Title

On the structural change of mechanically pulverized ironpowder due to the procedures of annealing (Commemorationvolume dedicated to Prof. Shinkichi Horiba in celebration ofhis sixtieth birthday)

Author(s) Hirata, Hideki; Fujihira, Hidekiyo; Fujii, Eiichi

Citation The Review of Physical Chemistry of Japan (1947), 20: 86-90

Issue Date 1947-09-15

URL http://hdl.handle.net/2433/46632

Right

Type Departmental Bulletin Paper

Textversion publisher

Kyoto University

The Review of Physical Chemistry of Japan Vol.

i

ON THE STRUCTURAL CHANGE OF MECHANICALLY

. PULVERIZED IRON POWDER DUE'TO THE

PROCEDURES OF ANNEALING.

<" 73y IltnLrt Hucsrn, 1[toet;iuo''Tuluuaa and latcxf P'upt.

Introduction.

During the last ten years and more, the mechauisnr of sintenno ritetallic

ponder has been a subject ̀ of the keenest research to many investigators't. \evertheless, any hamtonious conclusion seems to lulvc hardly been drawn even

up to the present time. -This may be mainly due to. the lack of experimeat-.d results a-ith regard to the fundamental phenomena connected with the aforesotid mechanism.

The writers have, therefore, induced, by ivay of a supplementation of the foregoing

investigations carried out concerning the sintering of variouspou'dcrcd metals, to

set up' the present experiment utilizing X-rays, to make clear tltc process of We

structural change of mech:mically pulveFied irun powder due to the procedures of

annealing. The experiment ~I results thus obtained) are hriefly described below.

Experimental Part.

i) Specimens: The specimens of iron powder examined in this experiment were pulverized according to the idea of 1'ro(. Bunsaku :lrakatsu at the IPukuda

Metal 1'otvder ivfanufactory and the factory of hc'Daiwa Co., to he used in the

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procedure of sintering. To prepare these specimens, the stamping and bulling mills were employed. It was repotted that the iron jwss-dcr thus prepared was of the

diameter o.4w„~o.r5,,,,°--0.06„,,,, and contained less. tluan o.04/0 of C.

ii) Outline of the .F.xpcrimental iHethod: The irun powder obtained as described above seas heated in vaccum or in the stream of Hq, at various

temperttu-es (ahvays loss•er than Roo°C) for t hour, .and then cooled- slowly in the furnace, before it «ss illuminated with X-rays. To examine the difference

of the inocr structure' of each specimen fi~um those of the others annealed • at different temperatures, Laue plwtograplts were taken with an ordinary Laud

camera as well as with aback-redectiou camera, utilizing heterogeneous X-ra}'s cort<iining characteristic radiations (k, and sometimes Ky radiations) emitted 1fo

i). e.g„ F. Saeerwald and Lis co-workers, 7., nr+ag. C.ieue, ]22, z77 (+9zz) ;L. Eleklrorlun+., 29, 79

fr9z3), 50, x75 f~9zq), 31, i5, t8 (t9z5), 38, 33 (+932); G dletrsllk., I6, 4t fI9zt), 20, zzy (i9z8), il, za (r9zg) ; K'. TreeLidtowski, L. fhyri.t. Chrnr., 24, 75, g7 f+934)-

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- _ -The Review~of Physical Chemistry of Japan Vol

- - i 9

• ON TFtE STRUCTURAL CHANGE OF 3fb;CHANICALLI' PULVERIZED IRON YOSVDER 87

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~ The Review of Physical Chemistry of Japan Vol.

tt. dTTRATA,~TI: tUJit[TRA ANT) E. PUJTT ~ -

Plnlc 11. ISncA-rellecfion Lmre Phningrnphs'nf Uon Powder - -

(L=6.8 cmh Pe liadiation Xo.g6 Reductions of lire (Triginnl hilms)

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_, ~~ Gig. S. Aufore Annealing .

(1'ulveriud wilt o ]3ulling \til])

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Pig, q. Before Annealing (Yulvcrized a•i(I, a tilamping \Sill)

or Pr anticathodc for the most pait.

photographs were usually obtained., keepi

and photographic film 8 cm., while to tal

the photoglaphic film ts•as ahvays lilaced. iii) Experimental Results: Some.

of the iron. powclcr beFore annealing. ar

annealed at various temperatures, were r: Pigs. 8~ I I, plate II. A set of .Deh}ae ; .vhich wcre•confinned to correspond to (7 t in the ordinary Laue photograpcs and to

the reflection from (370) plane in the 1 ' .observed in the dilTi:action patterns given

not only before but aker anncdling, :u s svithout doubt that a single piers of-the it structure composed of an aggregation of m after the pralure of annealing.

It can be observed in Pig. t, Plate I ring taken with the powder before aiiuealin

given rise to by li„ and K,3 radiatio7is i of Debye rings was somewhat reduced,

simple anncal_ing even at a temperahire ] recrystailiration temperature of iron. 7 ~.

broadening was not due to the e~treute

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Fig. ii. AnnnnleA a[ Sar°L in the Stream of 1I,

u this examination, the ordinary Laue

tg the distance L between the specimen

e the hack-reflection ~Iauc photographs, at a distance 6.8 cm. front the specimen. La_uc photographs obhincd with a touch d those t<lken with that of the powder

produced in and Fig. t•-6, Plate I,'and ngs,.coming to appear in. these figures,

o) reflection of the characteristic radiatious

(azo) reflection sometimes accornpvting uk-reflection photographu, could also be rise to by a single piccs of the lwwdcr

en in Fig.- j, Plate 1. This shows us

on powder was mostly of a polycrystalline cro-crystals without any regularity, even

an&Figs. 8, 9, Plate II, that each Debye rag ivas so much broadened that rivo rings melfinto one UancL Such a broadening as .may -be seen in Fig. 2, Plate I,'by~a ]nwerthan 3oo°C, which is Gar below the ]ins; we can deem .that the aforesaid fineness of micro-crystals (to,w~to~ in

or Fr anticathodc for the most part. I

photographs were usually obtained., keepit

and photographic film 8 cm., while to tak

the photograaphic film ts•as ahvays lilaccd. iii) Experimental Results: Some.

of the iron. powder before annealing. an

annealed at various temperatures, were re Figs. 8~ t t, plate TI. A set of .Dehye ri .vhich u•cre•confinned to correspond to (t i in the ordinary Laue photogrphs and to the reflection from (;to) plane in the b. observed in the dilTi:action patterns given not only before but aker annealing, :ts se , svithout doubt that a single piccs of the it structure composed of an aggregation of nti after the pralure of annealing.

It can be observed in Fig. t, Plate I ring taken with the powder before miueali given rise to by li„ and K,3 radiatious of Debye rings was somewhat reduced, simple anncal_ing even at a tempi:rahire recrvstalliration temperature of iron. T

_,

- ~ ~ The Review of Physical Chemistry of

oN THE STRUCTURAL. CHANCY: Op hi ECHANICALLY YULVERIZF.U IRON POWDER - 8g

diareter) itself, nut resulted from the largs inner strain of the clgstal lattice forming the specimen, which rendered the atoms in crystals easily activatable.

~Furthenuore, the trocedure of alifSealing aC a higher temperature made Debye rings sharper, until an assemblage of intense spots. teas obselvcd on them with the

specimens :untrilcd in the stream of H~ at ¢oo°C, as shoccn in Pig. 3, Plate I.

1•hcse intense spots were especially noticed; not always becoming predominant with

the rise of the annealing temperature contrary to our eslxctation ; in Figs. ¢ and

5, Plate I taken with the specimen annealed at 5oo°C in the stream of H„ the aforesaid spots completely disaplreared, but they were detectable again in the

diffraction patterns obtained after the procedure of annealing at about boo°C, i. e.,

the retry-stdllizatirnl temperature of iron, and above boo°C became more remark-..

able, as may be seed in_ Fig. G, Plate 1 or Fins. t t and -tz, ]'late II. Such a

tendency of the change. of diffraction patterns was also observed in the case of

annealing. in vacuum, thqugh not so remarkably as in the stream of I-h. From. the

facts above stated, we may co»dude, at ]east with- regard to the effects of the

procedure of annealing id l I„ tlv~t the diameter of micro-crystals forming they powder, which mostly amounts to the order of ro ' cm. before the procedure of annealing,

extends partly to the a•der of Io ' cm. by heating at about ¢oo°C ; and that, on the contrary, it remains almost unaltered when the annealing temperature is iaised

to about goo°C, thou~dl the growth of micro-crystals again takes place over the whole volume of each ponder, up to the order of to ' cm. in dizuneter by almealing,

the specimens at a temperatm'e higher than boo`C for t hour.

Discussion of Experimental Results. "L•he arguments tvltich have hithertq been advanced, lead us first ro infer that

the specimen of iron powder before annealing was of a polycq•st<illine structure

partly, but considerably strained by the mechanical work of ~ndverization,. micro- crystals of the dimension of to ' cm. im diameter ar}auging themselves irregularly

in a single piece of the poli~der, irrespective to.the procedure of its preparation. Furthermore, it can aleo be deemed, at least in connection with the structural

change in the stream of H, that the aforesaid inner 3tmia is gradually reduced by

heating the powdty even at a 'temperature lower than 3oo°C, and removed completely at the higher annealing temperature. The formation of crystal nuclei

due to the heating, which begins to take place at 4oo°C in the parts of the powder where the inner strain is large, bdcomes so vigorous at 5oo°C that the concentration

of the crystal nuclei in dte aforesaid parts severely strained, grows high enough to hinder the Growth of every nucleus owiugf to its reciprocal interference: But,

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growth of crystal nuclei by heating in the specimens severely strained is interrupted

in the course of varying the temperature so much as to take place in two steps.

To make clear e•Lether such a pheuomwnenon can also be observed or not with

i a specimen prepared mechanically by a different procedure, the writers repeated essentially the sam~X-ray examination with the specimens of iron and several

alloys mechanically rolled. :°1s the consequence of this examination; it must be

especially rentarkcd that the aforesaid phenomeno~t genertdly takes place in metals

and alloys undergone by severe mechanical strain. ,

\ ht conclusion, the writerfg wish to express their best thanks to professor S, r i

Horiba for the interests he has taken in this expcrintent, and to Professor U: Yoshida

for his efficacious advices Dn-ntany~oceasions. Their thanks are also chty to Pro-

fessor R, I~rahatsu, whop kindly ,applied them with many samples required for the

present investigation. Furthermore, it must be noted that the expense of this research has been defrayed from the Scientific P.esearch Expenditure of rthe

Deparhnent of Educ~ICion. '

- Lralikde_for Clremzml Piexeard~ (Ir<kalakr), lfyoto Imperial Unia~craify,

1

The Review of Physical Chemistry of Japan Vol.

J t

Y

g° ~ It. IIIRATA, IL.SUJITURA ANI) N:. FUjil -

when the annealing temperatw'c is higher than boo°C, the so-called ° Recrystalli-

-nation " due to the formation a..nd the growth of crpstll nuclei can be cxcelrted to

occur throughout the whole specimen, aEthe thorough expense of each micro-crystal,

which has hitherto existed with more or less inner strain in the pottmr. Such a

process of-the change of the imter structure of iron powder, though it is considerably

retarded, can, also be confirmed to take place in vacuum as in the stream of H,.

It seems rather strange in the experimental iesults above mentioned that the

20 (1946)