Pressureless sintering curve and sintering activation energy of Fe-Co-Cu pre-alloyed powders

摘要

The kinetic characteristics of Fe-Co-Cu pre-alloyed powders in the pressureless sintering process have been investigated. The expansion ratio, linear shrinkage, densification rate and effect of heating rate on the sintering have been analyzed. Based on the classical Arrhenius curve, the sintering activation energy has been calculated. Results show that the samples have a smaller expansion ratio before contracting when the Fe content is higher, and the final linear shrinkage ratio is larger too. The sintering carries out more efficiently and the final linear shrinkage ratio is larger when the samples at a lower heating rate. In the initial and final stage of sintering, the Arrhenius curve is suitable for the Fe-Co-Cu pre-alloyed powders and diffusion is the main transport mechanism. At the initial stage of sintering the sintering activation energy of Fe25%-Co15%-Cu60% powder is 453.11 kJ/mol, Fe45%-Co15%-Cu40% powder is 638.28 kJ/mol and Fe65%-Co15%-Cu20% powder is 504.6 kJ/mol, respectively. At the final stage of sintering the sintering activation energy of Fe25%-Co15%-Cu60% powder is 31.17 kJ/mol, Fe45%-Co15%-Cu40% powder is 20.09 kJ/mol and Fe65%-Co15%-Cu20% powder is 35.13 kJ/mol, respectively. The sintering activation energy in the middle stage is dominated by not only one diffusion mechanism so it is not suitable for the Arrhenius curve.