Transverse Specimens Research Articles

Experimental evaluation of fracture properties of bovine hip cortical bone using elastic-plastic fracture mechanics.

Understanding the fracture mechanics of bone is very important in both the medical and bioengineering field. Bone is a hierarchical natural composite material of nanoscale collagen fibers and inorganic material. This study investigates and presents the fracture toughness of bovine cortical bone by using elastic plastic fracture mechanics. The J-integral was used as a parameter to calculate the energies utilized in both elastic deformation (Jel) and plastic deformation (Jpl) of the hipbone fracture. Twenty four different types of specimens, i.e. longitudinal compact tension (CT) specimens, transverse CT specimens, and also rectangular unnotched specimens for tension in longitudinal and transverse orientation, were cut from the bovine hip bone of the middle diaphysis. All CT specimens were prepared according to the American Society for Testing and Materials (ASTM) E1820 standard and were tested at room temperature. The results showed that the average total J-integral in transverse CT fracture specimens is 26% greater than that of longitudinal CT fracture specimens. For longitudinal-fractured and transverse-fractured cortical specimens, the energy used in the elastic deformation was found to be 2.8-3 times less than the energy used in the plastic deformation. The findings indicate that the overall fracture toughness measured using the J-integral is significantly higher than the toughness calculated by the stress intensity factor. Therefore, J-integral should be employ to compute the fracture toughness of cortical bone.

Comparative investigation on the orthotropic viscoelastic properties of wood during cooling and heating variations

ABSTRACT Differences in the orthotropic viscoelastic properties of Chinese fir wood (Cunninghamia lanceolata) during cooling and heating variations were investigated in the temperature range between −120°C and 25°C. The stiffness and damping of the longitudinal (L), radial (R), and tangential (T) specimens were determined for five equilibrium moisture content (EMC) levels ranging from 0.6% to 25.2%. Results showed that the tensile storage modulus (E′) values in the cooling run were lower than those in the heating run at each temperature, regardless of the grain orientation and EMC level. The absolute value of the changing rate of E′ (|ΔE′|) in the cooling run was more pronounced than that in the heating run. The values of |ΔE′| demonstrated an anisotropy at all EMC levels, while the |ΔE′| of L specimens were lower than that of transverse specimens. Compared to per unit temperature, per unit moisture content exerted more influence on the stiffness of specimens. The γ-relaxation was observed in the loss modulus (E′′) and loss factor (tanδ) temperature spectrum. The γ-relaxation peak temperature in the E″ temperature spectrum was lower than that in the tanδ spectrum. The γ-relaxation peak temperature in the cooling run was lower than that in the heating run, irrespective of the grain orientation. Furthermore, the γ-relaxation peak temperature shifted to a lower temperature range with an increasing amount of adsorbed water, independent of cooling and heating runs.

Influence of Ni additions on the microstructure and tensile property of W-Cu composites produced by direct energy deposition

In this paper, the direct energy deposition technology was applied to produce the W-Cu composites. The Ni powder ranging from 1 to 10 wt% was added into the W-Cu mixed powder to improve the wettability between W and Cu. The influence of Ni additions on the microstructural characterization, phase composition, relative density, and tensile property of thin wall samples was investigated. The morphology and temperature history of the melt pool were detected to analyze the microstructure evolution. The research results show that there were plenty of aggregations of W particles and residual pores in the joint area of the 60W40Cu thin wall sample. Due to the effect of Ni additions on reducing the surface tension between W and liquid Cu, the W particles tended to be uniformly distributed in the matrix with the increase of Ni content. Meanwhile, Ni additions decreased the cooling rate of the melt pool, which promoted the transformation from columnar grains to dendrites in the matrix. Furthermore, the Ni additions could significantly increase the relative density and tensile strength of W-Cu composites. When Ni content was increased from 0 wt% to 10 wt%, the relative density rose from 83.1% to 98.4%, the tensile strength of longitudinal and transverse specimens was nearly 3 and 5 times respectively as high as that of the specimens without Ni content.

Response of Mechanical Properties of Polyvinyl Chloride Geomembrane to Ambient Temperature in Axial Tension

Aiming at the mechanical response of geomembrane (GEM) in membrane-faced rockfill dam (MFRD) to different ambient temperatures, the mechanical properties in axial tension of polyvinyl chloride (PVC) GEM were studied by experiment and theoretical analysis. First, fifteen groups of axial tensile tests for longitudinal/transverse specimens were conducted at different temperatures in the temperature environment laboratory, the stress–strain curve and Young’s modulus were obtained, and the variation of Young’s modulus with temperature was analyzed by Boltzmann function fitting. Second, the glass transition temperature of PVC GEM was obtained by differential scanning calorimetry (DSC), and the difference in mechanical properties between longitudinal and transverse specimens of PVC GEM was analyzed by thermomechanical analyzer (TMA) thermodynamic test. The results showed that the lower the temperature, the greater the Young’s modulus, and the smaller the linear interval of stress and strain, while the higher the temperature, the result is opposite. The difference in mechanical properties between the two directions is related to the ambient temperature. The orientation of polymer structure accounts for the difference in mechanical properties by theoretical analysis. The fitting results of Boltzmann function have a certain reference value for numerical simulation. In design of the membrane impervious structure in MFRD, the ambient temperature should be considered fully, and the longitudinal/transverse welding splicing should be avoided as far as possible. The current test specification should test the mechanical performance of GEM at normal operating temperature of reservoir instead of the test and quality evaluation at a single temperature. The temperature should be considered comprehensively in construction to avoid damaging the performance of impervious structure and ensure the service life.

Tensile mechanical properties and failure mechanism of bamboo scrimber under different strain rates

Bamboo Scrimber (BS) is a composite material with excellent mechanical properties fabricated by utilizing bamboo. This paper aimed to present the tensile properties and failure mechanism of BS under quasi-static and impact loading by quasi-static and split Hopkinson tensile tests. The Scanning Electron Microscope (SEM) photograph analysis was employed to investigate the failure process and modes of BS in both directions (longitudinal and transverse). Results show that the tensile properties of longitudinal specimens are much better than that of transverse. The strain rate effect increases tensile strength and ultimate strain as increasing strain rate from 10−5 to about 1300 s−1. The empirical formulas of dynamic increase factor were derived at various strain rates, and the turning strain rate is 689 and 525 s−1 for longitudinal and transverse specimens, respectively. The strength-to-weight ratio of BS is 83.54 kN.m/kg, higher than that of concrete and steel but lower than some timbers. Fiber fracture, matrix fracture, and interfacial debonding in the microscopic scale are reasons for the failure. Research on the impact tensile properties and failure mechanism of BS are helpful to its wide application for structure materials.

Microtensile failure mechanisms in lamellar bone: Influence of fibrillar orientation, specimen size and hydration

A mechanistic understanding of bone fracture is indispensable for developing improved fracture risk assessment in clinics. Since bone is a hierarchically structured material, gaining such knowledge requires analysis at multiple length scales. Here, the tensile response of cortical bone is characterized at the lamellar length scale under dry and hydrated conditions with the aim of investigating the influence of bone's microstructure and hydration on its microscale strength and toughness. For individual lamellae, bone strength strongly correlates with the underlying mineralized collagen fibrils orientation and shows a 2.3-fold increase compared to the macroscale. When specimen size is increased to a few lamellae, the influence of fibril orientation and the size effect on strength are significantly reduced. These findings highlight the critical influence of defects, such as canaliculi and interlamellar interfaces, when assessing larger volumes. Hydration leads up to a 3-fold strength decrease but activates several toughening mechanisms enabling inelastic deformation. In axial specimens, toughening is seen through fibril bridging and crack kinking. In transverse specimens, water presence leads to a progressive but stable crack growth parallel to the fibril orientation, suggesting crack-tip plasticity at the fibrillar interfaces. This work offers a better understanding of the role of interfaces, porosity, and hydration in crack initiation under tensile loading, which is a crucial step towards improved clinical management of disease-related bone fractures through multiscale modeling approaches. Statement of significanceBone features a complex hierarchical structure which gives rise to several toughening mechanisms across several length scales. To better understand bone fracture, particularly the changes associated with age and disease, it is essential to investigate bone mechanical response at different levels of its hierarchical structure. For the first time, we were able to observe the nucleation of a single crack in hydrated bone lamellae under well-controlled uniaxial tensile loading conditions. These experiments highlight the role of water, interfaces, defects, and the ratio of defect to specimen size on bone's apparent strength and toughness. Such knowledge can be used in the future to develop multiscale models enabling improved clinical management of disease-related bone fractures.

Metallurgical and Mechanical Characterization of Low Carbon Steel—Stainless Steel Dissimilar Joints Made by Laser Autogenous Welding

This paper addresses the metallurgical and mechanical characterization of dissimilar joints made by laser autogenous welding between thin sheets of low-carbon steel (CS) and austenitic stainless steel (SS). The welding technology applied, previously optimized to produce sound dissimilar joints, is based on the heat source displacement from the weld gap centerline towards CS, in order to reduce the SS overheating. The research includes optical microscopy observations, energy dispersive X-ray analysis (EDX) to assess the wt% of Cr, Ni, and Fe in all regions of the dissimilar welded joint, hardness measurements, and tensile tests of transverse-welded flat specimens. In comparison with classical determination of the joint overall mechanical characteristics, the novelty of this research consists of experimental assessment of the local mechanical behavior of the fusion and heat affected zones by using a digital image correlation technique (VIC-2D). This is an efficient tool for determining the constitutive properties of the joint, useful for modelling the mechanical behavior of materials and for verifying the engineering predictions. The results show that the positive difference in yielding between the weld metal and the base materials protects the joint from being plastically deformed. As a consequence, the tensile loading of flat transverse specimens generates the strain localization and failure in CS, far away from the weld.

Increased tissue-level storage modulus and hardness with age in male cortical bone and its association with decreased fracture toughness.

The incidence of bone fracture increases with age, due to both declining bone quantity and quality. Toward the goal of an improved understanding of the causes of the age-related decline in the fracture toughness of male cortical bone, nanoindentation experiments were performed on femoral diaphysis specimens from men aged 21-98years. Because aged bone has less matrix-bound water and dry bone is less viscoelastic, we used a nanoindentation method that is sensitive to changes in viscoelasticity. Given the anisotropy of bone stiffness, longitudinal (n=26) and transverse (n=25) specimens relative to the long axis of the femur diaphysis were tested both dry in air and immersed in phosphate buffered saline solution. Indentation stiffness (storage modulus) and hardness increased with age, while viscoelasticity (loss modulus) was independent of donor age. The increases in indentation stiffness and hardness with age were best explained by increased mineralization with age. Indentation stiffness and hardness were negatively correlated with previously acquired fracture toughness parameters, which is consistent with a tradeoff between material strength and toughness. In keeping with the complex structure of bone, a combination of tissue-level storage modulus or hardness, bound water, and osteonal area in regression models best explained the variance in the fracture toughness of male human cortical bone. On the other hand, viscoelasticity was unchanged with age and was not associated with fracture toughness. In conclusion, the age-related increase in stiffness and hardness of male cortical bone may be one of the multiple tissue-level characteristics that contributes to decreased fracture toughness.

Effect of Structural Factors on Difference in Structural Steel Longitudinal and Transverse Impact Specimen Embrittlement after Controlled Rolling and Thermomechanical Treatment

Using correlation-regression analysis, the effects of structure and chemical composition on KCV impact strength anisotropy and difference in critical brittleness temperatures for longitudinal and transverse specimens of ferrite-pearlite and high-strength (ferrite + bainite) steels after thermomechanical rolling are studied. The significant effect of pearlite content and sulfide inclusions on impact strength anisotropy and difference in critical brittleness temperatures for longitudinal and transverse specimens of ferrite-pearlite steels is demonstrated. For high strength ferrite-bainite steels prepared using thermomechanical rolling technology the effect of carbon and sulfur on degree of embrittlement for transverse specimens is considered that also depends on the content of titanium carbonitride and Al2O3-based aluminum oxides.

STUDY OF THE STRUCTURE, PHASE COMPOSITION, PHYSICOMECHANICAL PROPERTIES, AND ALSO OPTIMIZATION OF HEAT TREATMENT PROCESSES OF CAST HEAT-RESISTANT NICKEL ALLOY ЕР202 BY THE METHOD OF MATHEMATICAL MODELING

General information about the EP202 heat-resistant weldable alloy with a nickel-chromium matrix is given. Its chemical composition, manufacturing technology, recommended heat treatment modes for short-term and long-term parts, as well as recommended maintenance modes for castings and rodsheets are presented. A description of the structure and phase composition of the alloy in the cast state and after heat treatment is given. The mechanical properties of the alloy depending on the test temperature and heat treatment conditions for longitudinal and transverse specimens are given. The physical properties of the alloy at various temperatures are also described. Further, the study presents the study of the modes of stepwise aging on the structure and mechanical properties of the EP202 alloy. An increase in mechanical properties after two-stage aging in comparison with the initial heat treatment due to a more uniform distribution of the strengthening γ¢-phase over the volume of the alloy was established. With the help of the obtained regression equations, the optimal temperature of the first stage of two-stage aging (540 C) was established, which ensures an increase in the level of impact strength by (20...25) %.

Microstructure and mechanical properties of Be–Al alloy fabricated by laser solid forming

The microstructures and tensile mechanical properties of thin-walled Be-38 wt%Al samples produced by laser solid forming (LSF) are investigated. The results show that no cracking or significant porosity is observed in the thin-walled samples. The microstructure of the LSFed Be–Al alloy is primarily composed of columnar Be grains delineated by continuous Al networks. The columnar Be grains show almost the same crystallographic orientation, in which the preferred growth direction is the <0001> direction inclined towards the scanning direction at an angle of approximately 70°. The widths of the Be columnar grains gradually increase as the deposition height increases. The LSFed Be–Al alloy shows anisotropic tensile properties, exhibiting higher ultimate tensile strength and yield strength but smaller elongations for the longitudinal specimens compared to the transverse specimens. BeO and Al2O3 particles are observed to be primarily distributed at the Be/Al interface, resulting in a lack of bonding or cracking during the tensile test.

Variation of Mechanical Properties across the Dissimilar Joints: Ferritic steel and Stainless Steel

Grade 91 ferritic steel (also known as P91) is widely used for constructing steam generators in prototype fast breeder reactors (PFBR) because of their stress corrosion cracking resistance, high thermal conductivity and low thermal expansion co-efficient for intermediate heat exchangers and austenitic stainless steels (SS304L, SS316L and SS316LN.) Due to their high temperature creep strength and good corrosion resistance, the dissimilar metal weld (DMW) joints between these materials are unavoidable. Inconel 82/182 filler metal is recommended to join these materials since its thermal expansion co-efficient lies between that of ferritic steel and stainless steel. In the present investigation, the tensile properties of each region of DMW joint have been evaluated. DMW joint between P91 and SS 316LN were fabricated using manual metal arc welding (MMAW) process with inconel 82/182 filler metals. The tensile properties of various regions of DMW were examined at a nominal strain rate of 1×10-3 s-1. Microstructural features of various regions of DMW were examined through optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Out of different regions, P91 parent metal exhibited higher tensile strength while the transverse tensile specimens failed at the outer edge of the HAZ of P91 steel. This heterogeneity in mechanical properties may be due to the evolution of complex microstructures developed during welding.

WOOD QUALITY OF THE SPECIES Cedrelinga cateniformis Ducke THROUGH ULTRASONIC INSPECTION

The present work proposes a method of inspecting structural elements of wood blocks using non-destructive techniques. For this, three blocks of Cedrelinga cateniformis Ducke wood were longitudinally perforated in a grid form, then transversal ultrasound velocities were measured and used to make 2D graphics. Afterwards, the blocks were cut to make transversal specimens that were used to determine apparent densities. The graphs of both parameters were compared to visualize quality zones in the blocks from velocity and density bands. From this, a preliminary inspection protocol using ultrasound tests of structural elements was proposed.

Microtensile properties and failure mechanisms of cortical bone at the lamellar level

Bone features a remarkable combination of toughness and strength which originates from its complex hierarchical structure and motivates its investigation on multiple length scales. Here, in situ microtensile experiments were performed on dry ovine osteonal bone for the first time at the length scale of a single lamella. The micromechanical response was brittle and revealed larger ultimate tensile strength compared to the macroscale (factor of 2.3). Ultimate tensile strength for axial and transverse specimens was 0.35 ± 0.05 GPa and 0.13 ± 0.02 GPa, respectively. A significantly greater strength anisotropy relative to compression was observed (axial to transverse strength ratio of 2.7:1 for tension, 1.3:1 for compression). Fracture surface and transmission electron microscopic analysis suggested that this may be rationalized by a change in failure mode from fibril-matrix interfacial shearing for axial specimens to fibril-matrix debonding in the transverse direction. An improved version of the classic Hashin's composite failure model was applied to describe lamellar bone strength as a function of fibril orientation. Together with our experimental observations, the model suggests that cortical bone strength at the lamellar level is remarkably tolerant to variations of fibrils orientation of about ±30°. This study highlights the importance of investigating bone's hierarchical organization at several length scales for gaining a deeper understanding of its macroscopic fracture behavior. Statement of SignificanceUnderstanding bone deformation and failure behavior at different length scales of its hierarchical structure is fundamental for the improvement of bone fracture prevention, as well as for the development of multifunctional bio-inspired materials combining toughness and strength. The experiments reported in this study shed light on the microtensile properties of dry primary osteonal bone and establish a baseline from which to start further investigations in more physiological conditions. Microtensile specimens were stronger than their macroscopic counterparts by a factor of 2.3. Lamellar bone strength seems remarkably tolerant to variations of the sub-lamellar fibril orientation with respect to the loading direction (±30°). This study underlines the importance of studying bone on all length scales for improving our understanding of bone's macroscopic mechanical response.

Anisotropic mechanical properties and deformation behavior of low-carbon high-strength steel component fabricated by wire and arc additive manufacturing

Wire and arc additive manufacturing (WAAM) is an efficient technique for fabricating large and complex components that are applied in the manufacturing industry. In this study, anisotropic mechanical properties of a low-carbon high-strength steel component fabricated by WAAM were investigated via mechanical testing, and the transversal and longitudinal deformation behavior of the component were studied using the digital image correlation (DIC) method. Additionally, the features of microstructure, texture, and fracture mode of the inter-layer area and deposited area were also investigated to reveal the mechanism of anisotropy. The results showed the mechanical properties of longitudinal specimens were inferior to that of the transversal specimens. Several strain concentration zones in the longitudinal specimen were relevant to the inter-layer characteristics observed from the fracture surface and macrostructure, which was confirmed by the strain evolution recorded by DIC. The inter-layer areas were proved to be the weak link in the deposited component by scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) analysis results, including various phase composition, phase morphology, misorientation angle, grain size, Schmid factor, and texture. Finally, based on the fractography analysis, anisotropy resulted from inter-layer zones is also confirmed via the comparison of transversal and longitudinal fracture morphology.

Effect of Hydrogen Corrosion on the Brittle Fracture Resistance of an Oil Line Pipe 530 mm in Diameter Made of 12GSB Ferritic–Pearlitic Steel

The structure, the static tensile properties, the impact toughness, and the fracture mechanisms of the 12GSB pipe steel specimens cut from the defect regions in a pipeline 530 mm in diameter are studied. Hydrogen corrosion is found to affect the anomalous character of the temperature dependences of the impact toughness and the fraction of ductile component in a fracture surface. Sulfur is shown to substantially influence the ductile crack propagation energy in the transverse direction and to weakly influence this energy along the rolling direction. The development of hydrogen corrosion in the pipeline is found to be accompanied by a significant increase in the reduced fraction of intergranular fracture (15.8–35%) in brittle fracture surfaces, and this fraction in the separation plane reaches 50.5%. The relation between the impact toughness of the transverse specimens and the fraction of ductile component in a fracture surface has an anomalous character: this relation has two linear segments, the fracture energies in which differ by an order of magnitude. The segment with a low fracture energy (4.4–16.1 J/cm2) characterizes the action of the sear component of separation in the rolling plane, and the segment with a high fracture energy (38–246 J/cm2), the action of a ductile mode I fracture mechanism. The impact toughness anisotropy coefficient is found to be high, Ka = 2.31.

Orthotropic hygro-mechanical behavior of Chinese fir during cyclical relative humidity variation

The orthotropic free swelling–shrinkage and mechano-sorptive creep (MSC) during cyclical relative humidity (RH) variation (0–80% RH) and time-dependent viscoelastic creep (VEC) in a steady state (0% RH) were examined in Chinese fir (Cunninghamia lanceolata). During RH changing, the occurrences of local maximum or minimum strains of the free swelling–shrinkage and MSC lagged behind the corresponding maximum or minimum RH. The lagged time decreased with increasing cyclical times. Furthermore, the lagged time exhibited an orthotropic behavior: the longer lagged time was found in longitudinal specimen compared to transverse specimens. MSC exhibited a more pronounced anisotropy than VEC. According to the three tests, the performance of free swelling–shrinkage and the mechano-sorptive effect on the orthotropic MSC behavior was addressed. The free swelling–shrinkage mainly dominated the creep strain during cyclic RH variation, especially for longitudinal specimen. The mechano-sorptive effect on the MSC behavior exerted more influence on tangential specimen compared to radial and longitudinal specimens. The mechano-sorptive limit was observed for all specimens. Longitudinal specimen required more cyclic times to approach the mechano-sorptive limit than transverse specimens.

In-Service Brittle Fracture Resistance Degradation of Steel in a Ship-to-Shore Portal Crane

The assemblies of a ship-to-shore portal crane after 33 years of service were studied on the possible loss of the initial brittle fracture resistance level by rolled steel sheets. Strain gauge measurements were used to predict the level of operating stresses. The latter and a decrease in the Charpy impact strength were established to be distinctly related. Transverse specimens are shown to generally exhibit a lower impact strength level as compared to that of the longitudinal ones. The differences in the brittle fracture resistance of specimens, differently oriented with respect to the stamping direction, are revealed to be growing with the metal degradation level. This level along the stamped fibers is demonstrated to increase with a decrease in the sheet thickness, which can be explained by the effect of aggressive marine environment as a factor of metal hydrogenation.

Effects of solidification thermal parameters and Bi doping on silicon size, morphology and mechanical properties of Al-15wt.% Si-3.2wt.% Bi and Al-18wt.% Si-3.2wt.% Bi alloys

The use of bismuth (Bi) in aluminum (Al) industries is recognized as prime importance because of possible recycling as alloying element in special applications such as those enhancing machinability. The effects of Bi interaction on solidification progress as well as on the resulting microstructure of hypereutectic Al-Si alloys, i.e. the morphology and size of Si crystals are rare information. As such, the present research work investigates the characteristic parameters of eutectic and primary Si with addition of Bi for both ternary Al-15 wt.%Si- 3.2 wt.%Bi and Al-18 wt.%Si- 3.2 wt.%Bi alloys samples directionally solidified (DS) under various cooling rates. The alloy containing 15 wt.%Si showed that Bi acts in the suppression of the growth of primary Si crystals for samples solidified at cooling rates ranging from 2.0 to 31 K/s. For lower rates, a minor fraction of five-fold branched Si was recognized in transverse specimens. A mixture of globular-fibrous eutectic Si is shown to occur for eutectic cooling rates higher than 5 K/s. The Al-18 wt.%Si- 3.2 wt.%Bi alloy is characterized by a mixed structure of eutectic flaky Si and primary angular Si with intersecting spines at nearly 90º all over the entire range of experimental cooling rates (i.e., from 0.4 to 40 K/s). Despite the intricacy of the formed microstructures, it was possible to establish relationships between tensile properties and eutectic Si spacing in order to compare the properties between the tested alloys. Tensile strength and elongation decrease with increasing alloy Si content.

Effect of large-size carbides on the anisotropy of mechanical properties in 11Cr-3Co-3W martensitic heat-resistant steel for turbine high temperature blades in ultra-supercritical power plants

9–12%Cr martensitic heat-resistant steels (MHRS) are the key materials for making ultra supercritical (USC) unites turbine blades. In this study, the anisotropy of mechanical properties in Cr-Co-W-type MHRS 1Cr11Co3W3NiMoVNbNB is discussed. The samples were prepared for impact and tensile tests. By utilizing characterization techniques, such as OM, FESEM, TEM, and EDS, steel sample fracture surfaces and the microvoids as well as the microstructure-anisotropy mechanical properties relationship were thoroughly investigated. It was pointed out that a strong anisotropy of mechanical properties was observed as much lower impact toughness and tensile plasticity in transverse direction in the steel sample after a heat treatment process. The anisotropy was mainly due to the large-size directionally distributed M23C6-type and M6C-type carbides. Large-size directionally distributed carbides lead to anisotropy of mechanical properties mainly by promoting the formation of microcracks and the propagation of cracks in transverse specimens. For transverse impact specimens, the propagation of microvoids is promoted to banded brittle cracks by large-size directionally distributed carbides. These banded brittle cracks become the pre-cracks of matrix and markedly decrease the toughness. For transverse tensile specimens, the propagation of microvoids is promoted to shallow chain-distributed dimples by large-size directionally distributed carbides, which markedly decrease the plasticity.