Research of microstructure and mechanical properties in LS59-1A brass submicrovolumes

Abstract

The study covers the microstructure and mechanical properties in submicrovolumes of LS59-1A lead brass. Scanning electron microscopy (EDS) was used for metallographic analysis of the studied sample microstructures. It was found that the LS 59-1A brass microstructure along with the main phases ( α phase — solid solution of alloying elements in copper and β phase — solid solution based on the CuZn electronic compound) also contains globular inclusions of free lead (1—2 vol.%) localized on grain boundaries and in interdendritic regions. In addition, exogenous nonmetallic inclusions of CuO + ZnO and pores were found in the microstructure. Oxide inclusions and compounds containing iron and manganese are localized at the boundaries of α and β phases. A nanoindentation method was used to study hardness ( Н ) and Young’ modulus of α and β phases. An insignificant difference was found between H values for a phase dendrites with respect to the β phase interdendritic space indicating higher homogeneity of LS59-1A ingot mechanical properties. Calculation of additional pressure that occurs at the interface of a and β phases when external force is applied to the material due to a difference in Young’s moduli showed that it is 23 times higher than external force, which can cause destruction of LS59-1A brass ingots during machining. The results obtained are discussed from the standpoint of modern ideas about the metallographic method used to control brass ingot quality under industrial production conditions.