358
Y. Liu et al. / Journal of Alloys and Compounds 693 (2017) 357e365
More information about the crystal structure of the binary phases is
shown in Table 1.
2.2. The AleSieZr ternary system
ꢀ
The isothermal section at 400, 500 and 525 C of the AleSieZr
ternary phase diagram were reported by Drits et al. [32], however,
the knowledge is limited to the Al-rich part containing up to
1.73 at.% Si and 0.17 at.% Zr. The equilibrium phases in AleSieZr
ternary alloys containing up to 60 at.% Zr were determined at
ꢀ
7
00 C by Raman and Schubert [17]. Schob and Nowotny [16]
studied the isothermal sections of the AleSieZr system between
ꢀ
5
50 and 1200 C, the sole complete isothermal section was repli-
cated in Fig. 2. By analyzing microstructure and composition of
binary and ternary intermetallic compound formed in ternary
diffusion couples of Zr and AleSi eutectic alloy, the Zr-rich corner of
the isothermal sections was constructed tentatively by Jain and
Gupta [18]. Later on, Hirano et al. [19] determined the phase
equilibria of the AleSieZr ternary system based on the CALPHAD
method. The phase diagram contains three ternary compounds,
denoted as
range 7.5e10 at.% Si and 25 at.% Zr, appears in all of the experi-
mental temperatures. The second ternary phase occurring at
0e12.5 at.% Al and 50 at.% Zr has been reported by Schob et al. [16]
1 2 3 1
t , t and t . The t phase, with its composition in the
t
2
1
ꢀ
at 1200 C. The
t
2
phase was observed in the interface of Zr/AleSi
ꢀ
diffusion annealed at 900 C and above, while it disappeared when
the annealing temperature was 700 C and 800 C. Meanwhile, this
phase was not reported in the isothermal section at 700 C [17].
ꢀ
ꢀ
ꢀ
According to XRD analysis,
modification of ZrSi (CrB-type), which is stabilized at lower tem-
peratures by substitution of Al for Si [16]. A ternary phase with
was included in the isothermal section at
phase
2
t is the binary high-temperature
t
3
the composition Al
4
Zr
3
Si
5
ꢀ
700 and 900 C reported by Raman and Schubert [17]. The
t
3
was proposed to form by a ternary peritectic reaction, L þ ZrSiþ
t
1
ꢀ
4t
3
. This phase was reported to be unstable above 900 C in the
diffusion couple analyzing, and was proposed to be unstable above
ꢀ
9
50 C by Harmelin et al. [33] in their assessment of the ternary
phase diagram of the AleSieZr system. Another two phases,
denoted as Zr Al0.5Si0.5 and ZrAl0.5Si0.5, was reported by XRD
analyzing of annealed alloys. In particular, Zr Al0.5Si0.5 is not a
ternary phase, but solid solutions (Al,Si)Zr extending from binary
SiZr . The ZrAl0.5Si0.5 phase has the same structure with , which
2
2
2
2
t
2
ꢀ
ꢀ
exists at 1200 C [16] as well as 700 C [7]. The phases have
different designations in different references, more detailed infor-
mation on crystallographic data of phases in the AleSieZr system
has been listed in Table 2.
3. Experimental procedure
More than 70 alloy samples were prepared to study the 700 and
ꢀ
9
00 C isothermal sections of the AleSieZr ternary system. Purity
of the raw materials, i.e. Zr columns, and Al and Si particles, was
9.99 wt%. The mixture of raw materials (10 g in total for each
Fig. 1. Binary phase diagrams constituting the AleSieZr ternary system. (a) AleSi
system [22], (b) AleZr system [28], (c) SieZr system [29].
9
sample), with the weight of each constituent precisely measures,
was melted under argon atmosphere using a non-consumable
tungsten electrode. The ingots were repeated three times to
improve their homogeneity. Buttons with weight loss under 1%
after melting were conducted with the following thermal treat-
ment. Plate specimen cut from the button ingots was put into
corundum crucible and then sealed in an evacuated quartz tube
under an argon gas atmosphere. The quartz tube samples were
Al
the system. Their homogeneity ranges are quite restricted. Except
Al Zr and Al Zr , all the other phases are stable at both 700 and
00 C.
The SieZr binary system [29] shown in Fig. 1(c) has seven
3 2 4 5 3 4 3 5 2 3 2 3
Zr , Al Zr , Al Zr , Al Zr , Al Zr , AlZr and AlZr , are reported in
4
5
ꢀ
3
5
9
intermetallic compounds, i.e. Si
and SiZr
except the Si
transformations
4
Zr
5
, SiZr, Si
2
Zr
3
, Si
2
Zr, Si
3
Zr
5
, SiZr
2
ꢀ
ꢀ
placed in the annealing furnace and kept at 700 and 900 C for 30
days, respectively, followed by quenching in water to preserve the
equilibrium state at the annealing temperature.
3
. These intermetallics are stable at both 700 and 900
Zr phase. SiZr and Si Zr
SiZr / SiZr and Si Zr
C
3
5
a
4
5
compounds undergo
Si Zr respectively.
b
a
4
5
/
b
4
5
All the annealed samples were divided into two parts, one part