A cost-effective route to produce Al/AlN composites with low coefficient of thermal expansion

In this study, a novel process was developed to produce Al/AlN composites by infiltrating molten Al ingot into a mixture of Al and lamp carbon powders. The findings revealed that, during the process, Al2O3 on the surface of Al powder reacted with nitrogen gas and was transformed to AlN. The degree of nitridation was greatly enhanced by adding only less than 3 wt.% lamp carbon, because lamp carbon could act as a dispersion agent as well as a reduction agent. The Al-based composites containing in situ AlN phases showed coefficient of thermal expansion values of similar to 11 x 10(-6)/degrees C, which were comparable to those of composites containing 60% ex situ AlN particles.