atj from union carbide the mold was covered on a top surface thereof with a graphite cover plate the complete assembly of the buried zbc composite body was then placed into a closed atmosphere resistance heating furnace the atmosphere in the furnace was argon from matheson gas products inc the furnace was first evacuated at room temperature to a pressure of 1 u00d7 10 4 torr and thereafter backfilled with argon the furnace was then evacuated to a pressure of about 1 u00d7 10 2 torr and thereafter heated to a temperature of about 500 u00b0 c under vacuum the furnace was again backfilled with argon which then remained flowing at a rate of about one liter per minute and was maintained at a pressure of about 2 psi the furnace was heated to a temperature of about 1750 u00b0 c over a 6 hour period and then held at 1750 u00b0 c for about 12 hours the furnace was then cooled for about 6 hours after cooling the carburized zbc composite was removed from the furnace and any excess graphite powder was removed by grit blasting table 1 shows the mechanical properties of the zbc composite after the carburization treatment had been effected it is evident that the amount of residual zirconium parent metal was reduced from about 10 to about 1 2 by volume the hardness elastic modulus and shear modulus all increased however the increase occurred at the limited expense of flexural strength it is noted that a flexural strength of about 500 mpa is adequate for many aerospace applications table 1______________________________________ before after carburization carburization______________________________________zr content vol 9 9 0 5hardness 80 6 hra 81 9 hra 1011 hk 1388 hkelastic modulus gpa.