加入Al粉和Si粉对低碳MgO-Al_2O_3-C材料性能的影响

Effects of Al powder and Si powder additions on properties of low carbon MgO-Al_2O_3-C materials

以电熔镁砂、电熔镁铝尖晶石及鳞片石墨为原料,以酚醛树脂作结合剂,在MgO-A l2O3-C材料中加入A l粉和Si粉,混练后在180 MPa压力下成型,185℃12 h热处理,制成了加入4.5%质量分数A l粉、0~3.5%质量分数Si粉的AS系列试样和同时加入2%质量分数石墨的ASC系列试样,研究了试样的常温物理性能、高温抗折强度、抗热震性及其相组成和显微结构。结果表明：（1）AS系列中,仅加入4.5%A l粉试样的高温抗折强度从未加A l粉的3.0 MPa提高到22.3 MPa,热震后抗折强度保持率从60%提高到77%;再加入1.5%Si粉后,高温抗折强度提高到27.9 MPa,热震后抗折强度保持率提高到79%;（2）加入A l粉、Si粉和石墨的ASC系列试样的高温抗折强度略高于AS系列试样的,热震后抗折强度保持率在71%~75%之间;（3）这类复合材料具有良好的热态强度和抗热震性的原因为：A l粉、Si粉在埋炭加热过程中与C、N2原位生成针状A lN和SiC等非氧化物,填充、穿插在方镁石和尖晶石骨架中,起到增强、增韧的作用。

Two series of low carbon MgO-Al2O3-C specimens were prepared using fused magnesia,fused magnesium aluminate spinel as starting materials,resin as binder,adding Al powder（mass percent 4.5%）＋Si powder（0-3.5%）（AS series）,Al powder（4.5%）＋Si powder（0-3.5%）＋flake graphite（2%）（ASC series）,respectively,after mixing,moulding at 180 MPa,heat treated at 185 ℃ for 12 h.The physical properties,HMOR and thermal shock resistance,phase composition and microstructure were studied.The results show that：（1）For AS series specimens when adding 4.5% Al powder,the HMOR significantly increases from 3.0 MPa to more than 22.3 MPa,and the residual strength ratio after thermal shock increases from 60% to 77%.With further addition of 1.5% of Si,the HMOR further increases to 27.9 MPa and the residual strength ratio increases to 79%.（2）For ASC series specimens,the HMOR is slightly higher than that of AS series specimens,and the residual strength ratio is 71%-75%.（3）Main reasons for the superior HMOR and thermal shock resistance of these composite materials are as follows：Al and Si reacts with C and N2 under carbon embedded condition forming in suit needle-shaped AlN and SiC,which are well interlaced in the periclase/spinel skeleton structure creating strengthening and toughening effects.