The Influence Of The Microstructure And Properties Of Iron-based Powder Sintering, Small Addition Of Copper Nanoparticles

The sintering of powder metallurgy material and product is an important way of preparation and processing of new material currently. The sintering is a key segment of deciding the quality of powder metallurgy product. Because preparation and processing of new material requires sintering method strictly, corresponding new technology appears continuously. Nano technology has been advancing rapidly and its application broadening and deepening since 1990s. Nanometer order of powders has high surface activity and low melt point due to its size effect. The introduction of nano materials into powder metallurgy has been a important investigation field.In view of the abovementioned progresses, the effects of nano-copper powder addition to Fe-based powders on the sintering process and mechanical properties of the powder metallurgical parts have been investigated systemly in this study. The thermal stability of nano-copper powders was measured by heating the consolidified blank. With increasing temperature and prolonging cycle in the sintering process, the nano particles and their conglomerated micro particles resulting from weak attachment between nano particles each other grew up and the melt point of the resultant particles increased from 477℃of single nano-meter level of particle. It is a complex dynamic process of energy supplying, dimentional increasing and melt point climbing up due to decreasing of the surface energy towards balance in the system. Nano-copper particles almost melt at 900-960℃and were been sintered into big coarse grain materials at last. This is one impportant reason why Fe-based powders were mixed with nano-copper; this provided the experimental data to the investigation on the low temperature sintering at the range of temperature.In the following experiment,during milling the mixture with high energy on a milling machine, the surface activity of nano-copper particles. Then the milled mixed powders were consolidified and sintered. The copper particle on the boundaries of iron ones grew up due to the mechanism of melting and diffusion with temperature rising and during soaking. The nano-copper particles transformed into cells at the interfaces betweem Fe-based particles, this effectively united and promoted the mass transferring between ones.In the carbonization process at 960℃for 1 hours, the consolidified blanks resulting from Fe-based powders with addtion of 1.5 wt.% nano-copper powder after milling were sintered completely. This cancelled the high temperature sintering at 1120-1180℃and saved large quantity of energy.