The Study Of The Effect Of Particle Size Distribution On The Microstructure And Performance Of Fe-Cu-C Sintered Parts

In recent years,the rapid development of automotive car market provides a wide range consμmer market for the development of powder metallurgy parts, and the yield of private cars can’t meet people’s demands, in the meantime, the consμmers put forward higher requirements for the performance of the gear parts. For powder metallurgy parts, the compaction density and sintered density play a very important effect on the performance of the material, which has a great impact on the service life and mechanical properties of the material. To the enterprise, how to improve powder metallurgy parts’ density with a low cost becomes a question that is worth considering, by which the performance can be improved at the same time and greater profits can be got by the enterprise. So the development of low cost, high density, high performance of Fe-based powder metallurgy materials has important social significance and economic benefits.The 1000 mesh gas atomized copper powder and 400 mesh, 800 mesh, 3000 mesh atomized iron powder are added to 200 mesh Fe-based powder, a series of experiment are carried out after sintered in the box type furnace. The effect of different particle ratios,different pressing force and different sintering temperatures on the samples’ properties is researched by the means of metallographic test, density, hardness, X ray diffraction analysis, SEM and TEM analysis. The conclusions are shown as follows:1. The experiments show that when the addition of 1000 mesh aerosolization copper powder is 3%, and the content of 800 mesh iron powder is 4%, the sintered parts performance is better than other parts.2. Through the microstructure of the specimen observation and analysis, a conclusion can be drawn out that the combination degree of particles is higher in the condition of 3%addition of atomized copper powder and 4% addition of 800 mesh iron powder, 600 MPa pressing force and 1150℃sintering temperature. Grain boundary presents the trigeminal grain boundaries and angle grain boundaries is 120 degree, which plays an important role for the structural stability of the materials; and in this condition spheroidizing level is higher, and the pores are mainly distributed at the junction of grain boundaries.3. In the experiment of different pressing force, the density and hardness present a similar variation. When the gas atomized copper powder adding amount is 3% and 800 mesh iron powder reach 4%, the density and hardness of the parts reached the maximμm;The results of different pressing force experiments show that at the pressing force of 600 MPa, the sintered specimens show a good density and hardness. In different temperature of sintering experiments, the density reaches 7.2g/cm3 when the samples are sintered at1150℃, but the hardness variation shows a different tendency with the density variation.4. The X ray diffraction and TEM experiments show that micron copper powder has been completely melting in iron-based powder body coarse interface or boundary corner,forming Fe4Cu3 with FCC structure; and the thickness of the interfacial layer is very uniform, leading to effective connectivity of the iron particles.5. SEM surface scanning and fracture morphology test results show that after sintered copper distributes like a network in iron matrix, which suggests that the pores of the matrix particles are filled by melting copper; Fracture analysis results show the fracture type of the specimen with atomization copper powder is a mixture of ductile fracture and brittle transgranular fracture.