Effect Of Cr Addition Research Articles

Effect of chromium addition on microstructure and creep strength of as-cast Ti–48Al alloy

Abstract The microstructure and creep behaviour of as-cast gamma titanium aluminide based alloys with nominal composition of Ti–48Al, Ti–48Al–2Cr and Ti–48Al–4Cr (at.%) were investigated. Constant load tensile creep tests were performed at temperature and stress of 800 °C and 150 MPa, respectively. Creep characteristics such as steady-state creep rate, time to 1% creep deformation, creep deformed microstructures and creep fracture was analysed. The effect of Cr addition on creep strength were analysed with respect to solid solution strengthening by Cr in γ phase, formation of β phase and comparison with the base binary Ti–48Al alloy.

Effect of Cr additions on the microstructural stability of Ni electrodes in ultra-thin BaTiO3 multilayer capacitors

Microstructural control in thin-layer multilayer ceramic capacitors (MLCC) is one of the present day challenges to maintain an increase in capacitive volumetric efficiency. This present paper opens a series of investigations aimed to engineer the stability of ultra-thin Ni electrodes in BaTiO3-based multilayer capacitors using refractory metal additions to Ni. Here, pure Ni and Ni–1 wt.% Cr alloy powders are used to produce 0805-type BME MLCCs with 300 active layers and with dielectric and electrode layer thickness around 1 μm. To investigate the continuity of Ni electrodes, both MLCC chips with pure and doped electrodes were sintered at different temperatures for 5 h. It is found that the continuity of Ni electrodes is improved most likely due to the effect of Cr on the low-melting point (Ni,Ba,Ti) interfacial alloy layer formation. The interfacial alloy layer is not observed when Cr is segregated at Ni-BaTiO3 interface in the Cr-doped samples, while it is found in all undoped samples. The interfacial alloy layer is believed to increase mass-transfer along the Ni-BaTiO3 interfaces facilitating an acceleration of Ni electrodes discontinuities.

Effect of Cr on Strain Ageing Behaviour of Low Carbon Steel

This work explores the effect of Cr addition on the kinetics of strain ageing process. The strain ageing behaviour of low carbon steel with and without 0.7wt% Cr was investigated using transmission electron microscopy (TEM), atom probe tomography (APT) and tensile tests. The results have shown that Cr alloyed steel undergoes the same three stages of ageing as unalloyed low carbon steel. However, the alloying with Cr reduces the rate of strain ageing by ~2 times in comparison with non-alloyed low carbon steel. It especially delays the offset of stage III. This is explained by the reduction of carbon content in ferrite due to the enrichment of cementite with Cr leading to the reduction of its equilibrium solubility in ferrite.

Effects of Cr addition on the microstructures and electrochemical performances of La–Mg–Ni system (PuNi 3-type) hydrogen storage alloy

In order to improve the electrochemical cycle stability of La–Mg–Ni system (PuNi 3-type) hydrogen storage alloy, a trace of Cr was added in the alloy and La 2Mg(Ni 0.85Co 0.15) 9Cr x ( x = 0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of Cr addition on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The obtained results show that Cr addition engenders an inappreciable influence on the phase composition of the as-cast and quenched alloys, but it changes the phase abundance of the alloys significant. The Cr addition markedly enhances the cycle stability of the as-cast and quenched alloys, but it decreases the discharge capacity. When Cr content increased from 0 to 0.4, the discharge capacity of the as-cast alloy decreased from 396.3 to 355.6 mAh/g, and the cycle life prolonged from 72 to 97 cycles. For the as-quenched (30 m/s) alloys, the discharge capacity reduced from 364.2 to 334.2 mAh/g, and the cycle life extended from 100 to 131 cycles.

Effect of Cr addition on microstructure and wear resistance of hypomonotectic Cu–Pb alloy

The effects of Cr content on the microstructure, hardness, and wear resistance of Cu–Pb hypomonotectic alloys were investigated. Optical microscope and differential scanning calorimetry (DSC) analysis reveal that when the Cr content exceeds the solubility limit, primary Cr precipitates from the melt as dendrites that grow anisotropically with the crystallographic orientation of 〈1 0 0〉 as the fastest growing directions. The hardness of the alloys is found to increase with increasing Cr content. The wear resistance of the alloys was measured under dry conditions over a load range of 20–80 N using a pin-on-disc type wear testing machine. The worn surfaces were characterized by scanning electron microscopy and the wear mechanism of the alloys was studied. The results show that the wear resistance increases with increasing Cr content, due to a combined effect of strengthening of the matrix and better self-lubrication ability of the lead film.

Effect of Chromium Addition on Damping Capacity, Mechanical Property, and Corrosion Resistance of Fe-18%Mn Alloy

Effect of Cr addition on damping capacity, mechanical property, and corrosion resistance of Fe-18%Mn martensitic alloy has been studied. Martensite start temperature (Ms) of the alloy decreases linearly from 150 to 25 with increasing Cr content up to 15%. The damping capacity decreases gradually from 27 to 23% in SDC with increasing Cr content from zero to 10%, and decreases rapidly with further Cr content. The tensile strength of the alloy maintains a level of 60 / regardless of Cr content with an elongation of 20 to 25%. Immersion test in 5% NaCl solution leads to the result that the corrosion resistance of the alloy becomes excellent above 10% Cr. From the above results, it is concluded that the optimum Cr content to improve the mechanical property and corrosion resistance of the alloy with a lesser decrease in damping capacity is about 10%.

Effects of Cr addition on the microstructures and electrochemical properties of as-cast and quenched La 2Mg(Ni 0.85Co 0.15) 9 electrode alloys

A trace of Cr was added in La–Mg–Ni based (PuNi 3-type) electrode alloy and rapid quenching technique was used in order to improve its cycle stability. The electrode alloys La 2Mg(Ni 0.85Co 0.15) 9Cr x ( x = 0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching, and the effects of Cr addition on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the as-cast and quenched alloys have a multiphase structure, including two main phases of (La, Mg)Ni 3 and LaNi 5, a residual phase of LaNi 2. The Cr addition has an inappreciable influence on the phase compositions of the alloys, whereas it changes the phase abundance of the alloys. The results obtained by the electrochemical measurement indicate that the Cr addition obviously enhances the cycle stability of the as-cast and quenched alloys and leads to a different extent decrease of the discharge capacity of the alloys. When the amount of Cr addition changes incrementally from 0 to 0.4, the discharge capacity of the as-cast alloy decreases from 396.5 to 355.6 mAh/g, and the cycle life increases from 72 to 97 cycles. For the as-quenched (30 m/s) alloys, the discharge capacity decreases from 364.6 to 334.2 mAh/g, and the cycle life increases from 100 to 131 cycles. The Cr addition improves the discharge voltage characteristic and activation capability of the as-cast alloys, but it slightly decreases the activation capability of the as-quenched alloys.

Effect of Cr addition on the glass-forming ability, magnetic properties, and corrosion resistance in FeMoGaPCBSi bulk glassy alloys

The effect of Cr addition on the glass-forming ability (GFA), the magnetic properties, and corrosion resistance in Fe–Mo–Ga–P–C–B–Si glassy alloys was investigated. In addition to a slight increase of supercooled liquid region from 50to55K, the substitution of a small amount of Fe with Cr was found to be effective for approaching alloy to a eutectic point, resulting in an increase in GFA. By copper mold casting, bulk glassy alloy rods with diameters up to 3mm were produced. These glassy alloys exhibit a rather high saturation magnetization of 0.84–1.11T with good soft-magnetic properties, i.e., low coercive force of 2.3–2.9A∕m, and high effective permeability of 13 360–15 960 at 1kHz under a field of 1A∕m. The passive current density of the glassy alloy rod in 3mass% NaCl solution decreased significantly from 1×102to3×10−1A∕m2 with an increase in Cr content, indicating that the addition of Cr is effective in enhancing the corrosion resistance.

Effect of Cr addition on pitting behaviour of iron aluminide intermetallic

The effect of Cr addition on the pitting behaviour of iron aluminide based on ordered D0 3 structure has been investigated in detail. Iron aluminide of the composition Fe–28Al (at.%) and Fe–28Al–3Cr (at.%) was tested in Na 2SO 4 solution containing Cl − ions (pH 6, 3.2) and the results were compared with pure Fe and AISI SS 304. The results demonstrated that Fe–28Al–3Cr alloy showed pitting only at a high concentration of Cl − ions. The addition of Cr proved to be beneficial as it improved the pitting resistance of Fe–28Al–3Cr alloy in comparison to pure Fe and Fe–28Al. However, Fe–28Al–3Cr alloy showed pitting behaviour comparable to AISI SS 304.

Effect of Cr Addition on the Phase Equilibria of the Nb-Si System

AbstractNb-silicide based in-situ composites are promising materials for future high-temperature structural applications. Nb-silicide composites are typically alloyed with Hf, Ti, Cr, and Al to provide a balance of mechanical and environmental properties. A thermodynamic description of the Nb-Cr-Si system has been developed previously in literature based on reported isothermal sections. According to the previously calculated phase diagrams, selected alloys were directionally solidified. The as-solidified microstructures could not be interpreted using the liquidus projection calculated from the existing thermodynamic descriptions. Therefore, an improved thermodynamic description was developed by incorporating the new experimental data.

Ａｌ‐Ｍｇ‐Ｓｉ系合金の応力腐食割れ特性に及ぼすＣｒ添加の効果

Effect of Cr addition on properties of intergranular corrosion (IC) and stress corrosion cracking (SCC) in an acid sodium chloride (ISO) solution was evaluated by using four kinds of Al-Mg-Si alloys with a constant Mg content of 0.7mass% ; No. 5 (Al-Mg-1.1%Si), No. 7 (Al-Mg-0.44Si-0.34Cu), and alloys No. C5 and No. C7 with 0.2% Cr addition respectively. The excess Si alloys No. 5 and No. C5 showed little susceptibility to IC at any stage of aging at 443K, whereas the Cu containing alloys No. 7 and No. C7 exhibited some IC at the stage from underaging to peak-aging (for 28.8 ks at 448K). The alloy No. C7 however became immune to IC at the stage of overaging. Tensile tests by SSRT (slow strain rate technique) were carried out at strain rate 5.5×10-7/s to evaluate the index I of susceptibility to SCC as the ratio of reduction in elongation, compared to that in laboratory air. The index I of the peak-aged specimen was ranked on the order of alloy No. 5 (0.98)>No. 7 (0.72)>No. C7 (0.69)>No. C5 (0.23), which was in a good correspondence to the failure-time property obtained by a constant load SCC test. SSRT therefore should be useful as a rapid testing method to estimate SCC resistance. The Cr addition to the excess Si alloy resulted in a marked improvement of SCC resistance. The high resistance of alloy No. C5 were attributed to an increase in uniform corrosion due to a fine grain structure and distribution of dispersoids AlSi (Cr, Fe) or AlSiFe in grains.

Effects of Cr addition on the microstructural, mechanical and electrical characteristics of Cu–6wt.%Ag microcomposite

Abstract Cu–6 wt.%Ag and Cu–6 wt.%Ag–1 wt.%Cr microcomposites were prepared by heavy drawing. The morphology of filamentary bundles was observed and the tensile strength and electrical conductivity determined. The effect of Cr addition was discussed according to the changes in the microstructure, strength and conductivity with various draw ratios for both alloys.

Magnetic and electrical properties of amorphous Fe–Cr–P–C–Si

Magnetic and electrical properties of melt-spun amorphous Fe 100− y− z Cr y (PCSi) z alloys, 4⩽ y⩽11, 19⩽ z⩽22, have been investigated. The magnetic moment, μ Cr, of Cr has been estimated and the magnetic coupling constants, J Fe–Fe, J Fe–Cr and J Cr–Cr, between Fe–Fe, Fe–Cr, and Cr–Cr atoms respectively, have been evaluated using the molecular field theory of two-sublattice model. Temperature dependence of electrical resistivity of these amorphous alloys was also studied. The electrical resistivity was measured between 170 and 330 K. The alloys studied exhibit a resistivity minimum at a relatively high temperature. The temperature of resistivity minimum, T min, increases with increasing Cr content. The effect of Cr addition in these compounds is compared with that of Co and Ni addition on the electrical resistivity on Fe-based alloys.

Effect of Cr addition on oxidation behavior of Ti–48Al–2Ag alloys

The oxidation behavior of Ti–48Al–2Ag alloys with addition of 0–7% Cr (Cr substituting Ti) was investigated in air at 800 and 900 °C. It was found that alloys Ti–48Al–2Ag–1Cr and Ti–48Al–2Ag–3Cr exhibited increased oxidation rates compared to the Cr-free ternary alloy Ti–48Al–2Ag. If the Cr content was increased to 5% (alloy Ti–48Al–2Ag–5Cr), a similar oxidation resistance was found as for the ternary alloy Ti–48Al–2Ag, i.e. excellent oxidation resistance at 800 °C, but poor oxidation properties at 900 °C. The best oxidation properties were obtained for the quaternary alloy Ti–48Al–2Ag–7Cr, which exhibits excellent oxidation resistance at 800 °C as well as at 900 °C. The surface and cross-section microstructure of the oxidized samples were characterized with XRD, SEM/EDX, OM. It was found that optimum oxidation resistance was achieved if a continuous Ti(Cr,Al) 2 Laves or Z phase layer was formed in the depletion layer beneath the external Al 2O 3 scale. Alloys exhibiting higher oxidation rates appeared to form mixed oxide scales containing Al 2O 3 and TiO 2, whereby (Al,Cr,Ag) 3Ti or α 2-Ti 3Al phase was formed in the depletion layer beneath the oxide scales.

The effect of Cr addition on mechanical and chemical properties of Ni 3Si alloys

The alloying behavior and microstructure of the Ni–Si–Cr ternary alloys were firstly characterized by optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) with electron probe analysis. The microstructures of the Ni–Si–Cr ternary alloys consisted of largely dispersed Ni 5Si 2 phase and finely precipitated Ni 3Si phase in Ni solid solution. Then, the high-temperature mechanical properties, three-point bend test, oxidation and corrosion properties were investigated. The Ni–Si–Cr ternary alloys showed significant strengthening over a wide range of temperatures, and also large compressive plastic deformation at high temperatures. The strength and fracture toughness at ambient temperatures were correlated with the volume fraction of the Ni 5Si 2 phase. The Ni–Si–Cr ternary alloys showed substantially improved oxidation resistance in air at 1173 K, comparing with the Ni 3Si and Ni 3(Si,Ti) alloys. Also, the Ni–Si–Cr ternary alloys showed corrosion resistance comparable to the Ni 3Si and Ni 3(Si,Ti) alloys.

Effect of Cr addition on the properties of aluminide coating layers formed on TiAl alloys

TiAl alloys were coated by two different processes with a simple aluminide coating and a Cr+Al-type composite coating for the improvement of oxidation resistance of the alloy. Simple aluminizing was applied to TiAl– XCr ( X=1, 4, 6 at.%) alloys. A Cr+Al-type composite coating was performed by Cr evaporation on the TiAl substrate followed by pack aluminizing. A simple aluminide coating applied to the Cr-added TiAl alloys showed improvement of ductility and oxidation resistance. This was mainly due to grain refinement of the Cr-added coating layer. The coating layer formed by the composite coating process consisted of the Al 4Cr outer layer and TiAl 3 inner layer. However, these coating layers were transformed to a Ti(Al,Cr) 3 layer with a L1 2 structure during oxidation. This layer showed much better ductility compared to other coating layers and superior oxidation resistance in cyclic oxidation tests.

固体潤滑材分散青銅系焼結軸受の開発 第１報 青銅圧粉体へのＣｒ添加による焼結ち密化促進について

In order to develop Graphite dispersed sintered bronze bearing material standing in the use of a higher load application, effects of Cr addition on sintering properties and microstructures of the bronze matrix were investigated. Mixed powders were prepared from elemental Cr powders and atomized 90Cu-10Sn powders, of which particle sizes were 106-50μm and 1-38μm, respectively. Compacts pressed at 390 MPa were sintered at 670-1030 K for 0.3-180 ks in H2. With increasing sintering time at 1030 K, pores decrease rapidly with the refinement of grain size in the bronze matrix surrounding Cr particle. This indicates that the densification of the bronze is promoted by the diffusion of Cr.

Effect of Cr Addition on the Methane Aromatization Performance of the Mo/HZSM-5 Catalyst

The promotional effect of Cr addition on the methane aromatization performance of the Mo/HZSM-5 catalyst was investigated. It was found that much higher methane conversion was obtained over Mo–Cr/HZSM-5 catalyst than over Mo/HZSM-5. The results indicate that when the Cr/Mo molar ratio is 0.07, the methane conversion and aromatics selectivity reach 11.6 and 97.3% respectively at a reaction temperature of 973 K. Raising the temperature is beneficial to the methane conversion and 15.82% conversion is obtained at 1023 K. Modern measurements such as isopropyl alcohol decomposition and temperature desorption of ammonia (NH3-TPD) were used to characterized the catalysts. The results of isopropyl alcohol decomposition show that the surface acidity of Mo–Cr/HZSM-5 is increased at high temperature. The NH3-TPD findings imply that the Mo–Cr/HZSM-5 catalyst has much stronger acidity and more acid sites than Mo/HZSM-5, most likely one of the reasons for the enhanced activity for methane aromatization using Mo–Cr/HZSM-5 catalyst.

Newly developed electrical steel for high-frequency use

For high-frequency appliances, a new magnetic material was developed, and its properties were investigated and compared with conventional electrical steel and 6.5% Si steel. The new material has extremely low iron loss at high frequencies over 5 kHz as well as 6.5% Si steel, which was obtained by increasing electric resistivity, or by reducing its eddy current loss. Generally, increasing resistivity makes steels brittle and deteriorates their workability. However, the developed material showed a good workability with the effect of Cr addition. This material has a good property of pulse response, and also showed an excellent performance for power electronics device using an active filter operated at 15 kHz.

The effect of Cr addition on structure and corrosion resistance in FeTiN nanocrystalline soft magnetic thin films

FeTiN and FeCrTiN thin films were prepared by reactive rf magnetron sputtering. Fe/sub 92.3/Ti/sub 2.1/N/sub 5.6/ (at.%) films showed excellent thermal stability and soft magnetic properties; saturation magnetization (4/spl pi/M/sub s/)/spl sim/19.5 kG, coercivity (H/sub c/)/spl sim/1.2 Oe and effective permeability (/spl mu//sub eff/)/spl sim/2000 at 100 MHz. However, the corrosion resistance behaviors of the FeTiN films were similar to those of other FeMN films. For improving the corrosion resistance of the FeTiN films without the deterioration of magnetic properties, Cr was added to the FeTiN films. In an as-deposited Fe/sub 90.3/Cr/sub 1.2/Ti/sub 1.1/N/sub 7.4/ film, the permeability reached about 2700 at 100 MHz and 4/spl pi/M/sub s/ and H/sub c/ showed /spl sim/18.6 kG and 1.5 Oe, respectively. From XRD and TEM results, the sizes of /spl alpha/-Fe grains in the FeTiN and FeCrTiN films were observed to be below 10 nm and the grain orientations of the FeCrTiN films were more evenly distributed than the FeTiN films. Also, an addition of Cr in FeTiN films improved the corrosion resistance without the deterioration of soft magnetic properties on FeCrTiN films, caused by the formation of passivation layers in their surface.