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PRECIPITATION AND ITS INFLUENCE ON THE RECRYSTALLIZATION IN DILUTE AlMn AND AlCr
ALLOYS
S. Kiss, F. Kedves, I. Harangozó
To cite this version:
S. Kiss, F. Kedves, I. Harangozó. PRECIPITATION AND ITS INFLUENCE ON THE RECRYS-
TALLIZATION IN DILUTE AlMn AND AlCr ALLOYS. Journal de Physique Colloques, 1983, 44
(C9), pp.C9-279-C9-282. �10.1051/jphyscol:1983938�. �jpa-00223385�
JOURNAL DE PHYSlQUE
Colloque C9, supplCment a u n012, Tome 44, dicembre 1983 page C9-279
PRECIPITATION AND ITS INFLUENCE ON THE RECRYSTALLIZATION IN DILUTE
@Mn AND E C r ALLOYS
S. Kiss, F.J. Kedves and I.Z. Harango26
I n s t i t u t e f o r Applied Physics, Kossuth L . University, Debrecen, P.O. Box 2, H-4010, Hungary
A b s t r a c t
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I n t e r n a l f r i c t i o n and dynamic e l a s t i c modulus of c o l d drawn d i l u t e A l C r and WU!n a l l o y s were i n v e s t i g a t e d by an i n v e r - t e d pendulum i n as r e c e i v e d and p r e c i p i t a t e d s t a t e . I n t e r n a l f r i c t i o n peaks of n o t r e l a x a . t i o n a 1 c h a r a c t e r and modulus i n c r - e s occur on t h e s p e c t r a of A l C r a l l o y s . The e f f e c t s a r e a t t r i b u - t e d t o t h e p r i m a r y and secondary r e c r y s t a l l i z a t i o n d u r i n g t h e measurement. I n c r e a s i n g t h e C r c o n t e n t up t o t h e s o l u b i l i t y li- m i t t h e temperature range of r e c r y s t a l l i z a t i o n p r o c e s s e s i ss h i f t e d by a b o u t 100 K upwards. T h i s e f f e c t i s c o n s i d e r a b l y s m a l l e r t h a n i t w a s found f o r t h e d i l u t e AU1n a l l o y s . I n v e s t i g a - t i n g t h e r e c r y s t a l l i z a t i o n behaviour of and Q C r s a m p l e s i n p r e c i p i t a t e d s t a t e we found t h a t i n c e r t a i n c a s e s t h e p r e c i p i t a - t i o n s have a w e l l d e t e c t a b l e i n f l u e n c e on t h e r e c r y s t a l l i z a t i o n temperature. !Phis r e s u l t was confirmed by measurements made afbr d i f f e r e n t p r e c i p i t a t i o n t i m e s a t g i v e n temperature.
1. Experimental
The samples were p r e p a r e d by t h e Research I n s t i t u t e f o r L i g h t fvletals / ~ u n g a r i a n Aluminium C o r p o r a t i o n , Budapest/ from A 1 /99.99%/ u s i n g a p p r o p r i a t e m a s t e r a l l o y s of A l C r and AXlh, The c o n c e n t r a t i o n s of C r were 0,735; 0.566; 0.402: 0.216; 0.094 and 0,042 w%, The specimens were c o l d drawn w i r e s w i t h 1 mm dkameter. The measurements of t h e i,f.
were c a r r i e d out i n an i n v e r t e d Ke pendulum i n t h e t e m p e r a t u r e r a n g e of 20 t o 640°C, u s i n g a h e a t i n g r a t e of a b o u t 2.5 Ii/min.
2. R e s u l t s and D i s c u s s i o n
TdIost of t h e i , f . d a t a were measured on as r e c e i v e d / c o l d drawn/
w i r e s and a l l r e s u l t s showed common f e a t u r e s / ~ i g . l / t h e damping a t R!P i s c o n s i d e r a b l y high, background r a i s e s a t r e l a t i v e l y low t e m p e r a t u r e s /from a b o u t 10o°C/ and sometimes i t a r r i v e s a t a q u i t e h i g h /2
-
3000 x 10-4/ v a l u e too, The damping d e c r e a s e s from t h i s v a l u e i n t h e range of 250-
3500C and t h e r e a f t e r i n c r e a s e s , Between 450 and 5 5 0 ~ ~ i t d e c r e a s e s a g a i n and t h e n r a i s e s f u r t h e r . T h i s l a s t p a r t of t h e s p e c t r a can d i f f e r v e r y much f o r t h e d i f f e r e n t samples.The above mentioned p e a k s a r e n o t accompanied by an i n f l e x i o n i n t h e dynamic modulus t h e r e f o r e t h e y cannot have a r e l a x a t i o n c h a r a c t e r . But i n t h e c a s e of t h e lower t e m p e r a t u r e peak t h e dynamic modulus i n c r e a s e s a t t h e peak t e m p e r a t u r e r a p i d l y , i t can jump up t o t h e doubled v a l u e , I n t h e c a s e of t h e h i g h t e m p e r a t u r e peak t h e modulus change i s s i m i l a r b u t t h e amount of i n c r e a s e i s s m a l l e r and sometimes t h i s r a i s e can be observed from E, change i n t h e s l o p e of t h e decreas- i n g modulus curve, During a subsequent c o o l i n g t h e above behaviour cannot be observed, t h e damping d e c r e a s e s and t h e modulus i n c r e a s e s monotonously over t h e t e m p e r a t u r e r a n g e of t h e above peaks.
The m i c r o h a r a n e s s of samples h a v i n g h i g h e r C r c o n t e n t was measured a t room t e m p e r a t u r e a f t e r h a v i n g h e a t e d up a dozen of specimens w i t h t h e h e a t i n g r a t e used b e f o r e and t a k i n g o u t a specimen e v e r y 6
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20 Ii.Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983938
JOURNAL DE PHYSIQUE
Fig, 1
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I n t e r n a l f r i c t i o n and modulusdata f o r two as r e c e i v e d & C r samples
A decrease of t h e microhardness by 10% w a s found i n t h e temperature range of t h e h i g h e r temperature peak /560
-
580°C f o r ccr == 0.73 wt$ a n d 520
-
540°C f o r ccr = 0.56 nt%/.I n accordance w i t h m e t a l l u r g i c a l s t u d i e s
117
and w i t h our previous r e s u l t s [2] t h e above c h a r a c t e r i s t i c s of t h e s p e c t r a f o r t h e G C r system can be a t t r i b u t e d t o primary and secondary r e c r y s t a l l i z a t i o n /Pig.2/. These changes t a k e p l a c e i n a r e l a t i v e l y narrow /20-30 I</'Trecr
( * a AlMn
, ,
600
Pig. 2
-
Concentration dependence of t h e tem- p e r a t u r e range of400 primary and secondary
r e c r y s t a l l i z a t i o n .
O AlCr as received
200 f
a2 0.4 0.6 0.8 l.o(wt
temperature range a t t h e given h e a t i n g r a t e , however, tne s c a t t e r of t h e d a t a can be r a t h e r h i g h e s p e c i a l l y i n t h e samples of lov? concen- t r a t i o n s , I n s p i t e of this s c a t t e r i n g a d e f i n i t e i n c r e a s e of t h e re-
c r y s t a l l i z a t i o n temperature can be seen
w i t h i n c r e a s i n g C r content, The presence of C r up t o t h e s o l u b i l i t y
limit raises the recrystallization temperature /Tr/ by about 100
K.
Comparing the present results with those gained on uvh, we can con- clude that also here two pseudo peaks appear accompanied by a modu- lus increase. The difference in the properties of the two systems is that a decrease in hardness vras found near the lower temperature peak for but around the higher temperature peak for AlCr. It can be supposed that for both systems a decrease in the hardness occurs around both peaks but the ratio of this decrease can considerably be different. The scatter in the recrystallization temperatures was higher in the case of the LlCr samples. Both recrystallization tem- peratures are lower in the G C r thax in the evIn alloys for the same concentrations, This is in accordance with the well know^ fact that Bra is more effective in raising the recrystallization temperature
than Cr. It is especially true considenin the fact that the solubili- ty limit for h h is more than 505 higher 71, 33
.
In AlILTn alloys the primary and secondary recrystallization temperature raised by 250 and 150 K, respectively, for a Ivh content near the solubility limit.In order to study the effect of precipitates on the recrystalliza- tion process
[4,
51 a number of wires containing TvZn or Cr near the solubility limit were homogenized at 640°C for 2 h and precipitated at different temperatures. The samples then were cold drawn from 1 mm diameter to 0.9 mm and the i.f. and modulus were determined as described above /Pig, 3/,Pig. 3
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T~Iodulus and damping data of precipitated and then cold drawn @%I and&Cr samples
In the case of samples with 0.85, 1.12 and 1.20 wt% XTn we found a decrease of background and an increase of modulus, with respect t.o recrystallization. No second peak was observed. The recrystallization temperature in the two alloys with higher IsTn content depends on the temperature of precipitation. The recrystallization temperatures are approximately the same for the homogenized samples and for the Sam- ples precipitated below
C9-282 JOURNAL DE PHYSIQUE
4 0 0 ~ ~ .
On the contrary this q!~~n?i;it;. czn b 50-
80 K lower for sam- ples precipitated between 500 and 6000C. The effect of precipitates on recrystallizat&on is the highest for 1.12% Mn con- tent after precipitation at 570 C /~ig.4/ and for 1.20% P12n content after precipitation in the tenperature range 530-
550 OC.S Pig.4
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Dependence of the.I_..
*recrystallization tempera- ture on the temperature of pr-ecfpitetion belore cold
4 di3avring for A1
-
1-12 v~t%IkI.
400 500 600 TPip K)
The effect of the duration of precipitation at 570°c was also inves- tigated on B1/1.12/lin alloys. The recrystallization temperature of samples precipitated for 10 min vras close to the value for homogeni- zed condition as it was expected, But for 35
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120 min precipitation times it decreased by 20°C and after precipitation for 9-
20 h therecrystallization temperature decreased to 430
-
420°C,It is to be noted that in the case of the alloy with the lowest X i content and for G C r alloys with 0.75 and 0.56 Cr contentsno enhan- cement effect was found, Thus recrystallization temperature was in- dependent from the temperature of precipitation although the scatter in the measured data vias considerably higher and the temperature of the decrease of damping could differ about 30 K from the temperature of the modulus increase, In the QCr samples here there is a higher peak too accompanied by a very high modulus increase. The temperature of this peak lies at about 580
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6000C for 0.56 wt% Cr, and it raises from 500 to 600°C for 0.73 at% Cr if the precipitation temperature is raised from 400 to 6000Cs It is worth noting that the recrystalliza- tion temperature of the precipitated samples lies much higher than for the as received ones.References
h]
FJONDOLFO L, F,,
Aluminium Alloys: Strncture an Properties, Butter- worths, London-Boston /1976/,p]
KISS S., KEDVES F.J., HAWGOZ~ I,Z., J. Physique Colloque C5, Suppl4ment a u PTo10,g
/1981/ C5-963.p]
ALTEIIPOHL D., Aluminium und Aluminiumlegierungen, Springer-Verlag, Berlin, Gijttingen, Heidelberg, New York /1965/.ITES S., EP,lBURY J.D,, Z, fiir IfIetallkde 66 /1975/ 589.
GOEL D,B., mRRER P,, YJARLIIvIOIIT H,, ~1'i;iliiinium
