Influence Of Chromium Additions Research Articles

Influence of chromium addition and cooling rate on Kinetic and microstructural evolution in FexCr100-x Metallic Glasses

In this study, we utilized molecular dynamics simulations with the embedded-atom approach to explore how different cooling rates and concentrations of chromium (Cr) affect the vitrification of metallic glasses (MGs) composed of a binary alloy FexCr100-x. We assessed this impact by analyzing the glass transition temperature (Tg) and the activation enthalpy (Δh). The results reveal an interesting non-linear trend in the activation energy. Specifically, there is a sharp decrease observed at a chromium concentration of 50%, followed by a slight increase at the 75% concentration level. These kinetic observations are linked to microstructural data obtained through Voronoi polyhedral analysis (VPA). However, it's worth noting that the influence of varying cooling rates on the vitrification process appears to be relatively modest.

The influence of chromium addition on the metallurgical, mechanical and fracture aspects of Sn–Cu–Bi/Cu solder joint

One of the candidate alloying elements is Cr which is used to make solder suitable for severe conditions. The current study has been conducted to investigate the addition of Cr along with Bi to Sn–Cu base solder. Accordingly, the effect of adding Cr on the joint properties of the new Sn-0.8Cu-1.8Bi-xCr (x = 0, 0.01, and 0.1 wt%) solders is compared to Sn-0.8Cu and Sn-0.8Cu-1.8Bi base solders. For investigating the joint interfacial microstructure and phase transformation, the synthesized solders were bonded to the Cu-substrate. Also, to evaluate the joint properties, the shear test, fractography, and microhardness were carried out. The characterizations are carried out using SEM-EDS to predict the mechanism governing the grain refinement and decrease of intermetallic compounds (IMCs) thickness. The presence of Cr and Bi improved the IMC layer microstructure and changed the joint properties of Sn–Cu. The thickness of the IMCs at the solder/substrate interface decreased by the addition of selected alloying elements because of the Sn and Cu diffusion power changing. Also, the Sn–Cu–Bi-0.01Cr/Cu joint showed the best shear properties and elongation among the others. The best metallurgical, mechanical and fracture behavior results were obtained from the Sn–Cu–Bi-0.01Cr/Cu joint.

Concentration of Point Defects in Metal Deficient Zn1-yO

AbstractIn this paper the doping effect has been used to indirectly calculate point defect concentration in metal-deficient Zn1-yO zinc oxide. The proposed method consists of determining the concentration of prevailing point defects in the studied oxide from the influence of chromium addition on the point defect situation in doped zinc oxide. It has been found that chromium addition into the crystal lattice of zinc oxide changes its ionic disorder, enabling calculation of predominant point defects in Zn1-yO. The concentration of predominant point defects in Zn1-yO is the following function of oxygen pressure and temperature: $$\eqalign{\left[{\,{{\rm V''}_{\rm Zn}}\,} \right]\, &= \,{1 \over 2}\left[{\,{\rm h^ \bullet}\,} \right]\, = \,0.63 \cdot \,\rm p_{{O_2}}^{1/6}\, \cdot {K^{1/3}}\,_{}^{}\, \cr& = \,\,5.6 \cdot {10^{- 3}} \cdot \,\rm p_{{O_2}}^{1/6}\, \cdot \exp \left({- {{27\,kJ/mol} \over {RT}}} \right)\cdot}$$

Influence of chromium on microstructure and sintering properties of FeNiMoCu system prealloyed powders

The chromium was added to the FeNiMoCu system prealloyed powders by using Cr–Fe powders way, powder mixtures were uniaxially pressed at 600 MPa, and then cold pressing sintering, sintering hot-forging, and re-sintering process were respectively carried out. Influence of chromium addition on the microstructure and properties of the FeNiMoCu system prealloyed powders were studied. Results show that chromium can be homogenous diffused into structure, and improved properties of structure by the appropriate sintering process. Oxidation of chromium can be restrained. Microhardness and apparent hardness increase with increasing chromium addition, sintering density and temperature. After hot-forging re-sintering, microstructure and properties of FeCrNiMoCu system PM materials is the better.

Influence of chromium additions on corrosion resistance of Co75·5Si13·5B9Nb3Cu1metallic glass in marine environment

This study addressed the influence of Cr concentration on the corrosion resistance of Co73·5Si13 ·5B9Nb3Cu1 metallic glass in simulated marine atmospheres with 1000 ppm of chlorides. Anodic and cyclic polarisation measurements were carried out to study the susceptibility to passivation and localised corrosion. The corrosion kinetics were analysed using dc electrochemical techniques. Every test was conducted using the same material in different states: amorphous, nanocrystalline and crystalline. The study also focused on changes in the magnetic properties of the material as a result of Cr addition and exposure to an aggressive medium. These properties depend mainly on the Cr concentration and the material state (amorphous, crystalline or nanocrystalline).

Influence of chromium additions on the oxidation resistance of an austenitic Fe-30Mn-5Al alloy

The oxidation behavior of an austenitic Fe–30Mn–5Al (wt.%) alloy with chromium contents ranging from 3 to 9 wt.% was evaluated in air between 600 and 900°C. The alloy with the highest chromium content showed the best oxidation resistance over the entire temperature range. The high mass gains of chromium-free material result from internal oxidation from the earliest stages of oxidation over the entire temperature range. Chromium additions delay the beginning of internal oxidation for longer times and/or higher temperatures. The beneficial influence of chromium additions is linked to the establishment of a rather continuous, ferrite-rich subsurface. This subsurface, together with the secondary oxygen-getter effect of chromium, favor the rapid establishment of a protective alumina layer. The different processes occurring throughout the oxidation manifest the complexity of the mechanism controlling the oxidation in chromium-free and chromium-containing alloys.

The influence of chromium additions on the magnetic properties of Nd 2(Fe,Co) 14B-based nanocomposites

The phase transformation behavior of melt-spun nanocomposite alloys of composition Nd 2[Co 0.06 (Fe 1− x Cr x ) 0.94] 23.2B 1.48 (0 ⩽ x < 0.09) as a function of chromium content ultimately controls the final phase constitution, character and chemistry of the alloys, which in turn control their room-temperature hysteretic magnetic properties.

The influence of chromium addition on the toughness of [formula omitted] interfaces

Experimental studies designed to characterize the fracture resistance of interfaces between Al 2O 3 and either pure Ni or a γ-Ni alloy containing Cr have revealed a profound influence of Cr on the debond toughness. The interface between the pure Ni and Al 2O 3 is susceptible to stress corrosion caused by moisture, resulting in a fracture energy of the order of 10 J/m 2. The interface between the alloy and the Al 2O 3 cannot be fractured, even at strain energy release rates in excess of 100 J/m 2. An analysis of these interfaces has identified two influences of the alloy addition that might govern its role in eliminating stress corrosion: (i) the Cr “getters” the C near the interface by forming a Cr-carbide reaction product; and (ii) the alloy dissolves some of the alumina during bonding, exposing virgin material to the alloy at the interface. The factors that lead to carbide formation and alumina dissolution are discussed.

The influence of chromium addition on the environmental embrittlement of Ni 3(Si,Ti) alloys at ambient temperatures

The environmental embrittlement in ordered intermetallics as well as ordinary materials is caused via some microscopic processes involving the decomposition, absorption, permeation and condensation of hydrogen atoms in the associated region, and finally by the bond breaking of the materials. Therefore, it is expected that the substitutional solutes are also capable of influencing the environmental embrittlement of Ni{sub 3}(Si,Ti) alloys by affecting a microscopic process differently than boron and carbon do. In this study, it is shown that the embrittlement of Ni{sub 3}(Si,Ti) alloys in air is suppressed by the addition of chromium at a level of one atomic percent. The embrittlement/ductilization behavior and the associated alloying effect are characterized by the tensile tests at room temperature in several environmental media and strain rates, and the fractographic observation.

The influence of chromium additions on order and ductility in Fe3Al intermetallic

It has previously been shown that the addition of Cr to the Fe 3 Al alloy can lead to improvements in ductility. Initial interpretations of this effect were based on changes in the fault energies and dislocation configurations, but recently the influence of environmental attack has been invoked. In the present study the role of Cr and other elemental additions on the state of order, dislocation dissociations and configurations, and on ductility has been examined under conditions where environmental attack should not be important. The addition of Cr is shown to have only a minor affect on ordering kinetics, fault energies and dislocation configurations. However, for the alloys generally considered, containing 28% Al, it is shown that the ordered state and microstructure depends sensitively on the precise composition and heat treatments given. In particular, small amounts of solute elements such as B can lead to the appearance of two-phase ordered-disordered microstructures over a wide temperature range, to the appearance of imperfect long range and short range order, and to major changes in the kinetics of ordering and disordering. The mechanical properties achieved are shown to depend critically on the extent and distribution of disorder (the long range order parameter, the extent of short range order, the presence and distribution of thick disordered domain walls) and this factor may explain much of the variability in properties reported between similar alloys. By way of example, the presence of short range order will confine dislocations to well-defined shear planes, concentrating shear and inducing early failure; disordered domain walls will dissociate superdislocations thereby spreading shear homogeneously; the ordered domains/disordered walls morphology will lead to particle-dispersion hardening

Corrosion Properties of Cast Iron Ball Materials in Wet Grinding

Abstract The influence of chromium addition to grinding media on corrosion rates of various chromium containing cast iron ball materials was investigated using Tafel plot DC polarization resistance measurements under abrasion in a quartzite slurry. The high chromium cast iron ball materials exhibited low corrosion rates at low and non-abrasive conditions, and the corrosion rates were increased markedly with rotation speed. Whereas corrosion rates of low chromium cast iron ball materials were high, indicating little dependence on rotation speeds. To understand the properties of surface films of ball materials as a function of chromium content, AC impedance measurements were made at various cathodic and anodic potentials. The high chromium cast iron ball materials exhibited high polarization resistance values at an applied potential of −0.05 V (vs SCE). The polarization resistance values obtained by DC polarization resistance and AC impedance methods were correlated.

Effects of chromium on crack growth and oxidation in nickel aluminide

The influence of chromium additions on crack growth and oxidation have been examined in the nickel aluminide, Ni 3Al. Crack growth rates were measured in a chromium containing alloy as a function of stress intensity at temperatures between 600 and 760°C in air, together with rates of oxide film growth, and compared with previous measurements taken from Ni 3Al. The mechanisms of crack propagation and oxidation were investigated with a range of analytical techniques, including SEM, AES, XPS, SIMS, TEM and STEM. An addition of 8% chromium had a significantly beneficial effect on both crack growth resistance and oxidation resistance between 600 and 760°C. Low oxidation rates were associated with the formation of Cr 2O 3 together with Al 2O 3 at the metal/oxide interface, consistent with chromium acting initially as an oxygen getter, and promoting the formation of a protective Al 2O 3 layer, with little internal oxidation. It is proposed that chromium was also responsible for inhibiting oxygen access to and diffusion along grain boundaries at crack tips, modifying the mechanism of crack propagation from “step-wise cracking”, dominated by oxygen embrittlement (observed in the absence of chromium), to a more conventional creep crack growth process.

Influence of chromium on superplasticity in ultra-high carbon steels

The influence of chromium additions to ultra-high carbon steels has been investigated. A common bearing steel (52100 containing 1% C and 1.5% Cr), a 1.6%+1.5% Cr steel (designated 52160) and a plain 1.6% C steel have been compared. Chromium is found to enhance greatly the superplastic properties. This is because the chromium enters the cementite and thereby stabilizes it. This in turn allows very little grain growth in ferrite to occur during superplastic deformation. A value of 1220% elongation to failure in 52160 was found at 650° C at an initial engineering strain rate of 1% min−1. The influence of strain rate on the elongation to failure has also been investigated in this material.