Investigation into the Microstructure and Mechanical Properties in Submicrovolumes of LS591-A Brass

摘要

The microstructure and mechanical properties in submicrovolumes of lead brass of the LS59-1A brand are studied. Metallographic analysis of the structure of the samples under study is performed using scanning electron microscopy (EDS). It is revealed that globular inclusions of free lead (1-2 vol %), which are localized along grain boundaries in interdendritic regions, are also contained in the microstructure of LS59-1A brass along with main phases (the alpha solid solution of alloying elements in copper and beta phase-a solid solution based on the CuZn electronic compound). In addition, exogenous CuO + ZnO nonmetallic inclusions and pores are revealed in the microstructure. Oxide inclusions and iron and manganese-containing compounds are localized along the interfaces of alpha and beta phases. Hardness and Young modulus of alpha and beta phases are measured by the nanoindentation method. An insignificant difference between the values of H for dendrites of the alpha phase and the interdendritic space of the beta phase is found, which evidences a high degree of homogeneity of mechanical properties of the LS59-1A ingot. A calculation of the additional pressure appearing at the boundary of alpha and beta phases when material is loaded by an external force due to the difference of Young moduli showed that it is 23-fold higher than the external force, which can be the cause of fracturing the LS59-1A ingots during mechanical treatment. These results are discussed from standpoints of modern notions on the metallographic quality-control method of brass ingots in manufacturing conditions.