Shock consolidation of a rapidly solidified steel powder

Abstract

Rapidly solidified AISI 9310 steel powders were consolidated by shock waves produced from the impact of high velocity flyers. Dependence of the microhardness and the ultimate tensile strength of the compacts on the initial shock pressure (from 3.6 to 17.9 GPa) and the maximum shock pressure (from 6 to 37 GPa) was measured for an initial powder density 0.6 of the bulk density and a shock duration of 2–3 s. Photomicrographs and SEM fractographs were used to study the interparticle bonding in the compacts. Results show that for initial shock pressures below 4 GPa, the compacts have negligible strength. However, above this threshold the strength of the compact rises rapidly until a maximum value of 1.3 ± 0.1 GPa is reached for an initial shock pressure of 12.4 GPa. The strength then remains constant before decreasing at the highest initial shock pressure. In marked contrast, with increasing shock pressure, the diamond pyramid hardness increases very gradually from a value of about 340 for the powder to about 500 at the highest shock pressure. The maximum strength obtained correlates reasonably well with the strength-expected from microhardness measurements.