This study investigates the interaction of picosecond laser pulses with sapphire and brass in air using scanning electron microscopy. A picosecond laser system operating at a wavelength of 785 nm, pulse width of 110 ps, and variable repetition rate (1–1000 Hz) was used in this study. The pulse width applied in this work was not widely investigated as it lies in the gap between ultrashort (femtosecond) and long (nanosecond) pulse width lasers. Different surface morphologies were identified using secondary electron and backscattered electron imaging of the ablated material. Thermal ablation effects were more dominant in brass than in sapphire. Exfoliation and fractures of sapphire were observed at high laser fluence. Compared with brass, multiple laser pulses were necessary to initiate ablation in sapphire due to its poor absorption to the incident laser wavelength. Ablation rate of sapphire was lower than that of brass due to the dissipation of a portion of the laser energy due to heating and fracturing of the surface.

Hot compression tests were carried out on the duplex α + β leaded brass CuZn39Pb3 in temperature range of 600–800 °C and at strain rates of 0.001–1 s−1. A self-consistent model was used to analyze the flow behavior of the constituents and the material. A linear viscoplastic model was used to relate the flow stress of β and α + β composite to strain rate and the corresponding viscosity parameters were calculated at various deformation conditions. Using the viscosity parameters of β and α + β and the volume fractions of the constituents, the viscosity parameter of α was calculated. The values of the viscosity-like parameters and strain rate sensitivity for β and α + β composite were calculated using the nonlinear powerlaw viscoplastic equation. The results showed that the flow stress of α calculated using the self-consistent model was considerably higher than that of β. The difference could be attributed to the lower Zn content in α. The flow stress of α + β composite was calculated using the law of mixture rule. The law of mixture modeling of α + β composite for the iso-strain condition resulted to the overestimation of flow stress. The difference between the experimental and predicted results was attribute to the strain partitioning between α and β.

The interaction of near infrared femtosecond laser pulses with a Cu based alloy (brass) in ambient air at atmospheric pressure and under different laser conditions was investigated. The effects of laser fluence and number of pulses on surface morphology and ablation rate were studied using scanning electron microscopy (SEM) and optical microscopy. Ablation rates were found to rapidly increase from 83 to 604 nm/pulse in the fluence range 1.14–12.21 J/cm2. At fluence >12.21 J/cm2, ablation rates increased slowly to a maximum (607 nm/pulse at 19.14 J/cm2), and then decreased at fluence higher than 20.47 J/cm2 to 564 nm/pulse at 24.89 J/cm2. Large amounts of ablated material in a form of agglomerated fine particles were observed around the ablation craters as the number of laser pulses and fluence increased. The study of surface morphology shows reduced thermal effects with femtosecond laser ablation in comparison to nanosecond laser ablation at low fluence.