The influence of small additives on the structure and properties of brass

Abstract

The paper is devoted to research of the modifiers influence on the structure and properties of complex alloyed brass with a composition 70Cu-13Zn-7Mn-5Al-2Fe-2Si-1Pb. Mischmetal, magnesium-cerium, iron-boron, iron-titanium, niobium ligatures were used as modifiers. Laboratory and industrial experiments have been carried out. The macrostructure and microstructure of the ingots have been studied. The greatest effect on grain refinement was obtained using a magnesium-cerium ligature. It was found that when the magnesium-cerium ligature was introduced, there were no intermetallic accumulations, the average size of which did not exceed 80 μm. In order to facilitate the alloying of the modifier into the melt, it was proposed to use a nickel-magnesium-cerium alloy, since a significant amount of a fine fraction is formed during its production. The use of nickel-magnesium-cerium ligature as a modifier for complex alloyed brass is one of the possible options for using its fine fraction. The ligature amount was varied within 0.01...0.20 % of the melt mass. The experiments results showed that if the modifier amount increases, the average grain size decreases by more than two times. In this case, the average grain size does not change if the modifier amount is more than 0.1 wt. %. The influence of the modifier amount on the mechanical properties of complex alloyed brass has been studied. It was found that there is an increase in the ultimate tensile strength and elongation if a modifier is introduced in an amount of up to 0.05 wt. %. The dependence of hardness on the amount of the introduced modifier is determined. It has been found that the higher the added modifier amount, the higher the alloy hardness. The amount of the modifier is determined as 0.04...0.06 wt. %. It provides an increase in the level of mechanical properties of complex alloyed brass. Micro X-ray spectral analysis of the brass was carried out. The elements distribution in the α-phase, (α+β')-phase and intermetallic compounds in the test and control ingots structure has been studied. It was found that when the modifier is introduced in an amount of 0.05 wt. %, copper and zinc are present in significant amounts in the alloy structure in the α-phase and (α+β')-phase, and iron, silicon and manganese are present in the intermetallic compound. Industrial experiments were carried out using a modifier in an amount of 0.06 wt. %. The microstructure of the ingots has been studied. It has been established that when a modifier is added into the melt, the average area of intermetallic compounds in the alloy structure is 361 μm². This is almost two times less than the average area of intermetallic compounds in the structure of the alloy without a modifier introducing into the melt, which is 676 μm². The addition of a nickel-magnesium-cerium ligature in an amount of 0.06 wt. % to a complex alloyed brass with a composition 70Cu-13Zn-7Mn-5Al-2Fe-2Si-1Pb provides effective grinding of intermetallic compounds and excludes the formation of their conglomerates.