超微粒子噴射積層法および温度傾斜付加焼結法によるTi-Al_2O_3傾斜機能材料の試作 Fabrication of a Ti-Al_2O_3 Functionally Graded Material by Dry-jet Spraying of Ultrafine Particles and Subsequent Temperature-gradient Sintering
Ti-Al<SUB>2</SUB>O<SUB>3</SUB> functionally graded material (FGM) is tentatively fabricated by dry jet spraying of ultrafine particles (UFPs) onto a Ti substrate and subsequent temperature-gradient sintering. The FGM layer is formed by gradually decreasing the ratio, r=Ti/(Ti+Al<SUB>2</SUB>O<SUB>3</SUB>), during the dry-jet spraying. It is found to be effective to add Ti-or Zr-hydrides to the Ti substrate to decrease the number of cracks which appear in the FGM layer due to the difference in the amounts of shrinkage during sintering. Since the composition range between r=1 and r=0.5 is known to show large shrinkage, it is better to start the dry-jet spraying from r=0.5 than to start from r=1 to decrease the size of voids. Despite the existence of the skipped r range, the r in the sintered composite changes from r=1 to r=0, which is considered to be due to the abnormally rapid diffusion of Ti atoms. The fabrication of an FGM in the shape of a cylinder with locally different diameters is also tried and it is found that by adjusting the pressure of isostatic pressing of the dry jet sprayed composite the formation of cracks in the neighborhood of the protrusions is suppressed.
粉体および粉末冶金 44(4), 334-339, 1997-04-15
Japan Society of Powder and Powder Metallurgy