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YAG (Y3Al5O12) transparent ceramics have attractive application prospects for transparent armor protection modules because of their excellent light transmittance and anti-ballistic capability. Understanding the fracture behavior and damage mechanism of YAG is necessary for armor design. To explore the damage characteristics of YAG under compression and tension, shock compression and shockless spalling experiments with soft recovery technique are conducted. The spall strength of YAG is obtained and the recovered samples are observed by CT and SEM. It is shown that the macroscopic damage characteristic of YAG under compression is vertical split cracks with oblique fine cracks distributed in the entire sample, while that under tension is horizontal transgranular cracks concentrated near the main spall surface. The cracks generated by macroscopic compression, tension and shear stress extend in similar tensile form at the microscale. The proportion of transgranular fractures on spall surfaces is higher than that of cracks induced by macroscopic compression. Meanwhile, higher loading rate and longer loading duration increase the transgranular fracture percentage.

A sustained load holding period imposed during fatigue loading is detrimental to material performances, causing a sharp decline in the fatigue life of near-α titanium alloys. Therefore, the deformation discrepancies of dwell fatigue (DF) and low cycle fatigue (LCF) were studied for Ti834 titanium alloy with bimodal structures in this work. The fractographies after dwell fatigue and low cycle fatigue testing were characterized using scanning electron microcopy (SEM), and the crack propagation paths at the subsurface were investigated using an optical microscope (OM). In order to reveal the mechanism of fatigue damage, detailed dislocation structures were observed using transmission electron microcopy (TEM). The crack propagation paths in microscales and the dislocation distributions were observed in the LCF and DF. The reasons for the discrepancies are also discussed in this work, which effectively enhances the understanding of the dwell failure procedures. The results show that the near basal cracks are formed under dwell fatigue, and the deformation is highly localized at the boundary of αp grains under dwell fatigue. In contrast, during low cycle fatigue, the sample tends to deform homogenously. An intergranular fracture along the primary αp grains is formed due to the localized deformation during dwell fatigue. However, a transgranular fracture is formed in the primary αp grains under low cycle fatigue.

Sintering additives and micro-powder injection molding offer an effective method to densify boron carbide (B4C) and make B4C components with complex shapes. By adjusting the proportion of three kinds of powders (SiC, Al2O3 and Y2O3), four kinds of sintering additives were prepared. The feedstock uniformity, debinding behavior, phase composition and microstructure of micro injection molded B4C components with different sintering additives were studied. The results showed that the defects such as lattice distortion and vacancy were introduced into ball milling, which increase the surface energy and benefit subsequent sintering densification. The feedstock had good uniformity and rheology that met the requirements of micro powder injection molding. After debinding, B4C components had enough strength and showed certain sintering characteristics. The addition of sintering additives was beneficial to densification and sintering temperature reduction. The addition of sintering additives formed a second phase in the B4C crystal and at the grain boundary of B4C crystal, which changed the fracture mode from transgranular fracture to mixed fracture mechanism with transgranular fracture.

Monolithic B4C, B4C–TiB2, and B4C–TiB2–graphene nanoplatelets (GNPs) were fabricated by hot pressing (HP) at 1900 °C for 1 h under an axial pressure of 30 MPa. The microstructures and mechanical and electrical properties of the B4C composites were investigated. The results show that the GNPs are distributed homogeneously in B4C-based ceramic composites. Compared with monolithic B4C, the TiB2–GNPs-containing B4C composite exhibits an approximately 68 % increase in flexural strength and a 169 % increase in fracture toughness due to the synergistic effects of TiB2 particles and GNPs. The toughening mechanisms mainly include TiB2 crack deflection, crack branching, transgranular fracture and GNPs crack deflection, crack bridging, and GNPs pull-out. Additionally, the electrical conductivity of the B4C composite reinforced with dual fillers is three orders of magnitude higher than that of monolithic B4C due to the establishment of a conductive network. The addition of GNPs can efficiently connect the isolated conductive TiB2 particles in the B4C matrix and provides an additional channel for electron migration.

In the present work, the influence of sintering temperature and particle size of pristine ZrC particles on the microstructure, mechanical properties, and thermal properties of ZrC/ZTA ceramic composites are investigated. Specimens consolidated by spark plasma sintering at different sintering temperatures from 1500 °C to 1800 °C. XRD results revealed that α-Al2O3, t-ZrO2, ZrC, and a small quantity of m-ZrO2 phases are present in the composites. The microstructure of μm-ZrC/ZTA is found to be more compact than nm-ZrC/ZTA composites. There is an apparent increase in the average grain size with the increase in temperature. From the micrographs of fracture surfaces, step-wise transgranular fracture structures are observed. Relative densities and Vickers hardness are in proportion to sintering temperature from 1500 °C to 1700 °C. The maximum Vickers hardness of 1919 HV1 is obtained for μm-ZrC/ZTA composites. Indentation fracture toughness displays a gradual rise when the temperature rises from 1500 °C to 1700 °C, then deteriorates at 1800 °C for both nm-ZrC/ZTA and μm-ZrC/ZTA ceramic composites. The maximum fracture toughness values for nm-ZrC/ZTA and μm-ZrC/ZTA are 6.75 MPa m1/2 and 6.83 MPa m1/2, respectively. The thermal conductivity of the specimens decreased gradually as the temperature increases from 100 °C to 1000 °C. The obtained results indicated that the 1700 °C is the optimized sintering temperature where μm-ZrC/ZTA composites have excellent performance on microstructure, mechanical properties, and thermal properties than nm-ZrC/ZTA composites.

ZrO2-doped YTaO4 ceramics with different ZrO2 contents (Y1-xTa1-xZr2xO4 ceramics, 2x = 0, 0.1, 0.15, 0.2) are prepared by a solid-state reaction method. The high-temperature mechanical properties are determined by an in situ high-temperature three-point bending combined with the digital image correlation (DIC) method. The results show that when the temperature rises from 25 °C to 800 °C, the temperature dependence of the elastic modulus, fracture toughness and fracture strength with a ZrO2 doping content of 10% mol is relatively small. The elastic modulus, fracture toughness and fracture strength decrease from 105.4 GPa to 96.1 GPa, from 2.6 MPa m1/2 to 2.3 MPa m1/2 and from 73.8 MPa to 64.8 MPa, respectively. Transgranular fracture is the main fracture mode. When the crack propagates through the twin band, a phase transformation and a typical domain change occur. Furthermore, the crack propagating through the twin band at room temperature (25 °C) is more tortuous than that at 800 °C, and more energy needs to be consumed. This illustrates that the fracture toughness and fracture strength at room temperature (25 °C) are higher than those at high temperature.

Al2O3-Cr2O3 refractories have excellent slag corrosion resistance and can adapt to the oxidation/reduction atmosphere in the smelting reduction ironmaking furnace. However, Al2O3-Cr2O3 refractories have poor mechanical properties and sintering properties. In order to improve the mechanical properties of Al2O3-Cr2O3 materials, the CaAl12O19 reinforced Al2O3-Cr2O3 composites were prepared by pressureless sintering process, and the influences of CaO content on the sintering properties, mechanical properties, and microstructure evolution of the composites were studied. The results show that a small amount of CaO can significantly improve the compactness of the composites, which is mainly due to the formed sheet-like CA6 fill the gap between the solid solutions, and reduces the porosity of the composites. In addition, the sheet-like CA6 makes the connection between solid solutions closer, and the intergranular fracture gradually transforms into a mixed mode of intergranular and transgranular fracture. The best mechanical propertie is observed at S4 with the CaO content of 2 wt.%. Compared with sample S0 without CaO, the hardness, compressive strength and flexural strength of the S4 were increased by 35.19 %, 49.69 %, and 68.34 %, respectively. The addition of excessive CaO will deteriorate the mechanical properties of the composites, because the formation of a large number of layered CA6 increases the porosity of the composites. Furthermore, a small amount of CaO addition can significantly improve the thermal shock resistance of the composites. After 10 and 20 thermal shock cycles, the strength loss rates of S4 are only 5.83 % and 8.74 %, respectively.

The key problems restricting the wide development of Ti3AlC2 material are the low hardness and strength. In this paper, MAX phase Ti3(Al,Si)C2 solid solutions with different Si doping were successfully synthesized using an in-situ reaction of Ti–Al–C system by powder metallurgy route. The phase structures and microstructures of the as-synthesized Ti3(Al,Si)C2 solid solutions were analyzed, the mechanical properties were tested, and the fracture surface morphologies were characterized. The results show that doping Si can prevent the lath-like structure of MAX phase from coarsening. When doping 0.2 mol Si, the as-synthesized Ti3Al1.0Si0.2C2 sample offers fine microstructure and has excellent performance. Its Vickers hardness, flexural strength and the fracture toughness are 5.52 GPa, 546 MPa, 7.51 MPa m1/2, respectively. The fracture mode is transgranular cleavage fracture. During propagation, the main crack deflects and branches obviously. The crack extends in a zigzag like path, accompanied by transgranular fracture. When suffering external force, the particular layered structure of Ti3(Al,Si)C2 can absorbs and dissipates more energy through hybrid deformation modes such as extrusion, kink, fold, interlaminar separation and tearing. With this complex and mixed fracture mode, the crack propagation were effectively prevented, and its flexural strength and fracture toughness were enhanced.

The inherent brittleness of bioceramics restricts their applications in load-bearing implant, although they possess good biocompatibility and bioactivity. ZnO, MgO and 58S bioglass (BG) were incorporated as additives to further improve the mechanical properties and biocompatibility of β-TCP and ZnO/MgO/BG-β-TCP composite scaffolds were manufactured via digital light processing (DLP). The composite with the best comprehensive performance was selected for degradation behavior and biocompatibility evaluation. The effects of different proportions of ZnO/MgO/BG on mechanical strength were analyzed and ZnO0·5/MgO1/BG2-β-TCP (ZMBT) samples exhibited superior mechanical strength. The improvement by 272% and 99% respectively was achieved in fracture toughness and compressive strength with the optimal recipe. The enhancement effect is realized through phase transition, alterative sliding actions and transgranular fracture to effectively prevent the load transfer combining the functions of bioglass and metal oxide. ZMBT scaffolds exhibited a more desirable pH environment and an enhanced ability of apatite-mineralization formation, meanwhile Si4+, Mg2+ and Zn2+ were gradually released from scaffolds. Furthermore, in vitro evaluation indicated that ZMBT scaffolds presented not only excellent cell attachment, proliferation, alkaline phosphatase (ALP) activity, but they up-regulated osteogenic gene (ALP, OCN, Runx2). These results suggest that the addition of ZnO/MgO/BG to DLP-printed β-TCP scaffolds offer a smart strategy to fabricate porous scaffolds with conspicuously better biological and physicochemical properties including compressive strength, bioactivity, osteogenesis and osteogenesis-related gene expression. Metal-oxide and BG synergistically enhanced the mechanical and biological properties which make the ZMBT scaffolds a strong candidate for bone repair applications.

The effect of ultrasonic shot peening on the environmental hydrogen embrittlement behavior of the 7075-T6 aluminum alloy is investigated. The 7075-T6 tensile specimens were treated by ultrasonic shot peening for 50 s. Surface residual stress and the depth of residual stress under the surface were evaluated using an X-ray diffractometer. Then, the specimens were tensile tested in humid air and dry nitrogen gas by the slow strain rate technique. The results showed that the ultrasonic shot-peened specimen has a superior hydrogen embrittlement resistance. Further, the ultrasonic shot peening changes the fracture mode from an intergranular fracture mode to the transgranular one. It was suggested that ultrasonic shot-peening has two effects on hydrogen embrittlement behavior, the distribution of hydrogen inside the surface layer by introducing dislocations/vacancies as hydrogen traps and reducing the normalized amount of hydrogen trapped per unit length of the grain boundary.

Hydrogen diffusion and embrittlement in an austenitic steel with 0.2 wt pct carbon and 0.2 wt pct nitrogen were investigated. The simultaneous alloying of both carbon and nitrogen did not reduce hydrogen diffusivity more than single alloying of nitrogen due to the interaction between carbon and nitrogen. During tensile straining, a low density of cracks initiated at the grain boundaries at an early deformation stage. The cracks propagated either along the grain boundaries and twin boundaries, or the paths where e martensite was concentrated, which resulted in mixed intergranular and transgranular fracture modes. Still, the resistance to hydrogen embrittlement improved in comparison with the single alloying of either carbon or nitrogen due to enhanced austenite stability.

The effect of deformation temperature on tensile behavior of Inconel 718 alloy has been studied by a self-developed in-situ high-temperature tensile stage inside a scanning electron microscopy at a temperature range from room temperature (RT) to 750 °C. The dynamic microstructure evolution and mechanical properties at different temperatures were performed and compared by the uniaxial tensile tests. The in-situ test results showed that the mechanical properties and fracture mechanisms of Inconel 718 alloy were sensitive to deformation temperatures. From RT to 650 °C, the yield stress and ultimate tensile strength decrease slightly and the tensile ductility is comparable. While up to 750 °C, the yield stress and ultimate tensile strength decrease significantly, the elongation and reduction of cross section also showed a significant decrease from RT to 750 °C. It was found that at RT and 650 °C, tensile cracks tended to initiate around the carbide particles and the triple junctions of grain boundaries, also propagated transgranularly; at 750 °C, the cracks initiated at grain boundaries and propagated intergranularly. In fact, with the increase in deformation temperature, the fracture mechanism transformed from the ductile transgranular fracture to the brittle intergranular fracture.

The influence of electropulsing on the creep behaviour, strength, and microstructure of an Al−Cu−Li alloy during creep ageing was investigated. Electropulsing assisted creep ageing (ECA) and conventional creep ageing (CCA) were carried out under various stress levels and time conditions. Applying electropulsing results in a noteworthy change of creep behaviour, including a variation in creep curves, an increased creep rate in early stage, and an improved creep strain. The ECA specimen experiences a shorter time to the peak strength, and an increase in elongation by ~17.4% without loss of the peak-aged strength compared with CCA specimen. The ultrafine nano-size subgrains are observed to form under electropulsing, which can result in an increased creep strain by increasing grain-boundary sliding. The enhancement of both dislocation interactions and solute diffusion under electropulsing is considered as a primary cause of disappearance of a platform stage during early creep ageing. Some of T1 precipitates around the grain boundary are observed in the peak ECA sample, resulting in an occurrence of transgranular fracture, which is further responsible for an increased elongation of the ECA specimen.

WC-10Co cemented carbides reinforced with 0, 0.5, 1, and 2 wt% graphene nanoplatelet (GNP) were fabricated by ball milling and spark plasma sintering (SPS). The microstructure, structural and phase analysis, hardness, and fracture toughness of WC-10Co/GNP composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and Vickers indenter. Tribological behaviors of the fabricated composites against an alumina counterface were studied using a pin on disk configuration. It was found that GNP refined the microstructure, increased the fracture toughness, and postponed the stable-to-unstable friction transition. While transgranular fracture and crack deflection were observed in the base composite, crack bridging, micro-crack formation, and crack deflection were the major toughening mechanisms in GNP-reinforced cemented carbides. The addition of 1 wt% GNP resulted in the highest hardness and wear resistance. However, at higher GNP contents, both hardness and wear resistance decreased due to the agglomeration of GNPs. Widespread abrasive grooving and Co binder extrusion were characterized as the main controlling mechanisms of wear in GNP-free cemented carbides. The wear of GNP-reinforced cemented carbides was dominated by the formation of a lubricating surface layer and its cracking or fragmentation. Plastic flow is much less likely to occur in the presence of GNPs.

A ternary solid-solution piezoelectric ceramic of rare-earth oxides modified 0.03 Pb(Mn1/3Sb2/3)O3-0.97 Pb(Zr0.505Ti0.495)O3 + x wt.% CuO + y wt.% Bi2O3 (PMS-PZT + x wt.% CuO + y wt. % Bi2O3) (x, y = 0–0.2) was successfully prepared via a transient-liquid-phase sintering. Both Cu2+ and Bi3+ were believed to replace the A-site Pb ions and to evidently induce the lattice shrinkage and the distortion decrease. However, the addition of only a small amount of CuO was found to effectively reduce the sintering temperature, sustain good piezoelectric properties and predominant transgranular fracture modes, but obviously increase the average grain size and high-field dielectric loss. Further experimental results indicate that the grain growth of the ceramics was inhibited effectively and the high-field dielectric loss was reduced through CuO and Bi2O3 co-doping. The 0.05 wt% CuO and 0.15 wt% Bi2O3 co-doped PMS-PZT ceramics sintered at 1050 °C exhibit excellent dielectric and piezoelectric properties of d33 = 410 pC/N, kp = 0.62, Qm = 1478, er = 1550, tan δ = 0.8% (400 V/mm) and Tc = 330 °C. The experimental results can provide a solid fundament for multilayer piezoelectric actuating devices.

The purpose of this paper was to study the failure behavior of SUS304 stainless steel in view of cooling water leakage in actual service conditions. The temperature field and thermal stress distribution in the thickness direction of SUS304 stainless steel under actual service conditions were further analyzed by the finite element method. The results show that chromium-rich carbides are precipitated at the grain boundaries, which may cause intergranular corrosion. The morphology of the corrosion grooves is ditch structure, which has high intergranular corrosion susceptibility. The expansion direction of the cracks is from the contact surface of cooling water to the high-temperature contact surface. Fracture is characterized by a river pattern and rock candy pattern. Fracture morphology is characterized by brittle rupture. The Cl contained in the corrosion products comes from the circulating cooling water. XRD patterns show that the corrosion products are composed of CaCO3 (the high-temperature contact surface) and Fe3O4 (the contact surface of cooling water), respectively. EDS results of corrosion products are consistent with XRD results. The results of finite element simulation show that the temperature field along the thickness direction of SUS304 stainless steel plate is in the range of 436.6-450 °C. The peak of thermal stress is located in the middle of cross section. The cause of failure is acceleration of the initiation and extension of the cracks under the combined action of chloride ion stress corrosion, intergranular corrosion, and thermal stress. The form of crack fracture is mixture of transgranular and intergranular fracture, mainly transgranular fracture, which belongs to typical chloride ion stress corrosion.

In this study, the effect of Co addition on microstructural and mechanical properties of WC-B4C–SiC composites sintered by spark plasma sintering (SPS) method was investigated. For this purpose, three batches of WC-B4C–SiC with different contents of Co (10 vol%, 15 vol%, and 20 Vol %) were sintered at 1400 °C. The results of X-ray diffraction (XRD) analysis of the samples indicated the formation of W2B5, W3CoB3 as well as the remained C phases and unreacted SiC phase. It was observed that by increasing the Co content, the amount of W2B5 phase reduces and W3CoB3 and C contents increase. Therefore, W2B5 peaks were not detected in the sample containing 20vol% Co. Relative density values above 97% were obtained for all the composites. However, a decrease was observed in relative density by increasing the Co content in the composites. The highest flexural strength (510 ± 42 MPa), fracture toughness (10.34 ± 0.82 MPa m1/2), and hardness (20.63 ± 0.75 GPa) were also obtained for the sample containing 10vol% Co compared to the other samples. In addition, Transgranular fracture of SiC as well as pulling out of W3CoB3 and W2B5 particles were observed in the fracture surface micrographs of the samples. The presence of micro-cracks in the SiC grains, fracture of W3CoB3 grains, and crack deflection was reported as dominant toughening mechanisms.

Complete solid-solution Ti(C,N)-based cermet, with no typical core-rim structure, was synthesized through mechanical activation and subsequent in situ carbothermal reduction method. XRD, SEM, TEM, and C/N analysis were used to investigate the microstructure, phase transformation, and the interfacial characteristics of the present cermets. During solid-state sintering, the (Ti,Mo)C/(Ti,Mo)(C,N) phases formed through the transformation of Mo-based solid solution which generated by mechanical activation. Then, the formed (Ti,Mo)C/(Ti,Mo)(C,N) continuously dissolved into the nickel-based binder above 1100 °C. It was found that in the subsequent stage of liquid sintering, the mechanical activation and also the presence of extremely fine TiC/Ti(C,N) particles accelerated the Mo diffusion into the hard phase, resulting in a large quantity of (Ti,Mo)(C,N) solid solutions formed in the nickel-based binder. Finally, complete (Ti,Mo)(C,N) solid-solution phase was obtained via dissolution and re-precipitation. The higher toughness and transverse rupture strength (TRS) of the synthesized new cermet, as compared with traditional cermets, were mainly caused by the increased crack deflection and transgranular fracture of the novel cermets. Moreover, the interface among the Ni-based binder phase and complete solid solution hard phase exhibited a semi-coherency state with high-density dislocations, which also significantly improved the TRS and toughness of the synthesized cermets.

This paper examines the influence of 0-0.2 wt.%B-doping on the microstructure, mechanical properties, and pseudoelastic behavior of Cu-Al11.5-Be0.57 shape memory alloys (SMAs). This microstructure study reveals that the addition of boron leads to significant grain refinement in $$\beta_{1}$$ -type polycrystalline Cu-Al-Be SMAs. A maximum refinement size of 50 µm was achieved with the addition of 0.15 wt.%B. The fine-grained (Cu-Al11.5-Be0.57)-B0.15 SMA with serrated grain boundaries exhibited the maximum enhancement of ultimate tensile strength, 744.65 ± 29.34 MPa, and ductility of 21.93 ± 0.56%. The fracture morphology revealed the transformation of intergranular to transgranular fracture in the SMAs with boron-doping. Maximum pseudoelasticity of 4% was achieved in the SMA with 0.15 wt.%B and suits as a damper in seismic applications.

In this research, the effect of different amounts of Cr2O3 (2.5, 5, 7.5, and 10 wt.%) and sintering temperature (1850, 1900, and 1950 °C) on the sinterability and mechanical properties of liquid-phase sintered SiC-matrix composites was studied. First, raw materials were ground for 3 h using a planetary mill whose rotational speed was 180 rpm. The process of pressing the samples was completed using uniaxial pressing with the applied pressure of 90 MPa. Finally, the samples were sintered under an argon atmosphere at various temperatures for 1.5 h. In the end, the best sintered sample was annealed at 2000°C for 2 h. The phases, microstructure, and chemical composition of the samples were studied using X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FESEM), respectively. The results suggested that the composite that contained 5 wt.% Cr2O3 and that was sintered at 1900 °C exhibited the best properties. The relative density, microhardness, elastic modulus, flexural strength, indentation fracture resistance, and brittleness index were 97.45%, 27.50 GPa, 395 GPa, 549 MPa, 6.2 MPa m1/2, and 282.58 ×10−6 m−1 respectively. At 1850 °C and 1950 °C, the best mechanical properties were acquired for the samples containing 5 wt.% Cr2O3. According to microscopic images, the formation of elongated grains and the activation of crack deflection as well as crack bridging mechanisms were the most significant mechanisms enhancing the toughness of these composites. The results showed that the sintered sample at 1900 °C, containing 5% additive and annealed at 2000 °C for 2 h, reached the highest fracture toughness (6.92 MPa m1/2). The microscopic images showed that the matrix grains of the as-annealed samples were elongated. There were signs of transgranular fracture at the cross-section of the samples.

Grinding behaviour and wear mechanism of self-fabricated rail grinding stones (GS) using zirconia alumina (ZA), white fused alumina (WA) and brown fused alumina (A) were investigated in detail. The results illustrated that the grinding efficiency grew from GS-ZA and GS-A to GS-WA, and the GS-ZA gave the best ground rail surface quality. GS-ZA primarily consumed as attrition wear, while abrasive pull-out and fracture were dominant for the GS-WA and GS-A, thus making a better self-sharpness. The splintering mechanism of ZA was intergranular and transgranular fracture, and the macro-fracture and micro-fracture were presented by WA and A, respectively. Based on the experimental results, some suggestions about regulating the grinding performance of different GS, such as improving the grinding load of GS-ZA, reducing grinding heat of GS-WA, and the abrasive/bond interface modification of GS-A, were finally proposed.

Alumina inclusions in commercial as-cast 2.25Cr1Mo0.25V aluminum deoxidized steel exhibited a feature of porous structure. In order to investigate the crushing characteristics of alumina inclusion during hot working, a series of alumina blocks with different porosity whose properties are similar to the alumina inclusions in ingots were prepared using spark plasma sintering. The crushing behavior of alumina blocks during hot compression with quasi-static load was studied. A prediction model of compressive strength of alumina inclusions considering apparent porosity was established on basis of hyperbolic sine Arrhenius equation. A novel crushing mode diagram for alumina inclusions characterized by Z parameter was proposed. The crushing mechanism of alumina inclusions under different deformation parameters was clarified by fracture characteristics. The results showed that the hot compression process of alumina presented a typical brittle fracture, the compressive strength was more sensitive to deformation conditions at lower apparent porosity as compared with the conditions of higher apparent porosity. With the increase of Z, the crushing mode of alumina inclusions gradually changed from intergranular fracture to transgranular fracture.

In order to design and fabricate a new Al2O3/TiC/TiN micro-nano-composite ceramic tool material with high mechanical properties, a microstructure evolution model of ceramic tool material during sintering process was established to optimize the sintering parameters based on cellular automata. Furthermore, the effects of TiC nano-particles on mechanical properties of the prepared material were investigated. Toughening and strengthening mechanisms of TiC nano-particles were revealed by examining SEM images of microstructure and crack propagation. The results indicated that the mechanical properties increased first and then decreased as TiC nano-particles volume fractions of prepared material rose. When Al2O3, TiC, TiN micro-particles and TiC nano-particles were 60%, 20%, 10% and 10%, respectively, ceramic material prepared exhibited outstanding mechanical properties with Vickers hardness of 20.8 GPa, flexure strength of 881.4 MPa, and fracture toughness of 7.8 MPa m1/2 obtained at the sintering temperature of 1650 °C with holding time for15min through the simulation. The main strengthening and toughening mechanisms of the prepared materials could be attributed to transgranular fracture, intergranular fracture, crack deflection and crack bridging.