Analysis of sintering process of Alumix431-B4C composites

Abstract

This paper presents the results of a study on the sintering process of composites made of a mixture of Alumix 431 powders with B4C boron carbide. Sintering was carried out at the following temperatures: 550, 580 and 600 ℃. The process of sintering Alumix powders is a very complex issue due to the possibility of many types of mutual reactions of the elements constituting its components and their interaction with boron carbide. The study included the preparation of green compacts from a mixture of powders with the addition of 5 wt % B4C and sintering in a NETZSCH 402ES/3 differential dilatometer; the density and microstructure of the sinters were examined using scanning microscopy and X-ray phase analysis. Analysis of the dilatometric curves allowed the sequence of the emerging liquid phases and their impact on the course of dimensional changes as well as the microstructure of the finished composites to be determined, indicating the importance of the reaction of the aluminium matrix with magnesium, copper and zinc. It was also indicated that the B4C boron carbide addition may decompose, resulting in the appearance of B12Mg and Al4C3 phases. The research also showed that the addition of carbide did not adversely affect the density of the sinters as composites with a density exceeding 95 % of the theoretical density were obtained.