Crystal Phase Change Research Articles

Effect of ZnO/Li2O ratio on the structure and properties of Li2O-ZnO-SiO2-P2O5 glass-ceramics sealants

In order to meet the sealing temperature of copper alloy below 1000 °C, a kind of Li2O-ZnO-SiO2-P2O5-(B2O3+Al2O3+K2O) (LZS) glass-ceramics with high expansion coefficient and high resistivity was synthesized via the melting method and then crystallized through controlled cooling. The network structure, thermal properties, crystal phase transition, thermal expansion coefficient, and high-temperature resistivity have been investigated. As the mass ratio of ZnO/Li2O increases, the network structure of the LZS glass is strengthened, leading to an increase in the glass transition and crystallization temperature. Moreover, the predominant crystal phases in LZS glass-ceramics transit from Li2SiO3 to Zn[Zn0.1Li0.6Si0.3]SiO4 and subsequently to Zn2SiO4. At a ZnO/Li2O ratio of 3, a cristobalite phase with a high expansion coefficient emerges. The change in crystal phase results in a variation in the coefficient of thermal expansion (CTE) of glass-ceramics, ranging from 13.2 to 11.2 × 10−6 K−1. At a ZnO/Li2O ratio of 3, the softening temperature of glass-ceramics is minimized. Moreover, as the ZnO/Li2O mass ratio increases, the resistance of crystallized glass decreases first and then increases. The maximum resistivity is achieved at a ZnO/Li2O mass ratio of 5. By optimizing the mass ratio of ZnO/Li2O, it is determined that when the mass ratio of ZnO/Li2O is 3, the CTE is 12.4 × 10−6 K−1, and the softening temperature (Ts) is 679.8 °C, which is the best material for sealing applications.

Fabrication of α-W and β-W Films By Using CsF–CsCl–WO3 Molten Salt: Effect of Oxygen Contents in W Films

Electrodeposition of W films in CsF–CsCl eutectic melts was investigated after adding 2.0 mol% of WO3 at 773–973 K. The oxygen content in W films electrodeposited at various temperatures was analyzed using inert gas fusion and non-dispersive infrared spectroscopy (NDIR). Oxygen contents in the W films gradually decreased from 6.65 at% to 0.24 at% as the bath temperature increased from 773 K to 923 K along with the crystal phase change from β-W to α-W, confirmed by X-ray diffractometry (XRD). Then, vacuum annealing treatment was performed for the electrodeposited β-W films. The crystal phase was transformed to pure α-W after annealing at 973 K for 3 h and the oxygen content in W films decreased from 1.82 at% to 0.38 at%. Finally, based on the above findings, we provide a promising two-step method for preparing mirror-like and dense α-W films.

Effects of CaF2 and La2O3 on the phase structure of rare earth in CaO–SiO2–La2O3–CaF2 slags

The rare earth in the rare earth slag can be separated and enriched by heating and melting the rare earth slag and then slowly cooling crystallisation. In this process, it is of great significance to study the effect of chemical composition on the crystallisation of rare earth phase in slag and the effect of slag viscosity on crystal growth. The rare earth slag melt samples were prepared according to the main chemical composition of rare earth slag by using an analytical pure reagent. The effects of CaF2 and La2O3 contents on the phase structure and morphology of rare earth phase in CaO–SiO2–La2O3–CaF2 slags were studied by SEM-EDS and XRD. The relationship between the viscosity of the slag and the crystal growth behaviour was studied by measuring the melt viscosity with the cylinder rotation method. The results show that the rare earth in CaO–SiO2–La2O3–CaF2 slags exists in the form of CaLa4(SiO4)3O. The change of CaF2 and La2O3 content has no effect on the structure of rare earth phase, but the size of rare earth crystal phase changes obviously. With the increase of CaF2 and La2O3 content, the size of rare earth crystal phase increases gradually. CaF2 and La2O3 can reduce the viscosity transition temperature of slag melt and increase the crystallisation temperature range of rare earth phase to promote crystal growth.

Microheater Controlled Crystal Phase Engineering of Nanowires Using In Situ Transmission Electron Microscopy

AbstractCrystal Phase Quantum Dots (CPQDs) offer promising properties for quantum communication. How CPQDs can be formed in Au‐catalyzed GaAs nanowires using different precursor flows and temperatures by in situ environmental transmission electron microscopy (ETEM) experiments is studied. A III‐V gas supply system controls the precursor flow and custom‐built micro electro‐mechanical system (MEMS) chips with monocrystalline Si‐cantilevers are used for temperature control, forming a micrometer‐scale metal–organic vapor phase epitaxy (µMOVPE) system. The preferentially formed crystal phases are mapped at different precursor flows and temperatures to determine optimal growth parameters for either crystal phase. To control the position and length of CPQDs, the time scale for crystal phase change is investigated. The micrometer size of the cantilevers allows temperature shifts of more than 100 °C within 0.1 s at the nanowire growth temperature, which can be much faster than the growth time for a single lattice layer. For controlling the crystal phase, the temperature change is found to be superior to precursor flow, which takes tens of seconds for the crystal phase formation to react. This µMOVPE approach may ultimately provide faster temperature control than bulk MOVPE systems and hence enable engineering sequences of CPQDs with quantum dot lengths and positions defined with atomic precision.

Preparation of low thermal expansion, transparent LAS glass-ceramics via simplified heat-treatment method

Li2O–Al2O3–SiO2 (LAS) glass-ceramics are commercially significant due to their unique microstructure and exceptional properties, including near-zero thermal expansion coefficient, making them suitable for a wide range of applications. However, the content of SiO2 and Al2O3 in the composition of LAS glass is very high, which leads to high viscosity and very difficult melting of this type of glasses. In order to reduce the melting temperature of the glass, use of relatively high Na2O in the basic glass composition allows high-quality glass to melt. Employing a simplified heat-treatment method, LAS glass-ceramics are prepared with Australian spodumene as the primary material. By exploring the effect of crystallization temperature on the structures and properties of the resulting LAS glass-ceramics, samples with excellent comprehensive properties are achieved. The prepared glass-ceramics are thoroughly characterized using DSC, XRD, FTIR, SEM, and TEM, along with assessments of their viscosity, thermal, optical, and mechanical properties. Relatively more Na2O is introduced into the glass compositions, which can lower the melting temperature of the glass to below 1600 °C. The basic glass is annealed at 700 °C for 2 h, nucleation phenomenon Nucleation phenomenon can be generated in the LAS glasses. When the microcrystalline temperature of glasses increases from 835 °C to 910 °C, the main crystalline phase of glass-ceramics changes from β-quartz solid solution to β-spodumene solid solution. The change in the main crystal phase has significantly affected the properties of glass-ceramics. When the crystallization temperature is below 860 °C, the glass-ceramics exhibit a low negative expansion coefficient (<-0.5 × 10−6 K−1), high visible light transmittance (>85 %), and excellent average flexural strength (173.3 MPa).

Thermal Stability of Chalcogenide Perovskites.

Chalcogenide perovskites (CPs) have recently attracted interest as a class of materials with practical potential in optoelectronics and have been suggested as a more thermally stable alternative to intensely studied halide perovskites (HPs). Here we report a comparative study of the thermal stability of representative HPs, MAPbI3 (MA = CH3NH3+, methylammonium) and CsPbI3, and a series of CPs with compositions BaZrS3, β-SrZrS3, BaHfS3, SrHfS3. Changes in the crystal structure, chemical composition, and optical properties upon heating in air up to 800 °C were studied using thermogravimetric analysis, temperature-dependent X-ray diffraction, energy-dispersive X-ray spectroscopy, and diffuse reflectance spectroscopy. While HPs undergo phase transitions and thermally decompose at temperatures below 300 °C, the CPs show no changes in crystal phase or composition when heated up to at least 450 °C. At 500 °C CPs oxidize on time scales of several hours, forming oxides and sulfates. The structural origins of the higher thermal and phase stability of the CPs are discussed.

Improvement of heat resistance in silicone rubber by Fe-doped TiO2 nanoparticles prepared via flame spray pyrolysis

In recent years, the development of heat-resistant silicone rubber has been a research hotspot. In this paper, a kind of Fe doped TiO2 nanoparticles (Fe-TiO2) was prepared via flame spray pyrolysis, which can significantly improve the high temperature resistance of silicone rubber. The results show that, on the one hand, the prepared Fe-TiO2 can inhibit the breakage of Si-O main chain; on the other hand, because Fe is doped into the lattice of TiO2, it causes the change of TiO2 crystal phase and produces more oxygen vacancies, which is more beneficial to capture free radicals in silicone rubber matrix, so that Fe-TiO2 can effectively inhibit the excessive cross-linking of silicone chain caused by methyl oxidation on the side of silicone rubber. TGA results showed that after adding Fe-TiO2, the 5 % thermal weight loss temperature of methyl vinyl silicone rubber increased from 392.8 °C to 435.6 °C.

KBiFe2O5 triggered-phase transition of Bi2Fe4O9 and Fe3O4 in tellurite glass with huge nonlinear and magnetic properties

In the quest for glass materials with high nonlinearity and strong magnetism to meet the demands of advancing technology, magnetic nanocrystal (NC) doping emerges as a promising approach. The paper investigates the phase transition from KBiFe2O5 to Bi2Fe4O9 and Fe3O4 NCs within a TeO2–Bi2O3–B2O3 glass matrix. The novelty of this study lies in leveraging the coexistence of multiple phases to amplify both the polarization and magnetic moment of glass. Various techniques, including X-ray diffraction, transition transmission electron microscopy, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, and vibrational sample magnetometer were employed to analyze the impact of NCs content and heat treatment temperature on crystallization, structure modification, and properties. KBiFe2O5 NCs doping induces changes in crystal phases and modifies the glass network structure by forming multi-valence states and altering coordination numbers, such as FeO4→FeO6, TeO4→TeO3, and BO4→BO3. Concurrently, appropriate temperature conditions result in reduced NC size, preserving glass transparency and thermal stability. Spinel Fe3O4 NCs formation at higher temperatures enhances magnetic behavior. A glass sample containing 1 mol% KBiFe2O5 NCs, heat-treated at 410 °C, exhibits a narrow bandgap (Eg) of 1.82 eV, high nonlinear parameters (α3 = 3.98 × 10−10 m/W, χ(3) = 8.65 × 10−11 esu), and a low limiting threshold (1.01 × 1012 W/m2). Additionally, owing to the incorporation of high spin states and active magnetic exchange interactions, the same glass demonstrates robust ferromagnetic behavior (Ms = 2.3 emu/g and Hc = 850 G). The approach developed in this study has been demonstrated to be highly effective in producing transparent glass with promising nonlinearity and magnetic performance suitable for photonics applications.

Design of dual carbon encapsulated porous micron silicon composite with compact surface for enhanced reaction kinetics of lithium-ion battery anodes

Developing high-performance composites with fast charging and superior cycle life is paramount for lithium-ion batteries (LIBs). Herein, we synthesized a double-shell carbon-coated porous structure composite with a compact surface (P-Si@rGO@C) using low-cost commercial micron-sized silicon (Si) instead of nanoscale silicon. Results reveal that the unique P-Si@rGO@C features high adaptability to volume expansion, accelerates electron/ion transmission rate, and forms a stable solid electrolyte interphase (SEI) film. This phenomenon arises from the synergistic effect of abundant internal voids and an external double-layer carbon shell with a dense surface. Specifically, the P-Si@rGO@C anode exhibits a high initial coulombic efficiency (ICE) (88.0 %), impressive rate-capability (612.1 mAh/g at 2C), and exceptional long-term cyclability (972.2 mAh/g over 500 cycles at 0.5C). Further kinetic studies elucidate the diffusion-capacitance hybrid energy storage mechanism and reveal an improved Li+ diffusion coefficient (from 3.47 × 10-11 to 2.85 × 10-9 cm2 s-1). Ex-situ characterization confirms the crystal phase change of micron-sized Si and the formation of a stable LiF-rich SEI. Theoretical calculations support these findings by demonstrating an enhancement in the adsorption ability of Si to Li+ (from -0.89 to -0.97 eV) and a reduction in the energy migration barrier (from 0.35 to 0.18 eV). Additionally, practical LixSi powder is shown to increase the ICE of full cells from 67.4 % to 87.9 %. Furthermore, a pouch cell utilizing the prelithiated P-Si@rGO@C anode paired with LiNi1/3Co1/3Mn1/3O2 (NCM111) cathode delivers a high initial reversible capacity of 7.2 mAh and 76.8 % capacity retention after 100 cycles. This work provides insights into the application of commercial silicon-aluminum alloy powder in the anode of high-energy LIBs.

Stable and reliable PEG/TiO2 phase change composite with enhanced thermal conductivity based on a facile sol-gel method without deionized water

Some shortcomings exist in organic phase change materials, including leakage susceptibility, low thermal conductivity, and preparation complexity. Herein, polyethylene glycol/titanium dioxide shape-stabilized composite phase change material (PEG/TiO2 ss-CPCM) was fabricated by facile sol-gel method without deionized water using tetrabutyl titanate (TBOT) as precursor. In this composite, not adding deionized water prolonged the gelation time, allowing PEG to bind as much TiO2 as possible and enhancing energy storage capability; TiO2 acted as the supporting framework to maintain the material's shape stability and enhance thermal conductivity. The melting and crystallization phase change enthalpies of prepared PEG/TiO2 ss-CPCM were 128.3 J/g and 113.1 J/g with an encapsulation efficiency of 74.14 % when PEG: TBOT = 1.5: 1. After repeating 300 thermal cycles, the phase change enthalpy remained almost constant. Besides, the thermal conductivity of PEG/TiO2 ss-CPCM was 1.22 times that of PEG, and the potential for thermal management applications. The advantages (energy storage capability, shape stability in thermal environments, thermal reliability, and thermal management) of the PEG/TiO2 ss-CPCM prepared by facile synthesis, not only propose a phase change material with excellent thermal properties and shape stabilization but provide a green and feasible strategy for the fabrication of PEG/TiO2 composite phase change materials utilizing the sol-gel method.

Study on the ablative characteristics of steel target irradiated by nanosecond pulsed pseudo spark electron beams: Experiment and molecular dynamics simulation

A combination of simulation and experimentation is employed to explore the influence of the non-uniformity of energy distribution in nanosecond PSEB on the target ablation. Firstly, A spatiotemporally distributed heat source model is built using Monte Carlo computational method and an ablation phase transition model is established using molecular dynamics method. The results reveal the time evolution of multiple cavities in the sub-surface region, as well as the temperature and stress field distributions with electron beam irradiation. Phase explosion formation and lattice structure changes in the steel target during the ablation process is found for the first time. The PSEB modified AISI1045 steel samples is experimentally conducted. The characterization results show the changes in the crystal structure within AISI1045 steel, which is attributed to the formation of an amorphous layer resulting from grain refinement and structural defects, as well as the combined effects of thermal elastic stress waves, shock thermal stress waves and temperature gradient distribution. The experimentally obtained crystal phase changes are consistent with the simulation results, confirming the accuracy and validity of the modelling. The findings of this study provide a molecular-scale explanation for the formation of unique morphology and micro-structures during the PSEB ablated metal target.

Mechanistic Study of the Influence of Reactant Type and Addition Sequence on the Microscopic Morphology of α-Al2O3

To perform an in-depth study of the crystal growth habits and phase changes of alumina and its precursors in reaction systems, this paper studied the effects of reactant type and addition order on the morphology of alumina using hydrothermal methods with different precipitants and aluminum sources as reactants. Research has shown that sodium bicarbonate and ammonium bicarbonate can be used as precipitants to prepare adhered spherical alumina and irregular short rod alumina, while potassium bicarbonate can be used as a precipitant to prepare hexagonal flake alumina. Using aluminum sulfate octahydrate, aluminum chloride hexahydrate, and aluminum nitrate, nine hydrates were prepared as aluminum sources, and agglomerated alumina, irregular short rod-shaped alumina, and fused alumina were obtained. The order of reactant addition affects the precursor phase of alumina, thereby affecting the microstructure of alumina after calcination, resulting in flake alumina with pores and short rod alumina. The results of this paper will provide theoretical guidance for the preparation of alumina with different micromorphologies.

Exploring the microwave assisted sol-gel synthesized multivalent doped thin films of iron oxide for detailed impedance and magnetodielectric response

Extensive research is carried out now a days to explore multifunctional materials for electronic, optoelectronic and spintronic devices. Multifunctionality that depends on the coupling between magnetic and electronic polarization, is a big challenge particularly for electronic and spintronic applications. This research focuses on the development of material and methodology to produce strong coupling between two polarizations/orders. Thin iron oxide films are prepared by the combined effect of microwaves and sol-gel after irradiating the solution at 720W. Multivalent doped sols are synthesized with variation in aluminum (Al) and cobalt (Co) concentrations in the range of 2 to 10 wt%. Crystal phase change from maghemite to magnetite, at Al–Co content of 8 to 10 wt%, is observed by XRD results. Phase transformation from maghemite to magnetite shows that probability of occupancy of Al3+and Co2+ ions of vacancies on B and A sites is affected by the microwave irradiation. Structural phase transition is also accompanied by the increased saturation magnetization. Undoped thin films, i.e. maghemite, exhibit dielectric constant ∼100 (log f = 4.5). Various relaxation phenomena are observed in impedance analyses. Room temperature magnetic and dielectric coupling is observed under multivalent doping conditions.

Analysis and Mechanism Study of Residual Stress during the Spontaneous Crystallisation Process of Molten Titanium-Containing Blast Furnace Slag

Molten titanium-containing blast furnace slag can be used to obtain cast stone materials by controlling a reasonable heat treatment system. The material acquired during this process showcases residual stress, which additionally impacts the macroscopic characteristics of the material. This article simulates the process of manufacturing microcrystalline cast stones based on the self-crystallisation ability of titanium-containing products. This research employs X-ray diffraction to precisely and conveniently assess the residual stress of microcrystalline cast stones and investigates how viscosity and the thermal expansion coefficient influence the residual stress level. The study provides a theoretical foundation for explaining titanium-containing blast furnace slag and combines characterisation methods such as XRD (X-ray diffraction), SEM (Scanning electron microscope), DTA (Differential thermal analysis), and theoretical calculations such as Factpage and Fullprop to study the effect of the TiO2 content on the microstructure of self-crystallised mechanical characteristics of microcrystalline cast stones through residual stress. The results of the experiment indicate that as the TiO2 content in the system increases, the glass phase is reduced, the crystallinity improves, and the main crystal phase changes from a feldspar phase to a diopside phase. Furthermore, its viscosity, thermal expansion coefficient, and residual stress decrease while its corresponding compressive strength and bending strength increase.

Nanocavity tuning and formation controlled by the phase change of sub-micron-square GST patterns on Si photonic crystals.

It has been well established that photonic crystal nanocavities with wavelength sized mode volume enable various integrable photonic devices with extremely small consumption energy and small footprint. In this study, we explore the possibility of non-volatile functionalities employing photonic crystal nanocavities and phase change material, Ge2Sb2Te5 (GST). Recently, non-volatile photonic devices based on GST have attracted significant interest and are expected to enable energy-efficient photonic processing, especially for optical computing. However, the device size and the area of GST in previous studies have been rather large. Here, we propose and fabricate Si photonic crystal nanocavities on which submicron-square GST patterns are selectively loaded. Because of the strong light confinement, extremely small area of GST is sufficient to manipulate the cavity mode. We have succeeded to fabricate 30-nm-thick and several-100nm-square GST blocks patterned at the center of photonic crystal cavity with a high alignment accuracy. We confirmed that the resonant wavelength and Q-factor of cavity modes are controlled by the phase change of GST. Moreover, cavity formation controlled by submicron-sized GST is also demonstrated by GST-loaded photonic-crystal line-defect waveguides. Our approach in which we place sub-micron-sized GST inside a photonic crystal nanocavity is promising for realizing extremely energy-efficient non-volatile integrable photonic devices, such as switches, modulators, memories, and reconfigurable novel devices.

Effect of substituting Na2O with B2O3 on the crystallization and properties of MgO–Al2O3–SiO2 transparent glass-ceramics

MgO–Al2O3–SiO2 (MAS) transparent glass-ceramics were prepared with ZrO2 as a nucleating agent, and the substitution of B2O3 for Na2O on the properties of the MAS glass-ceramics was investigated systematically. The results show that the substitution of B2O3 increased the glass transition temperature, crystallization temperature, and crystallization activation energy. Additionally, there was no change in the main crystal phase of the glass-ceramics, which were ZrO2 (JCPDS PDF#.50-1089) and Al0.52Zr0.48O1.74 (JCPDS PDF#.53-0294). The crystal growth mode shifted from three-dimensional growth to two-dimensional growth, and the crystal morphology transformed from a spherical appearance to a star-shaped appearance. Moreover, the mechanisms of the property changes induced by B2O3 substitution are revealed and discussed. The transmittance of MAS glass-ceramics without B2O3 decreased from 88 % to 32 % as the crystallization temperature increased from 800 °C to 920 °C, and decreased from 90 % to 8 % when B2O3 was added. Additionally, the Vickers hardness of MAS glass-ceramics decreased from 6.37 GPa to 6.13 GPa, after the introduction of B2O3, while, the fracture toughness increased from 1.48 MPa m1/2 to 1.55 MPa m1/2. The scratch behaviour of glass-ceramics exhibits a negative correlation with the applied load, but a positive correlation with the crystallization temperature. In particular, the incorporation of B2O3 substantially enhances the scratch resistance of glass-ceramics. The conclusions provide researchers with the roles of B2O3 in crystallization kinetics, microstructure, transmittance, and mechanical properties of MAS transparent glass-ceramics for various applications such as covers.

Influence of Zn/Ba ratio on crystallization, sintering behavior and properties of CaO-Al2O3-SiO2 glass-ceramics

The influence of Zn/Ba ratio on crystallization, sintering behavior and properties of CaO-Al2O3-SiO2 (CAS) glass-ceramics was investigated. As the Zn/Ba ratio increases, the main crystal phase changes from wollastonite (CaSiO3) to hardystonite (Ca2ZnSi2O7). A proper Zn/Ba ratio facilitates the sintering and crystallization processes, thereby resulting in a dense structure and enhancing mechanical strength. CAS glass-ceramics with a Zn/Ba ratio of 4/6 sintered at 950 °C exhibit superior characteristics, including a flexural strength of 193 MPa, Young's modulus of 79 GPa, thermal expansion coefficient of 5.11 × 10−6/°C, dielectric constant of 6.58, and dielectric loss of 2.7 × 10−3.

Enhanced inactivation of Microcystis aeruginosa by heterogeneous interfacial Ag2MoO4/TACN under visible light

A novel photocatalytic material Ag2MoO4/TACN was synthesized, and the heterogeneous interfacial effect between them enhanced its photocatalytic algae removal performance. Meanwhile, the crystal phase change of Ag2MoO4 was also found during the recombination process, which cramped the band gap width from 3.35 to 3.06 eV. The improved algal removal efficiency of the synthesized photocatalyst was clearly demonstrated when nearly 100 % of Microcystis aeruginosa got removed under 3 h illumination. Moreover, better inactivation effect was observed under alkaline and neutral conditions. From the results, possible mechanisms for the photocatalytic activities were proposed. ROS (·OH, and·O2−), h+ and Ag+ produced by Ag2MoO4/TACN were the main substances causing algae inactivation, as they destroy the normal functions of cell membrane and consequently lead to the leakage of electrolytes as well as algal organic matter. In addition, under the continuous attack of ROS and Ag+, the photosynthetic and metabolic activities of algal cells were hindered, while the PB content, SOD and CAT activities were also continuously reduced, leading to the mortality of algal cells. Finally, recycling experiments confirmed the recyclability and reusability of Ag2MoO4/TACN, further illustrating its potential as a promising photocatalyst for practical applications.

Advancement in Sewage Sludge Dewatering with Hydrate Crystal Phase Change: Unveiling the Micro-Moisture Migration and Dewaterability Mechanisms

Advancement in Sewage Sludge Dewatering with Hydrate Crystal Phase Change: Unveiling the Micro-Moisture Migration and Dewaterability Mechanisms

High strength injection molding welding and interface crystal phase changes in polyamide 6

AbstractInjection molding is a widely used method for production of plastic components, offering both simplicity and high strength. In this study, secondary injection molding was utilized to weld polyamide 6 (PA6). The welded samples were evaluated for the welding strength via a shear tensile test. Three process parameters of mold temperature, injection temperature, and injection speed were varied to determine the optimal conditions for welding. A polarizing microscope analysis of the welding interface revealed formation of a shish kebab layer (SKL) structure, which significantly contributed to the welding strength. A differential scanning calorimetry analysis of the welded samples showed that changes in the crystallinity at the interface were closely related to the welding strength under different injection molding conditions. To analyze the crystal phase of the interface after welding, we propose the use of Fourier‐transform infrared spectroscopy area scanning to obtain the relationship between the phase transformation and welding strength. Additionally, microhardness testing is proposed as a means of evaluation of the welding effect. Overall, this study highlights the importance of optimization of process parameters in secondary injection molding to achieve strong welds in PA6, where the SKL structure and crystallinity changes at the interface have crucial roles.Highlights The high welding shear strength reaches 80% of the base material. The interfacial crystalline structure has a significant impact on the strength. The crystalline changes were analyzed using FTIR region scanning. The relationship between microhardness and welding strength was obtained. The wide‐ranging conditions have reference value for industrial production.