Imani , Elaheh Jooybar , Martin Ehrbar","doi":"10.1016/j.mtla.2025.102591","DOIUrl":"10.1016/j.mtla.2025.102591","url":null,"abstract":"<div><div>The treatment of significant bone defects often involves invasive surgeries and autologous bone grafting, highlighting the need for less invasive and more efficient alternatives. Existing injectable carriers often fail to provide both optimal mechanical support and a biologically favorable environment for mesenchymal stem cell (MSC) survival and osteogenic differentiation. Minimally invasive delivery of stem cells using engineered microcarriers represents a promising strategy to overcome these limitations. This study explores the potential of injectable hyaluronic acid (HA) and gelatin (Ge) microgels, chemically modified with tyramine (TA), for delivering human bone marrow-derived MSCs (hBM-MSCs) in bone regeneration. Microgels were fabricated via enzymatic crosslinking using horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂), and their physicochemical properties were systematically characterized. The average microgel sizes were 114.2 ± 42.2 µm (Ge-TA), 114.3 ± 31.6 µm (HA/Ge-TA), and 114.8 ± 30.0 µm (HA-TA). Surface analysis showed higher porosity in Ge-containing microgels, while enzymatic degradation revealed that HA incorporation improved structural stability. HA/Ge-TA microgels exhibited higher enzymatic stability than Ge-TA after 20 h of hyaluronidase and trypsin treatment, with average relative stability values of 1.53 and 1.22, respectively. Atomic force microscopy (AFM) measured stiffness as 1.83 ± 0.71 kPa (Ge-TA), 4.41 ± 0.68 kPa (HA/Ge-TA), and 11.79 ± 3.45 kPa (HA-TA). MTT assays demonstrated higher optical density (OD) in Ge-containing microgels at day 7 (Ge-TA: 0.328 ± 0.038; HA/Ge-TA: 0.299 ± 0.011; HA-TA: 0.143 ± 0.017). Osteogenic differentiation was significantly enhanced in HA/Ge-TA microgels, with alkaline phosphatase (ALP) activity at day 14 showing a 1.81-fold increase relative to TCP (1.807 ± 0.139), compared to 1.61 ± 0.072 for Ge-TA and 1.52 ± 0.284 for HA-TA. Alizarin Red S staining confirmed greater mineral deposition in HA/Ge-TA microgels (1.65 ± 0.08-fold increase relative to TCP). These findings suggest that HA/Ge-TA microgels offer an optimal balance of mechanical stability, cell viability, and osteoinductive capacity, representing a scalable, minimally invasive platform with significant potential for clinical translation in bone tissue engineering.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102591"},"PeriodicalIF":2.9,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474177","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 : 2025-10-29DOI: 10.1016/j.mtla.2025.102592
Mujtaba Rafique Ghoto , B. Hayden Daubert , Deborah ParraCervantes , August J. Hemmerla , Bret D. Ulery , W. David Hairston , Christopher G. Sinks , Stephan Young , Christopher S. O’Bryan
Phantoms are test specimens and models that mimic the material properties and imaging modalities of tissues. To replicate the high water content and low moduli of many soft tissues, phantom models often use highly swollen polymer networks, i.e., hydrogels, as surrogate tissue-like materials. These hydrogels begin as polymer solutions before undergoing gelation or crosslinking to form soft elastic solids. As such, manufacturing of hydrogel phantom models has largely focused on casting the polymer precursor into pre-defined molds before initiating gelation, limiting the ability to incorporate structural and chemical complexities within soft tissue phantom models. Alternatively, embedded 3D-printing enables hydrogel precursors solutions to be structured in their fluid phase, providing new opportunities for manufacturing anthropomorphic soft tissue phantom models. Here, we design a photo-crosslinkable poly(vinyl alcohol) methacrylate (PVA-MA) polymer by attaching methacrylate groups to poly(vinyl alcohol) through a transesterification reaction and demonstrate its application as a tissue-equivalent material to manufacture anthropomorphic phantom models that imitate material characteristics of soft tissues. As part of this study, we characterize the mechanical, thermal, and electromagnetic properties of the PVA-MA hydrogels and demonstrate that these properties can be tuned to replicate the material properties of native tissue. Further, we explore the relationships between the shear viscosity of the polymer solution, the material properties of the support bath, and the resulting cross-sectional area of printed filaments to identify design principles for 3D-printing PVA-MA polymer solutions. Finally, we apply these principles to manufacture a scale model of a human brain using a solid model generated from a medical scan of a human brain.
{"title":"3D-printing soft tissue phantom models from photo-crosslinkable poly(vinyl alcohol) methacrylate","authors":"Mujtaba Rafique Ghoto , B. Hayden Daubert , Deborah ParraCervantes , August J. Hemmerla , Bret D. Ulery , W. David Hairston , Christopher G. Sinks , Stephan Young , Christopher S. O’Bryan","doi":"10.1016/j.mtla.2025.102592","DOIUrl":"10.1016/j.mtla.2025.102592","url":null,"abstract":"<div><div>Phantoms are test specimens and models that mimic the material properties and imaging modalities of tissues. To replicate the high water content and low moduli of many soft tissues, phantom models often use highly swollen polymer networks, <em>i.e.</em>, hydrogels, as surrogate tissue-like materials. These hydrogels begin as polymer solutions before undergoing gelation or crosslinking to form soft elastic solids. As such, manufacturing of hydrogel phantom models has largely focused on casting the polymer precursor into pre-defined molds before initiating gelation, limiting the ability to incorporate structural and chemical complexities within soft tissue phantom models. Alternatively, embedded 3D-printing enables hydrogel precursors solutions to be structured in their fluid phase, providing new opportunities for manufacturing anthropomorphic soft tissue phantom models. Here, we design a photo-crosslinkable poly(vinyl alcohol) methacrylate (PVA-MA) polymer by attaching methacrylate groups to poly(vinyl alcohol) through a transesterification reaction and demonstrate its application as a tissue-equivalent material to manufacture anthropomorphic phantom models that imitate material characteristics of soft tissues. As part of this study, we characterize the mechanical, thermal, and electromagnetic properties of the PVA-MA hydrogels and demonstrate that these properties can be tuned to replicate the material properties of native tissue. Further, we explore the relationships between the shear viscosity of the polymer solution, the material properties of the support bath, and the resulting cross-sectional area of printed filaments to identify design principles for 3D-printing PVA-MA polymer solutions. Finally, we apply these principles to manufacture a scale model of a human brain using a solid model generated from a medical scan of a human brain.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"44 ","pages":"Article 102592"},"PeriodicalIF":2.9,"publicationDate":"2025-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474089","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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