Physical Metallurgy of Refractory Metals and Alloys

Abstract

All rights reservedNo part of this publication may be reproduced in any form without written permission from the publisher PREFACE TO THE AMERICAN EDITIONThe principal reasons which induced the authors to write this book and the features of the book are set forth in the preface to the Russian edition.That section of the science of metals which in Russian is called "metallovedenie" or the "physical chemistry of metals" is generally referred to in scientific and technical literature published in the English language by the term "physical metallurgy." These concepts are much broader than the term" metallography," used in the scientific and technical literature of various countries, and applied solely to research on the interrelationships of the structure and properties of metals and alloys.Each science must have its own subject and its own method of research. Certainly, all specialists will agree that metals and alloys, including their solid solutions, mechanical mixtures, and metallic compounds, form the subject of "physical metallurgy" or "physical chemistry of metals." The aim of this science. is to produce a theory and to elucidate the experimental relationships which ought finally to make it possible to calculate quantitatively alloys Of given properties for any working conditions and parameters.With regard to the methods of research on metals and alloys, we assume that "physical metallurgy" may properly employ any theoretical and experimental methods which will help to solve its basic problems. The experience of the last few decades has shown that among the experimental methods a leading position is occupied by the physicochemical analysis of metal systems developed by N. S. Kurnakov, that is to say, the systematic investigation of the phYSical properties of alloys as a function of he variation of their chemical composition and phase composition. This method has also been employed for investigating the interrelationship of the structure and properties of alloys at different temperatures and pressures (see E. M. Savitsky, The Influence of Temperature on the Mechanical Properties of Metals and Alloys, Stanford University Press, 1961). The "physical chemistry of metals" makes extensive use of physicochemical analysis. The science of metals and alloys absorbs all the achievements of the exact fundamental sciences, primarily physics and chemistry. It may even be said more precisely:The "physical chemistry of metals" or "physical metallurgy" is the synthesis of the physics of metals and the chemistry of metal alloys. The distribution and energy of electrons is the basic factor determining the crystal structure and all the properties of metals and alloys. The main problems which have to be solved in the framework of these sciences are the following: the electronic structure and nature of the interatomic bond in metal crystals, solid solutions of metals and metallic compounds, the development of methods for the quantitative measurement of the value of the interatomic forces with variation in the fundamental parameters...

On stability of mechanical properties of deformed rods from powder molybdenum

“…Analyzing the data of Table 1 we will see that the degree of deformation affects the plasticity of the extruded rods more considerably than their strength. The mechanism of plastic deformation of refractory b.c.c, metals (Mo, W) is known [2] to depend on the crystallographic orientation of the specimens relative to the direction of the deformation. In this connection it seemed expedient to study the textural state of the specimens.…”

Calculation of spinneret feeder elements for creep

“…The temperature in the region of 1250 to 1450°C is maintained in elements of the SF. The ratio of the working temperature to the melting point is equal to 0.7-0.8, which makes it necessary to perform a calculation for creep [1].Creep of platinum alloys has been widely investigated by foreign and domestic specialists [2][3][4]. It was found that the creep curves of platinum alloys are similar to the creep curves of pure metals.…”

“…Using the theory of aging in [1, 6,7] and considering the results of the experimental studies on creep of platinum alloys in [2,4], we obtain the following dependence of the intensity of creep deformation ε i * in steady-state creep on the intensity of stress σ i and time t:…”

“…Creep of platinum alloys has been widely investigated by foreign and domestic specialists [2][3][4]. It was found that the creep curves of platinum alloys are similar to the creep curves of pure metals.…”

“…For example, we will report the calculation for the following initial data: A = 7.8⋅10 -12 , n = 4.5 (the values of A and n were obtained as a result of processing the experimental dependences of the creep rate (c -1 ) on stress σ (MPa)a for the selected platinum and rhodium alloy at the working temperature reported in [2][3][4]; the plate width is 2b = 32.5 mm; the plate For the next time interval from 0.25 to 0.5 h, the initial sag indicator will be equal to Δf 1 . Let us determine the total sag f = 1.1⋅10 -3 + 1.43⋅10 -4 ≈1.24⋅10 -3 mm.…”