International Journal of Materials Research

Published by De Gruyter

Volume 92 Issue 11

November 2001

Issue of International Journal of Materials Research

Contents
Journal Overview

Publicly Available January 13, 2022

Frontmatter

Page range: 1193-1193

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Aufsätze/Articles

January 13, 2022

On the Formation of a Silver-Rich Ordered Phase in Ag–Pt Solid Solutions

Rolf Erni, Thomas Etter, Helge Heinrich, Gernot Kostorz

Page range: 1194-1196

Abstract

The most widely accepted phase diagram of Ag–Pt shows a limited solubility of Pt in Ag below 1220 K and the formation of an ordered (L1 2 structure) phase. Transmission electron microscopy of an Ag-15 at.% Pt alloy shows no indication of the formation of the Ag 3 Pt phase proposed in literature. Neither distribution maps for Ag acquired by energy-filtered transmission electron microscopy nor diffraction patterns indicate the existence of an ordered, stoichiometric phase. The absence of any L1 2 superstructure reflections and the absence of any modulation of the diffuse electron diffraction between the Bragg reflections leads to the conclusion that the ordered Ag 3 Pt phase does not exist.

January 13, 2022

Solid State Reactions in Transition Metal Diboride-Based Materials

Clemens Schmalzried, Rainer Telle, Bert Freitag, Werner Mader

Page range: 1197-1202

Abstract

The variety of microstructural features of the layered structures of transition metal borides in precipitation-annealed ceramics in the quasi-ternary system TiB 2 –WB 2 –CrB 2 have been investigated by high-resolution transmission electron microscopy (HRTEM) and electron-filtering transmission electron microscopy (EFTEM). The combination of the methods allows to resolve structure and composition of various precipitates. The reaction of the starting borides to the (Ti, W, Cr)B 2 solid-solution phase could be analysed to be a diffusive solid state reaction across the grain or interphase boundaries. The annealing leads to a partly reacted specimen which shows a microstructure consisting of unreacted TiB 2 cores with a shell of the (Ti, W, Cr)B 2 solid solution phase, where high stress due to the misfit between the lattices is relaxed by formation of dislocations in the interface. Plate-shaped precipitates of a β-WB-type phase with thickness of only one lattice constant could be characterised chemically by electron spectroscopic imaging (ESI) and their structure was identified by HRTEM. Spinodal decomposition of the matrix phase during annealing in the two-phase field was proven by ESI and electron diffraction. Frequently occurring stacking faults in the solid solution phase and in the WB 2 phase with W 2 B 5 structure could be structurally characterised with HRTEM.

January 13, 2022

Anisotropy in Thermal Transport Properties of Cast γ-TiAl Alloys

Dennis Lundström, Birger Karlsson, Mattias Gustavsson

Page range: 1203-1212

Abstract

The thermal transport properties have been determined for titanium aluminide with nominal composition Ti-48Al-2W-0.5Si (at.%), cast to cylindrical bars with different γ/(γ + α 2 ) microstructures. The amount of phases and the orientation of the lamellar plates vary from the core to the rim in each of the bars. Differences in the thermal conductivity of the two phases lead to anisotropy in the thermal transport properties, but with cylindrical symmetry in the bars. A newly developed, high-precision technique, the so-called transient plane source (TPS) technique, was used to resolve the anisotropy in a wide temperature range. Typically, the conductivity increases monotonously from about 12– 14 W/m · K at room temperature up to about 20–22 W/m · K at 700 °C for the different materials. The anisotropy in both conductivity and diffusivity is about 15% at all temperatures, but with fundamental differences between the different materials. The anisotropy of the transport properties is explained in terms of amounts of phases and directionality of the lamellar plates.

January 13, 2022

Local Orientation Changes and Shear Banding in {112} 〈111〉-Oriented Aluminium Single Crystals

Henryk Paul, Michel Darrieulat, Andrzej Piątkowski

Page range: 1213-1221

Abstract

The crystallographic aspects of the shear band formation in high purity Al single crystals deformed in plain strain compression tests at 77 K have been studied in detail. The structure observations as well as local orientation measurements clearly indicated that initially {112}〈111〉-oriented Al single crystals are stable only in a global sense. It is shown that the loss of the stability of the crystal orientation occurs as early as the plastic deformation begins. As a result of the crystal rotation within the macroscopic shear bands, two opposite tendencies of the scattering of the initial matrix orientation towards (100)[011] and (110)[001], and formation of two nearly symmetrically situated sets of these bands can be observed. The activation of new, highly stressed co-planar slip systems, situated along the shear plane, is documented. In agreement with the observed tendency of rotation, a crystallographic approach to the shear band formation is proposed.

January 13, 2022

Cyclic Saturation Dislocation Structures of Multiple-Slip-Oriented Copper Single Crystals

X. W. Li, Y. Umakoshi, S.X. Li, Z. G. Wang

Page range: 1222-1226

Abstract

The dislocation structures of [011] and [1̄11] multiple-slip-oriented Cu single crystals cyclically saturated at constant plastic strain amplitudes were investigated through transmission electron microscopy. The results obtained on [001] multiple-slip-oriented Cu single crystals were also included for summarization. Unlike the case for single-slip-oriented Cu single crystals, the crystallographic orientation has a strong effect on the saturation dislocation structure in these three multiple-slip-oriented crystals. For the [011] crystal, different dislocation patterns such as veins, PSB walls, labyrinths and PSB ladders were observed. The formation of PSB ladders is believed to be a major reason for the existence of a plateau region in the cyclic stress-strain (CSS) curve for the [011] crystal. The cyclic saturation dislocation structure of a [1̄11] crystal cycled at a low applied strain amplitude γ pl of 2.0 × 10 –4 was found to consist of irregular cells, which would develop into a more regular arrangement (e. g. PSB ladder-like) and the scale of which tends to decrease with increasing γ pl . Finally, three kinds of representative micro-deformation mode were summarized and termed as labyrinth-mode (or [001]-mode), cell-mode (or [1̄11]-mode) and PSB ladder-mode (or [011]-mode).

January 13, 2022

The Ultra-High Rate Superplastic Forming of a Zn–22Al Thin Sheet Material

Lung-Chuan Tsao, Shiuan-Sheng Wang, Chi-Fu Yang, Tung-Han Chuang

Page range: 1227-1230

Abstract

A superplastic Zn– 22Al (wt.%) thin sheet material has been shown to possess an ultra-high forming rate in the temperature range between 120 and 200 °C, which is about 80 °C lower than the optimized temperature range for the superplastic forming of Zn–22Al alloys as reported in the literature. The as-received material possesses a low microhardness of 20.1 HV, which increases by about 20% after superplastic forming. Experimental results also show that no cavities exist in these superplastically formed Zn–22Al thin sheet specimens, nor do the corrosion properties of this alloy after deformation exhibit any ostensible change.

January 13, 2022

Einfluss der Umformgeschwindigkeit und -temperatur auf das Fließverhalten der Magnesiumlegierung AZ80

Essam El-Magd, Mustapha Abouridouane

Page range: 1231-1235

Abstract

Das Fließ-und Bruchverhalten der hochfesten Magnesiumknetlegierung AZ80 wird im quasistatischen und dynamischen Druckversuch bei Umformgeschwindigkeiten im Bereich 0.001 –5000 s –1 und Temperaturen von Raumtemperatur bis zu 300°C untersucht. Druckversuche bei Umformgeschwindigkeiten bis zu φ̇ ≤ 100 s –1 werden an einer rechnergesteuerten, servohydraulisch angetriebenen Universalprüfmaschine durchgeführt. Für die Hoch-geschwindigkeitsdruckversuche φ̇ ≥ 1000 s –1 wird ein modifizierter Split-Hopkinson-Bar eingesetzt. Ein konstitutives Materialgesetz, dessen Parameter aus den Versuchsergebnissen bestimmt werden, kann im Falle der Hochgeschwindigkeitsbeanspruchung zur Fließkurvenbeschreibung herangezogen werden. Dabei ist im Schlag-Druckversuch neben der gesteigerten Geschwindigkeitsempfindlichkeit des Materials der adiabatische Charakter des Umformprozesses bei der Formulierung des Stoffgesetzes zu berücksichtigen. Mit Hilfe der experimentell ermittelten Fließkurven von AZ80 kann der Einfluss von Umformgeschwindigkeit und Temperatur auf den Stauchgrad beim Bruch bestimmt werden. Darüber hinaus sollen ergänzende metallographische Untersuchungen Aufschluss über Schädigungsbeginn, -art und -entwicklung im verformten Material geben.

January 13, 2022

Thermodynamic Evaluation of Nano-Particle Binary Alloy Phase Diagrams

Toshihiro Tanaka, Shigeta Hara

Page range: 1236-1241

Abstract

Nano-particle binary alloy phase diagrams have been evaluated from the information on the Gibbs energy and the surface tension of the bulk size on the basis of the regular solution model. As the size of the particle decreases, the liquidphase region is enlarged in those binary phase diagrams, in other words, the liquidus temperature decreases. Effect of the size of the particle on the phase equilibria is remarkable when the excess Gibbs energy is positive and its absolute value is large in solid and liquid phases.

January 13, 2022

Measurement of Surface Tension of Liquid Ga-Base Alloys by a Sessile Drop Method

Toshihiro Tanaka, Makoto Matsuda, Koji Nakao, Yoshiyasu Katayama, Daisuke Kaneko, Shigeta Hara, Xianran Xing, Zhiyu Qiao

Page range: 1242-1246

Abstract

The surface tensions and the molar volumes of liquid Ga– Bi, Ga–Sn, Ga–In, Sn–Bi, In–Bi and Sn–In binary alloys, and liquid Ga–Bi–Sn and Ga–Bi–In ternary alloys have been measured at 873 K by the sessile drop method. In addition, the calculation of the surface tension of the above binary alloys has been carried out to interpret the composition dependences of the surface tension of Ga-base liquid alloys from the thermodynamic point of view.

January 13, 2022

Structure Changes and Precipitation Kinetics in Melt Spun and Aged Al–Li–Cu Alloy

Jan Dutkiewicz, Otto Kabisch, Wilfried Gille, Otto Simmich, Roland Scholz, Janusz Krol

Page range: 1247-1252

Abstract

An Al-3.6 wt.% Li-2.0 wt.% Cu alloy was melt and cast in an argon atmosphere. The melt spun ribbons were cast at a linear rate of 10–20 m/s and aged at 200 °C. The kinetics and mechanism of the decomposition process during ageing were analysed. δ′ clusters of the size of 4–5 nm with a diffuse interface were identified, which after about 20 min ageing changes to a well-defined δ′ interface. After a long ageing time the δ′ phase transformed to the d phase. The existence of T 2 phase precipitates was found in the as-cast ribbons and also in the aged ones.

January 13, 2022

TEM Analyses of Heterogeneous Nucleation of Internally Oxidised Multi-Component Ag–Zn-Based Alloys

Joižca Bezjak

Page range: 1253-1257

Abstract

The aim of our research was to identify structures and chemical compositions of phases formed during internal oxidation of multi-component Ag –Zn – Mg-based alloys. Since the ability of inoculation mostly depends on large free energy of formation of oxides of microalloying elements and their crystallographic similarity,Mg in quantities of 0.001 – 0.5 mass% was selected as a micro-alloying element. These correspond to the quantities of 0.005 – 2.5 vol.% of MgO in the selected Ag– Zn-based alloys. Ag-based metal matrix, heterogeneous nuclei of MgO and oxide (ZnO) of the main alloying element were analysed by transmission electron microscopy (TEM). Structural inter-connections among them were also investigated and analysed. In situ phenomenon of heterogeneous nucleation of MgO and ZnO was proved.

January 13, 2022

Tensile Properties and Fracture of Ferritic SG-Iron Having Different Graphite-Shell Structure

Mahmoud Hafiz

Page range: 1258-1261

Abstract

A variety of graphite shell structures is developed in a ferritic spheroidal graphite (SG) iron. The graphite shell is obtained by rapidly heating to a temperature of about 1183 K, and then quenching into iced water or salt bath held at 633 K. These heat treatments developed a graphite shell of martensite and ausferrite, respectively. The SG-iron with martensitic graphite shell is superior in strength to that of a fully ferritic matrix. However, the elongation of the former is decreased by an amount of about 76% compared with that of the latter. In contrast developing an ausferrite graphite shell in a ferritic SG-iron leads to an improvement of about 15 and 31% in the 0.2% yield stress and the ultimate tensile strength, respectively, with no deleterious effect on the elongation. SG-iron having an ausferrite graphite shell fails in a ductile fashion. Introducing a graphite shell of martensite changed the ductile nature of the ferrite phase to a typical brittle fracture.

January 13, 2022

The Effect of Crystallographic Structure of Pure Metals on the Relation between their Specific Heat Content between Room Temperature and the Melting Point and the Magnitude of Some Mechanical Properties

Alfred Buch

Page range: 1262-1264

Abstract

It is shown in this report that when fcc and bcc pure metals are considered separately, an approximately linear relation between the specific heat content and some mechanical properties can be observed, whereas for the same metals no such relation of the same properties to the melting point can be found. The considered properties refer to very pure metals mostly with less than 0.01 percent of impurities, which were recrystallized to a finely polycrystalline microstructure.

Mitteilungen/Notifications

January 13, 2022

Personen

Page range: 1265-1266

January 13, 2022

Bücher/Books

Page range: 1266-1268

January 13, 2022

International Conferences

Page range: 1268-1268

About this journal

The International Journal of Materials Research (IJMR) publishes original high quality experimental and theoretical papers and reviews on basic and applied research in the field of materials science and engineering, with focus on synthesis, processing, constitution, and properties of all classes of materials. Particular emphasis is placed on microstructural design, phase relations, computational thermodynamics, and kinetics at the nano to macro scale. Contributions may also focus on progress in advanced characterization techniques.
All articles are subject to thorough, independent peer review.