Structural Factors Inducing Cracking of Brass Fittings

Abstract

Cu–Zn–Pb brasses are popular materials, from which numerous industrially and commercially used components are fabricated. These alloys are typically subjected to multiple-step processing—involving casting, extrusion, hot forming, and machining—which can introduce various defects to the final product. The present study focuses on the detailed characterization of the structure of a brass fitting—i.e., a pre-shaped medical gas valve, produced by hot die forging—and attempts to assess the factors beyond local cracking occurring during processing. The analyses involved characterization of plastic flow via optical microscopy, and investigations of the phenomena in the vicinity of the crack, for which we used scanning and transmission electron microscopy. Numerical simulation was implemented not only to characterize the plastic flow more in detail, but primarily to investigate the probability of the occurrence of cracking based on the presence of stress. Last, but not least, microhardness in specific locations of the fitting were examined. The results reveal that the cracking occurring in the location with the highest probability of the occurrence of defects was most likely induced by differences in the chemical composition; the location the crack in which developed exhibited local changes not only in chemical composition—which manifested as the presence of brittle precipitates—but also in beta phase depletion. Moreover, as a result of the presence of oxidic precipitates and the hard and brittle alpha phase, the vicinity of the crack exhibited an increase in microhardness, which contributed to local brittleness.

Effect of Rotary Swaging on Mechanical Behaviors of Axle Steel Rod

“…This could be induced and verified by the simulations above. In addition, it must be mentioned that the residual stress and texture formed in the RS of the bcc metal might also be influencing factors, as discussed in the research of Kocich and Charni et al [39][40][41]. The mutual effect of all these factors would change the fracture surface after swaging.…”

Machinable Leaded and Eco-Friendly Brass Alloys for High Performance Manufacturing Processes: A Critical Review

“…Kunčická et al further highlighted the importance of maintaining controlled manufacturing processes by studying the failure of CuZn40Pb2 brass fittings from a computational and experimental standpoint. They unveiled that an inhomogeneous temperature profile during the manufacturing process may produce residual stresses in the cooler regions and initiate undesired phase transformations which eventually lead to the manifestation of forming defects [53]. In another case, they investigated a hot-die forged component [53,54].…”

“…They unveiled that an inhomogeneous temperature profile during the manufacturing process may produce residual stresses in the cooler regions and initiate undesired phase transformations which eventually lead to the manifestation of forming defects [53]. In another case, they investigated a hot-die forged component [53,54]. There, failure originated from a region characterised by plastic flow instability and inhomogeneous stress distribution deeming the area prone to the generation of defects.…”