口腔温度下热处理对时效硬化型金合金力学性能的影响。

Watanabe I, Watanabe E, Cai Z, Okabe T, Atsuta M

Department of Fixed Prosthodontics, Nagasaki University, School of Dentistry, 1-7-1 Sakamoto, Nagasaki 852-8588, Japan.

Dent Mater. 2001 Sep;17(5):388-93. doi: 10.1016/s0109-5641(00)00096-8.

OBJECTIVE

The aim of this study was to investigate the effect of various heat treatments on the mechanical properties of gold alloys capable of age-hardening at intraoral temperature.

METHODS

Dumbbell-shaped patterns (ISO 6871) were cast with three gold alloys (Sofard; NC Type-IV; Aurum Cast, NihombashiTokuriki Co.). The Sofard alloy is age-hardenable at intraoral temperature. The castings underwent various heat treatments [as-cast (AC); solution treatment (ST); high-temperature aging (HA); intraoral aging (IA)]. After these heat treatments, ultimate tensile strength (UTS), 0.2% offset yield strength (YS), and elongation (EL) were measured at a strain rate of 1.7x10(-4)/s. Fracture surfaces of the specimens after tensile testing were observed using SEM. Vickers hardness was also measured after heat treating.

RESULTS

After IA, the hardness values of the Sofard alloy increased and reached values similar to the hardness of the Sofard specimens aged at high temperature (HA). The hardness values of the NC Type-IV and Aurum Cast specimens slightly increased after IA, but did not reach the values of the specimens after HA. All the Sofard, NC Type-IV and Aurum Cast specimens showed significantly (P<0.05) greater hardness values after HA, compared with the values after any other heat treatments (AC, ST and IA). The UTS and YS of the specimens indicated a tendency similar to the results obtained for hardness. The Sofard specimens with ST showed the greatest elongation compared to the corresponding NC Type-IV and Aurum Cast specimens. However, the elongation of the Sofard specimens was abruptly reduced after intraoral aging.

CONCLUSION

Intraoral aging significantly improved the mechanical properties and hardness of the Sofard alloy.

目的

本研究旨在探讨不同热处理对能够在口腔温度下时效硬化的金合金力学性能的影响。

方法

用三种金合金（Sofard；NC-IV型；日本桥徳力金属公司的Aurum Cast）铸造哑铃形试样（ISO 6871）。Sofard合金可在口腔温度下时效硬化。铸件经过各种热处理[铸态（AC）；固溶处理（ST）；高温时效（HA）；口腔时效（IA）]。经过这些热处理后，在应变速率为1.7×10⁻⁴/s的条件下测量极限抗拉强度（UTS）、0.2%屈服强度（YS）和伸长率（EL）。使用扫描电子显微镜观察拉伸试验后试样的断口表面。热处理后还测量了维氏硬度。

结果

经过口腔时效后，Sofard合金的硬度值增加，并达到与高温时效（HA）的Sofard试样硬度相似的值。NC-IV型和Aurum Cast试样的硬度值在口腔时效后略有增加，但未达到高温时效后试样的值。与任何其他热处理（AC、ST和IA）后的硬度值相比，所有Sofard、NC-IV型和Aurum Cast试样在高温时效后的硬度值均显著更高（P<0.05）。试样的UTS和YS显示出与硬度结果相似的趋势。与相应的NC-IV型和Aurum Cast试样相比，经过固溶处理的Sofard试样伸长率最大。然而，Sofard试样在口腔时效后的伸长率急剧降低。