| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an ultrasonic horn made of silicon nitride sintered compacts having enhanced fracture toughness and durability, which enables an ultrasonic treatment to be performed suitably, has improved wettability to molten aluminum, and efficiently micronizes aluminum cast structure. <P>SOLUTION: The molten aluminum is irradiated with ultrasonic waves by the ultrasonic horn made of the silicon nitride sintered compacts produced by sintering composite powder containing the group 4A element in an amount of 1.0-10 pts.mass in terms of metals to an amount of 100 pts.mass of Si<SB>3</SB>N<SB>4</SB>powder in the Si<SB>3</SB>N<SB>4</SB>composite powder containing an ordinary sintering additive. The group 4A element or the compound of the same as well as the sintering additive such as Al<SB>2</SB>O<SB>3</SB>or Y<SB>2</SB>O<SB>3</SB>are added in producing the silicon nitride compacts so that the wettability to the molten aluminum is improved to enable the ultrasonic treatment to be performed suitably. <P>COPYRIGHT: (C)2011,JPO&INPIT |
