Effect Of Cr Addition Research Articles

The Effect of Cr Addition on the Properties of Graphite-Like Carbon Film

The Effect of Cr Addition on the Properties of Graphite-Like Carbon Film

Effect of Cr addition on the structural, magnetic and mechanical properties of magnetron sputtered Ni–Mn–In ferromagnetic shape memory alloy thin films

The effect of Cr substitution for In on the structural, martensitic phase transformation and mechanical properties of Ni–Mn–In ferromagnetic shape memory alloy (FSMA) thin films was systematically investigated. X-ray diffraction results revealed that the Ni–Mn–In–Cr thin films possessed purely austenitic cubic L21 structure at lower content of Cr, whereas higher Cr content, the Ni–Mn–In–Cr thin films exhibited martensitic structure at room temperature. The temperature-dependent magnetization (M-T) and resistance (R-T) results confirmed that the monotonous increase in martensitic transformation temperatures (TM) with the addition of Cr content. Further, the room temperature nanoindentation studies revealed the mechanical properties such as hardness (H), elastic modulus (E), plasticity index (H/E) and resistance to plastic deformation (H3/E2) of all the samples. The addition of Cr content significantly enhanced the hardness (28.2 ± 2.4 GPa) and resistance to plastic deformation H3/E2 (0.261) of Ni50.4Mn34.96In13.56Cr1.08 film as compared with pure Ni–Mn–In film. As a result, the appropriate addition of Cr significantly improved the mechanical properties with a decrease in grain size, which could be further attributed to the grain boundary strengthening mechanism. These findings indicate that the Cr-doped Ni–Mn–In FSMA thin films are potential candidates for microelectromechanical systems applications.

Effect of Cr addition on the formation of the decagonal quasicrystalline phase of a rapidly solidified Al-Ni-Co alloy

Abstract The influence of Cr addition in a rapidly solidified Al-Ni-Co alloy was investigated. Melt spun samples of atomic composition Al71Ni20Co9, Al72Ni19Co7Cr2 and Al72Ni20Co5Cr3 were studied by X-ray diffraction and transmission electron microscopy. Aiming to develop quasicrystalline compositions enriched in corrosion resistant elements such as Cr and Ni this work presents, for the first time, the effect of Cr addition on the quasicrystalline phase formation of a high-Ni Al-Ni-Co rapidly solidified alloy chosen to be within the range of formation of the decagonal quasicrystalline phase observed in this ternary system. The composition of the quaternary alloys was chosen by reducing the Co content in favor of Cr on the ternary alloy and keeping the average valence electron per atom (e/a) around 1.86. The phase constitution of the ternary alloy consisted of the decagonal phase along with two intermetallic phases, Al3Ni and Al3Ni2. The addition of Cr resulted in the formation of a second quasicrystalline decagonal phase, rich in Cr. This was due to the low Cr solubility on the ternary Al-Ni-Co decagonal and intermetallic phases, which rejected Cr and resulted on the formation of the Cr-rich quasicrystal.

Effect of Cr Addition on Mechanical Properties and Wear Rate of Cast Al-Cu Alloy

Objectives: This paper investigates the effect of Cr addition on hardness, tensile properties and wear behaviour of Al-4.5Cu alloy A206. Methodology: The base alloy was melted and stirred well, fine Cr powder added in required amount, in oil fired pit furnace and poured into a permanent cast iron mold. The cast specimens were solution heat treated at 540⁰C for 4 hrs and were aged at 170⁰C for 17 hrs and 20 hrs. The as-cast and aged specimens were subjected to microstructure and EDAX evaluation followed by hardness, tensile and wear testing. Findings: The microstructure analysis and EDAX analysis reported an irregularly distributed polyhedral structures that appear blocky due to the phase formation of Al-Cr-Mn-Fe-Si. The hardness, ultimate tensile strength and yield strength were found to increase, reach a peak value and then decrease upon further chromium addition in aged condition. The wear rate decreased with increasing hardness and coefficient of friction remained constant with time. Application/Improvements: Evaluate the effect of Cr in Al alloys on the mechanical strength and wear properties.

Effects of Alloying Element Cr on Ni-Mn-Ga Alloys Studied by <i>Ab Initio</i> Calculations

The effects of Cr addition on the crystal structure, phase stability and magnetic properties of Ni8Mn4-xGa4Crx (x=0, 1 and 2) ferromagnetic shape memory alloys are systematically investigated by ab-initio calculations. The formation energy results indicate that the added Cr preferentially occupies the Mn sites in Ni2MnGa alloy due to the lowest formation energy. The evaluated Curie temperature decreases with increasing Cr content are derived from the decrease of the total energy difference between the paramagnetic and the ferromagnetic austenite.

Influence of icosahedral short range order on diffusion in liquids: A study on Al-Zn-Cr alloys

It has been shown recently that minute additions of Cr in Al-Zn alloys refine the solidified grain structure and induce multiply-twinned grains which can only be explained if the icosahedral symmetry is considered (Kurtuldu et al., 2013). It has been suggested that Cr addition to Al-Zn alloys promotes the formation of icosahedral short-range order (ISRO) in the liquid, leading to the formation of icosahedral quasicrystals (iQC) acting then as a template for the nucleation of the fcc Al-phase. If ISRO exists in liquid Al-Zn-Cr alloys, this should influence diffusion of solute elements in the liquid. The present study focuses on the effect of Cr addition on Zn diffusion in liquid Al-Zn-Cr alloys. The solute diffusion coefficients of Zn and Cr in the liquid were deduced from the solute profiles in the quenched liquid ahead of a planar solid-liquid interface. By comparison with the same measurement in Al-Zn alloys, it is shown that Cr indeed slows down the diffusion (and mobility) of Zn atoms, an effect which reinforces the hypothesis of ISRO in Al-Zn liquid induced by Cr.

Influence of Cr addition on microstructure of vacuum brazed NiCr–Cr3C2 composite coatings

Metallurgically bonded NiCr–Cr3C2 composite coatings modified by the additions of Cr were produced on a Ni-based superalloy substrate by high temperature vacuum brazing process. Effects of Cr addition on the microstructure, phases presented and the interfacial diffusion of the coatings have been investigated. Results show that the Cr additive consumed Si element to form Cr3Si and reduced the amount of brittle phase Ni3Si at the interface. The higher was the Cr addition in the coating, the thinner was the thickness of the secondary reaction zone, and the lower was the amount of the Ni3Si at the interface.

The corrosion behavior of nanocrystalline nickel based thin films

In this study, the effect of Cr addition on corrosion behavior of Ni thin films were investigated. Ni thin films and Ni films with three different Cr content were deposited on glass substrates by magnetron sputtering. After deposition process, thin films with different Cr content were thermally treated in a rapid thermal process system.Phase analysis and grain size calculations of the samples were carried out by X-ray diffraction analysis. In order to reveal corrosion properties, potentiodynamic tests were conducted on samples. Analysis revealed that, although Cr addition to pure-Ni thin films improved their corrosion resistance, occurrence of σ-Cr3Ni2 phase at higher Cr contents increased corrosion rate. The corrosion properties of the samples were also investigated by electrochemical impedance spectroscopy and surface related parameters caused by corrosion reactions were calculated. The analysis revealed that at 55% wt. Cr, rapid ion exchange occurred and highest corrosion current, 23.4 nA cm−2 was observed.

Thermodynamic analysis of nanostructured (Fe,Cr)3Al formation during mechanical alloying

Nanostructured (Fe,Cr)3Al compound was produced by mechanical alloying (MA) of the Fe50Cr25Al25 elemental powder mixture, and the effect of Cr addition on the formation of solid solution in the ternary Fe–Cr–Al system was investigated. The structural and phase changes of powder particles during MA were studied using X-ray diffractometry and transmission electron microscopy. The results showed that at early stages of MA, a BCC-Fe(Cr,Al) solid solution was formed, which transformed to the disordered (Fe,Cr)3Al compound by further milling. The thermodynamic analysis based on Miedema model showed that for all binary Fe–Al, Fe–Cr and Cr–Al systems and ternary Fe–Cr–Al system, the formation of solid solution is thermodynamically favourable for all compositions. It was also demonstrated that for the ternary Fe50Cr25Al25 alloy, more driving force is available to form solid solution compared with the Fe75Al25 binary alloy. The results of thermodynamic analysis were in agreement with the MA results.

Effect of Cr Addition on the Microstructure and Room-temperature Fracture Toughness of Nb-Si Based Ultra-high Temperature Alloys

Effect of Cr Addition on the Microstructure and Room-temperature Fracture Toughness of Nb-Si Based Ultra-high Temperature Alloys

Role of Mo/V carbides in hydrogen embrittlement of tempered martensitic steel

Abstract The vulnerability of tempered martensitic steel to hydrogen embrittlement (HE) has attracted attention from a number of researchers. Although utilizing carbide precipitation is one of effective methods to improve HE resistance, few studies have focused on the effects of carbide characteristics, such as the chemical composition and morphology of carbide. This work clarifies the role of Mo carbide and V carbide in the HE behavior of tempered martensitic steels with four steels whose chemical composition was carefully controlled. The beneficial effect of carbides is discussed in terms of hydrogen trapping and fracture mode. The low amount of trapped hydrogen and undissolved carbide led to excellent HE resistance of Mo carbides compared to V carbides. In addition, the superior mechanical performance of Cr-Mo steel was also interpreted by the effect of Cr addition as well as Mo carbides.

Microstructural evolution of mechanically alloyed Ni-based alloys under high temperature oxidation

To further improve the cost-benefit of MCrAlX (X is a reactive element like Y, Hf, Ta, etc.) alloys, the microhardness, microstructure and oxidation behavior of two Ni-based alloys, Ni60Co30Al10 and Ni60Co10Cr20Al10 without reactive elements were studied by scanning electron microscopy, X-ray diffraction and microhardness Vickers. These alloys were synthesized by mechanical alloying in a high energy ball mill and conventional sintering at 1100°C under inert atmosphere. Milling time and Cr additions have a significant effect on microhardness of as-milled and sintered samples. Bulk samples were oxidized at 1000°C for different times to analyze the possible growth of protective oxide scale, as well as the effect of Cr addition on the chemical composition of the oxide scale. After 3h of oxidation the formation of Al2O3 oxide scale in the Ni60Co30Al10 alloy is evident. By reducing the Co content and incorporating 20wt.% of Cr, the formation of an Al2O3 oxide scale with the presence of Cr2O3 was observed. Even the formation of homogeneous, continuous and protective oxide products in the surface of samples is evident, the microstructural changes after oxidation treatments have a significant effect on the decrease in microhardness of both alloys.

Effect of Cr addition on solid state sintering of WC–Co alloys

The effect of Cr addition and C content on densification and microstructural evolution of WC–Co alloys in the solid state was studied. Two alloys containing Cr and an excess of carbon or tungsten were investigated. They were compared with Cr free alloys. The intercept length distribution of the pore and binder phase was measured at several temperatures using image analysis. Cr addition delays the shrinkage whatever the C potential whilst better binder spreading and more effective rearrangement occur at lower temperature in the W rich alloy. When the temperature increases, the densification is accelerated in the C rich alloy. It is found that Cr addition has no significant effect on the solubility of W in the binder. The influence of Cr on the shrinkage behaviour is discussed putting emphasis on the grain boundary energies and on Cr oxides.

Effect of Cr Addition on Microstructure and Mechanical Property of Cu-17Ni-3Al-1.2Fe Alloy

Effect of Cr addition on microstructure and mechanical property of Cu-17Ni-3Al-1.2Fe alloy were investigated by means of tensile testing, optical microscope (OM), scanning electronic microscope (SEM) and transmission electronic microscope (TEM). The results showed that the morphology and type of second phases which exist among dendrites change significantly with the addition of 0.85 wt % Cr. A lot of rod-like and multi-branched Cr-rich phases can be observed while the formation of Ni3Al is suppressed. However, Cr addition does not change the type of particle-like Ni3Al which evenly distributes in the matrix. With the addition of Cr in Cu-17Ni-3Al-1.2Fe alloy, the tensile strength, yield strength and Brinell hardness increase, especially the yield strength with the increase of 31%, however, the elongation decreases slightly.

Effect of Cr Addition on Wetting Behavior Between Cu and High-Temperature Zn-25Sn-0.15Al-0.1Ga-xCr Pb-Free Solder

In this study the effect of Cr content (0.02 wt.% to 0.2 wt.%) on the wetting interaction between high-temperature Zn-25Sn-0.15Al-0.1Ga-xCr Pb-free solders and Cu has been investigated using the wetting balance method. Differential scanning calorimetry (DSC) investigation showed that Cr addition reduces the liquidus temperature slightly while raising the solidus temperature. Flux-assisted wetting experiments were carried out at an immersion rate of 15 mm/s at 435°C. The results show that the shortest wetting time of around 0.7 s was achieved when 0.1 wt.% Cr was added, but the wetting force tends to decrease with the Cr content. Cr addition enhances the formation of interfacial Cu5Zn8 intermetallic compound (IMC) during air cooling, but the opposite effect was observed for water cooling. The results suggest that Cr addition depresses the formation of the Cu5Zn8 layer in liquid/solid reaction, but enhances the formation of the Cu5Zn8 layer in solid/solid reaction.

Synergy of Cr concentration and withdraw rate on microstructure evolution of directionally solidified Nb–14Si–24Ti alloys

The synergy of Cr concentration and withdraw rate on the microstructure of directionally solidified and heat treated Nb–14Si–24Ti–xCr (x = 0, 2, 8, 10, 14 at-%) alloys was investigated. The phases present in the directionally solidified alloys were sensitive to Cr concentration and withdraw rate. The addition of Cr changed the solidification path of ternary alloys. High Cr concentration stabilised the Nb5Si3 and facilitated the formation of Cr2Nb during the directional solidification process. However, the effect of Cr was suppressed by the increase in withdraw rate. The competition between the effect of Cr addition and withdraw rate determined the microstructure of alloys and resulted in a four-phase microstructure. During heat treatment, the Nb3Si phases in Nb–14Si–24Ti–0Cr alloys were stable, while in the Cr contained alloys, the Nb3Si decomposed into NbSS/Nb5Si3 eutectoid through the eutectoid reaction (Nb3Si→NbSS+Nb5Si3).

Effect of Cr addition on the microstructure and abrasive wear resistance of WC-reinforced iron matrix surface composites

Abstract

Effect of Cr addition on the alloying behavior, microstructure and mechanical properties of twinned CoFeNiAl0.5Ti0.5 alloy

The effect of Cr addition on alloying behavior, microstructure and mechanical properties of multicomponent CoFeNiAl0.5Ti0.5 high entropy alloy (HEA) was studied in detail. Non-equiatomic CoFeNiAl0.5Ti0.5 and CrCoFeNiAl0.5Ti0.5 alloys were fabricated by the combination of mechanical alloying (MA) and spark plasma sintering (SPS). Alloying behavior, microstructure, phase evolution and mechanical properties of the two alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM), as well as by an Instron testing system. During MA, a supersaturated solid solution consisting of a metastable FCC phase was formed in CoFeNiAl0.5Ti0.5 alloy. With Cr addition, the alloy showed a supersaturated solid solution with an FCC phase and a BCC phase. After SPS, bulk CoFeNiAl0.5Ti0.5 alloy was composed of a main FCC phase, a minor BCC and a tiny unknown phase. The addition of Cr into CoFeNiAl0.5Ti0.5 alloy exhibited two FCC phases (FCC1 and FCC2) with similar lattice constant and a tiny unknown phase, meanwhile selected area electron diffraction (SAED) pattern of the FCC1 phase was the same as that of the FCC phase of CoFeNiAl0.5Ti0.5 alloy. Nanoscale twins presented in both of CoFeNiAl0.5Ti0.5 and CrCoFeNiAl0.5Ti0.5 alloys, but deformation twinning occurred only in the FCC phase of CoFeNiAl0.5Ti0.5 and the FCC1 phase of the Cr added alloy which displayed the same SAED pattern. Moreover, the addition of Cr lowered the formation ability of nanoscale twins evidently. The addition of Cr into CoFeNiAl0.5Ti0.5 alloy could decrease compressive strength and Vickers hardness slightly.

The Effect of Cr Addition on the Microstructure of TiNi: First-Principles Calculations

Based on the first-principles pseudo-potential plane wave method, the effect of Cr addition on the microstructure of NiTi alloys are characterized and assessed with the formation enthalpy (ΔH), binding energy (ΔE) and density of states (DOS) distribution of NiTi (Cr) crystals. The results show that the binding energy of NiTi (CrNi) is slightly smaller than that of NiTi (CrTi), but the formation enthalpy of NiTi (CrTi) is much smaller than that of NiTi (CrNi).So the Ms of NiTi alloy could be decreased by the addition of ratio for Ni/Ti. And the electronic microstucture of NiTi (CrNi) alloy are also illustrated clearly.

The Influence of Metallic Addition on Fluidity of Aluminum (LM6) Alloy

The effect of Cr addition on the fluidity of aluminum (LM6) alloy has been investigated by spiral fluidity test. Presence of 0.1 wt.% Cr decreased fluidity of melt due to formation of sludge. In fact Cr changes the morphology of the intermetallic phase from β-intermetallics less harmful polyhedral morphology (α-intermetallics). The β-phases have largest surface to volume ratio, hence they have the largest interfacial region with the melt and are the most detrimental intermetallic to drop off the fluidity. In Cr-containing alloys the effect of α-phase is less detrimental than β-phase to the fluidity. On the other hand sludge formation and consuming Si and shifts the local chemical composition of the melt to the aluminum side of the phase diagram which has lower fluidity than eutectic and hypereutectic compositions.