Preparation Of Fe-based Composite Materials By Liquid Sintering Technology

At first, the microstructure and the roasted products features of montmorillonite were studied. Then Al₂O₃ particles reinforced Fe-based composite materials were fabricated by powder metallurgical technology with the montmorillonite, Al powder and graphite powder as raw materials. The microstructure morphology of montmorillonite particles and the composite materials were observed by SEM; the phase composition of montmorillonite and the composite materials were analyzed by XRD; and the microstructure of montmorillonite was characterized at the atomic scale by HRTEM.The study of montmorillonite showed that the size of montmorillonite particles were in micron level, and the edge of montmorillonite particles appeared spine-like form. The particles were composed of many layers which were composed of subgrains with different orientation. The water which was adsorbed on the surface of montmorillonite particles and in the space between the layers lost in the temperature range of 25¹00℃, the water which has strong bindings with the ions in the space between the layers lost at 100℃ 700℃, and the hydroxywater lost at 700℃ 800℃. The structure of montmorillonite was destroyed after roasting at 800℃and appeared amorphous phase. With the roasting temperature increased, cristobalite, cordierite (Mg2Al4Si5O18) and other new phases generated, and the density and hardness of roasted products also increased. The hardness of the products after roasting at 1300℃reached to 1573.2HV.The study of preparation technology of the Fe-based composite materials showed that Al powder and montmorillonite can generate Al₂O₃ at high temperature. When the fabrication of Fe-based composite materials by particles addition method, the adding amount of powder which contain Al₂O₃ particle can not too much, otherwise, Al₂O₃ particles maybe segregated and the number of hole in the matrix would increased. So, the best adding amount of the powder should be controlled at about 10wt%. When the fabrication of Fe-based composite materials by in-situ method, the adding amount of Al powder can not too much, otherwise, the green body can not be sintered, the adding amount of Al powder should be controlled at less 2wt%. C Element can change the microstructure of Fe matrix and can increase its hardness. The hardness can increased from 168.7HV before C addition to 583.6HV after C addition. In this study, the optimal sintering temperature is 1250℃.