Papers by Author: Xiao Lei Shi

Abstract: Five-layered Al/Al-Cu functionally graded material (FGM) was fabricated by powder metallurgy technology. The microstructure and composition of the prepared specimen were studied. Vickers hardness, flexural strength and fracture surface morphology were also measured. The results showed that Al/Al-Cu graded material with dense structure and compositional continuous change was obtained by solution-precipitation method. The graded materials presented a compositional continuous change along the graded direction because of the diffusion effect, and the Vickers hardness was liner proportional to the distribution of Cu content. Compared with pure sintered Al, remarkable improvement on hardness and fracture strength was achieved due to the CuAl2 phase dispersively distributed in the matrix. With the increase of Cu content, the fracture mode changed from tough fracture to the tendency of brittle fracture.

Abstract: AlN ceramics were prepared by hot-pressing process with Y(NO3)3·6H2O as a sintering additive. Microstructure and mechanical properties of sintered AlN ceramics were measured and compared with that of monolithic AlN ceramic prepared by the same process. The results showed that the density and mechanical properties of monolithic AlN ceramics were drastically enhanced by adding Y(NO3)3·6H2O. Especially, the AlN ceramic with 3.24 wt% Y(NO3)3·6H2O (2 wt% Y2O3) displayed striking enhancement in mechanical propertie. However, such enhancement did not follow a consistent behavior with the increase of Y(NO3)3·6H2O content. A significant drop present at contents over inflection point (3.24 wt% Y(NO3)3·6H2O).