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Influence of alloying systems on the lattice parameters of nickel-based superalloys

Glotka O., Ol'shanetskii V., Byelikov S., Fasol Y.

Archives of Materials Science and Engineering

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2023

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Vol. 122, nr 1

5--12

EN

Purpose: The work aims to establish the relationship between the chemical composition, mechanical properties and dimensional mismatch of crystal lattices of heat-resistant nickel alloys. Design/methodology/approach: The results of experimental and calculated data formed based on experimental and taken from open sources results are presented. The XRD method used Bragg-Brentano determined the phase composition, focusing on a RIGAKU MINIFLEX 600 diffractometer (CoKα-radiation). After heat treatment, strength characteristics were determined on cylindrical samples with a working part (diameter 5 mm, length 25 mm). Testing of the alloy for short-term strength was carried out on samples at a temperature of 20°C on UME-10TM and GCM-20 tensile machines. Alloy tests for long-term strength were carried out on similar samples at a temperature of 1000°C on AIMA-5-2 and ZTZ 3/3 machines by uniaxial stretching under a constant load based on 100 hours. Findings: It has been established that with an increase in the value of the mismatch of crystal lattices, the strength of the alloys decreases due to significant internal stresses. It was revealed that for alloys of equiaxed and directional crystallisation, an extremum is observed at a value of 1.5 ... 1.6 K; this is associated with a decrease in the number of elements in the ϒ-solid solution. Research limitations/implications: An essential problem is predicting the structure and properties of heat-resistant alloys without or with a minimum number of experiments. The results of comparative tests of the XDR method and calculated data are analysed. Practical implications: The obtained dependences can be used both for designing new heat-resistant alloys and for improving the compositions of industrial alloys. Originality/value: The value of this work lies in the fact that the dependences of the influence of alloying elements on the mechanical properties and the dimensional mismatch of crystal lattices were obtained, which made it possible to determine the properties without conducting experiments. It has been established that changes in the course of the relationship closely correlate with the processes taking place in the structure of alloys.

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Modification of energy bandgap in lattice mismatched InGaAs/GaAs heterostructures

Gelczuk Ł., Dąbrowska-Szata

Optica Applicata

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2009

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Vol. 39, nr 4

845-852

EN

This paper addresses some physical aspects and presents experimental results concerning to phenomena which evoke modification of band structure in lattice mismatched InGaAs/GaAs heterostructures, namely the introduction of extra deep-lying energy levels in the bandgap. The deep level transient spectroscopy reveals commonly observed deep level defects in GaAs-based structures associated with native point defects as well as misfit dislocations related to strain relaxation processes.

3

Heteroepitaxial technology for high-efficiency UV light-emitting diode

Kamiyama S., Iwaya M., Amano H., Akasaki I.

Opto-Electronics Review

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2002

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Vol. 10, No. 4

225-230

EN

A high-quality AlGaN layer with a low density of threading dislocations is realised for the use of ultraviolet (UV) light-emitting diodes (LEDs). The new crystal growth method of using a GaN seed crystal with (1122) facets and lateral growth of Al₀.₂₂Ga₀.₇₈N through the low -temperature-deposited AlN interlayer enalbles the overgrown Al₀.₂₂Ga₀.₇₈N to have a low dislocation density of 2 x 10⁷ cm⁻² and be crack-free over the whole wafer. Applying the AlGaN as a base layer in UV-LEDs, high - performance devices with high output powers of more than 0.1 mW under 50 mA drive are demonstrated in a wide range of emission wavelengths from 323 to 363 nm. The highest output power of 1.2 mW at 50 mA driving current is obtained with 363 - nm emission wavelength.