Mechanical Properties of L1 2 Type Zn 3 Ti-Base Alloy
- PDF / 938,582 Bytes
- 7 Pages / 393.3 x 625.32 pts Page_size
- 85 Downloads / 218 Views
L1 2
Type Zn 3Ti-Base Alloy
Hideki Hosoda* and Shuji Hanada* Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan, [email protected]
ABSTRACT An alloy composed of L12-type Zn 3Ti was investigated in terms of phase stability and mechanical properties. Zn and Ti powders were mixed at a composition of Zn-25mol%Ti using a ball mill in Ar, and an ingot was made by melting the powders. Optical microscopy, X-ray diffraction analysis and thermogravimetry - differential thermal analysis were carried out. Mechanical properties were investigated by Vickers hardness tests at room temperature (RT) and compression tests from RT to 703K in Ar. It is found that (1) the alloy is mainly composed of L1 2 Zn 3Ti, (2) the alloy has weak positive temperature dependence of strength, and (3) normalized strength by melting point is comparable to that of L1 2 Al 3Ti-Cr alloys. L1 2 Zn3Ti has HV178 and is brittle at RT. Reaction temperatures of Zn-rich portion of the Zn-Ti phase diagram were also reinvestigated and a peritectic-reaction temperature between Zn 3Ti and liquid + Zn 2Ti is determined to be at 880K.
INTRODUCTION On the standpoint of high oxidation resistance and low density, transition metal trialuminides (TMTAs) are candidate to be high temperature structural materials. TMTAs exhibit good oxidation resistance and low density due to a large amount of Al. Moreover, the highest cohesion energy (322kJ/mol) of Al in nontransition metals [1] and strong interactions between unlike atoms [2] provide relatively high melting points to TMTAs. Table 1 shows crystal structures, melting or phase transformation temperatures (Tm) and densities (P0.4) of TMTAs. Table 1. Crystal structures, melting points and/or phase transition temperatures (Tm) and densities(p04) in transition metal trialuminides (TMTAs) represented in the periodic table.
group element
tru tu0re
T-7/K -----
element
IVA
VA
VIA
VIIA
Ti Sc 12........m.
V
C=r
Mn
lilA
13V3
-16"23
T2 SI1vlt~
structure
3
Zr .
D D0..
63 4
~
W Mo
...........
VillA Fe
2 143
3.5Y
Tc
D0•--------O.
73
~4.41 La
structure
DO, 9
-4.47 Hf
4.51 Ta
D022
DO 22
4.59 W
464 Re unkno
wn _T140
.553 3.6
R
Ru
----
.........•91953 3".......... .3 ............ f .......- ..''++' •m"+ .....•',•i" 1853 1253 .......•+T47 --T /'-K-_
element
i.
Co
4.2 Os
Ni
DO,, I7 3.62_
Pd
IB
1iB
Cu
Zn
3.175 38
Cd
A
-
--
X
-
.X
.. T . ."i'+ . . ; 3 . . • 4.7
Ir
D O,1
.8
Pt
.9
Au
-
wn . 7.04 7:7 7 6.93 6.80 te systemi hasother intermetallics than TMTAT "X":o comondsored. KK7.9.1 Mat. Res. Soc. Symp. Proc. Vol. 552 0 1999 Materials Research Society
50
Hi! X
These data except densities are shown in "Binary Alloy Phase Diagrams" by Massalski et al. [3]. Densities are calculated by assuming fcc and lattice constant of 0.4nm (actually 0.38-0.42nm in most fcc-based TMTAs [4]). It is clear in Table 1 that A13Ti and A13Nb are suitable in TMTAs on the balance of crystal structure, melting point and density in addition t
Data Loading...
