Influence of mean grain size with ultrasonic velocity on microhardness of B4C–Fe–Ni composite

• B4C–Fe–Ni composites have been developed powder metallurgy and electroless plating technique.
• Ultrasound has been used for evaluating mechanical and physical properties samples.
• Hardness and compressive strength show a peak around 1000 °C due to changings in structure.
• Mean grain size have effects on velocity, attenuation, hardness and compressive strength.

Composite samples were produced from boron carbide, iron and nickel matrix powders by using a powder metallurgy and electroless plating technique. Prepared samples were sintered at the temperature of ranging from 800 °C–1200 °C under Ar shroud. Ultrasonic velocity, ultrasonic attenuation and rate of screen heights of peaks were determined according to the pulse-echo method by using 2 MHz and 4 MHz probes. SEM (Scanning Electron Microscope), compressive testing and hardness measurements were employed to characterize the properties of the samples. Ultrasonic velocity, ultrasonic attenuation and rate of screen heights of successive peaks have showed a linear relation with mean grain size of samples. The ultrasonic velocity has been correlated with the hardness and the compressive strength and sintering temperature. We see that the sharp decrease in the hardness and a rapid increase in the ultrasonic velocities versus sintering temperature are attributed to the increase in the amount of grain size.