Alloy Design Edited by S

Edited by S. RANGANATHAN S. ARUNACHALAM R. W. CAHN INDIAN ACADEMY OF SCIENCES Bangalore 560 080 4 Digitized by the Internet Archive in 2018 with funding from Public.Resource.Org https://archive.org/details/alloydesignOOunse ACADEMY PUBLICATIONS IN ENGINEERING SCIENCES General Editor: R. Narasimha Volume 1. The Aryabhata Project Edited by U. R. Rao, K. Kasturirangan Volume 2. Computer Simulation Edited by N. Seshagiri, R. Narasimha Volume 3. Rural Technology Edited by A. K. N. Reddy Volume 4. Alloy Design Edited by S. Ranganathan, V. S. Arunachalam, R. W. Cahn ALLOY DESIGN Edited by S. RANGANATHAN Banaras Hindu University, Varanasi V. S. ARUNACHALAM Defence Metallurgical Research Laboratory, Hyderabad R. W. CAHN University of Sussex, U.K. INDIAN ACADEMY OF SCIENCES Bangalore 560 080 © 1981 by the Indian Academy of Sciences Reprinted from the Proceedings of the Indian Academy of Sciences, Engineering Sciences, Volume 3, pp 253-349, 1980 Volume 4, pp 1-56, 1981 Edited by S. Ranganathan, V. S. Arunachalam and R. W. Cahn and printed for the Indian Academy of Sciences by Macmillan India Press, Madras 600 002, India CONTENTS Foreword 1 R W CAHN: Alloy design: a historical perspective 3 H M BURTE and H L GEGEL: Metallurgical synthesis 9 T BALAKRISHNA BHAT and V S ARUNACHALAM: Strengthening mechanisms in alloys 23 M L BHATIA: Strengthening against creep 45 Y V R K PRASAD and P RAMA RAO: Alloy design for fracture resistance 63 S RANGANATHAN and P RAMACHANDRA RAO: Microstructural synthesis 81 V RAMASWAMY and V RAGHAVAN: New developments in carbon and alloy steels 99 D BANERJEE and R V KRISHNAN: Challenges in alloy design: Titanium for the aerospace industry 119 R KRISHNAN and M K ASUNDI: Zirconium alloys in nuclear technology 139 Author Index 155 Subject Index 161 Foreword Science has been late in coming to metallurgy. Until the last century, empirical knowledge together with the metal craftsmanship accumulated over generations pro¬ vided all the metals and alloys that society needed. The leap from the art to the science of alloy making came with the discovery of structure: structure within the atom, in the arrangements of atoms, and in the distribution of aggregates of atoms. In this hierarchy of structures, the metallurgist made microstructure his very own. With the experience accumulated over a century he began to find connections between structure and properties, and simultaneously, he began to understand how micro¬ structure develops. In spite of this, the day is still far distant when we can confi¬ dently say that to know the structure is to know the properties, and vice versa! How quickly we reach this state of knowledge will depend on how well we can grasp, not only the details of structure at various levels, but also how they are linked to each other. Together with the emergence of the possibility of 4 designing ’ alloys, technology has rapidly grown to envisage processes which occur under widely varying temperatures and aggressive environments. Steels—which for a long time appeared to have all the properties an engineer could ask for—were found to be inadequate for some uses. Thus nickel, titanium and zirconium alloys came into existence to meet some of the challenges posed by the designer. And now, our environmentalists and conservationists have rung a clear warning bell: technologies with inbuilt obsolescence must be on their way out. Materials must now not only be stronger, but more durable and last in service over longer periods. The optimum use of material for a given application requires that we reduce the factor of safety (an index of our ignorance) in design. A classic example is the emerging use of the fracture toughness criterion in materials specification, opening the way for the use of intrinsically defective mate¬ rials with greater confidence. This volume brings together a series of articles which cover comprehensively these various facets of the science of alloy design. Robert Cahn provides a historical pers¬ pective, while Burte and Gegel summarise the science of 4 Metallurgical Synthesis \ Specific means of strengthening a metal through processing, alloying and microstructure control are then evaluated. One article is devoted to the development of steels. Finally, the application of these principles in the design of titanium and zir¬ conium alloys in two critical technology areas, the nuclear and aerospace industries, is described. We feel this to be an opportune moment to review and assess our understanding of the behaviour of crystalline materials: for this decade marks the transition to a totally new concept in the design of alloys—the use of amorphous structures for a 1 Pro. C—1 2 wide variety of applications. As presaged in one of the articles, understanding the properties of metallic glasses will increasingly occupy the attention of metallurgists and material scientists in the years to come. S RANGANATHAN V S ARUNACHALAM R W CAHN Special Editors Alloy design: a historical perspective R W CAHN University of Sussex, Falmer, Brighton, U.K. MS received 10 January 1980 Abstract. This paper presents a historical perspective of the progress of mankind from the bronze age to the present stage in alloy development. In particular, the last four decades have seen empiricism giving way to intelligent and informed design of alloys. A spectacular example from this decade is the design of metallic glasses with optimum magnetic properties in 1979. Keywords. History of metallurgy; alloy design; microstructures. The first age of high material civilization, after the crudities of neolithic man, is today known as the bronze age. The first metallic material used by man to make tools, weapons and priestly objects was an alloy—or rather a range of alloys incorporating mainly copper, tin and arsenic—not a more or less pure native metal. Copper would not have made much of a sword or kitchen knife and would have been impossible to cast into the convoluted dragons of a thin-walled Chinese funerary urn. Only man’s (and woman’s) vanity required the malleability and beauty of pure gold, and where gold was concerned, unauthorised alloying was apt to lead to the dishonest metallurgist’s decapitation. Other copper alloys were introduced long before the scientific era of metallurgy. Thus, in the early twelfth century AD, the German monk Theophilus, in the earliest European manuscript on the metallurgical arts, describes how to make a hard solder out of one part of copper and two parts of silver, so that a silver handle might be soldered on to a silver church chalice. The iron age which followed the bronze age was a long period of very slow and wholly empirical development; we are still in the declining years of that age. C S Smith tells us that it was not till the late eighteenth century that the identity of carbon as the essential alloying element for quench-hardening was first recognised, and until that time the hardening and tempering of iron alloys was an erratic, rule-of-thumb affair, at any rate in Europe. The craftsmen of Japan, India and Mesopotamia deve¬ loped steel swords of very high and consistent quality long before the Europeans did, but their skills were nevertheless wholly empirical. It needed a combination of coke- based ironmaking, steel converters with blast, exact chemical analysis and accurate thermal measurements to make possible the development of steels with consistent properties, and this combination was not complete until well into the nineteenth century. By this time the crucial processes of quenching and tempering were well understood and it at last ceased to be necessary to assess the progress of tempering in terms of interference colours formed on the steel surface during the reheating opera¬ tion. 3 4 R W Cahn Some crucial developments which paved the way to alloy development as we under¬ stand it today came in just that decade, 1896-1906, which also turned physics upside down. Just after Rontgen had discovered x-rays and ushered in that remarkable decade, Roberts-Austen, building on the work of Osmond, in 1896 published the first true constitutional diagram of the iron-carbon system; Roozeboom the follow¬ ing year further improved it. Heycock and Neville in 1903 produced a superb consti¬ tutional diagram for the copper-tin system, and thereby opened the way to the subsequent great flood of constitutional work which is the bedrock of modern alloy design. To connoisseurs of the historical fitness of things it is satisfying that the first accurate constitutional diagrams referred to the two alloy types which were first used on a large scale by man. Two of the earliest major alloys to be discovered came from this same period. Tungsten steel had first been made by Mushet in 1868, but drastic improvements in lathe cutting tool performance awaited the systematic researches by Taylor and White, in 1898, on the heat-treatment of high-tungsten steels. Again, in 1899 Barrett and Hadfield stumbled upon the low-hysteresis silicon-iron, which ever since then has been used to build electrical transformers. Two further developments ushered in the modern era: one was the discovery of x-ray diffraction by von Laue and the other, the resolute turning of metallurgy away from a chemical to a physical orientation, largely the doing of Rosenhain. It is diffi¬ cult now to realize that at the end of the nineteenth century, metallurgists were quite uncertain about the crystalline nature of metals and alloys. Osmond in 1900 was still inclined to believe that only 4 grains ’ with geometrically regular external shapes were truly crystalline, and Rosenhain was one of the main protagonists of the view that amorphousness was common in alloys, and especially at grain boundaries, slip bands and polished surfaces.

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