there are some eutectoid and peritectoid transformations in this area. Phase χ
decomposes into β - and γ
1
-phases at 963°C. Eutectoid concentration corresponds to
15.4 wt. % Al. γ
1
-phase decomposes by eutectoid reaction on β- and γ
2
-phases at
780°C. γ -phase is formed by a peritectoid reaction at 873°C. It is assumed that in γ
2
-
phase there is a phase transformation in the range of temperatures 400 ... 700°C with
aluminum content at the eutectoid point of 11.8 ... 11.9% by weight. It is assumed in
the concentration range 9-16 wt. % Al, another stable phase χ or α
2
existence, which is
formed by the eutectoid reaction at 363°C and aluminum content at eutectoid point
≈11.2% by weight. Concentration limits of this phase homogeneity region are not
established.
Hence, Cu-Al diagram corner corresponds to the region of solid solution existence
up to 9.4 wt. % Al at 565°C. That is why aluminum bronzes containing Al up to the
specified value are single-phase [17, 18] and belong to tin-free pressure-worked
bronzes according to GOST 18175 [19]. Transition over the given concentration limits
causes formation in the final structure of copper - aluminum bronze eutectic structure,
which is an effective reinforcing structural component. In this case, products
processing by deformation become inappropriate. Such alloys belong to the group of
foundry bronzes according to GOST 493 [4]. In particular, studied in this work bronze
BrA9Zh3L belongs to this class.
Chemical composition of tin-free bronze BrA9Zh3L, subordinated to the
requirements of GOST 493 [4], is given in Table 2.1. Table 2.1 analysis indicates that
the main components of bronze BrA9Zh3L, in addition to copper and aluminum,
include iron in amount of 2.0 ... 4.0 wt. %.
Table 2.1 Chemical composition of tin-free bronze BrA9Zh3L per GOST 493
Grade
Chemical composition, wt. %
Main components
Impurities, no more
Al
Fe
Cu
As
Sb
Sn
Si
Ni
Pb
P
Zn
Mn Total
BrA9Zh3L 8,0- 10,5 2,0 - 4,0 Rest 0,05 0,05 0,2
0,2
1,0
0,1
0,1
1,0
0,5
2,7
Source: borrowed by the authors according to source [4]
Cu-Fe. Concentration 2.0 ... 4.0 wt. % Fe (see Table 2.1) dealt with the fact that
in the binary system Cu-Fe in ε-Cu solid solution at the temperature of peritectic
equilibrium (1083°C) solves to 4.0 wt. % iron [12-15]. In Cu-Fe system two peritectic
and one eutectic transformation at temperatures 1480, 1094 and 850°C,
correspondently, have been established. Iron solubility in copper at 1025; 900; 800 and
700°C is 2.5; 1.5; 0.9; 0.5 wt. % Fe, respectively. Period of copper solid solution with
2,39 wt. % Fe is 0,3609 nm. α-Fe lattice (BCC) parameter increases from 0,28662 ±
0,00002 to 0,28682 nm with 0,38 wt. % Cu added.
Cu-Fe diagram [12-15] analysis shows that in this case, these two chemical
elements do not have chemical interaction with chemical compounds formation.
- 1810 -