Effects of different sintering temperature and sintering time on the relative density of the sintered compacts were studied to obtain the optimal sintering parameters for the fabrication of NbC patti culate reinforced iron-base compos ire. With optimal sintering temperature of 1280℃ and sintering time of 80min, wear-resisting, high density NbC particulate reinforced iron-base composites can be obtained using warm compaction powder metallurgy. The microstructure, relative density, mechanical properties and tribologieal behaviors of the sintered composites were studied. The results indicate that the mechanical properties of the sintered compacts were closely related to the sintered density. The iron base composite materials with different combinations of mechanical properties and tribological behaviors were developed for different applications. One of the developed composite, which contains 10% NbC, possesses a high strength of 815MPa with a remarkable friction and wear behaviors. The other developed composite, which contains 15% NbC, possesses a lesser strength of 515 MPa but with exeeUent friction and wear behaviors.

he fine NbC particles are embedded on the surface of iron particles and evenly distributed in the mixed powders. Warm compaction was used not only to increase the green density but also to improve the formability of the mixed powder and to improve the compact's green strength to facilitate handling. The influences of fabrication parameters such as ball milling time, annealing temperature and time, warm compaction temperature, sintering temperature and sintering time were studied. Compacts with a relative sintered density of 97% and a tensile strength of more than 800MPa can he obtained by using a ball milling time of 5h, an annealing temperature of 800℃, a compaction pressure of 600MPa, warm compaction temperatore of 120℃, sintering temperature of 1 280℃, and sintering time of 80min. The shrinkage at this sintering condition was approximately 4.3%.

Die wall lubrication was applied on warm compaction powder metallurgy in the hope to reduce the concentration level of the admixed lubricant, since lubricant is harmful to the mechanical properties of the sintered material. Iron-based samples were prepared by die wall lubricated warm compaction at 135 and 175℃, using polytetrafluoroethylene (PTFE) emulsion as the die wall lubricant. Compacting pressures of 700 and 550MPa were used. An admixed lubricant concentration ranging from 0 to 0.6wt.% was used in this study. The results show that in addition to a decrease in ejection forces, the green density of the compacts increased linearly with the decrease in the admixed lubricant content. The mechanical properties of the sintered compacts increase sharply when the admixed lubricant concentration was reduced to 0.125wt.% or less, No scoring was observed in all of the experiments.

Iron-based powder metallurgy material was prepared by warm compaction at 125℃ using a compacting pressure of 700MPa. Sintering temperature ranging from 1100℃ to 1300℃ and sintering time ranging from 40min to 80min were used to study the effects of sintering parameters on the compacts. Die wall lubrication polytetrafluoroethylene (PTFE) emulsion was also applied in combination with warm compaction in hope to increase the compact density and the mechanical properties of the sintered material. Green and sintered density, spring back effect and sinter shrinkage were measured. Mechanical properties of both as-sinter and heat treated samples were also measured. Results show that mechanical properties of the sintered compacts increase with the increase of sintering temperature and sintering time. Sample prepared by die wall lubricated warm compaction always shows higher density and mechanical properties.

AZ31 Mg alloy was prepared through equal channel angular pressing (ECAP) by Bc route in two different dies, in which the intersecting angles between channels are 90