NATORE 

THURSDAY, JULY 29, 10915. 


THE STUDY OF METALS AND ALLOYS. 
An Introduction to the Study of Physical Metal- 
lurgy. By Dr. W. Rosenhain. Pp. xxii+ 368. 
(London: Constable and Co., Ltd., 1914.) 
Price 1os. 6d. net. 
T may be doubted whether the title of this 
book has been happily chosen. So far as its 
subject matter is concerned, with the exception of 
one chapter on the mechanical testing of metals, 
it has hitherto been described by the term 
“Metallography.”” The latter, which dates back 
to 1721, was originally used to . signify the 
description of metals and their properties. In 
this sense it is certainly obsolete, but it was 
re-introduced in 1892 to describe the microscopic 
structure of metals and alloys, since when, as 
Dr. Desch points out in his text-book, “ Metal- 
lography”” (Longmans and Co.), “it has been 
generally accepted, gradually receiving an exten- 
sion of meaning to include investigations by other 
than microscopic means.” Dr. Rosenhain, in using 
the term physical metallurgy to describe such 
subject matter, writes :—‘‘The scope of physical 
metallurgy is an exceedingly wide one, and one 
which brings it well over the borderland of several 
sister sciences—such as chemistry on the one side, 
physics on another, and that branch of knowledge 
generally known as ‘strength of materials’ in 
yet another direction. Besides these, crystallo- 
graphy bears largely on our subject.” This 
being the case, it appears to the writer that 
“Metallography”’ is the more appropriate title, 
as being both more accurate, more inclusive, and 
better suited to a rapidly growing science. No- 
where in this book, so far as can be seen, does 
the author attempt to bring the terms ‘“ Physical 
Metallurgy” and “Metallography” into relation 
with each other, and there are places where he 
appears to use them as interchangeable expres- 
sions. 
The book is divided into two parts. The first 
deals with the structure and constitution of metals 
and alloys, the second with the properties of metals 
as related to their structure and constitution. As 
the title indicates, it is an introduction to a par- 
ticular type of study, but it also serves as an 
introduction to a metallurgical series which is in 
course of publication under the author’s editor- 
ship. This being so, he writes :—‘‘ The treatment 
of the whole subject in the present work has been 
intentionally kept somewhat general, the object 
of the author being to awaken interest and to 
stimulate thought and ideas rather than to com- 
municate a great mass of detailed data.” The 
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author has certainly achieved his purpose. He 
has written an interesting book full of suggestions, 
and he has presented his subject with remarkable 
fairness, and due acknowledgment to other 
workers. Chapter xi, dealing with the effect of 
strain on the structure of metals, a field of 
investigation in which he has been one of the 
pioneers, is one of the best pieces of writing 
extant on this subject. 
No one acquainted with Dr. Rosenhain’s 
technique will be surprised to hear that the photo- 
graphic illustrations are excellent, but some of 
the diagrams are far from satisfactory. In 
describing the copper-aluminium equilibrium, 
certain letters are used in the text which are 
obviously meant to correspond to similar letters 
in the constitutional diagram, but which are con- 
spicuous there only by their absence. It is 
somewhat surprising to come across the state- 
ment (page 110):—‘No investigation of the 
constitution of a system of alloys can be regarded 
as really complete until a study of electrical con- 
ductivities and temperature coefficients has been 
carried out.” Very few systems are composed 
of alloys which are ductile from one end of the 
series to the other. In the great majority of 
cases, as the author himself points out, there 
exists in the middle regions of the binary series 
a zone of brittleness and weakness where, not only 
can the alloys not be drawn into wires, but where 
they cannot even be turned in a lathe. Deter- 
minations of electrical conductivity would in such 
cases have to be made on rods cast to shape, and 
owing to their proneness to contain cavities or 
blow-holes, they would not be suitable for exact 
work and therefore as evidence in questions of 
constitution. Microscopical and thermal analyses 
still remain the fundamental methods of investiga- 
tion in the determination of the constitution of 
alloys, and in most cases they are sufficient. 
The author regards as anomalous and as 
requiring further research (page 305) the fact that 
a brasses cannot as a rule be hot-rolled (although 
they can be cold-rolled) whereas a+ brasses can 
be hot-rolled even though f is considerably harder 
than a. He mentions, however (footnote to 
page 145), that he has recently seen an a brass 
successfully hot-rolled, and suggests therefore that 
“the hot shortness of the brasses may not be an 
inherent property of the alloys.” In reality the 
explanation is quite simple. Lead is an invariable 
constituent of all commercial brasses. It is almost 
insoluble in a brass and the red shortness of this 
material is due to the presence of films of liquid 
lead among the solid a crystals. If, however, 
a brass is made from copper and zinc free from 
lead it can be hot-rolled without difficulty. The 
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