Air-Hardening Die-Forged Con-Rods—Achievable Mechanical Properties of Bainitic and Martensitic Concepts

Three air-hardening forging steels are presented, concerning their microstructure and their mechanical properties. The materials have been produced industrially and achieve either bainitic or martensitic microstructures by air-cooling directly from the forging heat. The bainitic steels are rather conservative steel concepts with an overall alloy concentration of approximately 3 wt.%, while the martensitic concept is alloyed with 4 wt.% manganese (and additional elements), and therefore belongs to the recently developed steel class of medium manganese steels. The presented materials achieve high strengths (YS: 720 MPa to 850 MPa, UTS: 1055 MPa to 1350 MPa), good elongations (Au: 4.0 MPa to 5.9 MPa, At: 12.3 MPa to 14.9 MPa), and impact toughnesses (up to 37 J) in the air-hardened condition. It is shown that air-hardened steels achieve properties close to standard Q + T steels, while being produced with a significantly reduced heat treatment.

Piezoreflectance and Electronic Structure of Alloys of Copper with Polyvalent Solutes

<p>Piezoreflectance and other optical measurements have been made on other optical measurements have been made on a phase alloys of Cu with Zn Ga, Al, In and Ge. The samples were evaporated films deposited on the face of a resonant oscillator assembly. The application of this type of strain transducer to piezoref-reflectance alleviates systematic errors and allows the response to pure shear strains to be distinguished, even in amorphous materials, using the polarisation dependence of the results. The energies of the d band -> Fermi level threshold, the interconduction band threshold, and the L2' -> L1 critical point transition were determined for the alloys. Previous optical studies using more conventional methods either have not been able to resolve these features or have not located them with accuracy comparable with piezoreflectance. With increasing alloy concentration the d band threshold is found to shift slowly to higher energies, the inter-conduction band transitions more rapidly to lower energies. Zn impurities produced much smaller shifts than the others, indicating the importance of interactions between impurity d states and the d and conduction states of the host. Significant differences were found between the isovalent solutes Ga and A1. In concentrated alloys with Zn, Ga and Al the interconduction band threshold tended to a common value of about 2.5 eV. This lack of simple dependence on e/a, the electron per atom density in the alloy, is relevant to the understanding of the electronic structure of the Hume-Rothery alloys and the regularity of the [alpha] phase boundary.</p>

Piezoreflectance and Electronic Structure of Alloys of Copper with Polyvalent Solutes

<p>Piezoreflectance and other optical measurements have been made on other optical measurements have been made on a phase alloys of Cu with Zn Ga, Al, In and Ge. The samples were evaporated films deposited on the face of a resonant oscillator assembly. The application of this type of strain transducer to piezoref-reflectance alleviates systematic errors and allows the response to pure shear strains to be distinguished, even in amorphous materials, using the polarisation dependence of the results. The energies of the d band -> Fermi level threshold, the interconduction band threshold, and the L2' -> L1 critical point transition were determined for the alloys. Previous optical studies using more conventional methods either have not been able to resolve these features or have not located them with accuracy comparable with piezoreflectance. With increasing alloy concentration the d band threshold is found to shift slowly to higher energies, the inter-conduction band transitions more rapidly to lower energies. Zn impurities produced much smaller shifts than the others, indicating the importance of interactions between impurity d states and the d and conduction states of the host. Significant differences were found between the isovalent solutes Ga and A1. In concentrated alloys with Zn, Ga and Al the interconduction band threshold tended to a common value of about 2.5 eV. This lack of simple dependence on e/a, the electron per atom density in the alloy, is relevant to the understanding of the electronic structure of the Hume-Rothery alloys and the regularity of the [alpha] phase boundary.</p>

New Insight on Liquid Steel Microalloying by Pulse-Step Method in Two-Strand Slab Tundish by Numerical Simulations

Developing a technology for introducing alloy addition to liquid steel during the course of continuous casting process seems to be an interesting approach to enhancing the steelmaking process, especially as the effective introduction of micro-additives or non-metallic inclusion modifiers to the liquid steel is the key to the production of the highest-quality steel. This paper presents the results of investigation describing the process of liquid steel chemical homogenisation in the two-strand slab tundish. The alloy was fed to liquid steel by pulse-step method. Five tundish equipment variants with different flow control devices and alloy addition feeding positions were considered. The paper includes fields of liquid steel flow, alloy concentration vs. time curves, dimensionless mixing time, minimum time values and alloy concentration deviations at tundish outlets. The results pointed much more effectively with liquid steel mixing nickel than aluminium. For aluminium obtaining a 95% chemical homogenisation level requires three-fold more time. Moreover, it is definitely beneficial for chemical homogenisation to initiate the alloying process simultaneously in two sites. This procedure generates, among others, the least alloy deviation of concentration at tundish outlets.

The Sensitivity of Cu for Electrochemical Carbon Dioxide Reduction to Hydrocarbons as Revealed by High Throughput Experiments

Electrochemical CO2 reduction to valuable products is a centerpiece of future energy technologies that relies on identificaiton of new catalysts. We present accelerated screening of Cu bimetallic alloys, revealing remarkable sensitivity to alloy concentration that indicates the segregation of alloying elements to critical sites for hydrocarbon formation.

The Sensitivity of Cu for Electrochemical Carbon Dioxide Reduction to Hydrocarbons as Revealed by High Throughput Experiments

Electrochemical CO2 reduction to valuable products is a centerpiece of future energy technologies that relies on identificaiton of new catalysts. We present accelerated screening of Cu bimetallic alloys, revealing remarkable sensitivity to alloy concentration that indicates the segregation of alloying elements to critical sites for hydrocarbon formation.

Electronic and optical properties of ternary alloys ZnxCd1−xS, ZnxCd1−xSe, ZnSxSe1−x, MgxZn1−xSe

The empirical pseudopotential method (EPM) within the virtual crystal approximation (VCA) is used to calculate the electronic and optical properties of ternary alloys ZnxCd1−xS, ZnxCd1−xSe, ZnSxSe1−x and MgxZn1−xSe. The alloy band structures and energy gaps are calculated using VCA which incorporates the compositional disorder as an effective potential. The calculated band structures for the ZnxCd1−xS, ZnxCd1−xSe and ZnSxSe1−x alloys show a direct band gap in the whole range of the concentration except for the MgxZn1−xSe alloy which presents a crossover from the direct gap to the indirect one.Also the dependence of the refractive index on the concentration is calculated for each ternary alloy. This parameter is found to depend nonlinearly on the alloy concentration. A detailed comparison of our results with experimental data and works of other authors has led to a good agreement.

A theoretical investigation of orientation relationships and transformation strains in steels

The identification of orientation relationships (ORs) plays a crucial role in the understanding of solid phase transformations. In steels, the most common models of ORs are the ones by Nishiyama–Wassermann (NW) and Kurdjumov–Sachs (KS). The defining feature of these and other OR models is the matching of directions and planes in the parent face-centred cubic γ phase to ones in the product body-centred cubic/tetragonal α/α′ phase. In this article a novel method that identifies transformation strains with ORs is introduced and used to develop a new strain-based approach to phase-transformation models in steels. Using this approach, it is shown that the transformation strains that leave a close-packed plane in the γ phase and a close-packed direction within that plane unrotated are precisely those giving rise to the NW and KS ORs when a cubic product phase is considered. Further, it is outlined how, by choosing different pairs of unrotated planes and directions, other common ORs such as the ones by Pitsch and Greninger–Troiano can be derived. One of the advantages of our approach is that it leads to a natural generalization of the NW, KS and other ORs for different ratios of tetragonalityrof the product body-centred tetragonal α′ phase. These generalized ORs predict a sharpening of the transformation textures with increasing tetragonality and are thus in qualitative agreement with experiments on steels with varying alloy concentration.

Modulation of the band structures and optical properties of holey C2N nanosheets by alloying with group IV and V elements

The band gap and optical absorption can be tuned effectively by the alloy concentration x in the C2N1−xPx and C2N1−xAsx alloys.