Grain Boundary Area Research Articles

Predicting image processing-normalized DL-EPRT performance from Rudimentary Cihal method-based counterpart

Conventional DL-EPRT was extrapolated into accounting for inherent inconsistencies amongst grain boundary (GB) dimensions whilst correlating two distinct methods of ir/ia normalization, namely the approximate Cihal method (CM) and the relatively involved image processing (IP). Inasmuch as facilitating the forecast of IP- from CM-based normalizations, the full spectrum of plausible predictive models was subjected to cross validations that revealed those emanating from GB length-based endeavors to be quadratic with R2 and mean error (E) of 0.9215 and 0.5769, respectively. Meanwhile, GB area normalizations succumbed to a linear polynomial yielding R2 and E values of 0.8795 and 0.3664, respectively.

Micromechanical and microstructure evolution of leaded (SnPb) and lead-free (SAC305 and SnCu) mixed solder joints during isothermal aging

This paper studies how isothermal aging affects the micromechanical and structural properties of mixed solder joints made of 60Sn-40Pb (SnPb) with Sn-3.0Ag-0.5Cu (SAC305) and SnPb with Sn-0.7Cu (SnCu). The nanoindentation test was done to measure the micromechanical properties of SnPb/SAC305 and SnPb/SnCu mixed solder joints. These properties are hardness, reduced modulus, and stress exponent. Scanning electron microscopy (SEM) was used to look at the microstructure of a cross-section of mixed solder joints. The micrographs that were taken were then examined with open-source image processing software called ImageJ. It was found that the rate and distribution of intermetallic compound (IMC) formation and the reduction of Sn-rich phase grain size affect how the hardness and stress exponent values of mixed solder joints change after 1000 h of high temperature storage (HTS). ImageJ analysis shows that the Pb-rich phase particle count and distribution can be used to figure out how mixed solder joints respond to indentation creep and how that relates to isothermal aging. Using ImageJ, it’s clear that the indentation creep behavior of the GBS mechanism of an as soldered SnPb/SnCu mixed solder joint is caused by the highest number and size of Pb-rich phase particles that are not well distributed across the dendritic area of Sn-rich phase grain boundaries.

Crystal plasticity modeling of grain boundary softening and fatigue in U75V pearlite steel under low strain conditions: A study of cyclic rolling contact fatigue

Grain boundaries (GBs) exhibit fatigue-induced softening under low strain conditions, making them the weakest and most vulnerable regions within the material. This phenomenon significantly influences plastic deformation, plastic strengthening, and the initiation and propagation of microcracks, leading to material fatigue failure. This investigation presents a comprehensive model for the rolling contact fatigue (RCF) damage mechanism of U75V railway steel. Leveraging data from Electron Backscatter Diffraction (EBSD) and employing the Crystal Plasticity Finite Element Method (CPFEM), intragranular mechanical responses are elucidated. A modified bilinear Traction Separation Law (TSL) Cohesive Zone Model (CZM) is developed to capture the impact of GBs fatigue. Integrating this CZM with CPFEM, mechanical properties, scalar stiffness degradation (SDEG), fatigue damage factors, and crack evolution patterns are analyzed to explore the effects of grain morphology, orientation, GB angle, and area on GB fatigue damage and crack initiation. Results indicate a significant increase in GBs damage with increasing GBs angle or decreasing GBs area, highlighting the potential for reducing RCF damage through deliberate grain morphology design. Additionally, GBs are found to impede crack propagation, suggesting that grain refinement can mitigate crack propagation rates. This study enhances our understanding of intergranular fracture, mechanical responses, and microstructure evolution in U75V rail steel under cyclic rolling contact loading, offering novel methodologies for investigating metallic materials' deformation behavior concerning GB fatigue.

Creep deformation and cavitation in an additively manufactured Al-8.6Cu-0.4Mn-0.9Zr (wt%) alloy

Creep deformation and cavitation were investigated at 300 ºC in both tension and compression for an additively manufactured Al-8.6Cu-0.5Mn-0.9Zr (wt%) alloy in the as-fabricated state and after various aging treatments (aging at 300 °C/200 h or 350 °C/24 h and overaging at 400 °C/200 h). Creep mechanisms at 300 °C were determined by relating the measured creep response to corresponding microstructural and X-ray computed tomography observations. In compression, alloys in the as-fabricated and two aging conditions exhibited similarly high creep resistance. Overaging (400 °C/200 h) led to substantial coarsening of intragranular θ-Al2Cu precipitates and an expected drop in their Orowan strengthening contribution. In tension, minimum strain rates comparable to those in compression were obtained at any given stress; however, upon accumulation of some plastic strain in the matrix, creep cavities started to form, leading to accelerated tertiary stage creep deformation and rupture. Cavitation occurred exclusively along melt pool boundaries due to locally enhanced diffusion enabled by (ⅰ) large grain-boundary area in adjacent fine-grained zones and (ⅱ) localization of creep strain in nearby heat-affected zones. Although cavity growth was initially diffusion-controlled, its rate was determined by matrix creep rate, consistent with constrained cavity growth mechanisms. This study reveals how microstructural complexities induced by the additive manufacturing process affect the creep and cavitation behavior of Al-Cu-Mn-Zr alloys. The underlying creep and cavitation mechanisms uncovered in this study point to pathways that improve the high-temperature properties of additively manufactured alloys.

Hydrogen Embrittlement Susceptibility of Ti-6Al-4V Alloys Fabricated by Electron Beam Melting in Simulated Deep-Sea Environment

The hydrogen embrittlement susceptibility of electron beam melted Ti-6Al-4V alloy (ET) was compared with that of conventional wrought alloy (WT). Hydrogen permeation, electrochemical, and slow strain rate tensile tests as well as surface observation were conducted under a simulated sea environment. The results show that the hydrogen embrittlement susceptibility of ET is lower than that of WT, which can be attributed to the intense texture of ET with a smaller specific surface area of grain boundary, preventing hydrogen permeation. Moreover, with increasing depth of the ocean, the hydrogen embrittlement susceptibility of both ET and WT TC4 alloys increases considerably. This reduced hydrogen embrittlement resistance can be attributed to the degradation of the passivation film, accelerating the permeation flux of hydrogen.

Densification and grain growth of UO2 and MnO-UO2 during pressureless sintering

Large-grain UO2 has attracted much attention due to its advantage of suppressing fission gas release by reducing the specific surface area of grain boundaries. In this study, a single grain growth additive MnO is selected to modify UO2 by conventional pressureless sintering method. The effect of MnO modification on UO2 densification and grain growth at temperatures between 1200 and 1700 °C was investigated in detail. 0.5 wt%MnO-UO2 pellets can reach nearly 95% T.D. when sintered at 1200 °C for 24 h. An average grain size greater than 300 µm can be obtained at 1700 °C for 24 h. A series of sintering experiments were designed and conducted to verify the specific mechanism of MnO on the grain growth of UO2. The classical grain growth kinetics indicates that the grain growth exponent of MnO modified UO2 in the early stage is 3, which corresponds to the lattice diffusion under pore control, while that of UO2 is 2 and conforms to the grain boundary migration control. The SEM results show that there is solute segregation of MnO at the grain boundaries, followed by nucleation of lamellar structure in the form of piles and plates on the boundaries after high temperature treatment and traces of liquid phase in some region. Diffusion sintering experiments show that the mechanism of MnO-promoted UO2 grain boundary migration is based on solid phase diffusion. The XRD results of UO2 modified with different amounts of MnO demonstrate that the growth degree of UO2 grains can be related to the variation of lattice parameters resulted from the MnO modification. This is due to the enhanced mobility of UO2 grain boundaries because of the large distortion of surrounding lattice caused by Mn modification. These results can provide new ideas for the manufacture of UO2 ceramic fuels.

Significantly improved weldability in laser welding of additively manufactured haynes 230 superalloys by tailoring microstructure

Owing to restrictions on forming dimensions, laser powder bed fusion (LPBF) components will continue to require laser welding in the future. The post-weld thermal cracking of LPBF-Haynes 230 superalloys has become a key issue hindering their assembly in service. In this study, it was found that both the continuous TCP phase and M5Si3 silicides near the crack have a large interface strain with the matrix. Replacing the C and Si atoms with B atoms at the crack reduces the melting point of the carbides and silicides at the grain boundaries (GBs), thereby inducing solidification cracking under the residual tensile stress in the weld waist. The weldability of the alloy is influenced by the grain characteristics of the base metal (BM). Compared to parallel welds, vertical welds are inherited from the BM and exhibit smaller grains. Moreover, by reducing the heat treatment (HT) time and temperature, the grain size and grain misorientation of the BM are reduced and inherited into the weld. The GB area of the weld increases by 37% and the GB energy decreases by 7.3%, increasing the resistance to crack extension. In addition, the decreased HT temperature inhibits the carbide growth at the GBs, thereby reducing the interface strain between the matrix and carbides in the heat-affected zone and correspondingly its cracking sensitivity. This study provides theoretical guidance for improving the laser weldability of LPBF superalloys and will help accelerate the successful application of LPBF superalloy assemblies in engines.

Enhanced thermoelectric properties of NbCoSn half-Heuslers through in-situ nanocrystallization of amorphous precursors during the consolidation process

Tailoring nanostructures is a general approach used to obtain enhanced thermoelectric properties for half-Heusler compounds because the wide areas of grain and phase boundaries could be scattering centers that lower lattice thermal conductivity. However, a common fabrication method based on the sintering of crystalline precursors crushed from as-cast alloy ingots has limitations in obtaining a homogeneous microstructure without microsized impurity phases, owing to residual elemental segregation from casting. In this study, we used amorphous NbCoSn alloys as a precursor for the sintered specimen to obtain a homogeneous NbCoSn bulk specimen without microsized impurity phases and segregation, which led to the enhanced Seebeck coefficient due to the high purity of the half-Heusler phase after crystallization. Moreover, superplasticity originating from amorphous features enabled the powders to be largely deformed during the sintering process, even at a low sintering temperature (953 K). This resulted in less oxidation at both, the grain boundary and the interior, as the O diffusion pathway was blocked during the sintering process. As a result, the NbCoSn0.95Sb0.05 specimen using an amorphous precursor exhibited an enhanced zT of 0.7, due to the increase in the power factor and a decrease in lattice thermal conductivity compared to the specimen using a crystalline precursor.

Quantitative hydrogen trap states on high-angle grain boundaries and at dislocations in iron

Low-temperature thermal desorption spectrometry (L-TDS), by which specimens can be heated from -200 °C, was used to quantitatively evaluate the hydrogen desorption peak temperatures (Tp), the hydrogen desorption activation energies (Ea), and the hydrogen occupation ratios (θ) of high-angle grain boundaries and dislocations in iron. Cold-rolled iron was subjected to recrystallization and grain growth to produce three kinds of specimens with different areas of high-angle grain boundaries, in which low-angle grain boundaries were annihilated. L-TDS spectra of specimens containing dislocations and high-angle grain boundaries displayed two hydrogen desorption peaks, denoted as Peak 1 and Peak 2. Peak 1 corresponded to dislocations and displayed Tp, Ea, and θ values of 23 °C, 28.6 kJ·mol−1, and 1.1 to 2.7 atom·nm−1, respectively. In contrast, Peak 2 corresponded to high-angle grain boundaries and displayed Tp, Ea, and θ values of 85 °C, 43.7 kJ·mol−1, and 2.3 to 2.9 atom·nm−2, respectively.

Laves Phase Precipitation Behavior in HiperFer (High Performance Ferritic) Steel with and without Boron Alloying

High-chromium ferritic stainless HiperFer steels were developed for high-temperature applications in power conversion equipment. The presented research describes the precipitation behavior of the Laves phase after the thermomechanical treatment of Fe-17Cr-0.6Nb-2.4W HiperFer alloys with and without the addition of 55 ppm boron. The boron-alloyed variant was produced with the aim of enhancing grain boundary strengthening and consequently increasing creep resistance. The focus is set on the effect of boron on the thermomechanically induced precipitation of (Fe,Cr,Si)2(Nb,W) Laves phase at grain boundaries. The addition of boron modifies the diffusion conditions in the area of grain boundaries. Consequently, the formation of Laves phase is promoted and the particle growth and coarsening process are suppressed. The impact of boron addition was validated by performing creep and thermomechanical fatigue testing in the standard processing state of HiperFer steel. In the B-alloyed variant, increased creep ductility through the modification of the particle-free zone widths at high-angle grain boundaries was encountered. Nevertheless, an optimized thermomechanical treatment is necessary to fully utilize the increased ductility effect for the creep strength optimization of the B-alloyed grade.

Microstructure, macro-, and nano-hardness assessment of AISI 302 steel aged at 1000°C

Changes in the microstructure of the AISI 302 steel must be analyzed in order to optimize its mechanical performance. In this paper, we studied the thermal aging behavior of the AISI 302 steel. The aging treatments of the steel were carried out at a fixed temperature of 1000°C and for durations between 0 and 6000 minutes. A metallographic microscope was used to see changes in the AISI 302 steel microstructure. In addition, the steel was mechanically characterized using the nano-indentation technique and macro-hardness tests. At the temperature investigated, the aging time increase caused a microstructure composed of large austenitic grains and a small area of grain boundaries per unit volume. For the mechanical characterization, the nano-indentation responses also showed a decrease in the nano-hardness and plasticity of the austenite as the aging time increased. The steel macro-hardness decreased significantly by incrementing the aging time.

Влияние структурного состояния на упругие и микропластические свойства алюминиевого сплава AД1

The results of a study of aluminum alloy AD1 in four structural states before and after severe plastic deformation are presented. Both the initial coarse-grained state (supply state) and three fine-grained states, which differ from each other in the method of obtaining, are considered. Elastic and microplastic properties (modulus of elasticity, decrement of elastic vibrations, microplastic deformation) were determined by the acoustic method of a composite vibrator. It is shown that the modulus of elasticity changes to a large extent under the influence of the evolution of internal stresses; the attenuation of ultrasound after severe plastic deformation increases due to an increase in the area of grain boundaries. Key words: AD1 aluminum, modulus of elasticity, microcrystalline aluminum, decrement of elastic vibrations, microplastic deformation.

Влияние термической обработки на образование соединения MNS в низкоуглеродистой конструкционной стали 09Г2С

Introduction. The properties of steels are determined by many factors, including the manufacturing process and subsequent treatment. Some features of these processes lead to the fact that in steel, apart from alloying elements added to obtain a certain level of physical and mechanical properties, there are also foreign impurities that enter it at various stages. Foreign elements can not only dissolve in the matrix, but also participate in the formation of particles of nonmetallic inclusions acting as defects. Its presence significantly affects the performance characteristics of the material. That is why it is necessary to understand the processes that lead to the appearance of nonmetallic inclusions and affect its shape. Purpose: to consider the effect of heat treatment, leading to the appearance of a ferrite-martensitic structure, on the shape and size of nonmetallic inclusions; to determine its influence on the physical and mechanical properties of the material. In the work, samples of rolled steel 09Mn2Si after heat treatment are studied. Research methods. To study the properties and structure of steel 09Mn2Si, the following methods were used: scanning electron microscopy – to study the structure of the material, chemical composition in the local area and the site under study and to determine the accumulation of impurities; SIAMS 800 software and hardware complex – to compare the structure of the material with the atlas of microstructures, to determine the score of the grain structure, differences in the structural and phase composition occurring during heat treatment; portable X-ray fluorescence analyzer of metals and alloys X-MET 7000 - to determine the chemical composition of the samples under study in percentage terms; Vickers hardness tester with a preload of 20 kg – to measure the hardness of the samples under study. Results and discussions. It is found that in the low-alloy low-carbon structural steel 09Mn2Si in most cases there are nonmetallic inclusions of the type of manganese sulfide formed during its manufacture. When this steel is heated to the temperatures of the intercritical transition, this compound is formed in the area of grain boundaries in the form of spherical inclusions. The presence of these inclusions significantly affects the strength and corrosion properties. Manganese sulfide acts as the point of the corrosion process initiation.

Ni solute segregation and associated plastic deformation mechanisms into random FCC Ag, BCC Nb and HCP Zr polycrystals

Different types of grain-boundary (GB) solute segregation in nanocrystalline alloys have been described in the literature as being either homogeneous or heterogeneous, which differently impacts their mechanical properties. In heterogeneous segregation, solute atoms tend to cluster along certain GB areas, while other GB regions remain solute-free. This phenomenon is evidenced with the segregation of Ni solute in nanocrystalline FCC Ag. Yet the physical origin for this segregation behavior and its existence in non-FCC alloys are not fully determined. Here, hybrid Monte-Carlo and molecular dynamics simulations were used to study the segregation of Ni solutes (4 at.%) into nanocrystalline FCC Ag, BCC Nb and HCP Zr metals at their solubility limit temperature and the same homologous temperature (0.405·Tm), respectively. A range of segregation configurations was found: Fully heterogeneous segregation in Ag96Ni4 at 500 K, homogeneous segregation with second-phase precipitates in Nb96Ni4 at 1110 K, homogeneous segregation with dispersion of small-scale Ni clusters in Nb96Ni4 at 1564 K and Zr96Ni4 at 464 K, and fully homogeneous segregation with amorphous intergranular films in Zr96Ni4 at 1118 K. We rationalize these changes by quantifying the Ni solute interactions at GBs. Furthermore, significant variations in mechanical behavior and associated plastic deformation mechanisms are shown for each alloy due to their different segregation behaviors. It is found that strain-localized shear banding is the most significant at interfaces with homogeneous solute segregation containing second-phase precipitates and absent with segregation leading to amorphous intergranular films. These findings underscore the importance of solute interactions in profoundly altering segregation and mechanical behavior in stable nanocrystalline alloys.

Optimisation of Solidification Structure and Properties of Hypoeutectic Chromium Cast Iron.

This paper presents a comprehensive approach to optimising the structure and properties of chromium cast iron that is intended for use in the production of castings that operate under abrasive-wear conditions. In the study, chromium cast iron was inoculated to reduce the grain size in the solidification structure. The finer-grained structure of the casting has a positive effect on its mechanical properties. A number of inoculants have been used that allow the elimination of many types of casting defects: hot cracks and porosities that often occur during the production of chromium cast iron castings. Another advantage of the developed inoculation procedure is the resulting increase in the toughness of chromium cast iron. It should be emphasised that this cast iron does not have a high impact strength in its as-cast condition due to the formation of chromium carbides in the structure. This work also proposes a specially designed heat treatment for inoculated cast iron. The parameters of the applied heat treatment were determined on the basis of dilatometric tests. The visible deviation on a dilatogram at a temperature of about 600 °C is the result of a partial martensitic transformation in the area of grain boundaries. Therefore, the increase in abrasion resistance chromium cast iron is mainly due to the appearance of martensite. The microstructure of the investigated cast iron is particularly desirable in the case of alloys that work with lubrication. The microcavities that are formed by the abrasion of the softer phase constitute natural grease, which reduces abrasive wear. Under the influence of heat treatment, only a part of austenite located near the carbides is destabilized and transformed into martensite. Therefore, this phase of composition formation provided much greater resistance to abrasive wear and hardness.

Texture and Grain Boundary Network Evolution of Laser Powder Bed Fusion Processed Pure Ni During Post-printing Annealing

Commercially pure Ni was additively manufactured using laser powder bed fusion. The printed specimens were then subjected to annealing treatments in a range of 700 °C to 1200 °C to investigate the evolution of the microstructure using electron backscatter diffraction mapping and a five-parameter analysis of the grain boundary character distribution. The post-printing annealing treatment resulted in microstructural changes in respect to grain shape and size, the grain boundary character distribution and the overall texture. However, the extent of these changes strongly depended on the annealing temperature. The grain structure and overall texture changed only modestly when annealed below 900 °C. The grains grew by about 10 pct and this led to a small (≈ 15 pct) increase in the areas of boundaries with low energy (111) planes at the expense of higher energy grain boundary planes with the (001) orientation. Static recrystallization was the dominant microstructure evolution mechanism at annealing temperatures greater than 1000 °C, where new equiaxed grains replaced the initial printed microstructure, enhancing the relative areas of low energy grain boundaries (i.e., sum 3 and sum 9) by a factor of more than five. This change increased the population of boundaries with the low energy (111) plane by a factor of five and decreased the strength of the texture by more than 50 pct through twinning. The resultant microstructure is expected to ultimately improve the material properties, where the increase in the relative areas of sum 3 boundaries would enhance the corrosion resistance and fracture toughness of material, and the texture weakening diminishes the anisotropy in mechanical behaviour.

A synergistic effect of the ion beam sputtered NiO x hole transport layer and MXene doping on inverted perovskite solar cells

The synergistic effect of high-quality NiO x hole transport layers (HTLs) deposited by ion beam sputtering on ITO substrates and the Ti3C2T x MXene doping of CH3NH3PbI3 (MAPI) perovskite layers is investigated in order to improve the power conversion efficiency (PCE) of p-i-n perovskite solar cells (PSCs). The 18 nm thick NiO x layers are pinhole-free and exhibit large-scale homogeneous surface morphology as revealed by the atomic force microscopy (AFM). The grazing-incidence x-ray diffraction showed a 0.75% expansion of the face-centered cubic lattice, suggesting an excess of oxygen as is typical for non-stoichiometric NiO x . The HTLs were used to fabricate the PSCs with MXene-doped MAPI layers. A PSC with undoped MAPI layer served as a control. The size of MAPI polycrystalline grains increased from 430 ± 80 nm to 620 ± 190 nm on the doping, as revealed by AFM. The 0.15 wt% MXene doping showed a 14.3% enhancement in PCE as compared to the PSC with undoped MAPI. The energy-resolved electrochemical impedance spectroscopy revealed one order of magnitude higher density of defect states in the band gap of MXene-doped MAPI layer, which eliminated beneficial effect of reduced total area of larger MAPI grain boundaries, decreasing short-circuit current. The PCE improvement is attributed to a decrease of the work function from −5.26 eV to −5.32 eV on the MXene doping, which increased open-circuit voltage and fill factor.

Influence of grain boundaries on the loop-punching mechanism and shape of helium bubbles in tungsten

In the present work, the growth of helium bubble at Σ3(112)[110], Σ5(013)[100] and Σ13(015)[100] three grain boundaries in tungsten is studied using molecular dynamics simulation. The simulation results show that interstitial dislocation loops are pushed out earlier for the case He bubble growing at the Σ3(112)[110] and later for the case bubble growing at the Σ5(013)[100], while no prismatic interstitial dislocation loop is pushed out for the case bubble growing at Σ13(015)[100] by the end of the simulation. This is because the larger the excess volume per area of grain boundary, the later the prismatic interstitial dislocation loop pushed out. The shapes of helium bubbles are monitored by measuring bubbles sizes along three dimensions during their growing process. Helium bubble grows into a shape slightly deviating from the sphere at Σ3(112)[110] twin boundary; while grows into ellipsoid at Σ5(013)[100] and Σ13(015)[100] grain boundaries. Based on a two-dimensional model, the shapes of helium bubbles are then investigated quantitatively in terms of wetting theory. The theoretical shapes of helium bubbles at the three grain boundaries are in agreement with those obtained by molecular dynamics simulation method, indicating that the growth of helium bubble at grain boundaries obeys the wetting theory.

Structural and dielectric properties of ultra-fast microwave-processed La0.3Ca0.7Fe0.7Cr0.3O3−δ ceramics

Perovskite La0.3Ca0.7Fe0.7Cr0.3O3-δ (LCFCr) is a mixed ionic and electronic conductor (MIEC) that can be employed as an electrode material in reversible solid oxide fuel cells (RSOFCs). In this work, an ultra-fast (15 ​min) one-step microwave (MW)-assisted combustion synthesis route has been developed to obtain phase pure and highly crystalline LCFCr powder. The synthesized powders exhibited a sponge-like microstructure with increased electrochemical reaction sites. Neutron thermodiffraction analysis revealed a structural transition above 500 ​°C from the room temperature (RT) orthorhombic Pnma to a rhombohedral R3c perovskite phase. The oxygen vacancy concentration was found to increase from δ ​= ​0.272(7) at RT to δ ​= ​0.333(5) at 900 ​°C. Furthermore, a 3-dimensional G-type antiferromagnetic structure was detected at RT. MW-sintering of pressed green ceramic pellets was carried out at 950 ​°C for 1 ​h, using a MW-transparent quartz fiber crucible or alternatively a SiC crucible acting as a MW-absorber. Impedance spectroscopy data on sintered ceramic pellets revealed electronic inhomogeneity as demonstrated by the occurrence of three dielectric relaxation processes associated with two grain boundary (GB)-like contributions and one bulk. The dielectric inhomogeneity encountered may be restricted to the extrinsic GB areas, which may be rather thin. More homogeneous dielectric properties of the GBs were found in the pellet that was sintered in the SiC crucible.

Phosphorene grain boundary effect on phonon transport and phononic applications

Grain boundaries (GBs) widely exist in black phosphorene (BP), which plays a vital role in determining the properties of 2D materials. Significant GB effect on the thermal boundary resistance in BP structures is found by using molecular dynamics calculations and lattice dynamic analysis. A remarkably high interface thermal resistance is observed. By analyzing the strain distribution and phonon vibrational spectra, we reveal this high thermal resistance originates from phonon localization and strong phonon boundary scattering induced by the local stress at the GB area. Particularly, it is interesting to find that the partial phonon modes display weak localization when GBs present. The fraction of atoms participating in a particular phonon vibrational mode has been quantified through the calculation of phonon participation ratio. In addition, the thermal boundary resistance is found size-dependent, which further induces interesting thermal rectification effect in the BP structures. A high rectification ratio is obtained by adjusting the structural length and temperature bias. These findings provide a through insight into the GB effects on individual phonon mode transmission across the GBs, and highlight that the GB effect is an important factor and should be taken into account for the applications of BP-based phononic devices.