Conclusion on negative effects of zinc with certain concentration in alloy on
bronze BrA9Zh3L mechanical properties level has been confirmed by elongation (see
Figure 4.2, a) and the impact toughness (see Figure 4.2, b) dependences behavior.
Figures 4.2, a, b show sharp dropping in plasticity and impact toughness in the range
0,2 ... 0,6 wt. % of doping element concentrations (See Figure 4.2). When
concentration limit is exceeded by 0,6 wt. % Zn, both characteristics δ and KCU reach
almost zero values (see Figure 4.2, a, b). This means that bronze BrA9Zh3L
additionally doped with zinc reaches the brittle state at zinc concentrations lower (see
Figure 4.2), than this material characteristic becomes obvious according to tensile
testing results (see Figure 4.1).
Hence, in order to prevent the castings and foundry products brittleness, for
industrial practice bronze BrA9Zh3L doping with zinc should be used with zinc
amount not exceeded 0,2 wt.% against normatively [4] permitted concentration 1,0 wt.
% Zn.
In general, new technological solutions implementation of bronze BrA9Zh3L
effective structural formation allows in industrial practice to increase the yield of
conformed castings, reduce the failure of casting by cracks in 2 ... 8 times and provide
the stable high level of mechanical properties, which will improve the reliability and
durability of products.
CONCLUSION
Based on Cu-Al, Al-Fe, Cu-Fe, Cu-Al-Fe phase diagrams analysis, structure and
phase composition of bronze BrA9Zh3L have been observed. It has been established
that bronze structures with Zn ≤ 1% contents consist of structure-free α-Cu solid
solution crystals and eutectoid component, which basis forms on γ
2
+ α eutectoid of
Cu-Al system.
In addition, in bronze structure branched star-like small crystals of iron-containing
phase have been discovered. These star-like iron-containing crystals with 81,20 ...
82,79 wt. % Fe and 9,86 ... 10,39 wt. % Al have been identified as β
1
-phase, i.e. Fe
3
Al.
It has been found that the structure of bronze containing Zn> 1,0 wt. % consists
of α-Cu solid solution and multiphase eutectoid component. Additionally, continuous
amount of eutectic component (from 12,47% to 58,02%) in alloy structure rising with
Zn concentration increasing has been fixed.
It has been shown that homogeneity of α-Cu solid solution in Cu-Al-Fe-Zn system
extends to dissolve alloying elements total amount of almost 14,0 wt. %.
Essential difference of alloying elements Σ = Al + Fe + Zn (14,82 ... 17,92 wt.%)
total amount in eutectoid structural components, in which partial concentrations also
have a wide margins: 8,24 ... 2,72 wt. % Al; 0,88 ... 1,43 wt. % Fe; 3,40 ... 6,50 wt. %
Zn, has been established. Revealed fact is evidence that eutectoid component existed
- 1821 -