Effect of fast-neutron irradiation on mechanical properties of stainless steels: AISI types 304, 316 and 347

JOURNAL OF NUCLEAR MATERIALS 55 (1975) 177-186.0

NORTH-HOLLAND PUBLISHING COMPANY

EFFECT OF FAST-NEUTRON IRRADIATION ON MECHANICAL PROPERTIES OF STAINLESS STEELS: AISI TYPES 304,316 AND 347 H.R. HIGGY and F.H. HAMMAD Atomic Energy Establishment, Cairo, Egypt Received 11 June 1974 Revised manuscript received 9 September 1974

The effect of low-temperature (< 100°C) fast-neutron irradiation on the room-temperature tensile and hardness properties of stainless steels, AISI Types 304, 316, and 347, was investigated up to a fluence of 1.43 X lo*’ n/cm* (E > 1 MeV). Several methods were used for analysis of results and the approach using the irradiation-induced increase in yield stress, Au = “1 - 0, where pi and o are the yield stresses of irradiated and unirradiated specimens, respectively, proved to be the best for describing irradiation-hardening. Below saturation fluence, = 4-5 X 1019 n/cm* (E > 1 MeV), it was shown that Au a(@)%in agreement with Seeger’s model. Yield points were observed at a fluence of 1.3 X 1019 n/cm* (E > 1 MeV) and above. The results are discussed in relation to transmission electron microscopy results of irradiated materials. The relation between irradiation-induced changes in yield stress and Vickers hardness was described by AH = KAo, where K = 2.82 for AISI Type 304, and 3 for both AISI Type 316 and AISI Type 347. L’effet de 1 ‘irradiation B basse tempbature (< 100°C) par des neutrons rapides sur les propri&tis de traction et de duretk 21la temperature ambiante des aciers inoxydables AISI de types 304, 316 et 347 a 6th itudie jusqu’8 une fluence de 1,43 X lo*’ n/cm2 (E > 1 MeV). Plusieurs methodes ont &tb utiliskes pour analyser les r&ultats. L’approche consistant i utiliser l’accroissement induit par l’irradiation de la limite klastique, soit Au = oi - o ok “3 et D sont ies limites blastiques des Bchantillons irradiks et non irradiis respectivement s’est r&&e stre la meilleure approche pour d&r&e le durcissement par irradiation. En dessous de la fluence de saturation = 4-5 X lo’? n/cm2 (E > 1 MeV), iI a BtBmontrh que Au 0: ($t)‘h, en accord avec ie mod& de Seeger. Des dicrochements B la limite ilastique furent observds pour une fluence de 1,3 X 10’ ’ n/cm* (E > 1 MeV) et au-dessus. Les r&ultats sont disc&s en relation avec les rCsultats de microscopic dlectronique par transmission obtenus sur les mathriaux irradiis. La relation entre les variations de limite elastique et de dureti induites par l’irradiation s’exprime par l’iquation AH = XAa, oit K = 2,82 pour l’acier AISI de type 304 et 3 pour Ies deux aciers AISI de types 316 et 347. Es wurde der Einfluss der Bestrahlung bei niedrigen Temperaturen (< 100°C) mit schnellen Neutronen (E > 1 MeV) bis zu einer Dosis von 1,43 X lo*’ n/cm* auf die Festigkeit und HIrte der rostfreien StLhle AISI 304, 316 und 347 bei Raumtemperatur untersucht. Die Gewinnung der Ergebnisse erfolgte nach verschiedenen Methoden. Es wird gezeigt, dass die bestrahlungsinduziert~ Zunahme der Streckgrenze Au = oi - o mit Oi und CJals Streckgrenze der bestrahlten und unbestrahlten Proben die beste N;bheruna zur Beschreibung der Bestrahlungsverfestigung ist. Unterhalb der Sittigungsdosis von etwa 4 bis 5 X 10” n/cm* ist Au= (@t)‘h und stimmt mit dem Seegerschen Model1 iiberein. Streckgrenzen wurden bei einer Dosis von 1,3 X 1019 n/cm2 und dariiber beobachtet. Die Ergebnisse werded in Zus~menh~g mit tr~smissi~,n~Iektronenmi~oskopischen Beobachtungen an bestrahltem Material diskutiert. Die Beziehung zwisehen der bestrahlungsinduzierten inderung der Streckgrenze und der Vickers-Hirte ist AH = KAcr mit K = 2,82 fiir AISI 304 und K = 3 fiir AISI 316 und 347.

1. Introduction Several types of stainless steels are widely considered as cladding and structural materials in nuclear reactors because of their excellent corrosion resistance and adequate strength at various temperatures. The

types of stainless steels commonly used are AISI Type 304, AISI Type 316, and AISI Type 347. The effect of neutron irradiation on the tensile properties has been investigated extensively in AISI

Type 304 [l-14], especially for elevated-temperature irradiation, and to a lesser extent in AISI Type 347 [l f 9, f 5-2Sf, while few data are available in the literature for AISI Type 3 16. The available data pertaining to the effect of fast neutron fluence on the change in yield strength (YS) showed considerable scatter. This may be attributed to variations in experimental and material conditions, as well as differences in measuring and reporting neutron fluence. Irradiation-hardening in various types of stainless steels was found to depend on the amount of cold work. The change in YS due to neutron irradiation was found to be considerably higher in annealed than in cold-worked material. For example at a fluence of = 6 X 102” n/cm2, the change in YS of AISI Type 304 reached 400% for annealed materials, while it reached 70% for the cold-worked specimens [2). Although the relationship between YS and fluence has not been reported for AISI Type 304,3 16 and 347 steels, a (#t)l” relationship has been found in copper single crystals ]26],Zircaloy-2 and Zircaloy-4 after low-temperature irradiations f27], and zirconium [28], whilst a (qJ# dependence has been reported for polycrystalline copper 1291. The change in Vickers hardness due to neutron irradiation and its relation to a similar change in YS was previously investigated for several steels, Cu, Fe, Ti, and an aluminium alloy [30], but not for AISX Types 304,316, and 347. In the present work, carefully designed experiments in which.the material and irradiation conditions were characterized,,were carried out to study the effect of low-temperature irradiation (< 100°C) on room-temperature tensile properties and Vickers hardness of AISI Type 304, AISI Type 3 16, and AISI Type 347, and to determine the dependence of the Table 1 Chemical compositian Material

AISI Type?04 AISI Type 3 16 AISI Type 347

of the stainless

change in YS and hardness of these alloys on fast fluence (E > 1 MeV).

2. Experimental Flat tensile specimens were cut in the rolling direction from 1 mm sheet. The specimen had a gauge length of 20 mm, and a width of 3 mm. The chemical composition of the material is given in table 1 for AK1 Types 304,3 16, and 347. Some of the asreceived specimens were annealed in vacuum at 950°C for 90 min. The grain-size of both annealed and as-received materials was in the range of 10 to ISfim. Six capsules were prepared and irradiated in the High Flux Reactor (HFR) at Petten, Holland, to fast fluences ranging from 1. IS X I 018 to 1.43 X 102* n/cm2 (E > I MeV). Three spec~ens of both annealed and as-received materials were put in each capsule. The capsules were designed in such a way as to allow the cooling water of the reactor (= SO”C) to always be in contact with the specimens during irradiation to ensure low-temperature irradiation {< 100°C). Two flux monitors (Co and Fe foils, and Ni wire) were put in contact with the specimens for exact determination of both thermal and fast neutron fluences. Two positions in the reactor core were used in the irradiation. The instantaneous flux in the first position was 4 X 1Ol3 n * crnv2 * se1 thermal and 5 X 10lz n * cmA2 1s- 1 fast (E > 1 MeV), while in the second the flux was 2 X lOI n . cmW2 . S-I tkmrml and 5 X 1013 n ’ cmh2 - s-l fast (E > 1 MeV). Room-temperature tensile testing was performed using an Instron machine at an extension rate of

steelsused.

Major constituents

E%)

cr

Ni

Mn

MO

Si

c

Fe

18.7 ‘ 17.1 17.4

9.1 11.45 9.55

1.49 1.8 1.06

0.22 0.234 0.24

0.465 0.5 1 0.42

0.a44 0.046 0.048

rest rest rest

H.R. Higgy, F.H. Hammad, Mechanical properties of stair&w steels

0.5 mm/min. Also, the Vickers hardness for each tensile specimen was measured using a Wulpert Diastor Type 2 RC, and a load of 5 kg. The reported data are the average obtained from three specimens tested in each condition.

3. Results and discussions The load-elongation curves of irradiated specimens of AISI Type 304, AISI Type 3 16, and AISI Type 347 are shown in figs. 1,2, and 3 respectively. A yield point phenomena was observed at a fluence of 1.3 X 10lg n/cm2 (E > 1 MeV) and above, and the yield drop increased with the fluence. The lower yield stress was determined for the three types of stainless steel at various exposures. The effect of fast fluence on the tensile properties of AISI Types 304,3 16, and 347 is represented in figs. 4,5 and 6, respectively. The irradiation behaviour of the three alloys was similar. The exposure to the highest fluence (1.43 X 1020 n/cm2) caused about 15% increase in the YS of annealed AISI Type 304. The change in ultimate tensile strength (UTS) and duc240.1

,

,

20 Fig. 1. The stress-strain

,

,

,

,

,

,

179

tility due to neutron irradiation was much less than in YS. The increase in UTS reached about 16% and the drop in both uniform and total elongation was about 38 and 32%, respectively, at maximum dose (1.43 X 1020 n/cm2). Considerable increase in Vickers hardness resulted due to irradiation (table 2). The increase was similar in the three alloys and reached about 57% at maximum dose. In irradiation-hardening studies, log-log plots are commonly used for representing fluence dependence of the YS. In some cases, the YS of irradiated specimens (oi) was used [3 I-331. In a few cases the increment (oi2 - u2)1/2 was plotted against the fluence @t [34,35], where u is the YS of unirradiated specimens. In others, the irradiation-induced increase in YS, AU = Ui - U, was adopted [36]. Fig. 7 shows a straight line relationship between Ui and @ in the form: Ui =

A (@t)” .

(1)

The exponent m (slbpe of line) equals 0.16 for the t.ested types of stainless steel. Saturation effects at

, ,

40 60 80 slnAIW.% curves of irradiated AISI Type 304.

20 Fig. 2. The stress-strain

40 STMIH,%

00

80

curves of irradiated AISI Type 316.

HR. Biggy, F.H. Hammad, Mechanical properties ofstainlesssteels

180

iI: I-;

O6(

40 SlWW,~

20

Fig. 3. The stress-strain

curves of irradiated AISI Type 347.

high fluences are apparent in the plots. The exponent m is less than that expected from the dispersed barrier model [37]. Bement [31], using the same approach, found m = 0.1 for Zircaloy-2. Diehl and

Seidel [32], and Koppenaal [33] analysed the irradiation-h~dening data for C&-Au and Cu-Al alloys, and cold-worked Cu, using a log-log plot of irradiated YS versus fluence. The exponent m decreased continuously with increasing solute content. This approach was criticized on the basis that it does not allow for superposition of irradiation-hardening and hardening from another source [32]. The approach shown in fig. 8 has the advantage that the increment (Ui’ - c~~)~”is intensitive to prior meta~urgi~al conditions, as was shown for Zr-Nb alloys [34, 351, The plots show that the fluence dependence is 0.3 for the three stainless steel alloys. The dependence cannot be compared with the predictions of the dispersed barrier model. Saturation in hardening appears at high doses. The log-log plots of Au versus fast fluence q% shown in figs. 9-11 for AISI Types 304,316 and 347. respectively, indicate a straight-line relationship at low doses with saturation at high fluences. Saturation appeared to take place at a fast fluence of 4 X lOI9 n/cm2 (E > 1 MeV) for both AISI Type 304 and AISI Type 347, and 5 X 1Olg n/cm2 (E > 1 MeV) for AISI Type 3 16. The slope of the linear portion, as calculated using a statistical method for determining the best linearity, is 0.45 for the three types of stainless steels. The rate of hardening was found to be the same in both annealed and as-received material

STAINLESS STEEL-304 LOW-TFMR lRRADlATlON 0

0.2

OA

0.6

0.8

1.0

1.2

IA-IO

FAST FlUENiX lMe~).n/cd

Fig. 4. The effect of fast fluenceon the tensile properties of AISI Type 304.

H.R. H&y, F.H. Hammad, Mechmical properties

ofstainlesssteels

181

60

STAIHLESSSTEEL-316 I 0.2

I 0.4

i 0.6

I

LOW-TEII!IRRADIATIS~ I I

0.8

1.0

1.2

i iA*1

FAST FLUENCE (E>~WOV~N~~~

Fig. 5. The effect of fast fluence on the tensile properties of AN Type 316

(the slope is the same, as shown in the plots). The effect of fast fluence before saturation on irradiation-induced change in YS can be described by log Au = log C - 0.45 [log(@) - Iog(1017)] or Ao = 6’ [#r/1017] o*45,

(4

where C is the intercept on the 1017-line, @is the fast neutron flux (n f cme2 . secwi) and t is the time of

irradiation (set). The constant C was found to be about 10 for the as+eceived materials and about 14 for the annealed. This indicates the dependence of Con the pre-irradiation metalhrrgical condition. Eq. (2) predicts a (@)1/2 dependence of the irradiated-induced change in YS (Au). The dispersed barrier harde~ng model proposed by Seeger predicts a (Ipt)Ifi dependence of the critical shear stress (CSS). In this model the motion of dislocation under applied shear stress is hindered by randomly d~st~buted, radiation-produced localized bar-

60

3

e

Q 40 t fw ”

a 20

STAllLESSSTEEL-347

0

t

I

t

0.2

OA

0.6

LIIW-TEMP. IAIIAOIA~UM f

I

I

0.8

1.0

1.2

I

7.4x1(

FAS7 FLUENCE (E>lMsWd

Fig. 6. The effect of fast fluence on the tensile properties of AISI Type 347.

H.N. Higgy, F.H. Hammad, Mechanical properties of stainlesssteels

182

Table 2 Effect of irradiationon VickershardnessHVSOrg/mmz). A-R

A

AISI Type 316 A A-R

0

188

1.18 x lo’&

206 216 223 240 258 210

166 188 200 210 230 241 261

180 206 218 228 251 271 282

Fast fluence (n/cm’1

2.6 x 4‘4 x 1.3 x 4.05 x 1.43 x

10” 1o18 lOi 1org 10ZO

a) A-R: as-received.

AISI Type 304”)

164 193 210 221 245 260 277

AI.81Type 347 A-R A 187 219 230 241 268 282 300

184 219 222 230 263 280 281

A: annealed.

Tiers. The barriers can be either individual point defects or point defect clusters; their concentration is assumed to be proportional to the fluence. It was shown that the CSS should be proportional to the square root dose at 0 K. There is a discrepancy about the dependence of CSS on irradiation dose. Diehl [29] showed that Cu follows ($Q)~/~dependence, while others [26,36] indicated that it follows a (@t)li3 law. It was pointed out [38] that the approach of irradiation-induced increase in YS and not the YS of irradiated specimens, is the one that should be used for describing irradiation hardening in terms of the dispersed barrier mod-

el. Owing to the presence of two types of barriers (irradiation-induced as well as unirradiated barriers) the effective stress, which is the difference between the applied stress ai (YS of irradiated specimens) and YS of the unirradiated specimens o, should be used. Using this approach, it is shown that the behaviour of stainless steels, due to irradiation, can be described by the dispersed barrier model. Blewitt et al. [26] reported a (#t)lj2 law in Cu crystals when the absolute value of CSS of irradiated cystals was used. Diehl and coworkers (29,39,40] showed that this is due to the method of representation. They used single crystals of identical orientation and showed that the

FA6TFlUElEE fEZlMuUbmn’

Fig, 7. The effect of fast fluence on yield stress of bradiited stainless steels: AISI 304,316 and 347.

. 8. The effect of fast fluence on the increment

- i~‘)l~ of AISI Types 304,316 and 347.

H.R. Higgy, F.H. Hammad, Mechanical properties of stainlesssteels

183

ld([ ldd

t

STAINLESSSTEEL-304 1

I

10"

I

I

I

I

lo'

lo"

I

I

,

,

,

,

STAlN,LES; flEEl-34;

Id'

lo"

I

10%

10"

FAST FLUENCE (E>lMeVl,n/cm’

Id'

IO"

FAST FLUENCE (E>IM,Vh n/cd

Fig. 9. The effect of fast fluence on the change in YS of AISI Type 304.

Fig. 11. The effect of fast fluence on the change in Y S of AISI Type 341

irradiation-induced increase in YS, below saturation, shows a (@t)li2 dependence. The agreement of stressdose dependence, in present work, with the dispersed barrier model is probably due to presence of small defect clusters in irradiated stainless steels as was shown by transmission electron microscopic (TEM) investigations. In AISI Type 304, no defects were observed after irradiation to 1019 n/cm2 at T irr< 100°C [41]. A high density of small unresolved defect clusters was observed for the first time by

‘%----l

Armjo et al. [2], after irradiation to 1020 n/cm2 at T h < 100°C. Similar observations were reported by Bloom [42] after irradiation to 7 X 1020 n/cm2 at T b between 93 and 300°C. The formation of small size clusters may be due to stabilization of vacancies by He produced by a (n, (u) reaction with l”B impurities. Above a fluence of 4 X 1019 n/cm2 (E > 1 MeV) for AISI Type 304 and AISI Type 347, and 5 X 1019 n/cm2 for AISI Type 3 16, saturation takes

40-

32-

"s, ?24I 3 _..11s1Tllr-304 _o_ . . 316 _+_ . . 347

STAINLESSSTEEL-316

LOW KM

I Id'

I

I

Id"

kits FAST FLUEICE (E>l MeV),

1

lo'

n/cm’

Fig. 10. The effect of fast fluence on the change in YS of AM Type 3 16.

lnnmll7lon

I IO" 0

2

4

6

8

10

12.d

IFAS~ ~~k~flCE~bt~+

Fig. 12. Correlation between the change in YS and (@t)lj2.

184

H.R. Higgy, F.H. Hammad, Mechanical properties of stainless steels

I

0'

20

40

60

CHANGE IN HARDNESS

80

100 01

(HY5)

Fig. 13. Correlation between irradiation-induced YS and Vickers hardness of AI.91Type 304.

change in

The constant K (slope of the line) was found to be 2.82 for AISI Type 304, and 3 for both AISI Types 316 and 347.

I

20

1 I

40 CHAN6E

I

60

I

80

1

100

,

120

IN HARDNESS (HV5)

Fig. 14. Correlation between irradiation-induced YS and Vickers hardness of AISI Type 316.

I

I

60

80

CHANGE

AH,, = K Au .

0

I

40

change in

1

I

100

J

120

IN HARDNESS (NY5)

Fig. 15. Correlation between irradiation-induced YS and Vickers hardness of AISI Type 347.

place and eq. (2) cannot be used for describing irradiation-hardening. Makin and Minter’s [43] equation [Au = A ((1 - exp (-B$t)}1/2 ] can be used to describe irradiation-hardening in the three types of stainless steel as shown in fig. 12. The value of B (B =uu , where a is the number of obstacles generated per neutron, u is the effective volume of each neutronintroduced obstacle to deformation) was found to be 0.2 to 0.3 X 10h20. Bement [31] found the value of B to be 0.29 X 10w20 for Zircaloy-2 irradiated at 280°C. The change in Vickers hardness due to irradiation as a function of related change in YS is plotted, and a straight-line relationship resulted for both annealed and as-received specimens (figs. 13-15 for AISI Types 304, 3 16, and 347, respectively):

He0

I

20

change in

The relation between hardness and the flow stress is important, since the YS can be determined by a quick and easy hardness test using a small amount of material. Tabor [44] showed that the Vickers hardness of several metals is proportional to the YS, the proportionality constant theoretically and experimentally being 3. Nunes and Larson [30] showed that this correlation also holds for some metals over a wide temperature range. Oku and Usui [46] have recently established the correlation of flow stress with hardness for W, MO and mild steel and showed that the constant varies from 2 to 5. An irradiation-induced yield point in AISI Type 347 was noted by Wilson and Berggren [15]. Broomfield et al. [47] obtained similar results on AISI Type 3 16 and 25% Ni-20% Cr-Nb stabilized austenitic steels. Bloom et al. [42] reported the observation of a yield point in AISI Type 304 irradiated at low temperature in the range 94-149°C. However, upon irradiation in the temperature range 300-371°C, no yield point was observed. The yield point could also be removed by annealing irradiated specimens in the temperature range 400-500°C and above [42]. The tensile stress-strain curves of de Vries [48] for AISI Type 304 and AISI Type 3 16, irradiated at similar conditions to ours, showed yield points. Annealing at 400°C and above eliminated the yield points. It is interesting to note that TEM investigations showed that the defect clusters introduced in the specimens vanished in the temperature range 400-600°C. Thus the yield point phenomena are associated with the presence of defect clusters. The yield point phenomena can be related to the interaction of dislocations with irradiation-produced

H.R. Higgy, F.H. Hammad, Mechanical properties of stainlesssteels

defects. It is known that deformation removes radiation damage f49, SO] and produces defect-free channels [45,49]. The examination of austenitic stainless steel irradiated at low-temperature (containing small defect clusters) after a small amount of deformation (5-l%) showed that deformation was concentrated in very narrow bands or channels [48f. The channels are free from damage, which has been swept out by moving dislocations. The stress necessary to initiate the first dislocation is that required to overcome the line tension and the defect repulsive force. The stress needed to produce the second dislocation is less, because the defect density is less. Therefore, a decrease in flow stress is observed after the onset of plastic deformation. At the upper yield stress rapid initial dislocation multiplication takes place in irradiated metals. It seems that this mechanism requires the presence of a certain density of defect clusters. Thus, a certain fluence is needed for the yield point to be observed. When the density of defect clusters is increased by increasing the fluence, the magnitude of the yield drop is also increased. Similarly, when the defect clusters are eliminated either by irradiation at elevated-temperature or annealing at a temperature sufficient to remove the clusters, the yield point is elevated. It is also possible that dislocation locking by irradiationinduced defects may contribute to yield point formation.

185

(4) Irradiation hardening showed saturation at 4 X 10lp n/cm2 for AISE Types 304,347, and 5 X 1Olp n/cm2 for AISI Type 3 16. (5) Below saturation, the relation Au=(@)~/~ was obtair?d in agreement with Seeger’s model, while over the entire fluence range used the results were described by Makin and Minter’s inverse exponential equation. (6) The relation between the change in Vickers hardness, due to low-temperature irradiation, and the related change in YS was AH, = KAu, where K was found to be 2.82 for AISI Type 304, and 3 for AISI Types 3 16 and 347.

Acknowledgements The authors wish to express their gratitude to Prof. Dr. J.A. Goedkoop and the board of RCN, Petten, The Netherlands, for providing experimental facilities used in this research prograrnme. Special thanks are due to Ing. H.J. Wervers, Drs J.D. Elen, and Mr. A. Glas for assistance. One of us (H.R. H.) is specially grateful to the IAEA for fellowship support.

References (11 M.J. Graber and J.H. Ronsick, IDG-16628 (1961).

4. Con~l~ions The effect of low-temperature irradiation (< 100°C) on the room-temperature mechanical properties of AISI Types 304,316, and 347, exposed to a fluence ranging from 1.18 X 1O1*to 1.43 X 10zo n/cm2 (E > 1 MeV) was investigated. The main results can be summarized as follows: (1) Irradiation-hardening behaviour was found to be similar in the three types of stainless steels used. (2) A yield point that increases in magnitude with increasing fluence was observed at fluences of 1.3 X lOI n/cm2 and above (3) The log-log plots of irradiation-induced increase in YS, versus fiuence, were found to be the most suitable and theoretically justified approach for analyzing irradiation hardening below saturation.

[2] J.S. Armijo et al., Nuclear Apportions, 1 (1964) 462. [3] J.C. Tobin,HW-SA-3268 (1963). [4] M.H. Bartz, TID-7515 (pt. 2) (1956). [ 5 ] H.M. Finiston and J.P. Howe, Metallurgy and Fuels (Pergamon press, Oxford, 1959). [6] J. Chaw and R. Jones, BNL-50082 (1967). ]7] J.E. Irvin et al., BNWL-1 (1965). [ 81 J.W. Joseph, DP-669 (1962). [P] J.J. Prislinger, ORNL-TM-337 (1962). [lo] A.L. Bement, HAPO, private communication. [li] T.T. Claudson, BNWL-SA-1193 (1967). [ 121 DO. Leeser and W.F. Murphy, CF-53-3-276 (pt. 2) (1953). [ 131 R.E. Robbins et al., Trans. Amer. Nuci. Sot. 10 (1967) 488. 1141 J.W. Joseph, DP-534 (1960). [15] J.C. Wilson and R.G. Berggren, Proc. ASTM 55 (1955) 689. [16] C.A. Brush et al., J. Metals, 8 (1956) 1362. [17] D.L. Keller, BMI-1862 (1969). [18] W.E. Murr and F.R. Shober, ASTMSTP-341 (1962) 325.

186

H.R. Higgy, F.H. Hammad, Mechanical properties of stainless steels

[ 191 M.H. Bartz, Proc. Second UN Conf. of the Peaceful

Uses of Atomic Energy, Geneva, vol. 5 (1958) p. 1878. [20] W.E. Murr et al., BMI-1609 (1963). [21] F.R. Shober and M. Kangilaski, HW-83398 (1964). [22] R.S. Kemper and W.S. Kelly, Proc. ASTM 56 (1956). [23] S.H. Paine et al., ANL-6102 (1960). [24] R.E. Bailey and M.A. Silliman, ASTM-STP-233 (1963) p. 84. [25] A. van der Linde, RCN-lnt.-69-118 (1969). (261 T.H. Blewitt et al., J. Nucl. Mater., 2 (1960) 277. [27 ] H.R. Higgy and F.H. Hammad, J. Nucl. Mater., 44 (1972) 215. [28] A.H. Hammad et al., BARC-578 (1971) (291 J. Diehl, Radiation Damage in Solids, vol. 1 (IAEA, Vienna, 1969) p. 129. [30] J. Nunes and F.R. Larson, J. Inst. Metals 91 (1962) 114. [31] A.L. Bement, HW-74955 (1963) p. 181. [ 321 J. Diehl and G.P. Seidel, Radiation Damage in Reactor Materials, vol. 1 (IAEA, Vienna, 1961) p. 187. [33] T.J. Koppenaal, Acte Metall. 12 (1964) 487. [34] T.J. Koppenaal and D. Kuhlmann-Wfisdorf, Appl. Phys. Letters 4 (1964) 59. 1351 C.E. Ells and V. Fidleris, Electra. Chemical Technology 4 (1966) 268.

[36] D.O. Thompson and V.K. Pare, ORNL-3840 (1963). [37] A. Seeger, Second UN lnt. Conf. on the Peaceful Uses of Atomic Energy, vol. 5 (1958) p. 998. [38] J. Diehl, in: Vacancies and lnterstitials in Metals, ed. A. Seeger et al. (North-Holland, Amsterdam, 1970) p. 765. [39] J. Diehl et al., Phys. Letters 4 (1963) p. 236. [40] A. Rukweid and J. Diehl, Z. Metallkunde 55 (1964) 266. [41] H.G.F. Wilsdorf and D. Kuhlmann-Wilsdorf, J. Nucl. Mater. 22 (1967) 68. [42] E.E. Bloom et al., J. Nucl. Mater. 22 (1967) 68. [43] M.J. Makin and F.J. Minter, J. Inst. Metals 24 (1957) 399. [44] D. Tabor, Brit. J. Appl. Phys. 7 (1956) 159. [45] B.L. Eyre and A.F. Bartte, Phil. Mag. 12 (1963) 261. [46] T. Oku and T. Usui, J. Nucl. Mater. 40 (1971) 93. 1471 G.H. Broomfield et al., J. Iron Steel Inst. 203 (1965) 502. [48] M.J. de Vries, RCN (1971), private communication. [49] J.V. Sharp, Phil. Mag. 61 (1967) 827. [SO] A.A. lbrahim, F.H.. Hammad and A.A. Ammar, J. LessCommon Metals 30 (1973) 97.