Multiple Thermal Cycles Research Articles

Ferroelectric, Switchable Dielectric and Nonlinear Optical Properties in Inorganic-Organic Lead-Free 1D Hybrids Based on Bi(III) and Azetidine: (C3NH8)2[BiCl5], (C3NH8)2[BiBr5

This study investigates lead-free organic-inorganic hybrids (C3NH8)2[BiCl5] (ABC) and (C3NH8)2[BiBr5] (ABB), focusing on their structural, dielectric, ferroelectric, and optical properties. Both compounds exhibit paraelectric (I) to ferroelectric (II) phase transitions (PTs) at 230/233 K and 228/229 K, respectively, transitioning from orthorhombic (Pnma) to monoclinic (P21) phases, with distorted [BiX6]3- octahedra forming 1D chains. Quasielastic neutron scattering and solid-state 1H NMR studies reveal the localized motion of azetidinium cations. Dielectric measurements of ABC and ABB show step-like permittivity changes by 11-12 units post-transition I → II, demonstrating reversible switching behavior. Absorption studies reveal band gaps of 3.24 eV for ABC and 2.76 eV for ABB, classifying them as insulators. Luminescence spectra at 77K display 578 nm (ABC) and 708 nm (ABB) emissions, attributed to 3P1,0 → 1S0 transitions. Both compounds demonstrate stable second harmonic generation (SHG) switching of the on-off type. The switching performance is evaluated over multiple thermal cycles using the treq metric, which decreases with increasing temperature change rate and indicates that ABB's SHG switching is approximately 30% faster than that of ABC.

Hybrid α -Ta/ β -Ta lumped element kinetic inductance detectors with photon noise limited sensitivity and stability

The terahertz (THz) band is of immense interest in astronomy as it encompasses significant energy generated following the Big Bang, offering critical insight into processes invisible in other bands, such as the earliest stages of planet, star, and galaxy formation. Kinetic inductance detectors (KIDs) have emerged as a formidable contender in the field of THz astronomy, attributed to their exceptional sensitivity and scalability. In this study, we introduce a kind of KIDs incorporating a lumped element (LE) resonator design, with inductors fabricated on β-Ta film and capacitors on α-Ta film. We characterize the noise of the hybrid α-Ta/β-Ta LEKIDs, achieving an optical noise equivalent power of 8.3 ± 5.7 × 10−19 W/Hz1/2, demonstrating high sensitivity. Additionally, the LEKIDs exhibited stability across multiple thermal cycles. The combination of high sensitivity and stability makes the hybrid LEKIDs promising for the stringent demands of THz astronomy.

Effect of heat treatment on microstructure and mechanical properties of WE43 alloy fabricated by wire arc additive manufacturing

Heat treatment is an effective method to improve the mechanical properties of Wire Arc Additive Manufacturing (WAAM) WE43 alloy. This study investigates the effects of heat treatment on the microstructure and mechanical properties of the WE43 alloy processed by WAAM. The as-deposited samples exhibit a uniform equiaxed crystal structure, with grain size gradually increasing as the number of deposited layers grows. The as-deposited microstructure comprises eutectics and a small amount of cubic phases, and the phase content escalates as the amount of deposited layers increases, influenced by the cumulative effect of multiple thermal cycles. At lower solid solution temperatures (480 ℃ × 8h), most of the eutectic phase remains undissolved. During tensile testing, undissolved eutectics tend to cause stress concentrations, leading to cracks that result in sample fractures, negatively affecting the mechanical properties. At higher solid solution temperatures (520 ℃ × 8h), most of the eutectic dissolves, but abnormal grain coarsening (AGC) in the interlayer fine-grain region occurs, causing a significant reduction in the sample's mechanical properties. After solid solution treatment at 500 °C for 8hours, only a small amount of eutectics remains undissolved, and the AGC phenomenon is not observed, resulting in an optimal solid solution effect. Subsequently, after aging treatment at 225 °C for 18hours, dense nanoscale β′′ phases precipitated within the alloy grains, significantly improving the mechanical properties. The samples achieved optimal performance, with UTS, YS, and EL of 323±15.2MPa, 225±11.3MPa, and 8.4±1.1%, respectively.

Quantitative revealing the solute segregation behavior at melt pool boundary in additively manufactured stainless steel using a novel processing method for precise positioning by HAADF-STEM

Laser-powder bed fusion (LPBF) enables the fabrication of complex metallic components by manipulating various laser scan strategies to control microstructure and texture. Multiple thermal cycling and rapid solidification lead to non-equilibrium, non-uniform microstructure, and micro-segregation at the melt pool boundary (MPB), whose accurate location is still invisible by transmission electron microscopy (TEM), and quantitative concentration remains imprecise. In this study, we proposed a novel method to make it clear by controlling the crystallographic texture of 316 L stainless steel through unique LPBF processing parameters to obtain a single-crystal-like microstructure of the cellular structures along the laser scanning direction. The accurate location of the track-track MPB is distinguishable by means of the transverse and longitudinal cellular dislocation structures on both sides. The edge-on state of the track-track MPB makes the quantitative concentration analysis precisely using high-angle annular dark-field scanning TEM with energy-dispersive X-ray spectroscopy, which is in good agreement with the Scheil-Gulliver solidification simulations.

Crystallization and luminescence properties of stable CsPbBr3 Nanocrystals in Li2B4O7 glass

All-inorganic CsPbX3 (X = Cl, Br, and I) perovskite nanocrystals (NCs), have achieved unprecedented advances in opto-electronic applications. However, issues such as poor stability and the volatility of halides in the preparation process continue to hinder their practical applications. Here, lithium tetraborate (Li2B4O7) was chosen as the glass matrix to prepare CsPbBr3 NCs glasses through traditional melting-quenching and heat treatment processes, effectively reducing the glass synthesis temperature to 940 °C. The heat treatment temperature and duration are examined. The Li2B4O7 glass matrix exhibits a uniform structure and high transmittance and CsPbBr3 NCs precipitated uniformly after heat treatment. Among these glasses, the sample heat-treated at 510 °C for 5 h exhibited an optimal photoluminescence quantum yield of 76.1 % and the narrowest full width at half maximum values of 24 nm. Its photoluminescence intensity maintained 96.6 % of its original value after multiple thermal cycles and thermal shocks, demonstrating the sample's robust thermal stability. Finally, by integrating the CsPbBr3 NCs glass sample with a blue chip in simple device packaging, a green light-emitting diode was successfully fabricated, featuring excellent luminescence stability and a color purity of up to 96.4 %, promising for applications in solid-state lighting and display technologies.

The integrated performance of adaptive temperature control and temperature measurement of PTC materials with high thermal cycle repeatability

Abstract As the temperature increases, the resistance of the positive temperature coefficient (PTC) material becomes larger. Using this material can reduce the complexity of the temperature control system. In this paper, a new PTC material is developed by means of melt blending, which still has operable PTC characteristics after 60 high and low temperature cycles. The data points collected in multiple thermal cycles were fitted to obtain the relationship between the sample’s temperature and resistance. In addition, the integrated performance of adaptive temperature control and temperature measurement of PTC materials is proposed for the first time. Based on the prepared samples, the temperature control characteristics of PTC materials on the controlled object under different environmental conditions are studied experimentally, and the temperature value converted from the resistance value is compared with the temperature value measured by the platinum resistance. The results show that the prepared sample has good temperature control performance, and the material has an operable temperature measurement function in the PTC effect range.

Microstructure-Linked Mechanical Properties of P91-Incoloy 800HT Dissimilar Metal Welds

Dissimilar metal welds (DMWs) between P91 steel and Incoloy 800HT® using shielded metal arc welding (SMAW) with ENiCrCoMo-1 filler electrode were characterized in detail. The impact of multiple weld passes on microstructure in the heat-affected zone (HAZ) and weld fusion zone (WFZ) was thoroughly investigated. Postweld heat treatment (PWHT) impacts on mechanical characteristics and microstructure were also observed. The DMW was observed with heavy C, Cr, and Mo microsegregation in the WFZ, which deteriorated mechanical strength. The microstructural changes directly affected the mechanical behavior of the DMW. The ultimate tensile strength of the weld fusion zone was low at 576 MPa compared to the base metals’ strength. The tensile specimens failed in the IN 800HT base metal and WFZ. The WFZ had significant microsegregation near the solidified grain boundaries (SGBs). The metallurgical heterogeneity in the WFZ caused the formation of localized stress zones, which directly affected the mechanical behavior of the WFZ. The carbide particles influenced the microhardness in the WFZ and P91 HAZ regions. The PWHT successfully homogenized the microhardness in the WFZ and P91 HAZ regions. The impact toughness decreased to 64 J from 82 J after PWHT due to precipitation at SGBs and its coarsening. The SMAW process involves multiple thermal cycles during welding. The deposition of filler metal in multiple welding passes created uncontrolled variations in the solidification behavior of the WFZ. Microsegregation had a detrimental impact on the microstructure and mechanical properties of the P91 and IN 800HT dissimilar metal welds.

Effect of Multiple Thermal Cycles on Microstructure and Mechanical Properties of Cu Modified Ti64 Thin Wall Fabricated by Wire-Arc Directed Energy Deposition

Effect of Multiple Thermal Cycles on Microstructure and Mechanical Properties of Cu Modified Ti64 Thin Wall Fabricated by Wire-Arc Directed Energy Deposition

The role of zinc addition on the microstructural evolution and mechanical properties of wire-arc directed energy deposited Mg-Gd-Y-(Zn)-Zr alloys

Wire-arc directed energy deposition (WA-DED) demonstrates significant potential in the rapid and free forming of high-strength magnesium rare-earth (Mg-RE) alloys. This highlights a growing demand for tailored wire alloy compositions to promote engineering applications of this technology. In this work, the role of zinc addition on WA-DED processed Mg-Gd-Y based alloys has been thoroughly investigated by utilizing Mg-6Gd-3Y-0.5Zr (wt.%, GW63K) and Mg-6Gd-3Y-0.5Zn-0.5Zr (wt.%, GWZ631K) alloy wires as model materials. The microstructure evolution of these two alloys during deposition and heat treatment is revealed by multi-scale microstructure characterization techniques. The influences of Zn addition on mechanical properties of these deposited alloys are investigated comparatively. Obtained results indicate that addition of Zn element into Mg-Gd-Y based alloys promotes phase transformation between eutectic phases and long period stacking order (LPSO) phases during the WA-DED deposition process owing to the multiple thermal cycling. More importantly, the addition of Zn element increases the tendency of solidification shrinkage of the deposited metal. During high-temperature solid solution treatment, the presence of Zn is conducive to improving the thermal stability of the as-deposited grain boundaries and thus suppressing grain coarsening. After optimized T6 treatments, the strength of GW63K alloys increases to 374±7MPa, and is obviously higher than that (315±6MPa) of GWZ631K alloys. The addition of Zn element weakens the precipitation strengthening effect. This can be attributed to the formation of LPSO phases, which consumes a substantial amount of RE elements, and in turn decreases the density of aging precipitated nanoscale β´ phases. This work promotes the understanding of the non-equilibrium solidified microstructure evolution of multi-component Mg-RE alloys and guides the optimization of alloy composition of WA-DED specific wire materials.

Effect of multiple laser remelting on microstructure and corrosion resistance of Fe0.5CoCrNi1.5Nb0.68Mo0.3 high entropy alloy coatings

High entropy alloy (HEA) coatings of Fe0.5CoCrNi1.5Nb0.68Mo0.3 was prepared on 304 stainless steel using laser cladding and subsequently remelted multiple times. The effects of multiple thermal cycles on the phase composition, grain size, microstructure evolution, and corrosion resistance of the coatings are thoroughly investigated. The original coating consisted of face-centered cubic (FCC), Laves, and NbC phases, and the phase composition does not change obviously, but the distribution and microstructure of the phase change significantly after multiple remelting. As the number of remelting times increased, the bar-like eutectic structure decreased while the lamellar eutectic structure became more prominent. Laser remelting induced dynamic recrystallization in the coating, resulting in a transformation from columnar grains to equiaxed grains, and then back to columnar grains. The grain size also changes significantly with different remelting times. Potentiodynamic polarization and electrochemical impact spectroscopy measurements were conducted in a 3.5 wt% NaCl solution to evaluate the corrosion resistance of the coating. The results revealed both the original coating and the once-remelted coating exhibited lower corrosion current density and higher corrosion potential, but the latter had a higher Faraday impedance. Additionally, immersion tests were performed in 10 wt% FeCl3 solution, which demonstrated that the once-remelted coating displayed fine and uniform corrosion pits with shallow depth. This study provides theoretical support for the regulation of microstructure and the optimization of coating performance. Furthermore, the microstructure evolution law discovered in this research is also applicable to additive manufacturing.

The Impact of Multiple Thermal Cycles Using CMT® on Microstructure Evolution in WAAM of Thin Walls Made of AlMg5

Wire Arc Additive Manufacturing (WAAM) of thin walls is an adequate technology for producing functional components made with aluminium alloys. The AlMg5 family is one of the most applicable alloys for WAAM. However, WAAM differs from traditional fabrication routes by imposing multiple thermal cycles on the material, leading the alloy to undergo cyclic thermal treatments. Depending on the heat source used, thermal fluctuation can also impact the microstructure of the builds and, consequently, the mechanical properties. No known publications discuss the effects of these two WAAM characteristics on the built microstructure. To study the influence of multiple thermal cycles and heat source-related thermal fluctuations, a thin wall was built using CMT-WAAM on a laboratory scale. Cross-sections of the wall were metallographically analysed, at the centre of a layer that was re-treated, and a region at the transition between two layers. The focus was the solidification modes and solubilisation and precipitations of secondary phases. Samples from the wall were post-heat treated in-furnace with different soaking temperatures and cooling, to support the results. Using numerical simulations, the progressive thermal cycles acting on the HAZ of one layer were simplified by a temperature sequence with a range of peak temperatures. The results showed that different zones are formed along the layers, either as a result of the imposed thermal cycling or the solidification mode resulting from CMT-WAAM deposition. In the zones, a band composed of coarse dendrites and an interdendritic phase and another band formed by alternating sizes of cells coexisted with the fusion and heat-affected zones. The numerical simulation revealed that the thermal cycling did not significantly promote the precipitation of second-phase particles.

Highly stable mesoporous-controlled corncob biochar confined paraffinic material with exceptional latent heat retention performance

Bio-based composites fabricated from bio-sourced waste feedstocks have attracted increasing interest and have shown potential applications in sustainable energy infrastructure development. Thermal management using phase-change materials (PCMs) has appeared as an innovative approach for energy storage and cooling, where pure PCMs that lack thermal stability are encapsulated in solid matrices to ensure the charge/discharge of the latent heat of the composite. However, their energy storage density, thermal stability, and durability are reduced after multiple thermal cycles, besides the complicated and expensive nonrenewable fossil feedstock utilization. Biochar, mostly used for soil remediation, can be redirected and repurposed for the encapsulation of PCMs in renewable energy storage infrastructures. In this study, a “greener” biochar-based composite was fabricated from agricultural corncob-derived biochar (88.9 % mesopore proportion) and a commercially available paraffinic PCM (n-hexadecane) following vacuum impregnation strategies. Corncob biochar combined with hexadecane exhibited an efficient energy per unit mass of 250.6 kJ kg−1 and a latent heat retention of 110.3 % after 500 consecutive thermal cycles. In addition, the corncob biochar/hexadecane composite demonstrated high fractional crystallinity and relative latent heat efficiency (98.9 %). The composite exhibited promising chemical compatibility with composite components, stability, and competitive energy density even compared with a composite made of nonrenewable fossil-based materials, like exfoliated graphene nanoplatelets, which demonstrated reduced latent heat retention after multiple heating-cooling cycles. Intermolecular interactions, such as hydrogen bonding, between the guest molecular chains and host materials played a significant role in the thermal performance of the as-synthesized composite materials. This approach will contribute to overcoming the complexities and costs of composite PCM development in thermal management and thermal energy storage applications and support and advance the UN's sustainable development goal (affordable and clean energy).

Hardness Distribution and Growth Behavior of Micro-Arc Oxide Ceramic Film with Positive and Negative Pulse Coordination.

Micro-arc oxidation (MAO) is a promising technology for enhancing the wear resistance of engine cylinders by growing a high hardness alumina ceramic film on the surface of light aluminum engine cylinders. However, the positive and negative pulse coordination, voltage characteristic signal, hardness distribution characteristics of the ceramic film, and their internal mechanism during the growth process are still unclear. This paper investigates the synergistic effect mechanism of cathodic and anodic current on the growth behaviour of alumina, dynamic voltage signal, and hardness distribution of micro-arc oxidation film. Ceramic film samples were fabricated under various conditions, including current densities of 10, 12, 14, and 16 A/dm2, and current density ratios of cathode and anode of 1.1, 1.2, and 1.3, respectively. Based on the observed characteristics of the process voltage curve and the spark signal changes, the growth of the ceramic film can be divided into five stages. The influence of positive and negative current density parameters on the segmented growth process of the ceramic film is mainly reflected in the transition time, voltage variation rate, and the voltage value of different growth stages. Enhancing the cathode pulse effect or increasing the current density level can effectively shorten the transition time and accelerate the voltage drop rate. The microhardness of the ceramic film cross-section presents a discontinuous soft-hard-soft regional distribution. Multiple thermal cycles lead to a gradient differentiation of the Al2O3 crystal phase transition ratio along the thickness direction of the layer. The layer grown on the outer surface of the initial substrate exhibits the highest hardness, with a small gradient change in hardness, forming a high hardness zone approximately 20-30 μm wide. This high hardness zone extends to both sides, with hardness decreasing rapidly.

Effect of Fusion Boundary Microstructure on Flow-Accelerated Corrosion Cracking.

Flow-accelerated corrosion (FAC) preferentially attacks the downstream heat-affected zone of the root-pass weld in steam pipe systems. A detailed characterization identifies the fusion boundary as the initiation location for the attack. Alloying elements are found depleted along the weld fusion boundary, and multiple welding thermal cycles and repetitive austenite-to-ferrite phase transformations result in an increased proportion of grains with Goss {110}<001> texture along the fusion boundary. The synergistic effects of chemical segregation and the Schmid factor may contribute to the preferential initiation of FAC cracks along the root weld fusion boundary, making it the weakest link for FAC attack in steam pipe girth welds.

Thermal fatigue life prediction and intermetallic compound behaviour of SAC305 BGA solder joints subject to accelerated thermal cycling test

PurposeThis study aims to investigate the thermal fracture mechanism of moisture-preconditioned SAC305 ball grid array (BGA) solder joints subjected to multiple reflow and thermal cycling.Design/methodology/approachThe BGA package samples are subjected to JEDEC Level 1 accelerated moisture treatment (85 °C/85%RH/168 h) with five times reflow at 270 °C. This is followed by multiple thermal cycling from 0 °C to 100 °C for 40 min per cycle, per IPC-7351B standards. For fracture investigation, the cross-sections of the samples are examined and analysed using the dye-and-pry technique and backscattered scanning electron microscopy. The packages' microstructures are characterized using an energy-dispersive X-ray spectroscopy approach. Also, the package assembly is investigated using the Darveaux numerical simulation method.FindingsThe study found that critical strain density is exhibited at the component pad/solder interface of the solder joint located at the most distant point from the axes of symmetry of the package assembly. The fracture mechanism is a crack fracture formed at the solder's exterior edges and grows across the joint's transverse section. It was established that Au content in the formed intermetallic compound greatly impacts fracture growth in the solder joint interface, with a composition above 5 Wt.% Au regarded as an unsafe level for reliability. The elongation of the crack is aided by the brittle nature of the Au-Sn interface through which the crack propagates. It is inferred that refining the solder matrix elemental compound can strengthen and improve the reliability of solder joints.Practical implicationsInspection lead time and additional manufacturing expenses spent on investigating reliability issues in BGA solder joints can be reduced using the study's findings on understanding the solder joint fracture mechanism.Originality/valueLimited studies exist on the thermal fracture mechanism of moisture-preconditioned BGA solder joints exposed to both multiple reflow and thermal cycling. This study applied both numerical and experimental techniques to examine the reliability issue.

Reliability of micro-resistance welded dissimilar connection between Ag-plated Kovar foil and GaAs space solar cell: Processing, microstructure and bonding strength

Solar panels in low earth orbit (LEO) can suffer from damage caused by atomic oxygen (AO) exposure and thermal shock, which may shorten the service life of their interconnectors and joints. Ag-plated Kovar foil has emerged as a promising material for interconnecting solar cell arrays. This study uses parallel gap resistance welding (PGRW) to conduct ultrafast Ag-plated Kovar foil and solar cell bonding in just 190 ms. The bonding strength depends on the current densities, with a diffused interface observed at a density of 475 A/mm2. The EBSD results show that grains of Ag layer and Au layer grow at the central bonding interface, whereas grains of Ag layer and Au layer form a weakened bonded line at the edge bonding interface. The thermal reliability of joints with Ag-plated Kovar foil is better than traditional Ag foil, with no decline in tensile-shear force observed even after multiple thermal cycles. Although the Ag layer of Kovar foil oxidizes as AgO and Ag2O in an AO environment, the joining interface remains unaffected. This investigation into PGRW joints of Ag-plated Kovar foil is critical for enhancing the high reliability of solar arrays in harsh temperatures and AO space environments.

Numerical Simulation-Based Study on the Microstructure of TC4 Titanium Alloy in CMT Additive Manufacturing

This thesis explores the thermal and mechanical phenomena occurring during the Cold Metal Transfer (CMT) additive manufacturing process of TC4 titanium alloy. The investigation delves into the effects of layer-by-layer deposition on the thermal cycles, stress distribution, and microstructural evolution of the additive manufactured specimens. Key findings include the identification of thermal accumulation with increasing deposition layers, leading to a decrease in cooling rates and a slight increase in the peak molten pool temperatures. The temperature profiles on the substrate exhibit cyclic patterns of peaks and troughs, which become smoother and exhibit less variance between maximum and minimum temperatures as deposition progresses. Stress analysis reveals that equivalent stress within the deposited layers decreases with the number of layers. This is attributed to the thermal stress accumulation and stress cycles induced by multiple thermal cycles, which initially increase the equivalent stress. However, a reduction in cooling rates over time and the effects of remelting facilitate the release of interlayer stress, resulting in minimal residual stress within the cooled specimens. Microstructurally, the TC4 titanium alloy specimens are characterized by the presence of primary β phase spanning across multiple deposition layers, growing in the direction of additive manufacturing. The accumulated heat input from increased layering enhances the growth of the primary β phase.The specimens' microstructure features a basketweave pattern comprised of α' martensite, α, and β phases, with α' martensite directly transformed from the primary β phase. Repeated heating cycles foster diverse pathways for the secondary α phase's formation, leading to more pronounced, directionally parallel α phases and extensive basketweave structures within the specimen layers. Higher temperature gradients at specimen edges encourage the formation of needle-like α' martensite. This thesis contributes to the understanding of the thermal behavior, stress dynamics, and microstructural characteristics in TC4 titanium alloy during CMT additive manufacturing, highlighting the interplay between process parameters, thermal management, and material response.

Thermal shakedown in granular materials with irregular particle shapes

Granular materials with irregular particle shapes undergo a myriad of temperature variations in natural and engineered systems. However, the impacts of cyclic temperature variations on the mechanics of granular materials remain poorly understood. Specifically, little is known about the response of granular materials to cyclic temperature variations as a function of the following central variables: particle shape, applied stress level, relative density, and temperature amplitude. This paper presents advanced laboratory experiments to explore the impacts of cyclic temperature variations on the mechanics of granular materials, with a focus on sands. The results show that cyclic temperature variations applied to sands induce thermal shakedown: the accumulation of irreversible bulk deformations due to microstructural rearrangements caused by thermal expansions and contractions of the constituting particles. The deformation of sands caused by thermal shakedown strongly depends on particle shape, stress level, relative density, and temperature amplitude. This deformation is limited for individual thermal cycles but accumulates and becomes significant for multiple thermal cycles, leading to substantial compaction in sands and other granular materials, which can affect various natural and engineered systems.

Physical simulation of low temperature phase separation during multipass welding of super duplex stainless steel

This study aimed to investigate the degree of low-temperature phase separations and 475 °C -embrittlement in physically simulated multipass super duplex stainless steel (SDSS) welds. A single bead weld was produced using gas metal arc welding and multiple thermal cycles with different peak temperatures were applied using a Gleeble physical simulator with fixed and moving jaws to simulate the influence of constrained designs, to mimic the welding of thick SDSS components. The samples were studied using atom probe tomography and the results were correlated with toughness and ferrite microhardness. The results showed that the microhardness of the ferrite in the constrained simulated multipass reheated weld increased from 304 HV to 374 HV after 5 min aging at 475 °C. The amplitude of the Cr concentration of the same sample, showing the level of Fe-Cr phase separation, increased from 1.025 to 1.045 after 5 min aging at 475 °C. Despite the clear development of phase separation in the ferrite, the toughness did not drop. It can be concluded that reheated SDSS welds are not susceptible to 475 °C -embrittlement during short fabrication times of up to 5 min for the austenite level of 50%.

Pressure induced thermal conduction paths in liquid metal-boron nitride fillered thermal interface materials with high thermal conductivity

With the continuous evolution of wearable and mobile devices, flexible electronics, and intelligent thermal management, there is a growing interest in thermal interface materials (TIMs) that combine high thermal conductivity with low modulus for stretchability. However, materials with high thermal conductivity often come with elevated Young's modulus. Here, we have developed a TIMs by combining liquid metal and BN with polydimethylsiloxane (PDMS), achieving a blend of low modulus and high thermal conductivity. To enhance thermal conductivity, we introduced boron nitride sheets as “scalpel”, puncturing the oxide layer of the liquid metal under pressure to establish a continuous thermal path. After pressure induction, the LM-BN/PDMS composite exhibits a thermal conductivity of 4.3 W/(m K), with a Young's modulus of only 193 kPa and a fracture strain of 483%. Furthermore, it demonstrates outstanding thermal stability under multiple thermal shock cycles, indicating significant potential for applications in future thermal management for flexible electronic devices, wearable devices, and beyond.