In general, analysis results clearly indicate that in investigated Cu-Al-Fe-Zn
system α-Cu solid solution homogeneity distributes to the total amount of dissolved
alloying elements up to 14,0 wt. % (13,91 wt. % - see Table 3.1). Table 3.2 data confirm
the fact of investigated alloys transition from single-phase structural state to structures
with eutectic component, starting with a total concentration of alloying components
greater than 14,0 wt. % (14,82 wt.% - see Table 3.2). Instead, eutectic component X-
ray local energy-dispersive data analysis (see Table 3.2) demonstrates significant
difference of alloying elements total amount Σ = Al + Fe + Zn (14.82 ... 17.92 wt. % -
see Table 3.2) in local zones of specified structural component. Elemental analyzes
(see Table 3.2) are characterized by the same inhomogeneous arrays of quantitative
indices: 8,24 ... 12,72 wt. % Al; 0,88 ... 1,43 wt. % Fe; 3,40 ... 6,50 wt. % Zn. This is
not abnormal for multicomponent system. In multicomponent systems (in particular
eutectoid in studied system Cu-Al-Fe-Zn) any component (e.g. Zn) in alloy varying,
the elemental and phase ratio at the temperature of multicomponent phase equilibrium
changes.
This state of affairs proves in favor of authors’ assumption [24] that structural
components in Figure 3.3 have not only different morphologies but also genesis of
origin. But the nature of electron microscopy contrast formation in secondary electrons
is such that it does not allow to clearly positioning of eutectic sites with different
morphologies according to specific sets of chemical elements. In addition, amount of
zinc poured into alloy (<5,0 wt. % – see Chapter 1) and its content fixed in local
microstructure volumes (see Table 2.3 – max. 0,68 wt. % and Table 3.1 – max 6,50 wt.
%) is significantly lower than the limit of its solubility in α-Cu solid solution (39 wt.
%) according to binary system Cu-Zn diagram [12-15]. Therefore, the final answer to
this question belongs to further researches.
4. Mechanical properties of industrial bronze BrA9Zh3L additionally doped
with zinc. Results of industrial bronze BrA9Zh3L additionally doped with zinc
mechanical properties study are graphically illustrated in Figures 4.1 and 4.2.
Effect of zinc (up to 4,0 wt. %) on bronze BrA9Zh3L strength properties studies
results (see Figure 4.1) show that when Zn content increasing, ultimate tensile strength
level monotonously decreases (see Figure 4.1, a).
But, at the same time, yield strength (see Figure 4.1, b) increases with zinc amount
in bronze increasing to 2,5 wt. %. Despite the fact that yield strength curve is extreme,
the difference between UTS and YS values with concentrations of zinc increasing,
continuously decreases, reaching the minimum at 4,0 wt. % zinc content (300 MPa
versus 290 MPa, respectively). Fact that characteristics of these properties with zinc
content 4,0 wt. % reach the minimal value and almost equalize, indicates that this
concentration of zinc causes absolute brittleness achievement of doped with Zn bronze
BrA9Zh3L.
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