| 1235 Optimizing Quality of Laser-welded Gold Alloy through Heat Treatment | ||||||||||||||||||||||||||||||||||||||||
| I. WATANABE1, J. LIU2, Y. TANAKA2, M. ATSUTA2, and T. OKABE2, 1Baylor College of Dentistry, Dallas, TX, USA, 2Nagasaki University, Japan | The aim of this study was to improve the joint strength of laser-welded gold alloy with age-hardenability at intraoral temperature. Gold alloy (Au-22.0%Cu-3.0%Ga-0.5%Ir; Sofard, Nihombashi-Tokuriki, Japan) was cast conventionally in plate patterns (0.5 mm x 3.0 mm x 20 mm). After bench-cooling the mold to room temperature (AC; as-cast state), transverse sections of the plate were made at mid-span. After the cut surfaces were polished with No. 600 SiC paper, they were butted against one another and welded using Nd:YAG laser (Tanaka TLL7000, Japan) (current: 320 A; time: 10 ms; spot diameter: 1 mm). Three laser pulses were applied from both sides to cover the joint width (3.0 mm) of the specimens before or after solution heat treatment at 700°C/5 min (ST). Uncut control specimens (non-welded) were also prepared. After ST, two different heat treatments were given the laser welded specimens: aging at 250°C/15 min (HA), or aging at 37°C/3 d (IA). Control specimens underwent all of the heat treatments after ST. Tensile testing was conducted at a crosshead speed of 2 mm/min and a gauge length of 10 mm, and the breaking stress (Bs: MPa) was recorded. Results [mean (SD), n=5] were:
Identical letters indicate no statistical differences (p>0.05) in the same row (Duncan's test). For the control specimens, the Bs value of the IA specimens increased after ST and was not different (p>0.05) from that of the HA specimens. The Laser ®ST specimens showed significantly greater Bs value compared to the ST®Laser specimens after any heat treatment. The joint strength of laser-welded gold alloy will be improved by solution heat treatments with aging at high or intraoral temperature. Partially funded by NIH grant 11787. | |||||||||||||||||||||||||||||||||||||||
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| Seq #121 - Casting Alloys I 3:45 PM-5:00 PM, Thursday, 7 March 2002 San Diego Convention Center Exhibit Hall C | ||||||||||||||||||||||||||||||||||||||||
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Back to the Dental Materials: VII - Others-Metallic Program
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