발간논문

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This study aims at establishing the correlation of microstructure and mechanical properties of 2124-T6 Al composites reinforced with 7, 15, 20 v/o SiC whiskers. Tensile tests along with Charpy impact tests were conducted over the test temperature range from -196℃ to 100℃. Notched round tensile tests and subsequent metallographic observations as well as in-situ SEM observation of crack opening processes were performed for the purpose of identifying the micro-mechanical processes involved in void initiation. The experimental results indicated that the impact energy was found to increase monotonically with decreasing the amount of SiC whiskers and with inceasing the test temperature. Microvoids were observed to nucleate at the interface between the aluminum matrix and SiC whikskers, confirming that the formation of voids at the interfaces is the main metallurgical factor which contributes to the reduction of fracture toughness. In addition, the Mn-containing intermetallic particles strongly affect the fracture processes in these composites.

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The solid state diffusion joining of ZrO₂to AISI 304 stainless steel produced using Cu interlayer was studied between 900℃ and 1050℃ for times ranging from 30 min to 120min. The joining was carried out in Argon atomospher with the materials in the shape of discs, maintained in contact under a pressure between 30㎫ and 100㎫. Reaction bond consisting of ZrO₂/Cu was dominated by the surface reaction with a undetectable very thin layer. On the metal side, Cu/stainless joining was dependent on the diffusion of Cr and Fe elements of stainless steel to Cu interlayer. Furthermore it was found that Cr and Fe elements in stainless steel were diffused to ZrO₂/Cu joint under the good bonding reaction. The maximum shear strength about 30㎫ was obtained in the couple bonded at 1000℃ for 60min under pressure 50㎫.

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