The effects of mixing and Cu particle size on the tensile strength of sintered Fe-Cu were investigated. The copper content was kept constant as 8%. The tensile specimens were prepared by usual powder metallurgy techniques. The compacts were pressure of 4t/㎠ and sintered at 1120 ℃ in hydrogen atmosphere. After sintering the specimens were cooled to room temperature at about 50 ℃/min.
Hoeganaes NC 100.24 iron powder and an electrolytic copper powder were used. Well mixed and poorly mixed specimens were prepared by mixing the iron powder with copper powder of -200 + 270 mesh size for 60 and 1 minute, respectively. Casual observation did not reveal any difference in the degree of mixedness between the two types of specimens, but when observed under the microscope the poorly mixed compacts showed regions of larger copper clusters. When the specimen compacts were sintered for various times from 0 to 180 minutes, the tensile strengths of both types of specimens increased rapidly with sintering time initially and after 180 minutes of sintering it appeared that the maximum strength was almost reached. The strength of the well mixed specimen was about 5-10% higher than the poorly mixed specimens at various stages of sintering. The lower strength of the poorly mixed specimens is attributed to the lower degree of interdiffusion between copper and iron and to the larger pores created by clusters of copper particles.
To investigate the effect of copper powder size, Fe-Cu compacts containing copper powders of -200 +270, -325 +400, and -400 mesh size were prepared. The observed tensile strength of the specimens sintered for various times from 0 to 180 minutes showed very little variation with the size of the copper powder used.
