Alloying and Properties of C14-NbCr? and A15-Nb?X (X = Al, Ge, Si, Sn) in Nb-Silicide-Based Alloys.

Title Alloying and Properties of C14-NbCr? and A15-Nb?X (X = Al, Ge, Si, Sn) in Nb-Silicide-Based Alloys.
Authors P. Tsakiropoulos
Journal Materials (Basel)
DOI 10.3390/ma11030395
Abstract

The oxidation of Nb-silicide-based alloys is improved with Al, Cr, Ge or Sn addition(s). Depending on addition(s) and its(their) concentration(s), alloyed C14-AB? Laves and A15-A?X phases can be stable in the microstructures of the alloys. In both phases, A is the transition metal(s), and B and X respectively can be Cr, Al, Ge, Si or Sn, and Al, Ge, Si or Sn. The alloying, creep and hardness of these phases were studied using the composition weighted differences in electronegativity (??), average valence electron concentrations (VEC) and atomic sizes. For the Laves phase (i) the VEC and ?? were in the ranges 4.976 < VEC < 5.358 and -0.503 < ?? < -0.107; (ii) the concentration of B (=Al + Cr + Ge + Si + Sn) varied from 50.9 to 64.5 at %; and (iii) the Cr concentration was in the range of 35.8 < Cr < 51.6 at %. Maps of ?? versus Cr, ?? versus VEC, and VEC versus atomic size separated the alloying behaviours of the elements. Compared with unalloyed NbCr?, the VEC decreased and ?? increased in Nb(Cr,Si)?, and the changes in both parameters increased when Nb was substituted by Ti, and Cr by Si and Al, or Si and Ge, or Si and Sn. For the A15 phase (i) the VEC and ?? were in the ranges 4.38 < VEC < 4.89 and 0.857 < ?? < 1.04, with no VEC values between 4.63 and 4.72 and (ii) the concentration of X (=Al + Ge + Si + Sn) varied from 16.3 to 22.7 at %. The VEC versus ?? map separated the alloying behaviours of elements. The hardness of A15-Nb?X was correlated with the parameters ?? and VEC. The hardness increased with increases in ?? and VEC. Compared with Nb?Sn, the ?? and hardness of Nb?(Si,Sn) increased. The substitution of Nb by Cr had the same effect on ?? and hardness as Hf or Ti. The ?? and hardness increased with Ti concentration. The addition of Al in Nb?(Si,Sn,Al) decreased the ?? and increased the hardness. When Ti and Hf, or Ti, Hf and Cr, were simultaneously present with Al, the ?? was decreased and the hardness was unchanged. The better creep of Nb(Cr,Si)? compared with the unalloyed Laves phase was related to the decrease in the VEC and ?? parameters.

Citation P. Tsakiropoulos.Alloying and Properties of C14-NbCr? and A15-Nb?X (X = Al, Ge, Si, Sn) in Nb-Silicide-Based Alloys.. Materials (Basel). 2018;11(3). doi:10.3390/ma11030395

Related Elements

Niobium

41 Nb 92.906380000 Niobium

See more Niobium products. Niobium (atomic symbol: Nb, atomic number: 41) is a Block D, Group 5, Period 5 element with an atomic weight of 92.90638. Niobium Bohr ModelThe number of electrons in each of niobium's shells is 2, 8, 18, 12, 1 and its electron configuration is [Kr] 4d4 5s1. The niobium atom has a radius of 146 pm and a Van der Waals radius of 207 pm. Niobium was discovered by Charles Hatchett in 1801 and first isolated by Christian Wilhelm Blomstrand in 1864. In its elemental form, niobium has a gray metallic appearance. Niobium has the largest magnetic penetration depth of any element and is one of three elemental type-II superconductors (Elemental Niobiumalong with vanadium and technetium). Niobium is found in the minerals pyrochlore, its main commercial source, and columbite. The word Niobium originates from Niobe, daughter of mythical Greek king Tantalus.

Silicon

14 Si 28.085500000 Silicon

See more Silicon products. Silicon (atomic symbol: Si, atomic number: 14) is a Block P, Group 14, Period 3 element with an atomic weight of 28.085. Silicon Bohr MoleculeThe number of electrons in each of Silicon's shells is 2, 8, 4 and its electron configuration is [Ne] 3s2 3p2. The silicon atom has a radius of 111 pm and a Van der Waals radius of 210 pm. Silicon was discovered and first isolated by Jöns Jacob Berzelius in 1823. Silicon makes up 25.7% of the earth's crust, by weight, and is the second most abundant element, exceeded only by oxygen. The metalloid is rarely found in pure crystal form and is usually produced from the iron-silicon alloy ferrosilicon. Elemental SiliconSilica (or silicon dioxide), as sand, is a principal ingredient of glass, one of the most inexpensive of materials with excellent mechanical, optical, thermal, and electrical properties. Ultra high purity silicon can be doped with boron, gallium, phosphorus, or arsenic to produce silicon for use in transistors, solar cells, rectifiers, and other solid-state devices which are used extensively in the electronics industry.The name Silicon originates from the Latin word silex which means flint or hard stone.

Related Forms & Applications

Silicides
Publish your research on the American Elements website