Abstract
The anisotropies of mechanical strength and sound velocities in sintered Sr-ferrite compacted under a magnetic field were investigated by a bending test and an ultrasonic pulse method, respectively. The aim of this study was to clarify the effect of the orientation forming on the mechanical strength and the elastic modulus of the compact. The direction of the applied magnetic field was parallel to that of the compacting pressure. The magnetic field strength was 675 kA·m−1, while the green compact was 32 mm long, 7 mm wide and approximately 7 mm high. Compacting pressures of 50 MPa and 100 MPa were used and three different sintering temperatures were employed, namely 1200°C, 1225°C and 1250°C. The two directions of the applied sound waves were parallel to the direction of the magnetic field and the compacting pressure (Face A), and perpendicular to these directions (Face B). The directions of the applied bending load were same conditions to the sound waves.
The flexural strength of the orientated sintered compact was smaller than that of non-orientated one. The anisotropy of the longitudinal sound velocities was greatest in the orientated sintered compact; the maximum difference between the two velocities was about 8% for such samples. In addition, some anisotropy in the longitudinal sound velocities in the non-orientated sintered compact was detected. This is due to the fact that mechanical alignment of the magnetic particles occurred during the compacting process.
