Cold pressing (CP) of the amorphous-like Co powder suppressed most of the XRD peaks, in particular the peak along (100) plane. The DSC curve of unmilled CP Co powder has shown a distinct sharp exothermic peak at615C°. Upon annealing at700C°, only the FCC phase with lattice parameter of 3.51 Å was detected by XRD. Our results implied that the exotherm at615C°corresponds to compaction-pressure-assisted HCP to FCC first-order phase transition. The XRD analysis of 30 h milled powder revealed for the first time the FCC phase witha=3.80 Å. However, due to presence of (100) and (210) peaks, this phase is thought to be FCT with lattice parametersa=b=3.80andc=3.07 Å. Consequently, the high-energy milling carried out in the current work induced for the first time HCP to FCT transition in Co. Upon CP of milled powder, the lattice parameterashrunk from 3.80 to 3.75 Å. However, during annealing of the CP milled Co powder at750C°, the FCT to FCC transition occurred, yielding the FCC phase witha=3.51 Å.
Density functional theory (DFT) based on the first-principles technique, CASTEP, was used to explore the possibility of inducing martensitic transformation (MT) in a stable B2 TiRu alloy by systematic introduction of palladium (Pd) on the ruthenium (Ru) site. The structural, mechanical and electronic properties of pure, as well as, Pd-doped TiRu were calculated. The elastic constants obtained show that the addition of Pd seems to induce MT in the ordered TiRu, as shown by mechanical instability (C΄= C11-C12 < 0) of the B2 phase against shear deformation at 0 K. This is an indication that B2 is likely to transform to low symmetry phases such as L10/B19/B19’. Moreover, the calculated total density of states (T-DOS) also indicated that the addition of Pd shifted the Fermi level (EF) from the centre of the pseudogap of the ordered pure TiRu towards the right (anti-bonding region), rendering the resulting B2 ternary phase unstable at certain Pd compositions higher than 10 atomic percent (at.%). The predicted induced martensitic transformation is one of the key characteristics of shape memory behaviour in B2 Ti-based alloys such as NiTi, TiPd and TiPt. Further work on the possible low temperature phases resulting from B2 Ti-Ru-Pd ternary alloys is underway.
Magnetic functional materials remain an area of research interest for applications in electronic devices. Among these materials, Mn50Pt50 alloy has received a great deal of attention in practical potential applications such as spintronics due to its high-thermal and magnetic stability. It was reported previously that L10 Mn50Pt50 alloy shows ferromagnetic ordering at room temperature. In this study, the effect of the partial substitution of Pt with Co was investigated using density functional theory (DFT) approach. The thermodynamic, magnetic and mechanical properties were determined to check the stability of Mn50Pt50-xCox alloys. The results showed that the L10 phase has the lowest heat of formation when the c/a ratio is 1.10 for 6.25 at.% Co. Overall magnetic moments improve with an increase in Co compositions when the c/a ratio is 1.10. The obtained results reveal that Mn50Pt50-xCox alloys exhibit attractive magnetic and mechanical properties for future magnets in spintronics applications. Graphical Abstract
South Africa is known to be one of the mineral endowed countries in the world, bearing large quantities of iron, chrome, manganese and vanadium reserves that are key to iron and steel industries. It is thus vital to leverage on this natural resource endowment to build a dynamic industrial economy capable of creating sustainable jobs. Central to achieving this goal is the need to derive greater economic value from these natural resources, which will reduce import levels and create export opportunities. Currently, however, the local iron and steel industry is forced to navigate some of the known challenges such as the cost of energy, transportation, labour and steel, in order to remain competitive and operational. These matters which hamper the realization of beneficiation aspirations do not only have a huge impact on the downstream value-adding steel industry but also make the cost of doing business in SA unattractive. Consequently, based on its capability, relevancy and experience in supporting the iron and steel sector for many years, Mintek has been entrusted with the responsibility to host the Ferrous Materials Development Network (FMDN) by government through advanced materials initiative (AMI) programme to coordinate research on ferrous materials in the country. The purpose of this paper is to illustrate the need for interdependent research activities in ferrous materials in South Africa, which is underpinned by collaborative research, development and innovation (RDI) efforts between science councils, academia and industry. These activities are aimed at generating local know how, fostering local and international collaboration, development of human capital (HCD), supporting job creation through beneficiation, identification of relevant advanced technologies to improve competitiveness, localization of designated castings, design and development of new ferrous materials with enhanced properties to enable access to niche export markets as well as improving local capability to produce high-end ferrous products for critical sectors of the economy such as petrochemical, energy generation, transportation, mining, etc.
Most CsCl-type intermetallics composed of group IV and VIII–XI transition metals have shape memory effect (SME), a phenomenon that occurs on a certain class of materials with an ability to undergo martensitic transformation (MT) during cooling. This advanced functional materials’ property is enabled by MT from high-temperature B2 phase of high symmetry to lower symmetry phases such as L10, B19 or B19’ upon cooling. Peculiarly, Ti50Ru50 with similar ordered B2 at high temperature remains ordered and stable with no phase transition down to room temperature. In this study, first-principles calculations based on density functional theory (DFT) are used to investigate the structural, thermodynamic and electronic properties of the stable Ti50Ru50 compound by systematically substituting part of the Ru atoms with ductile group 10 metal (Ni, Pd and Pt). This is an attempt to destabilizing B2 phase at 0 K through Ti50Ru50-xYx ternary alloying to promote MT that could yield SME. Graphical Abstract
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