Effect of Ru additions on microstructure and mechanical properties of Cr–TaCr2 alloys

Early work indicated that Ru reduced the ductile-to-brittle transition temperature of Cr even at small concentrations. To evaluate the potential of Ru as a beneficial alloying element in the two-phase Cr–TaCr₂ alloys, a number of Cr–8 at.%Ta alloys with 0–10 at.%Ru were prepared, and their microstructures and mechanical properties were evaluated. The Ru addition was found to move the eutectic point of Cr–TaCr₂ to a higher Ta level, as compared to the binary Cr–Ta system. Ru partitioned preferentially in the Laves phase over in the Cr matrix, with a partitioning ratio of 2–5:1, depending on the Ru addition level. Ru was also found to mainly occupy the Cr site in the TaCr₂ Laves phase. The hardness of both the primary Cr matrix and the eutectic microconstituent increased slightly with the increase in Ru addition. At a higher Ru addition level (i.e. 10 at.%), the hardness of the primary Cr matrix increased significantly, probably due to the precipitation of extremely fine Laves-phase precipitates. The Ru addition did not noticeably affect the fracture toughness of the two-phase alloys.     

Effect of Si addition on microstructure and mechanical properties of Ti–Al–N coating

Ti–Al–N coatings are widely used to prevent the untimely consumption of cutting tools exposed to wear. Increasing requirements on high speed and dry cutting application open up new demands on the quality of wear-protective quaternary or multinary Ti–Al–N based coating materials. Here, we investigated the microstructure and mechanical properties of Ti–Al–N and Ti–Al–Si–N coatings deposited on cemented carbide by cathodic arc evaporation. The formation of nanocomposite nc-TiAlN/a-Si₃N₄ structure by incorporation of Si into Ti–Al–N coating causes a significant increase on hardness from ∼ 35.7 GPa of Ti–Al–N to ∼ 42.4 GPa of Ti–Al–Si–N. Both coatings behave age-hardening during thermal annealing, however Ti–Al–Si–N coating reveal better thermal stability. Therefore, the improved cutting performance of Ti–Al–Si–N coated inserts is obtained compared to Ti–Al–N coated inserts.     

Effect of interlayer on microstructure and mechanical properties of Al–Ti ultrasonic welds

Joints of Al6061 and Ti6Al4?V alloys with pure Al-particle interlayers were conducted using ultrasonic spot welding. The microstructure, hardness, lap shear strength and fracture energy were measured for different welding energies. With increasing welding energy delivered through the sonotrode, the lap shear strength of the joints increased, reaching about 106?MPa at a welding energy of 1100?J, at which failure occurred in the pull-out mode. In the weld region, the hardness of Al6061 alloy increased with increasing weld energy, whereas the hardness of Ti6Al4?V did not change discernibly. No brittle intermetallic compounds were observed in the joints. Moreover, two simple mechanisms were described for the formation of ultrasonic spot-welded Al–Ti joints with and without the pure Al interlayer.     

Effect of deformed microstructure on mechanical properties of Ti-22Al-25Nb alloy

Effect of the deformed microstructure on mechanical properties of an orthorhombic （Ti2klNb） based alloy of Ti-22Al-25Nb （mole fraction, %） has been investigated. It was found that the deformed microstructures in different portions of a flee forged rod with diameter of 30 mm were quite different and thus resulted in the different mechanical properties after the same subsequent heat-treatment. One deformed microstructure with less primary α2/O particles and a larger and equiaxed B2 grains resulted in poor RT ductility, but the other one with a relatively larger amount of the primary α/O particles and non-equiaxed B2 grains had good combination of the tensile strength and ductility both at RT and 650 ℃. It was also found that two different deformed microstructures were obtained for the hot rolling plates with thickness of 3 mm even processed under an identical nominal rolling and the same post-deforming heat treatment conditions. One only has 3.5% of RT tensile elongation and the other up to 8%.     

The influence of Cr and B additions on the mechanical properties and oxidation behaviour of L21-ordered Fe–Al–Ti-based alloys at high temperatures

Several Fe25AlTiX (X = Cr, B) L2₁-ordered (Heusler phase) alloys with 15 or 20 at.% Ti and varying Cr and B contents have been investigated with respect to their mechanical properties and their oxidation behaviour at elevated temperatures. The mechanical properties have been characterized by means of high-temperature compression tests, four-point-bending tests and creep tests at 750, 800 and 850 °C. The oxidation behaviour has been examined using thermogravimetric analysis at 800 °C in synthetic air. The results show that when Cr and B are added, the latter results in the formation of TiB₂, is beneficial for the creep resistance and has no influence on the still-excellent oxidation resistance. However, the alloys show rather high brittle-to-ductile transition temperatures, which can be lowered by the addition of TiB₂ as a result of grain refinement.     

Effect of Nb addition on microstructure evolution and nanomechanical properties of a glass-forming Ti–Zr–Si alloy

The glass-forming Ti₇₅Zr₁₀Si₁₅ alloy is regarded as a potential material for implant applications due to its composition of non-toxic, biocompatible elements and some interesting mechanical properties. The effects of partial substitution of 15 at.% Ti by Nb on the microstructure and the mechanical behaviour have been investigated by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray analysis, transmission electron microscopy and nanoindentation techniques. Copper mold casting and melt-spinning methods have been applied to study the influence of the cooling rate on the properties of both alloys, Ti₇₅Zr₁₀Si₁₅ and Ti₆₀Zr₁₀Nb₁₅Si₁₅. As a result of different cooling rates, significant microstructural variations from multiphase crystalline states in cast rods to nanocomposite structures in ribbons were observed. The limited glass-forming ability (GFA) of the Ti₇₅Zr₁₀Si₁₅ alloy results for melt-spun ribbons mainly in nanocomposite structures with β-type nanocrystals being embedded in a glassy matrix. Addition of Nb increases the glass-forming ability. Raising the overheating temperature of the melt prior to melt-spinning from 1923 K to 2053 K yields for both alloys a higher amorphous phase fraction. The mechanical properties were investigated using compression tests (bulk samples) and the nano-indentation technique. A decrease of hardness (H), ultimate stress and reduced Young's modulus (E_r) is observed for Ti₆₀Zr₁₀Nb₁₅Si₁₅ rods as compared to Ti₇₅Zr₁₀Si₁₅ ones. This is attributed to an increase of the fraction of the β-type phase. The melt-spun ribbons show an interesting combination of very high hardness values (H) and moderate reduced elastic modulus values (E_r). This results in comparatively very high H/E_r ratios of >0.075 which suggests these new materials for applications demanding high wear resistance.     

Effect of composing element on microstructure and mechanical properties in Mo–Nb–Hf–Zr–Ti multi-principle component alloys

A series of non-equiatomic Mo–Nb–Hf–Zr–Ti alloys are synthesized to investigate the effects of the concentration variation of each composing elements on the microstructure and mechanical properties. It is found that all studied alloys form single body-centered-cubic (BCC) phase only with the variation of the lattice parameter, which indicates that the concentration variation of each composing elements has no effect on the phase constitutes. All studied alloys exhibit typically dendritic and interdendritic structure while the concentration variation of each composing elements has different effects on the microsegregation. The concentration variation of Zr leads to the most serious microsegregation. Elements with a higher melting point such as Mo and Nb solidify preferentially and thus are enriched in the dendrites. Both the increase and decrease of the concentration of each composing element reduce the hardness and strength of non-equiatomic Mo–Nb–Hf–Zr–Ti alloys compared with the equiatomic MoNbHfZrTi alloy.     

Effect of Cu on microstructure and mechanical properties of 2519 aluminum alloy

The effect of Cu on the microstructure and mechanical properties of 2519 aluminum alloy was investigated by means of tensile test, microhardness test, transmission electron microscopy, and scanning electron microscopy. The results show that when the content of Cu is less than 6.0%, the strength of 2519 aluminum alloy increases with the increase of Cu eontent; when the content of Cu is more than 6.0%, the strength of the alloy decreases. The hardening effect of the aged alloy is accelerated at 180℃ and the time to peak age is reduced, but the plasticity of the alloy gradually decreases with the increase of Cu content. However, the hardening effect of the aged alloy decreases with the increase of Cu as the content of Cu is over 6.0%. The optimal content of Cu of 2519 aluminum alloy is 6.0%, at which the alloy has best tensile strength and plasticity.     

Effect of carbon and oxygen on microstructure and mechanical properties of Ti–25V–15Cr–2Al (wt%) alloys

The effect of carbon additions on microstructure and mechanical properties of alloys with different levels of oxygen was studied in β titanium alloys of the general composition Ti–25V–15Cr–2Al (all compositions are in wt% unless otherwise indicated). The microstructures were studied using optical microscopy (OM), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that titanium carbides with vacancy-ordered structure formed in all alloys with C additions of over 1000 w.p.p.m. Grains were refined by carbides. Wavelength-dispersive X-ray (WDX) analysis showed that oxygen was much higher in carbides than in β matrix. After long-term exposure at 550°C α precipitation was significantly reduced in samples with titanium carbides compared with those without. A significant improvement in room temperature tensile ductility was achieved by the addition of carbon to the alloys. Elongations of ∼10% were obtained in samples which were exposed at 550°C for 500 h following heat treatments at 1050 and 700°C.     

Effect of heat treatment on mechanical and wear properties of Zn–40Al–2Cu–2Si alloy

In order to determine the effect of heat treatment on the mechanical and wear properties of Zn–40Al– 2Cu–2Si alloy, different heat treatments including homogenization followed by air-cooling (H1), homogenization followed by furnace-cooling (H2), stabilization (T5) and quench–aging (T6 and T7) were applied. The effects of these heat treatments on the mechanical and tribological properties of the alloy were studied by metallography and, mechanical and wear tests in comparison with SAE 65 bronze. The wear tests were performed using a block on cylinder type test apparatus. The hardness, tensile strength and compressive strength of the alloy increase by the application of H1 and T6 heat treatments, and all the heat treatments except T6, increase its elongation to fracture. H1, T5 and T6 heat treatments cause a reduction in friction coefficient and wear volume of the alloy. However, this alloy exhibits the lowest friction coefficient and wear volume after T6 heat treatment. Therefore, T6 heat treatment appears to be the best process for the lubricated tribological applications of this alloy at a pressure of 14 MPa. However, Zn–40Al–2Cu–2Si alloy in the as-cast and heat-treated conditions shows lower wear loss or higher wear resistance than the bronze.     

Effect of hot-dip aluminizing on the oxidation resistance of Ti–6Al–4V alloy at high temperatures

Hot-dip aluminizing and interdiffusion treatment were used to develop a TiAl₃-rich coating on Ti–6Al–4V alloy. Interrupted oxidation at temperatures from 600 to 900 °C and isothermal oxidation at 700 and 800 °C of the coating were conducted. The coating markedly decreases the oxidation rate in comparison with the alloy at temperatures below 800 °C during the interrupted oxidation. The oxidation kinetics follows parabolic relations at 700 and 800 °C during the isothermal oxidation. A layered structure of Al₂O₃/TiAl₃/TiAl₂/TiAl/alloy from the outside to the inside forms after oxidation at 700 °C without changing the main body of the coating.     

Effect of Y addition on microstructure and mechanical properties of Mg–Zn–Mn alloy

The effects of Y on the microstructure and mechanical properties of Mg–6Zn–1Mn alloy were investigated. The results show that the addition of Y has significant effect on the phase composition, microstructure and mechanical properties of Mg–6Zn–1Mn alloy. Varied phases compositions, including Mg₇Zn₃, I-phase (Mg₃YZn₆), W-phase (Mg₃Y₂Zn₃) and X-phase (Mg₁₂YZn), are obtained by adjusting the Zn to Y mass ratio. Mn element exists as the fine Mn particles, which are well distributed in the alloy. Thermal analysis and microstructure observation reveal that the phase stability follows the trend of X>W>I>Mg₇Zn₃. In addition, Y can improve the mechanical properties of Mg–Zn–Mn alloy significantly, and the alloy with Y content of 6.09% has the best mechanical properties. The high strength is mainly due to the strengthening by the grain size refinement, dispersion strengthening by fine Mn particles, and introduction of the Mg–Zn–Y ternary phases.     

Oxidation behavior of Nb–24Ti–18Si–2Al–2Hf–4Cr and Nb–24Ti–18Si–2Al–2Hf–8Cr hypereutectic alloys at 1250°C

Nb-24Ti-18Si-2Al-2Hf-4Cr and Nb-24Ti-18Si-2Al-2Hf-8Cr alloys were prepared by arc melting in a water-cooled crucible under argon atmosphere.Microstructural characteristics and oxidation resistance of the alloys at 1250 ℃ were investigated.The results show that,when the Cr content is 4 at%,the microstructures consist of(Nb,Ti)_(ss) and Nb_5Si_3;as Cr content increases to8 at%,C14 Laves phase Cr_2Nb is formed.The isothermal oxidation tests show that the oxidation kinetics of the two alloys follow similar features.The weight gains of the two alloys after oxidation at 1250℃ for 100 h are 235.61 and198.50 mg·cm~(-2),respectively.During oxidation,SiO_2,TiO_2,Nb_2O_5 and CrNbO_4 are formed at first.Then,Ti_2Nb_(10)O_(29) is formed after oxidation for 20 min and begins to change into TiNb_2O_7 as the oxidation proceeds.SiO_2 is formed as solid state at first but later evolves into glassy state to improve the cohesion of the scale.After oxidation for 100 h,oxidation products consist of SiO_2,TiNb_2O_7,Nb_2O_5 and CrNbO_4.     

Effect of neutron irradiation and postradiation annealing on the microstructure and properties of an Al–Mg–Si alloy

The effect of long-term neutron irradiation and postradiation thermal-induced aging on the microstructure and mechanical properties of an aluminum-based reactor Al–Mg–Si alloy grade SAV-1 has been studied. The material under study is the shell of an automatic fine-control rod used to control the reactivity of the core of a VVR-K research reactor. Successive 1-h annealings of specimens of the SAV-1 alloy irradiated to doses of 0.001 and 5 dpa in the temperature range of 100–550°C have been carried out. The evolution of the fine structure of the material and changes in its mechanical characteristics have been studied. The phenomenon of the acceleration of the aging of the SAV-1 alloy under the effect of a high neutron fluence at an irradiation temperature of 80°C has been observed, which involves the formation of numerous lineage (stitch) Guinier–Preston zones in the alloy. It has been shown that the strength characteristics of the SAV-1 alloy depend significantly on the degree of its radiation- and thermal-induced aging.     

Effect of Mg-Zn-Y quasicrystals on microstructure and mechanical properties ofAZ91 alloy

The influence of the additions of Mg-Zn-Y quasicrystals-containing master alloy on the microstructures and mechanical properties of AZ91 alloy under conventional casting condition was studied using XRD, SEM equipped with energy dispersive spectrometer （EDS）. The results show that the microstructure of Mg-Zn-Y quasicrystals reinforced AZ91 alloy consists of a-Mg supersaturating solid solution, β-Mgl7All2 phase and quasicrystals phase. Quasicrystals particles with excellent elevated temperature stability are dispersively distributed in the α-Mg matrix or at grain boundaries. After the addition of quasicrystals-containing master alloy, the matrix microstructure of AZ91 alloy is obviously grain-refined. The morphology of β-Mg17Al12 phase changes from continuous nets to discrete nets. At room and elevated temperatures mechanical properties of AZ91 alloy are also improved dramatically. The utility of Mg-Zn-Y quasicrystals as a reinforced phase provides new theoretical basis and technical support for the composite strengthening of magnesium alloys.     

Microstructural evolution and mechanical properties of an Nb–16Si in-situ composite with Fe additions prepared by arc-melting

This paper deals with phase constitutions, microstructural evolutions, and mechanical properties of Nb–16Si–xFe in-situ composites (where x = 2, 4, 6 at.%, referred as to 2Fe, 4Fe and 6Fe alloys, hereafter) prepared by arc-melting. It is found that with additions of Fe, Nb₄FeSi silicide arises and microstructures of as-cast samples are consisted of dendritic-like Nb_SS phase, Nb₃Si block, and Nb₄FeSi matrix in the 2Fe and 4Fe alloys, and of the dendritic-like Nb_SS phase and Nb₄FeSi matrix in the 6Fe alloy. When heat-treated at 1350 °C for 100 h, part of the Nb₃Si phase decomposes in the 2Fe and 4Fe alloys, and the 6Fe alloy shows no change in microstructure as compared with the as-cast one. The Nb₄FeSi silicide is found to be brittle, its fracture toughness and elastic modulus are first obtained, having values about 1.22 MPa m^1/2, and 310 GPa, respectively. The fracture toughness of the bulk as-cast and heat-treated Nb–16Si–xFe samples are changed slightly by the Fe additions, which is in a range of 9.03–10.19 MPa m^1/2. It is interesting that at room temperature, strength is improved by the Fe additions, whereas at 1250 °C and 1350 °C the strength decreases. As the Fe content increased from 2 at.% to 6 at.%, for example, the 0.2% yield strength increases from 1410 MPa to 1580 MPa at room temperature, decreases from 479 MPa to 385 MPa at 1250 °C.     

Effect of hot extrusion on microstructure and mechanical properties of quasicrystal-reinforced Mg-Zn-Y alloy

The microstructure and mechanical properties of as-cast and as-extruded Mg-Zn-Y alloy （Mg-11 %Zn- 0.9%Y, mass fraction） containing Mg3 YZn6 quasicrystal were studied. The eutectic icosahedral quasicrystal phase （I-phase） is broken and almost distributes along the extrusion direction, and fine I-phase with nano-size is precipitated during the extrusion. The a-Mg matrix grains are refined due to recrystallization occuring during the hot extrusion. Some {1012} twins are observed in the extruded ZW1101 alloy. And {0002}（1010） fiber texture is formed in matrix alloys after hot extrusion. The extruded alloy exhibits high strength in combination with large elongation at room temperature. The strengthening mechanism of the as-extruded alloy was discussed.     

Influence of different solution methods on microstructure,precipitation behavior and mechanical properties of Al–Mg–Si alloy

The effects of different solution methods on microstructure, mechanical properties and precipitation behavior of Al–Mg–Si alloy were investigated by scanning electron microscope, transmission electron microscope, tensile test, and differential scanning calorimetry. The results revealed that the recrystallized grains of the alloy after the solution treatment with hot air became smaller and more uniform, compared with solution treatment with electrical resistance. The texture of the alloy after two solution treatment methods was different. More rotated cube components were formed through solution treatment with electrical resistance, which was better for improving the drawability of the alloy. The strength of the alloy under the solution treatment with hot air was higher before stamping, because of the small uniform grains and many clusters in the matrix. The alloy solution treated with hot air also possessed good bake hardenability, because the transformation occurred on more clusters in the matrix.     

Effect of minor Sc and Zr on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy

1 Introduction The microstructure and properties of aluminium alloys are strongly affected by adding small quantities of scandium. Minor Sc may improve the temperature of recrystallization and fracture toughness, decrease the sensitivity of stress corrosi…     

Effect of Y content on microstructure and mechanical properties of 2519 aluminum alloy

The effects of yttrium（Y） content on precipitation hardening, elevated temperature mechanical properties and morphologies of 2519 aluminum alloy were investigated by means of microhardness test, tensile test, optical microscopy（OM）, transmission electron microscopy（TEM） and scanning electron microscopy（SEM）. The results show that the tensile strength increases from 485 MPa to 490 MPa by increasing Y content from 0 to 0.10%（mass fraction） at room temperature, and from 155 MPa to 205 MPa by increasing Y content from 0 to 0.20% at 300 ~C. The high strength of 2519 aluminum alloy is attributed to the high density of fine 0＇ precipitates and intermetallic compound AICuY with high thermal stability. Addition of Y above 0.20% in 2519 aluminum alloy may induce the decrease in the tensile strength both at room temperature （20 ℃） and 300℃.