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A new lightweight magnesia refractory for working linings of high-temperature furnaces was prepared by using microporous magnesia aggregates instead of conventional dense magnesia aggregates. The median pore size of the microporous magnesia aggregates was 2.97 μm, while the apparent porosities of the microporous and dense aggregates were 33.3% and 5.5%, respectively. The phase composition, microstructures, fracture behaviors and strengths at room and high temperature of the lightweight magnesia refractory in comparison with those of the dense one were measured by means of XRD, SEM and three-point bending instrument. After the dense aggregates were replaced by the microporous ones, a better aggregate/matrix interface bonding was observed and the fracture mode changed from intergranular to transgranular fracture, which significantly improved the mechanical properties. Thus, the lightweight magnesia refractories had a lower bulk density of 11.8%, a higher apparent porosity of 56.2% as well as a higher flexural strength at room and high temperature of 48.4% and 160.0% comparing with the dense one, respectively.

The monolithic Ti5Si3 was synthesized by mechanically activated self-propagating high-temperature synthesis (MASHS) from elemental powders and sintered by Spark plasma sintering (SPS) technique. The synthesized powders were sintered at three different temperatures of 1400, 1500 and 1600 °C by SPS with 5 min holding time and reached 84, 91 and 99% of the theoretical density, respectively, while the density of the pressureless sintered sample at 1600 °C reached to 86% after 2 h. The phase composition and microstructural analyses show that titanium silicide retained its phase composition and microstructure during the sintering. The mechanical properties of the compound were measured by the Vickers hardness test and nanoindentation technique. The Young's modulus of 268 ± 8 GPa and nanohardness of 16 ± 1.7 GPa were determined by nanoindentation, while the hardness value of 12.5 ± 0.14 GPa was measured by Vickers indentation test. The crack induced by Vickers indenter was used to measure fracture toughness of the compound and the value of 4 ± 0.1 MPa m1/2 was achieved. The transgranular fracture mode can be identified from the fracture surface of the compound.

The mechanical behavior of cast nickel-based superalloy Inconel 718 was investigated via hot tensile experiments at 650 °C, 800 °C, and 950 °C to understand the thermal instability of its metallurgic microstructure. Test specimens, which were machined from investment casting, were subjected to a standard heat treatment. Post-tensile testing, microstructure characterization, and fractography observations were conducted with a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The resulting data revealed that the deterioration of toughness and ductility occurred at temperatures above 650 °C. Numerous shear bands and lattice mismatch suggested that plastic deformation through slip movement dominated the ductile fracture mode of the nickel-based superalloy at 650 °C. In contrast, surficial microporosity and grain boundary weakening caused early brittle rupture, before the material yielded, at 800 °C. Significant strain accumulation within grains contributed to plastic flow in the direction of the applied stress load, resulting in intergranular and transgranular fracture at 950 °C. Microstructural evidence displayed the interface debonding between the carbide and the matrix at 950 °C, indicating the temperature limitation of the carbide pileup.

To explore the influence of sintering temperature on mechanical properties of Al2TiO5 (AT) flexible ceramics, the XRD/Raman, SEM and acoustic emission (AE) technology were used to estimate the phase composition, microstructure evolution and damage behaviors of AT ceramics, respectively. Results show that the diffraction peaks of AT increase before rising sintering temperature from 1300 °C to 1500 °C and then start to decrease at 1600 °C due to the decomposition of AT grains. In specimens with sintering temperature of 1300 °C and 1400 °C, intergranular fractures are more likely to occur, which controls the origination of AE events in the whole stage. And the fracture of big bodies composed by large number of fine AT grains is the main source of AE events with high energy level at initial stage. In addition, Thanks to the more transgranular fracture in specimens with sintering temperature of 1500 °C and 1600 °C, the number of AE events in these two specimens are more than that of specimens with sintering temperature of 1300 °C and 1400 °C.

The Mo-10Si-(0, 5, 10, 15)B (at.%) alloys located in Moss (Mo solid solution) +Mo3Si +T2 (Mo5SiB2) region were prepared by arc melting. The effect of B content on the microstructure, microhardness, fracture toughness and oxidation resistance of the alloys was studied. In the Mo-10Si alloy, there are primary Moss and peritectic Mo3Si phases. With the addition of B, (Moss + T2) binary and (Moss + T2 + Mo3Si) ternary eutectics emerge in Mo-10Si-(5, 10)B alloys. For Mo-10Si-15B alloy, primary Moss disappears and the microstructure is only composed of binary and ternary eutectics. With the increase of B content, the proportion and grain size of Moss decrease. The microhardness of alloys increases with the increase of B content due to the increasing intermetallics. The fracture toughness of alloys decreases obviously in single-edge notched three-point bending testing (SENB) and the fracture mode transforms from transgranular fracture to intergranular fracture because of the refinement of Moss. In the high-temperature oxidation test at 1250 °C, the oxidation weight loss of the alloys decreases with the addition of B due to the densification of the borosilicate layer.

The research of Nickel-based superalloys with excellent mechanical properties is of significance for aerospace. Here we report the effect of sintering temperature of 850 °C, 900 °C and 950 °C with the heating rate of 100 °C/min via spark plasma sintering (SPS) on Inconel 718 (IN718) superalloy reinforced with 0.25 wt. % reduced oxide graphene (RGO). The microstructures and mechanical properties of IN718-RGO composite were investigated by scanning electron microscopy (SEM) and MTS servo hydraulic testing machine, respectively. SEM results demonstrate that the RGO is almost uniformly distributed into the IN718 powders after 3D rock-milling for 8 h. The mechanical properties of the composite increase with increasing the sintering temperature. When the sintering temperature is 950 °C, a relative density of 92.5%, a microhardness of 375 Hv and an ultimate compressive strength of 1748.20 MPa after aging heat treatment was obtained for the IN718–0.25 wt. % RGO, respectively. The fracture mechanism of the composite changes from intergranular fracture to transgranular fracture with the sintering temperature increasing.

Effects of creep aging on strength and toughness and microstructure evolution of Al-Cu-Li alloy were investigated by tensile test and Kahn tear test at room temperature, combined with fractograph and transmission microstructure analysis. The specimens of pre-strain creep aging state (CA) have been studied and compared with artificial aging state (AA) and pre-strain artificial aging state (PA). It is demonstrated that pre-strain before artificial aging process can improve the strength property and the fracture toughness of Al-Cu-Li alloy. On top of that, both of them can be further improved by creep aging process: the yield strength was increased by 8.7% and the unit initiation energy of Kahn tear was increased by 11.7%. The increasing of fracture toughness has also been verified by Kahn tear fractographs that the dominating fracture type changes from the ductile intergranular fracture to the ductile transgranular fracture. Transmission electron microscopy revealed that creep aging promotes the nucleation of T1 phase, resulting in a fine and dense distribution of precipitates in the matrix, and the enrichment of subgrain boundary T1 precipitates was greatly reduced.

Effects of HfN content and metallic additives on microstructure and mechanical properties of TiC 0.7 N 0.3 -based ceramics were investigated. HfN had very weak inhibition effect on TiC 0.7 N 0.3 grain growth. When HfN content increased from 10 wt% to 20 wt%, flexural strength and fracture toughness became higher, but Vickers hardness was around 20 GPa without significant changes. The optimal mechanical properties of TiC 0.7 N 0.3 -20 wt%HfN-Ni-Co were that Vickers hardness was 18.93 GPa, flexural strength was 876.17 MPa and fracture toughness was 7.58 MPa m 1/2 in this investigation. Ni-Mo additive exhibited better wettability with TiC 0.7 N 0.3 than the other metallic additives. Ni-Mo additive could inhibit TiC 0.7 N 0.3 grain growth effectively and improve mechanical properties of TiC 0.7 N 0.3 -based ceramic. The optimal mechanical properties of TiC 0.7 N 0.3 -20 wt%HfN-Ni-Mo ceramic was that Vickers hardness was 19.43 GPa, flexural strength was 1235.88 MPa and fracture toughness was 8.46 MPa m 1/2 in this investigation. Its toughening mechanism mainly included crack deflection and crack bridging. In addition, the mixed intergranular/transgranular fracture also could improve fracture toughness.

This paper reports a study on mechanical behavior during tensile testing of nanostructured (NS) Al and ultra-fine grained (UFG) Al containing nanoscale oxide particles that were produced via consolidation of nano-sized Al powders using spark plasma sintering (SPS) only and SPS plus extrusion, respectively. Our results show that the NS Al exhibits ∼370 MPa in 0.2% offset yield strength and ∼0.9% in elongation to failure, whereas the UFG Al presents ∼430 MPa in 0.2% offset yield strength and ∼1.5% and ∼1.9% in uniform elongation and elongation to failure, respectively. Based on the tensile stress vs. strain curves, microstructural features and fractured surface characteristics, mechanical behavior of NS Al and UFG Al was analyzed and discussed in detail. We suggest that the lower yield strength and ductility in the NS Al than those in UFG Al can be attributed to the strong stress concentration at grain boundaries (GBs) as a result of (i) the presence of highly segregated nanoscale oxide particles and of residual porosity at GBs to induce, and (ii) the absence of dislocation sources and thus of activated dislocation slip at nano-sized grain interiors (GIs) to release, the stress concentration. Immediately after yield in the as-SPSed Al, the stress concentration debonded GBs and further tensile straining rapidly led to connection between debonded GBs and the occurrence of intergranular fracture. In contrast, in the UFG Al the extent of oxide particle segregation and the porosity at GBs were reduced due to materials flow during extrusion, avoiding the occurrence of intergranular fracture at a very low strain level and thus sustaining plastic straining; as a result, yield strength and ductility were improved. However, the residual porosity and nano-sized/ultra-fine grains still induced early strain localization shortly followed by transgranular fracture via growth, coalescence and connection of nano-sized pores, leading to limited ductility.

Spray forming (SF) is a near net shape manufacturing process in a wide variety of alloys. A titanium- and cobalt-modified repair alloy has been prepared by the SF process and was presented excellent properties of friction and wear in previous published article. In this paper, the microstructural evolution of the alloy exposed at 750 °C for different isothermal aging time was analyzed. Microstructure observations reveal that equiaxed grains formed in the ingots whether after aging process or not. The size and the volume fraction of γ′ precipitates increase with the ongoing of aging process, which could result in the change of the lattice misfit of γ′/γ and the precipitation of new σ, η phases. Intergranular fracture and transgranular fracture are main fracture mechanisms in aged state. Its tensile properties were attributed to the size and the volume fraction of γ′ precipitates, γ′/γ misfit, grain boundary carbides and the number of harmful phases (σ and η phases) during aging process.

The graphene network (GN) reinforced Ti6Al4V composites with concurrently enhanced strength and ductility are fabricated based on powder metallurgy, in which the GN interlocks with the matrix intimately via the in-situ generation of interfacial TiC. The strengthening and toughening mechanisms of the composites are investigated through experiments and molecular dynamics (MD) simulations. Grain refinement, deformation compatibility, dislocation blocking, together with the restraint and bridging of cracks are provided by the embedded GN, improving both the strength and ductility of the composites. Interestingly, with a better ductility than Ti6Al4V, the composites possess a more brittle-like fracture surface. With the introduction of GN, the fracture mode of the composites is diverted from the transgranular fracture in Ti6Al4V to the mix of intergranular and quasi-cleavage fracture. The intergranular fracture is mainly ascribed to the brittle fracture of the TiC shell. And the propagation of cracks along cleavage plane in the matrix, working together with the impediment of cracks by GN, results in the quasi-cleavage fracture. Despite the brittle-like fracture surface, the restraint of crack propagation by dislocation-GN interactions, as well as the crack-bridging of GN, postpones the failure of the composites and thereby conduces to a good ductility.

Fused deposition molding and sintering (FDMS) technology has the characteristics of low cost and low damage to diamonds. In order to explore more possibilities of additive manufacturing diamond tools, FDMS technology was considered to manufacture Co-based diamond composites at different temperatures in this paper. Also, specimens of Co-based diamond composites were manufactured under the same sintering process by using the powder hot-pressed sintering technology. And the matrix microstructure and properties of the specimens made by those two different technologies were analyzed and compared. The results show that a lot of porosity defects were developed inside the specimens manufactured by FDMS. This is because of the specific process characteristics of FDMS. Also, the matrix forms a special coating state for diamond particles due to the binder system used in this study, which causes some diamond particles to suffer slight thermal damage. These all will reduce the density and holding ability of the FDMS specimens. However, when the sintering temperature increases from 800 °C to 880 °C, the performance loss of FDMS samples caused by the porosity defects gradually decreases, thereby reducing the performance difference when comparing with the powder hot-pressed sintering specimens. In addition, the matrix structural uniformity of the FDMS specimens is significantly improved during this process, and the fracture feature changes from intergranular fracture to transgranular fracture. But there is still a certain difference in the overall performance of the two kinds of specimens at the optimal sintering temperature. Therefore, the further optimization of FDMS process parameters and binder system is of great significance for the application of FDMS in diamond tools.

Pure molybdenum and ZrO2 dispersion strengthened Mo alloy were prepared by liquid-liquid doping method. The effects of adding ZrO2 on their microstructure and properties were investigated by tensile test and low cycle fatigue (LCF) test at room temperature, and the fracture mode and energy absorption were analyzed. The research shows that ZrO2 can refine the grain size and increase the recrystallization temperature of molybdenum alloy. The enhancement of yield strength by ZrO2 is mainly reflected in grain boundary strengthening. The tensile fracture mode is related to grain size, and changes from transgranular fracture to transgranular-intergranular fracture with the decrease of grain size. At the initial stage of the cycle, the increase of strain amplitude changes the cyclic hardening into cyclic softening, and the addition of ZrO2 accelerates the cyclic hardening/softening. With the increase of strain amplitude, the loading energy and absorption energy of a single stable cycle increase, while the unloading energy is basically unchanged. ZrO2 can increase the total fatigue absorption energy of molybdenum alloy at the same strain amplitude, and the single cycle absorption energy is lower than that of pure Mo, thus increasing the fatigue life.

La(NO 3 ) 3 and La 2 O 3 doped titanium-zirconium-molybdenum (TZM) alloys were fabricated by using powder metallurgy method, and their room and high temperature mechanical properties were studied in this paper. Results show that the mechanical properties of La(NO 3 ) 3 -TZM alloy sheet is better than that of La 2 O 3 -TZM alloy sheet in room temperature and the high temperature mechanical properties of both alloys have similar change trend but different sensitivity of temperature. The tiny grains in La(NO 3 ) 3 -TZM alloy sheet is more sensitive to temperature and the lanthanum doping significantly influences the temperature sensitivity of the alloy. When the temperature is lower than 1400 °C, both TZM alloy sheets present a transgranular fracture mode. It is ductile intergranular fracture mode when the temperature is higher than 1400 °C, and the temperature of fracture mode transition is 1400 °C.

In this study, the effects of carbon additions on the microstructure, hardness, transverse rupture strength and abrasion resistance of Ti(C,N)-Fe cermets manufactured by powder metallurgy method were investigated by scanning electron microscopy, X-ray diffraction and mechanical properties tests. The results show that the microstructure of sintered Ti(C,N)-Fe cermets exhibits the homogeneous distribution of Ti(C,N) hard phase when 1.0 wt% carbon was added into the cermets. The transverse rupture strength of cermet can reach the peak of 2435 MPa and the fracture morphology can include a vast of transgranular fracture. Moreover, the comprehensive performance of Ti(C,N)-Fe cermets can improve significantly through the heat-treatment process. The hardness and transverse rupture strength of cermets after heat-treatment are 70.0HRC and 2483.2 MPa. The Ti(C,N)-Fe cermets have a potential application in machining.

The effects of europium oxide addition on microstructure, bulk density, grain-boundary cohesion and wear resistance of high-alumina ceramics (>97 wt% Al 2 O 3 ) composed of CaO-MgO-SiO 2 -Al 2 O 3 have been investigated by normal pressure sintering. The content of Eu 2 O 3 varies from 0 to 0.8 wt%. Test results show that doping with a small amount of Eu 2 O 3 decreases the bulk density and wear resistance of high - alumina ceramics. The phase compositions and microstructure of samples were measured by XRD and FESEM, respectively. XRD result shows that Eu can be dissolved into CaAl 12 O 19 crystallites to form a solid solution. SEM result shows that adding Eu 2 O 3 is easier to generate the plate-like grain and decrease grain size compared with undoped-Eu 2 O 3 of alumina ceramics. The wear resistance mechanism was discussed. The break form of cross-section happened from transgranular fracture to intergranular fracture, which causing by weaker grain-boundary cohesion, leads to the reduction of wear resistance.

Densification, microstructure and mechanical properties of Al2O3-CA6-ZrO2/Ni multi-phase composites depend on different parameters, particular the holding time and pressure during the hot pressing sintering process at 1650 °C. In this study, the fine grain size, low porosity and dense structure of composites obtained for a holding time of 30 min under a pressure of 30 MPa. Meanwhile, the wettability between the Ni particles and the matrix was significantly improved owing to the homogeneous distribution of Ni phase. In addition, the systematically optimized sintering parameters resulted in the achievement of a relative density of 98.07% with an excellent Vickers hardness of 16.2 GPa, combining a flexural strength of 458.24 MPa with an acceptable fracture toughness of 7.20 MPa m1/2 for a holding time of 30 min under a pressure of 30 MPa. The toughening mechanisms of composites are also discussed in detail around the sintering parameters while the dominant ones are the transgranular fracture and crack deflection.

An in situ SiC-TiB2 ceramic composites was fabricated by infiltrating the Al-Si alloy melt into pre-sintered porous preforms with different B4C/TiC weight ratios. The phase composition and microstructure of the SiC-TiB2 ceramic composites were analyzed to understand the synthesis mechanism of the composites. TiB2 and SiC were originated from the reaction among B4C, TiC and Al-Si melt. When the B4C/TiC weight ratio was 35:65, the fabricated TiB2-SiC ceramic composites but no byproduct or raw powders displayed the optimal microstructure, and the TiB2 and SiC particles were homogeneously distributed in Al-Si melt. The SiC-TiB2 ceramic composites with the optimal microstructure owned the outstanding integrated mechanical properties: flexural strength of 245 MPa, fracture toughness of 4.32 MPa m1/2 and Vickers hardness of 10.46 GPa. The fracture surface of SiC-TiB2 ceramic composites showed the mixed fracture mode with intergranular and transgranular fracture. The strengthening and toughening mechanisms were investigated from particle reinforcement, pulling out of grains and crack deflection found in the SiC-TiB2 ceramic composites.

Al2O3/Y3Al5O12(YAG) eutectic ceramic with the dimension of 180 mm × 140 mm × 30 mm was firstly grown in vacuum by Horizontal Directional Solidification (HDS) method. Half of the sample was annealed for 100 h at 1973 K in the air. The oxygen vacancies were found to be fully compensated by annealing in X-ray photoelectron spectroscopy. The HDS-Al2O3/YAG eutectic showed no grain growth after longtime annealing treatment and the two constituent phases were three-dimensionally interpenetrated without grain boundaries. The average eutectic interspacing is 3.1 ± 1.8 μm. The density ρ, hardness Hv, fracture toughness KIC, compression stress σc (to 8% strain) and flexural stress σf of the as-grown and annealed samples were measured at room temperature, the values changing from 4.26 g/cm3 to 4.39 g/cm3, 16.04 ± 0.75 GPa to 16.79 ± 0.45 GPa, 2.69 ± 0.06 MPa m1/2 to 3.07 ± 0.05 MPa m1/2, 1188 MPa–1278 MPa and 320–340 MPa to 345–370 MPa, respectively. The crack arrest, deflection and branching enhanced the resistance of crack propagation after Vickers experiments. The flexural fracture surface of the as-grown samples shows mainly transgranular fracture, while mixed fracture of intergranular and transgranular is observed for the annealed samples.

Fe–30%Ni alloys were produced by sintering in the hybrid hot press spark plasma sintering system using iron and nickel as raw materials. The results indicate that the relative density, microhardness and fracture morphology depend on the sintering temperature which also affects the microstructure. The densification and grain size of the alloys increased with increasing sintering temperature, facilitating necking of grains. In the case of the sintering temperature at 1230 °C, a relative density of 98.7% and a maximum grain size of around 200 μm were obtained, and the maximum microhardness of 284Hv1.0, and the microhardness indentations revealed pincushioning indicating better sintering. Microhardness indentations at 1100 °C and below were characterized by barreling, indicating poor densification and/or microhardness. The fracture type changing from intergranular fracture to transgranular fracture is an indication of improved consolidation of the Fe–30%Ni alloy with increasing sintering temperature.

The influences of Al–10Sr or/and Al–5Ti–1B on the as-cast microstructure and the mechanical properties of Al–12Si–4Cu–2Ni–0.8 Mg alloys at elevated temperature were studied. Studies have shown that the addition of 0.1 wt% Ti has little effect on 0.02 wt% Sr modification, and the grain size decreases significantly. The addition of 0.1 wt% Ti could increases the mechanical properties at the room temperature and elevated temperature due to the grain refinement. However, owing to the modification of eutectic Si, the mechanical properties of the alloys increase at ambient temperature and then slightly decrease at elevated temperature. The Ultimate tensile strength and Yield strength of the alloy with 0.01 wt% Ti and 0.02 wt% Sr at ambient temperature were the maximum values of 249.5 Mpa and 207.5 Mpa, respectively. The specimen tensile fracture morphology under different temperature in most test temperature (25 °C, 200 °C) were characterized by brittle transgranular fracture, and when the test temperature reaches 350 °C, it is characterized by ductile fracture.

The environment-induced cracking (EIC) of as cold-rolled Ni 3 (Si,Ti) and Ni 3 (Si,Ti) with 2Mo has been investigated as functions of applied stress, chloride ion concentration, test temperature, and pH by using a constant load method in NaCl solutions. The EIC susceptibility of both intermetallic compounds increased with increasing Cl − ion concentration and test temperature; and increased with decreasing pH. Both intermetallic compounds had the same transgranular fracture appearance and the relationship between log t f (time to failure) and log l ss (steady state elongation rate) became the identical straight line irrespective of applied stress, Cl − ion concentration, test temperature, and pH, which means that l ss becomes a relevant parameter for predicting t f . The EIC susceptibility of Ni 3 (Si,Ti) with 2Mo was lower than that of Ni 3 (Si,Ti), which showed the beneficial effect of Mo. From the results obtained, EIC of both intermetallic compounds was presumed to take place by hydrogen embrittlement (HE).

High-performance TiB2–SiC composites were fabricated with a new reaction system of B4C–TiC–Si by reactive hot pressing. The reaction process was controlled by the diffusion of boron atoms and hindered by the accumulated product layer of TiB2 and C. The melting Si can offer another diffusion path for boron atoms, thereby promoting the reaction process. The Vickers hardness, flexural strength, and fracture toughness of the fabricated TiB2–SiC composites respectively reached 28.6 ± 0.6 GPa, 654 ± 49 MPa, and 6.8 ± 0.5 MPa m1/2. Both the intergranular fracture resulting from mismatch in thermal expansion coefficient between TiB2 and SiC and the transgranular fracture resulting from the network structure of TiB2 can enhance the fracture toughness of the TiB2–SiC composite.

In this work, the effects of micron grained WC additions on the microstructure and properties of ultrafine WC–(micron WC–Co) cemented carbides produced through low pressure sintering processes were investigated by scanning electron microscope and mechanical properties tests. The results show that the obvious crack deflection and transgranular fracture phenomenon could be observed with the addition of micron WC, which can resist the crack propagation and improve the toughness of cemented carbides. The sintered ultrafine WC–(micron WC–Co) hardmetals demonstrate excellent hardness and fracture toughness values (HV30: 1700 kg/mm2, KIC: 13.82 MPa m1/2). These inhomogeneous ultrafine WC–(micron WC–Co) cemented carbides have considerable potential for use in structural applications.

The influences of recrystallization and heat treatment on strength, stress corrosion cracking (SCC) of an Al–Zn–Mg–Cu alloy have been investigated by tensile testing, slow strain rate testing combined with scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that with increasing the volume fraction of recrystallization, the strength and SCC-resistance decrease, and the predominated fracture mode transforms from transgranular fracture to intergranular fracture. Over-aging reduces the effect of recrystallization on SCC susceptibility. The differences of strength and SCC resistance are explained on the basis of the role of recrystallization and grain boundary precipitates.

In this study, high-quality large billets of 7055 aluminum alloy were successfully fabricated by spray forming rapid solidification technology. Microstructure observation showed that there were equiaxed grains with the size of about 50 μm in diameter. The dendrite microstructure was suppressed and the undesirable macrosegregation did not exist in the as-deposited 7055 alloys, attributable to rapid solidification effects. The secondary phases were the main η -Mg(Zn,Cu,Al) 2 expansion phases and the very small amounts of Al x Fe 3 Cu Iron-bearing phase. As-deposited 7055 billet was subsequently processed by hot extrusion, solid solution treatment at 450 °C/24 h and aging at 120 °C for 12 h. The as-aged alloy was then subjected to tensile testing. The results revealed that yield strength, tensile strength and elongation rate of the alloy reached 608 MPa, 667 MPa and 10%, respectively. After extruding, the observation of the microscopic fracture morphology of as-extruded specimens manifested that fracture mode was the transgranular dimple fracture.

The diffusion-bonded Mg–Al joints with and without silver interlayer prepared by Magnetron Sputtering have been investigated. The addition of silver interlayers eliminated the formation of Mg–Al intermetallic compounds and improved the bonding strength of Mg–Al joints. Mg 3 Ag, MgAg and Ag-based solid solution were observed in the interface of Mg/Ag/Al joint. The microhardness value of the interface in Mg/Ag/Al joint with a maximum value 125 HV of Mg 3 Ag layer is much lower than that in Mg/Al joint with a maximum value 225 HV of Mg 2 Al 3 layer. Fracture failure in Mg/Ag/Al joint occurred between Mg 3 Ag layer and MgAg layer. Transgranular fracture and plastic deformation observed on fracture surfaces of Mg/Ag/Al joint differ from cleavage fracture features of Mg/Al joint.

Equal channel angular pressing (ECAP) was applied to modify the microstructures of Cu–Al–Be–B shape memory alloys (SMAs). The alloy was greatly refined because of the interaction of the large plastic deformation and physicochemical effects. With an increase of ECAP passes, the specimens showed a change from plastic fracture to brittle fracture, increased proportion of transgranular fracture, and decreased ultimate strength from 460 MPa to 340 MPa. These were caused by the precipitation of the γ 2 -phase and the disappearance of thermoelastic martensite. After appropriate heat treatment, the content of thermoelastic martensites increased, while the grain size remained smaller than that of the as-cast alloy. Further tests showed that the ultimate strength of this alloy improved to 703 MPa and the attenuation of shape recovery ratio was alleviated.

Lanthanide hexaaluminates including LaMgAl 11 O 19 , NdMgAl 11 O 19 , SmMgAl 11 O 19 and GdMgAl 11 O 19 were synthesized via Sol–Gel method. Due to the anisotropic crystal growth, these oxides crystallize in the form of platelets and the platelet thickness increases with the decrease of rare-earth ionic radius. It was observed that the thermal-shock resistances of LaMgAl 11 O 19 , NdMgAl 11 O 19 and SmMgAl 11 O 19 oxides were superior to 8YSZ as proved by water quenching tests. In addition, the thinner the platelet, the more interstices are retained in the sintered specimen, and the better thermal-shock resistance the oxide has. Based on SEM images, it can be seen that the SmMgAl 11 O 19 sample exhibits a mixture of the intergranular and transgranular fracture after thermal cycling failure.

There are various methods for production of thixoforming stock. One of these methods is strain induced melt activation (SIMA) process. In the present study, the effect of thixoforming process on morphological properties of silicon particles that affect fracture mode of A356 alloy was investigated. Microstructure and fracture surfaces of thixoformed samples were investigated by image analyzing technique and scanning electron microscopy. A new combination parameter, called silicon particle appearance (SPA) index, was introduced. SPA index approximates the collective effects of silicon particles morphological characteristics on microstructure transparency of alloy in crossing the dislocation. It is suggested that samples with lower SPA index have superior mechanical properties, especially tensile elongation, and consequently intergranular fracture mode. On the contrary, samples with higher SPA index have inferior mechanical properties and fracture path tends to propagate along the cell boundaries leading to transgranular fracture.

The annealing characteristics of the forged and upset pure molybdenum bar were investigated by bending measurement, optical microstructure (OM) observation, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the modified forge and upset technique is effective to refine the grains and interpenetrate the fiber structures, which largely improve the transverse ductility of the pure molybdenum bar. For the bar deformed by 85%, recovery is the main behavior at the annealing temperature of 1073 K for 1 h; at 1253–1323 K for 1 h, recrystallization begins; over 1423 K, further recrystallization continues and results in the decrease of transverse ductility. For the pure molybdenum bar with good transverse ductility, its fracture is mainly a transcrystalline fracture type accompanied by little intergranular cracks and some dimples.

The effect of antimony addition (0.2, 0.5 and 1 wt%) on the microstructure and mechanical properties of Mg–8Zn–4Al–0.2Mn alloy has been studied. Sb-addition to ZA84 alloy refines the ternary Mg32(Al,Zn)49 phase besides forming Mg3Sb2 precipitates and having a little effect on the grain refinement. Both the room and elevated temperature strength properties (yield and ultimate tensile strengths) are found to increase in Sb added alloys with slight reduction in ductility. However, the maximum strength properties are obtained with 0.2 wt% Sb-addition. Fractograph of the tensile tested ZA84 alloy shows intergranular and brittle type failure, whereas 0.2% Sb-addition facilitates transgranular fracture, relating to high strength.

The deformation response of Ti3SiC2 ternary ceramics have been investigated by performing ballistic impact experiments at a range of low velocities. The reactively hot pressing compacts with an off-stoichiometric ratio were predominantly Ti3SiC2 phase (99.13 vol.%) and the grains were elongated in shape with a grain size of 3–8m. The bulk modulus (196 GPa) was slightly lower than that calculated by fitting the pressure versus lattice volume data with the Birch–Murnaghan equation (206 GPa), and that predicted by using the first-principle computational technique (204 GPa). The typical fracture surface of the fragments was failed by transgranular fracture combined with intergranular fracture. Most fracture mechanisms were similar to energy-absorbing mechanisms observed in the vicinity of the indentation. The dynamically impacted fragments of Ti3SiC2 contained dislocations and stacking faults, grouped in bands extending from the grain boundaries and ending in the grain. The Si plane was depleted and the remaining thin lamella consisted of six close-packed Ti planes, with five C planes in-between, showing identical stacking as { 111 } planes in TiC. The Hugoniot elastic limit and the hydronamic pressure at the HEL point were estimated to be 6 and 3 GPa, respectively. © 2007 Elsevier B.V. All rights reserved.

A study of fatigue behaviour in an Fe-28Al-3Cr-Ce (at.%) based alloy was carried out on compact tension (CT) specimens 5 mm in thickness. The specimens were loaded in tension at 20, 300 and 500 °C with 10 Hz frequency and R in the range from 0.05 to 0.1. The fatigue crack growth rate was measured by the potential method. The number of cycles to failure decreases rapidly with temperature. The fatigue crack propagation rate at RT and elevated temperatures is different. The slope of v (Δ K ) curves is much steeper at RT, while it remains almost the same at 300 and 500 °C. The fatigue crack growth rate at 500 °C is nearly two orders higher than at 300 °C. Fractographic analysis showed that at room temperature (RT) fatigue crack growth is controlled by several mechanisms. The main failure mechanism is transgranular cleavage, crack growth by the brittle or ductile striation mechanism is localized only in several areas along the crack front.