Microstructural Features in Multicore Cu–Nb Composites

The study is devoted to heavily drawn multicore Cu–18Nb composites of cylindrical and rectangular shapes. The composites were fabricated by the melt-and-deform method, namely, 600 in situ rods of Cu–18%Nb alloy were assembled in a copper shell and cold-drawn to a diameter of 15.4 mm (e = 10.2) and then rolled into a rectangular shape the size of 3 × 5.8 mm (e = 12.5). The specimens were analyzed from the viewpoints of their microstructure, microhardness, and thermal stability. The methods of SEM, TEM, X-ray analysis, and microhardness measurements were applied. It is demonstrated that, at higher strain, the fiber texture <110>Nb <111>Cu DD (drawing direction), characteristic of this material, becomes sharper. The distortions of niobium lattice can be observed, namely, the {110} Nb interplanar distance is broadened in longitudinal direction of specimens and compacted in transverse sections. The copper matrix lattice is distorted as well, though its distortions are much less pronounced due to its recrystallization. Evolution of microstructure under annealing consists mainly in the coagulation of ribbon-like Nb filaments and in the vanishing of lattice distortions. The structural changes in Nb filaments start at 300–400 °С, then develop actively at 600 °С and cause considerable decrease of strength at 700–800 °С.

From Photon to Oganesson: Lie Algebra Realization of the Standard Model Extending over the Periodic Table

As reported in a series of previous PIRT conferences, a direct SU(3) structural realization of the Standard Model has been developed based upon Marius Sophus Lie’s original Norwegian Ph.D. thesis Over en Classe Geometriske Transformationer from 1871 (and thus due for a most deserved 150-year anniversary). It elucidates how “the theory of main tangential curves can be brought back to that of rounded curves”, anticipating a coherent linear representation of the elementary particles instead of the rotational chosen since they were considered point-like and amorphous when they many years later entered the stage. Under these premises the Standard Model has built a magnificent, undoubtedly true but congested multi-particle system whereas the Lie continuous transformation element, the partial derivative ’straight line of length equal to zero’ outlines an isotropic vector matrix lattice of crystallographic Killing root space diagram A3 form which from the Nucleon and inwards can backtrack the Standard Model geometrically, as well as continue outward iterating to a space-filling solid state R3×SO(3) wave-packet complex tessellating the whole periodic table with electron shells and subshells, isotope spectrum, neutron captures, radiative channels, oxidation states, molecular binding sites etc. in successive layers also including the Lanthanides in the sixth period and the Actinides in the seventh, in which now the concluding Oganesson has been reached in perfectly well-built saturated noble gas shape and condition.

Hardening mechanisms for rails metal during long-term operation

A quantitative comparative analysis of the mechanisms of hardening of the surface layers of differentially hardened 100-m rails is carried out. It was based on structure formation, phase composition, defect substructure regularities revealed by the methods of modern physical materials science. The studies were carried out at different depths of up to 10 mm in the rail head along the central axis and along the axis of symmetry of the fillet in the initial state and after various periods of extremely long-term operation (passed tonnage of 691.8 and 1411 mln. tons brutto). The contributions due to the friction of the matrix lattice, interphase boundaries, dislocation substructure, presence of carbide particles, internal stress fields, solid-solution hardening of the pearlite component of the steel structure are estimated.

Binary niobium alloying with low-melting metals by precipitation of nanoparticles

Binary niobium alloys with tin, lead and cadmium were obtained by precipitation of nanosized metal particles dispersed in lowpressure plasma using the thermal fluctuation melting effect. The thermal fluctuation melting effect implies that a small particle is in the quasi-liquid state up to a certain critical size which, if exceeded due to steam condensation or fusion (coalescence) of other quasiliquid particles, results in the drop crystallization. The critical sizes of particles being in the quasi-liquid state and capable of coalescing and forming an alloy – solid solution – were found: Nb – 2.1÷2.2 nm, Sn – 0.4 nm, Pb – 0.6 nm, Cd – 3.2 nm. The following concentrations were determined as the boundary of a range where solid metal solutions exist in niobium, at%: Sn – 25.5, Pb – 23.0, Cd – 64.5. The solid solution is a crystal lattice of the niobium as a matrix metal comprising lead, cadmium and tin atoms. The Nb matrix lattice parameters change with additional stresses arising in it up to its destruction due to the fact that the atom sizes of embedded metals differ from those of matrix niobium. The body-centered cubic lattice parameters of solid solutions increase with the rising Pb, Cd и Sn concentrations since they have larger atomic sizes as compared to niobium. A change in the crystal lattice growth rate was observed for lead and cadmium alloys due to a change in the impurity atom arrangement in the niobium matrix lattice. The critical sizes of metal particles obtained were used to estimate surface tension parameters at the crystal/melt interface as follows: 1.17–1.22 J/m2 for Nb, 1.15·10–2 – for Sn; 1.48·10–2 – for Pb; 0.142 – for Cd. Refractory niobium alloying with tin, lead and cadmium is an example of using the size effect to produce new materials.

Precipitation of ScAl3 Phase during Solutionizing and Ageing of Hypoeutectic Al-Sc Alloys and its Impact to Mechanical Properties

In this paper, precipitation of ScAl3 phase during solutionizing and ageing and its impact to mechanical properties of hypoeutectic Al-Sc alloy and effect of Sc addition amount were investigated by TEM and SEM microstructure observation and mechanical property testing. During solutionizing at 640oC for 24h, for Al-0.2wt.%Sc and Al-0.4wt.%Sc alloy, ScAl3 particles formed in the course of solidification become smaller, indicating, as a whole, Sc is partially dissolved into Al solution. Simultaneously, precipitation of two types of ScAl3 particles are observed by TEM. One has a size of 200~300nm, and the other is much small, 5~20nm in size. Though re-dissolution of Sc solute into Al solution and precipitation of large and fine ScAl3 particles occur in the solutionizing course, but the strength and hardness are decreased. The key reason for it is thought to be the softening effect of high level of vacancies in matrix lattice from the high solutionizing temperature. After further aging at 300oC for 3h, a great number of fine ScAl3 particles are precipitated in the Al matrix, which leads to a considerable precipitation hardening effect, thus the strength and hardness are increased obviously. Increasing the Sc content in the alloy results in a considerable rise in as-cast and as-aged strength and hardness, due to the solution strengthening and precipitation hardening respectively.

Precipitation Hardening Analysis of an Al-8%Ag Alloy

Aluminum alloys are important in aerospace industry, due to their mechanical properties, low specific weight and good corrosion resistance. Such properties are achieved due to a heat treatment of solubilization, quenching and aging, in order to precipitate metastables phases, which act as dislocation obstacles, increasing the strength of the alloy. In the present study, the precipitation sequence of Al-8%Ag alloy was analyzed via Vickers hardness and Transmission Electron Microscopy. The size and morphology of the precipitated particles, involved in the stages of precipitation process was characterized. It was determined the microstructure at the peak hardness, which is mainly composed of spherical GP zones with about 6 nm average diameter, which are responsible for the alloy achieve a value of 72 HVN. It was observed that this hardness value does not compete with others well known alloys, like AA 6061 and AA 2024, which can be precipitation hardened. The main reason for the low values of HVN, is because of there is no enough difference between the matrix and the precipitated particles lattice parameters, and dont cause a significant elastic strain by coherence in the matrix lattice, that could produce a substantial hardening. To ascertain this assumption, the aged material was severely plastic deformed, achieving 94 HVN, and the grain refinement and high dislocations density were the major hardening mechanisms, since the precipitates behavior was similar as the matrix, because particles were distorted instead of acting as impediment to material flow.