Titanium and 1ts Alloys

7/27/2019 Titanium and 1ts Alloys

1/5

TITANIUM AND 1TS ALLOYS

P R O P E R T I E S A N D H E A T T R E A T M E N TTi - Fe - At ALL OYS

V . N . M o f s e e v

O F T i - F e A N D

U D C 6 2 0 . 1 7 : 6 2 1 . 7 8 : 6 6 9 . 2 9 5 ' 7 h 5 4 6 . 7 2

We inves t igat ed bina ry al loys of the Ti- Fe sys tem containing 0.5, 2, 4, 9, 12, and 15 Fe and alsoTi- Fe al loys with 3 At. The al loys were prep are d from t i tanium sponge (Vb=38 kg/mm2), elec trol yt iciron, and A-00 aluminum. The al loys were melt ed in a vacuum arc furnace with consumable elec tro desand poured in ingots 120 mm in diameter weighing about 6 kg.

The chemi cal comp osit io n of the ingots is given in Table 1.Rods 12 mm in diam eter were p repa red from the ingots . The ini t ia l forging temp era t ure s were in

the ]3-region (1050~ and the finishing tem per atu res in the a + l?-reg ion (800-750~ with defor mation atlea st 50 at te mp er at ur es below the c+ + fi-.~fl tra ns fo rma tio n. Alloy s of titan ium with 12 and 15 F e with andwithout aluminum fractured in the grain boundaries during hot working.

The bri t t len ess of these al loys containing a large amount of i ron is ev idently due to eutectoid dec om-posi t ion. The mechanica l prop ert i es in tens ion were de termin ed wi th Gagarin samples pr epare d from therods 12 mm in diam eter . Hig h- temp era tur e heat t rea tmen ts were conducted on the blanks (annealing and

, kg F . . . . v- -~ - .. . . . -+ +/ram+ / / ~ .... ' - -I i ' - ' ~ z , g -~ : ~% I

: > f f ) / / / z I I \ \ [5 8 I J ~ - i - - |

+e ~- - . -+- - - - - - - - 4 - -~

o,5 o 7 t? F eFig. 1. Variat ion of mec han i-ca l propert ies wi th i ron con-tent of Ti - Fe and Ti - Fe- AIalloys annealed at 800 (1) and900~ (2). @- -@) Ti- Fe ;e - - o ) r i - F e - A I .

quenching), and aging on the finished samples. The har dne ss was mea-sured on pol i shed micros ec t ion s of the rods 12 mm in diameter .

Figure 1 shows the variat ion of the mechanical propert ies withthe iron content for the annealed Ti- Fe and Ti -F e- Al al loys. Theallo ys were an nealed 1 h at 800 and 900~ and cooled in the furnace atthe rate of 2-4 deg/min.

With increas ing i ron concent ra t ions the s t rength increases andthe plas t ici t y dec rea ses . Alloys with 3 AI have a higher strength thanthe binary Ti -F e a l loys .

An incr ease of annealing tem per atu re fr om 800 to 900~ is ac-companied by sl ight changes in the stren gth and plas t ici ty of the T i- Feand Ti - Fe- AI a l loys .

The mechan ical pro per t ies of the al loys after water quenchingfro m 700-1000~ with holding 1 h, are shown in Fig. 2. In the Ti- Fe

T A B L EC o m p o s i t i o nI n g o t N o . Fe AZ

1 0 , 5 62 2 , 1 0 - -3 4 , 0 0 - -4 8 , 8 0 - -5 1 1 , 2 3 - -6 1 5 , 6 0 - -7 0 , 5 6 2 , 8 78 2 , 0 6 2 , 9 29 4 , 0 0 2 , 9 110 8,55 2 8811 11,15 2 7512 14.65 2,99

N o t e : T h e i m p u r i t i e s w e r e 0 . 0 4 - 0 . 0 6 S i ,0 . 0 3 - 0 . 0 4 C , 0 . 0 8 - 0 . 0 9 O ; a n d 0 . 0 1 -0 . 0 2 N .

Tra nsl ated fro m Metal lo vedenie i Ter mic hes kay a Obrabotka Metal lov, No. 5, pp. 2-7, May, 1969.

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b

7 0 o ,~ _ _l5 7 8 900 lOOO 00 800 900 1000 700

e f

_ ]

e

8 gOg

Quenching temperature

3,

d [

1 7 8 gO ~

F ig . 2 . M e c h a n ic a l p r o p e r t i e s o f T i - F e a n d T i - F e - A 1 a l lo y s i n r e -l a t i o n t o q u e n c h i n g t e m p e r a t u r e , a ) 0 .5 F e ; b ) 2 F e ; c ) 4 F e ;d ) 9 F e ; e ) 0 .5 F e + 3 A I ; f ) 2 F e + 3 A 1 ; g ) 4 F e + 3 A I ;h) 9 Fe + 3 At .

50'~0

S J:Z )100

65O03t;'ZOCO

a n d T t - F e - A I a l l o y s n o t q u e n c h e d t o /? - p ha s e (0 .5 a n d 2 .0 F e ) a n i n c r e a s e o f q u e n c h i n g t e m p e r a t u r e i nt h e ( ~ + f i - r e g [ o n i n d u c e s a s l i g h t i n c r e a s e o f t h e s t r e n g t h a n d d e c r e a s e o f p l a s t i c i t y , w h i c h i s d u e t o t h ef o r m a t io n o f m a r t e n s i t i c a ' - p h a s e .

A n i n c r e a s e o f t h e q u e n c h in g t e m p e r a t u r e i n t h e f i - r e g i o n i s a c c o m p a n i e d b y a r e d u c t i o n o f s tr e n g t ha n d p l a s t i c i ty a s t h e r e s u l t o f i n t e n s i v e g r o w t h o f m t c r o g r a i n s .I n a l l o y s w i t h 4 F e a n i n c r e a s e o f t h e q u e n c h in g t e m p e r a t u r e s h a r p l y r e d u c e s t h e p l a s t i c i ty , e v i d e n t -

l y d u e t o t h e f o r m a t i o n o f w - p h a s e i n a l l o y s o f t h e c r i t i c a l c o m p o s i t i o n , t . e . , i n a l l o y s w h e r e t h e m a r t e n s t -t ic t r a n s f o r m a t i o n t e m p e r a t u r e i s c l o s e t o r o o m t e m p e r a t u r e .

I n a l l o y s o f s u p e r c r i t i c a l c o m p o s i t i o n w i t h 9 F e t h e /3 - p h a se i s f i x e d b y w a t e r q u e n c h i n g a n d in t h ea l l o y w i t h a l u m i n u m a c e r t a i n q u a n ti t y o f w - p h a s e i s f i xe d i n q u e n c h in g f r o m h i g h t e m p e r a t u r e s . T h e a l l o y sw i t h 1 2 a n d 1 5 F e a r e b r i t t l e a f t e r q u e n c h i n g .

B y c o m p a r i s o n w it h t i t a n i u m a l lo y s c o n t a in i n g o t h e r 3 - s t a b i l i z in g e l e m e n t s , i n t h e T i - F e a n d T i - F e- A I a l l o y s t h e r e i s o n ly s l ig h t m a r t e n s [ t i c d e c o m p o s i t i o n o f t h e m e t a s t a b l e / p h a se u n d e r s t r e s s , w h i c h i sm a n i f e s t i n t h e g r e a t e r d i f f e r e n c e b e t w e e n t h e u l t i m a t e s t r e n g t h a n d y ie l d s t r e n g t h o f s a m p t e s q u e n c h e df r o m t he c r i t ic a l t e m p e r a t u r e .

A s l i g h t e f f e c t o f / ? -p h a s e d e c o m p o s i t i o n d u r i n g d e f o r m a t i o n o f t h e s a m p l e s w a s n o t e d o n l y in th e T i- 3 A 1 - 2 F e a l l o y q u e n c h e d f r o m 8 5 0~

T h e e f f e c t o f d i f f e r e n t q u e n c h i n g a n d a g i n g c o n d i t io n s o n t h e m e c h a n i c a l p r o p e r t i e s o f t h e a l l o y s w a sa l s o d e t e r m i n e d .

T h e s a m p l e s w e r e w a t e r q u e n c h e d f r o m t e m p e r a t u r e s 5 0~ b e l o w a n d a b o v e th e ( ~ + /3 :~- f i -r e g i o n , b u tn o t b e l o w 7 3 0 ~ ( F i g . 3 ) . T h e s a m p l e s w e r e a g e d a t 3 0 0 , 4 0 0 , 5 0 0 , a n d 60 0 ~ f o r 0 .2 5 , 1 , 4, 1 6 , a n d 6 4 hw i t h s u b s e q u e n t c o o l i n g in a i r .

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I r i g F r ~ I ~ l [ ] ] ] l l n023 83 O

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I J I I I II I H I I I II J l J l I I 1 1 1

I I I I I l ll l l ~[~ JJ l l l~ I I l l llU I IHI[ I J J F J

L . . . I ] l t l t l l l I l l lh , , ~ t ~ l [ l l l ~ I I [ l l

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F i g . 3 . E f f e c t o f q u e n c h i n g t e m p e r a t u r e a n d a g i n g c o n -d i t i o n s o n t h e h a r d n e s s o f T i - F e a n d T i - F e - A L a l -l o y s .

T h e h a r d n e s s o f t h e T i - F e a n d T i - F e - A I a l l o y s i n r e l a t i o n t o t h e q u e n c h i n g a n d a g i n g c o n d i t i o n s i ss h o w n i n F i g . 3 .

I n a l l o y s o f s u b c r i t i c a l c o m p o s i t i o n , c o n t a i n i n g u p t o 4 F e , t h e h a r d n e s s a f t e r q u e n c h i n g i s h i g h d u et o t h e p r e s e n c e o f t h e m a r t e n s i t i c ~ ' - p h a s e . S u b s e q u e n t a g i n g a t 3 0 0 - 6 0 0 ~ i s a c c o m p a n i e d b y c o n s i d e r a b l er e d u c t i o n o f t h e h a r d n e s s d u e t o t h e t r a n s f o r m a t i o n o f ~ ' - p h a s e t o t h e e q u i l i b r i u m ~ + f i - c o n d i t i o n , o r as l i g h t i n c r e a s e o f h a r d n e s s d u e t o p r e c i p i t a t i o n h a r d e n i n g .

I n a l l o y s o f s u p e r c r i t i c a l c o m p o s i t i o n , c o n t a i n i n g o v e r 4 F e , t h e s o f t m e t a s t a b l e f i - p h a s e i s f i x e db y q u e n c h i n g . S u b s e q u e n t a g i n g i s a c c o m p a n i e d b y i t s d e c o m p o s i t i o n a n d p r e c i p i t a t i o n h a r d e n i n g , c o a l -e s c e n c e o f t h e d i s p e r s e d p a r t i c l e s , a n d s o f t e n i n g , w h i c h i s m o s t n o t a b l e a t 5 0 0 a n d 6 0 0 ~

I n a l l o y s o f t h e c r i t i c a l c o m p o s i t i o n , c o n t a i n i n g a b o u t 4 F e , t h e ~ ' - , / 3 - , a n d w - p h a s e s m a y b e f i x e d ,d e p e n d i n g o n t h e q u e n c h i n g t e m p e r a t u r e a n d t h e a l u m i n u m c o n t e n t . T h e r e f o r e s u b s e q u e n t a g i n g m a y b ea c c o m p a n i e d b y a n i n c r e a s e o r d e c r e a s e o f h a r d n e s s .

F i g u r e 4 s h o w s t h e v a r i a t i o n o f t h e m e c h a n i c a l p r o p e r t i e s o f r o d s q u e n c h e d f r o m t e m p e r a t u r e s 5 0 ~b e l o w t h e ( ~ + / 3 ~ S - r e g i o n i n r e l a t i o n t o t h e a g i n g t e m p e r a t u r e ( 1 6 h ) .

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Ob

807060,5O40

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130120110 '100

880

kg/mm2a l loy 1 qu ~ns

120 'from 850~i g ~

lO0go

Alloy7 quenchedTrom 880~

800 100 400 900 600

MI@ 2 quench'edfrom 820~

~ ~

lloy queneied~rom 850~ / tts,r ~,

\\

Alloy [---- quenched [ 5g/ from 76 ~ 03i I\ 30\ 20

O03~20

.~gO OO 500 600 0 3r 400 5 g 600 309 ,~00 ggO ~Aging temperatureFig. 4. Effect of aging temp erat ure on the mechanical p ropertie s of

Ti - Fe and Ti -F e- AI alloys quenched from the ~ +/?-region.

1o

Fig. 5. Micr ost ruc tur e of Ti - Fe alloys after different heat trea tme nts ( 500). a) Ti + 2Fe quenc hed fro m 820~ 1 h, wate r; b) Ti + 2 Fe, quenche d fro m 920~ 1 h, wate r; c)Ti+ 4 Fe, quenche d fro m 790~ 1 h, wate r; d) Ti+4 Fe, quenched fro m 890~ t h,wa te r; e) Ti + 4 Fe, quench ed fr om 890~ 1 h, wat er, aged at 600~ 16 h.

338


5/5

o b , kg/mm 2~ 2 0 ~

/20 ~ ~ ' ~ - '

00 ~20 5508

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4,50 ~ P

o/J y 4, 9 72 0,5 2 4 , g re %a bF i g . 6 . V a r i a t i o n o f s h o r t - t e r m s t r e n g t h a t d i f f e r e n tt e m p e r a t u r e s w i t h t h e F e c o n t e n t o f T i - F e (a) a n dT i - F e - A I a l l o y s ( b). 9 A n n e a l e d; 9 8 )q u e n c h e d .

A s c a n be s e e n , t h e u l t i m a t e s t r e n g th o f T i - F e a nd T i - F e - A I a l lo y s i n t he t h e r m a l l y h a r d e n e d c o n -d i t io n i n c r e a s e s w i t h t h e F e c o n te n t . W i th 9% F e th e a ll o y s a r e e m b r i t t l e d a f t e r q u e n ch i n g a n d a g i n g . T h eu l t i m a t e s t r e n g t h i s h i g h e s t i n t h e a l lo y s a g e d a t t e m p e r a t u r e s a r o u n d 4 0 0 ~

M e t a l l o g r a p h i c e x a m i n a t i o n o f t h e a l lo y s s h o w e d t h a t t h e c h a r a c t e r o f t h e s t r u c t u r a l c h a n g e s i n r e l a -t i o n t o t h e c o m p o s i t i o n a n d h e a t t r e a t m e n t i s s i m i l a r t o t h a t in a l lo y s o f t i t a n i u m w i th o t h e r f i - s t a b i l i z i n ge l e m e n t s ( C r , M n , M o , e t c . ). A f t e r w a t e r q u en c h i n g f r o m th e ~ + f i - r e g i o n , t h e m i c r o s t r u c t u r e o f a l l o y so f s u b c r i t i c a l c o m p o s i t i o n c o n s i s t s o f a f i n e - g r a i n e d m i x t u r e o f ~ - , f l- , a n d a ' - p h a s e s ( F ig . 5 a ), w h i l e a f t e rq u e n c h i n g f r o m t h e / ? - re g i o n it c o n s i s t s o f l a r g e g r a i n s o f a ' - p h a s e i n t h e b o u n d a r i e s o f d e c o m p o s i n g f i -g r a i n s ( F i g . 5 b ) .

T h e m i c r o s t r u c t u r e o f a l l o y s o f s u p e r c r i t i c a l c o m p o s i t i o n q u e n c h e d f r o m t h e c~ + / ? - r e g i o n c o n s i s t s o fa f a i r l y f i n e m i x t u r e o f c~ + f i - p h a s e s ( F i g . 5 c ), w h i l e a f t e r q u e n c h i n g f r o m t h e f i - r e g i o n i t c o n s i s t s o f r e l a -t i v e l y l a r g e g r a i n s o f m e t a s t a b l e f l - p h a s e ( F i g . 5 d ).

S u b s e q u e n t a g i n g a t 3 0 0 - 60 0 ~ i n d u c e s n o s u b s t a n t i a l c h a n g e s i n t h e s t r u c t u r e o f t h e q u e n c h e d a ll o y so f s u b c r i t i c a l c o m p o s i t i o n , o r a l l o y s o f s u p e r c r i t i c a l c o m p o s i t i o n q u e n c h e d f r o m t h e c~ + f i - re g i o n .A g i n g of t h e a l lo y s o f s u p e r c r i t i c a l c o m p o s i t i o n q u e n c h ed f r o m t h e f i - r eg i o n is a c c o m p a n i e d b y d e c o m -

p o s i t i o n o f t h e f i - p h a se w it h t h e o c c u r r e n c e o f d i s p e r s e d p a r t i c l e s o f a - p h a s e , w h i c h is c l e a r l y v i s i b l e o nt h e m i c r o g r a p h s ( F ig . 5 e ).

T h e m e c h a n i c a l p r o p e r t i e s o f a n n e a l e d an d t h e r m a l l y h a r d e n e d T i - F e a nd T i - F e - A I a l l o y s w e r ed e t e r m i n e d a t 4 5 0 a n d 5 5 0~ i . e . , t e m p e r a t u r e s a t w h i c h t h e p r e c i p i t a t i o n h a r d e n i n g a l l o y s w e a k e n ( F ig . 6 ).In t h e b i n a r y T i - F e a l l o y s c o n t a i n i n g u p t o 9% F e th e s h o r t - t e r m s t r e n g t h a t 45 0 an d 5 5 0~ i s lo w b y c o m -p a r i s o n w i th t he s t r e n g t h at r o o m t e m p e r a t u r e . W i th i n c r e a s i n g F e c o n c e n t ra t i o n s i n t he T i - F e a l l o y s t h es h o r t - t e r m s t r e n g t h a t 45 0 a nd 55 00 C i n c r e a s e s .

I n t h e a ll o y w i t h 12% F e th e s h o r t - t e r m s t r e n g t h i n t h e t h e r m a l l y h a r d e n e d c o n d i t io n i n c r e a s e s s h a r p -l y a t 4 5 0 a n d 5 5 0~ T h e s h o r t - t e r m s t r e n g t h a t 5 5 0~ i s e v e n s o m e w h a t h i g h e r t h a n t h a t a t 4 5 0 ~P r o b a b l y t h i s i s d u e to t h e e u t e c t o i d d e c o m p o s i t i o n u n d e r s t r e s s i n t h e a l l o y w i t h 12% F e a t 4 50 ~a n d p a r t i c u l a r l y a t 5 5 0 ~

i n T i - F e a l l o y s w i t h 3 A I t h e s h o r t - t e r m s t r e n g t h i n t h e t h e r m a l l y h a r d e n e d c o n d i t i o n i s h i g h e r t h a ni n t h e b i n a r y T i - F e a l l o y s .

I n t h e a l l o y s w i t h 4 a n d 9 F e t h e s h o r t - t e r m s t r e n g t h a t 5 5 0 ~ i s a l s o h i g h e r t h a n a t 4 5 0 ~ C , w h i c h i sa l s o d u e t o t h e e u t e c t o i d d e c o m p o s i t i o n a t 5 5 0 ~

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Titanium and 1ts Alloys