Acoustic Assessment of Microstructural Deformation Mechanisms on a Cold Rolled Cu30Zn Brass

• Published in: Materials Vol. 17; no. 13; p. 3321
• Main Authors: Sosa, María, Carvajal, Linton, Salinas Barrera, Vicente, Lund, Fernando, Aguilar, Claudio, Castro Cerda, Felipe
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 04.07.2024
• Subjects: Acoustic measurement; Acoustic properties; Acoustics; Alloys; Aluminum; Banded structure; brass; Brass plating; Cold; Cold rolling; Deformation effects; Deformation mechanisms; Diamond pyramid hardness tests; Dislocation density; Edge dislocations; Grain size; Longitudinal waves; Mechanical twinning; Metal fatigue; Microstructural analysis; Microstructure; nonlinear parameter; nonlinear ultrasonic measurement; Optical microscopy; Parameters; Plastic deformation; Precipitation hardening; Propagation; Scanning electron microscopy; Second harmonic generation; Shear bands; Shear strain; Strain hardening; Tension tests; Thickness measurement; twinning; Ultrasonic imaging; Ultrasonic methods; Velocity; Wave diffraction; Wave velocity; twinning; nonlinear ultrasonic measurement; brass; nonlinear parameter; second harmonic generation; shear bands
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17133321

The relationship between acoustic parameters and the microstructure of a Cu30Zn brass plate subjected to plastic deformation was evaluated. The plate, previously annealed at 550 °C for 30 min, was cold rolled to reductions ranging from 10% to 70%. Linear ultrasonic measurements were performed on each of the nine specimens, corresponding to the nine different reductions, using the pulse-echo method to record the times of flight of longitudinal waves along the thickness axis. Subsequently, acoustic measurements were conducted to determine the nonlinear parameter β through second harmonic generation. Microstructural analysis, carried out by X-ray diffraction, Vickers hardness testing, and optical microscopy, revealed an increase in deformation twins, reaching a maximum at 40% thickness reduction. At higher deformations, the microstructure showed the generation and proliferation of shear bands, coinciding with a decrease in the twinning structure and an increase in dislocation density. The longitudinal wave velocity exhibited a 0.9% decrease at 20% deformation, attributed to dislocations and initial twin formation, followed by a continuous increase up to 2% beyond this point, resulting from the combined effects of twinning and shear banding. The nonlinear parameter β displayed a notable maximum, approximately one order of magnitude greater than its original value, at 40% deformation. This peak correlates with a roughly tenfold increase in twinning fault probability at the same deformation level.