Influence of the electronic polymorphism of Ni on the classification and design of high entropy alloys

According to a recent Hume-Rothery approach, the electron concentration, e/a, and the average radius can be used to identify the domain of stability of HEAs and to estimate the phases that may occur in the alloy. The present study investigates the influence of the electronic polymorphism of nickel on the efficiency of the classification and on the design of HEAs for magnetic applications. Many different compositions were used, based on 4 to 7 elements out of a total 13 different elements (Co, Cr, Fe, Ni, Al, Cu, Pd, Ti, Mn, V, Nb, Sn, Ru). Phases have been determined by X-ray and neutron diffraction as well as in some cases high energy X-ray diffraction. The e/a for the constituent elements is calculated according to Massalski. The two polymorphic electronic structure of nickel, namely (e/a)Ni = 1 or (e/a)Ni = 2 are considered. The average e/a for the alloy is calculated assuming a solid solution case. The electronic structure [Ar] 3d9 4s1 seems to be more appropriate for the classification of HEAs. Based on a Self-organising Map predictions are made for the average magnetic moment at saturation for this electronic structure of Ni. Non-saturated values and data from the literature are compared with the predictions. The consequences of such results when modelling the structure and properties of Ni containing HEAs are presented, in particular the consideration of the shape and transformation of the Brillouin zone

Alien Registration- Dahlborg, Simon H. (Rockland, Knox County)

https://digitalmaine.com/alien_docs/14800/thumbnail.jp

Exploring connectivity : invention, innovation and knowledge transfer in the university-industry interface

Universities are expected to create knowledge and be involved in knowledge transfer with society. This is accomplished through the universities’ three missions; 1) teaching, 2) research and 3) innovation and social engagement. The focus of this thesis is knowledge transfer for the purpose of innovation in the university-industry interface. Policy makers have strong faith in innovation and emphasise the importance of innovation and knowledge transfer in the intersection between universities and industry for future economic growth and employment. University scholars have, in the multi-disciplinary field of innovation studies, spent considerable effort to shed light on knowledge transfer processes and to investigate the myriad of mechanisms through which knowledge is exchanged. For instance, efforts have been made to measure knowledge transfer itself or the outcomes of knowledge transfer. A better understanding of knowledge transfer processes, outcomes and impact could provide a foundation for more efficient and tailored innovation support infrastructures, regulations and management of university-industry interaction. However, many prior studies are built on quantitative and unidimensional methods, often based on statistics that either over- or under estimates innovation and knowledge transfer. This thesis argues that there is a need to widen the perspective to get a better understanding of the knowledge transfer activities taking place in the university-industry interface. Also, there is a need of a more comprehensive innovation statistics and metrics in the university innovation interface. This thesis draws on, and aims at contributing to the research areas of university-industry relations, knowledge transfer and social network theory. Thus, this thesis addresses the question of how the mapping of ‘hidden’ connections could provide insights into the management of knowledge transfer in the university-industry interface. The four included papers address this overarching question in different ways with different methodological approaches. Based on the problem of lacking statistics on university patenting, Paper I investigates how inventive productivity can be measured in the academic setting. Paper I also introduces the Karolinska Institutet Intellectual Property (KIIP) project which included a description of the construction of the KIIP database. The KIIP database contains comprehensive statistics on patented inventions derived from Karolinska Institutet between 1995 and 2010. Paper II, is a longitudinal study of knowledge transfer paths from the university to third parties. It suggests the ABC-framework of patent ownership transfer modes. Using social network analysis, Paper III investigates the board network structure, composition and evolution of 65 university spin offs. Findings show that investors hold central network positions in the network over time and are therefore in a position to both facilitate and hinder knowledge transfer. Results also show that the board network has a stabile ‘small word’ feature over time indicating dense clustering and short transfer distances across the network. Paper IV takes an individual level perspective and addresses the question of how individuals search for knowledge to solve problems in product development processes. Based on grounded theory methodology, an emergent theoretical framework of individual level knowledge search processes is suggested that emphasises the importance of social networks. In conclusion, the findings of this thesis suggest the there is a need to apply a more holistic and multi-level methodological and theoretical perspectives to gain better understanding of knowledge transfer in the university-industry interface. This includes building comprehensive innovation statistics, applying analysis methods, such as social network analysis on micro-, meso- and macro level, developing qualitative impact oriented innovation measures, and using pedagogical strength of social network visualisations. By bringing such ‘hidden’ connections to the surface a more tailored management of knowledge transfer and innovation support systems could be developed

Temperature and time dependent structure of the molten Ni81P19 alloy by neutron diffraction

The temperature and time dependent structure of molten NiP alloy of eutectic composition has been studied by neutron diffraction. Ni particles were found to exist in the melt at temperatures at least up to about 150 degrees above liquidus. The amount varies reversibly as temperature increases but decays slowly with time. Remarkably, particles still exist even after that the melt has been kept more than 30 h at different temperatures in the molten state. The static structure factor and the pair distribution function obtained at 1050 °C are presented

Multi-phase nature of sintered vs. arc-melted CrxAlFeCoNi high entropy alloys - experimental and theoretical study

High entropy CrxAlFeCoNi alloys with x = 0, 0.5, 1.0 and 1.5 were synthesized using arc-melting and sintering preparation techniques. Three crystal structures (fcc, bcc and σ) were observed using XRD technique, while EDX measurements showed the presence of up to three chemically different phases (FeCr-rich phase with fcc structure, AlNi-rich phase with bcc structure and Cr-rich phase with bcc and/or σ structures). The reasons for the observed phase coexistence were addressed to total energy electronic structure calculations using KKR-CPA method accounting for chemical disorder effects. Such theoretical analysis confirmed that the multi-phase system was energetically more favorable than the single-phase one. Furthermore, DSC measurements allowed to identify two phase transitions in melted samples, unlike sintered ones due to high-temperature nitrogen corrosion. This process turned out to be highly selective, resulting in the formation of the scales consisting of AlnNm–phases at the cost of total Al loss in the HEA alloy

Effect of Heat Treatment of a Melt on the Structure and Properties of the Corresponding Crystalline Ingots or Castings

Abstract: The modern concepts of the structure of liquid metals and alloys are considered. Several types of microinhomogeneity and microheterogeneity are shown to exist in liquid metal solutions. Their structural state changes as a result of variations in composition, history, temperature, and pressure or the influence of various external actions. Upon subsequent cooling at an appropriate rate, these changes can persist up to liquidus and affect the structure and properties of the solidified alloy. The main attention is paid to the influence of the heating temperature of a liquid metal. For aluminum-based alloys, the possibility of developing the optimum heat-treatment conditions for melting using the results of studying the structure and properties of melts has been shown. This optimized heat treatment of melts is shown to be an effective method to improve the quality of alloys. © 2020, Pleiades Publishing, Ltd

Hume-Rothery for HEA classification and self-organizing map for phases and properties prediction

The Hume-Rothery approach applied in terms of e/a to classify and design quasicrystals and BMG is revisited for the case of HEAs. The results were compared with other parameters used in the literature, namely VEC and delta. The Self-Organizing Map tool is used to classify the experimental results and the experimental map is used to compare the predictions of phases and properties of compositions reported in the literature. According to the Hume-Rothery approach, e/a and the average radius can give a precise rule of thumb to identify the domain of stability of HEAs and to estimate the phases that may occur in the alloy: i) e/a 2.05: bcc. Moreover, e/a is to be preferred to VEC to classify phases in HEAs. Self-organizing maps can be used to make interpolative predictions for new compositions of HEAs with suitable phases for specific properties. Thus, simple combination of e/a and r gives an accurate first estimation to identify compositions with simple phases giving simple diffraction patterns, thus true HEAs as opposed to other compositional domains where complex phases occur

Comment on "Atomic jumps in quasiperiodic Al72.6_{72.6}Ni10.5_{10.5}Co16.9_{16.9} and related crystalline material"

We disagree with a number of statements by Dolinsek et al. about the specificity of phason dynamics in quasicrystals (QCs).Comment: 2 pages, 0 figures, submitted to Physical Review

Structure of some CoCrFeNi and CoCrFeNiPd multicomponent HEA alloys by diffraction techniques

The structure of CoCrFeyNi (y = 0, 0.8 and 1.2) and CoCrFeNi-Pdx (x = 0.0, 0.5, 0.8, 1.0, 1.2 and 1.5) High Entropy Alloys has been investigated by neutron and standard X-ray as well as by high-energy X-ray diffraction techniques. The alloys were produced by arc melting and afterwards heat treated under several different conditions. It has been concluded that the CoCrFeNi alloy in as-cast condition is, contrary to what is claimed in the literature, not single-phase but consists of at least two different phases, both of fcc type. The difference in lattice constant between the two phases is close to 0.001 Å. Diffraction patterns measured by X-ray and neutron diffraction have shown that the structure of the alloy is not affected by 3 h heat treatment up to 1100 °C. Changing the amount of Fe has no drastic effect on alloy structure. The Pd-containing alloys have also all been found not to be single-phase but to consist of at least four different phases, all being of fcc type. The lattice constants for all phases increase with Pd content. The relative amounts of the different phases depend on Pd concentration. Furthermore, heat treatments of 3 h duration at different temperatures have a significant effect on the alloy phase composition. It is suggested that HEAs should be considered as multicomponent alloys presenting “simple” diffraction patterns, e.g. consisting of one or several lattices of fcc, hcp or bcc type with very close lattice parameters

Effect of Y2O3 addition on the microstructure and mechanical properties of an Al1.8CoCrCu0.5FeNi BCC HEA

The present study investigated the influence of Y2O3 addition by mechanical alloying (MA) on the microstructure evolution of a BCC High Entropy Alloy (HEA). The characterisation and mechanical properties of the alloy were explored using X-ray diffraction, SEM, EBSD, and nano-indentation. The sintered Al1.8CoCrCu0.5FeNi HEA shows a microstructure formed by an ordered BCC phase (Al-rich) and a second disordered BCC (Cr-rich), while a minor FCC (Cu-rich) appears. These BCC phases show a wide morphology evolution from cuboidal and wave-like structures to irregular shapes. The minor FCC phase also adopts several morphologies as the MA is performed. The introduction of oxide reinforcements and microstructure refinement through mechanical alloying yields a change in phase quantification and grain structure. In accordance with the hardness and elastic modulus values from ordered/disordered BCC phases, the disordered BCC shows higher values than the ordered one. The grain size reduction as well as the solid solution strengthening from the microstructure evolution consequence of the MA are shown to be the main contributors to the increase in hardness and elastic modulus in the consolidated samples.This research was supported by the Regional Government of Madrid under the programme S2018/NMT-4381-MAT4.0-CM project. Funding from PID2019-109334RB-C32 awarded by the Spanish Ministry of Science, Innovation and Universities is also acknowledged. J. Cornide also acknowledges funding from the Spanish Ministry of Science and Innovation (IJCI-2017-31348) and TED2021-130831B-I00 funded by MCIN/AEI/10.13039/501100011033 and NextGenerationEU/PRTR. Funding for APC: Universidad Carlos III de Madrid (Read & Publish Agreement CRUE-CSIC 2023)