Reisbick M H, Brantley W A
Section of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus 43210-1241, USA.
Int J Prosthodont. 1995 Jul-Aug;8(4):346-50.
Using polystyrene plastic patterns meeting the dimensional requirements of ANSI/ADA specification no. 5, tension test specimens were recast multiple times from a popular Type III gold (46%) alloy. The alloy was melted by electrical heating in a graphite crucible and four conditions were compared: new alloy and alloy cast two, three, and four times (n = 4). After casting, age-hardened specimens were loaded at an elongation rate of 0.5 mm/min until failure, and the stress-strain plots were recorded. Values of yield strength, tensile strength, and percentage elongation for the specimen groups were analyzed by one-way analysis of variance, followed by the Student-Newman-Keuls multiple range test. Significant decreases (P < .01) in yield strength and percentage elongation occurred with recasting, although there were no significant differences (P > .05) in tensile strength. Scanning electron microscope examination revealed that the number of casting defects increased with remelting, and that their presence dominates the tensile fracture process. The variation in mechanical properties of the alloy with remelting was attributed to these casting defects.
使用符合美国国家标准学会/美国牙科协会第5号规范尺寸要求的聚苯乙烯塑料模具，从一种常见的III型金（46%）合金多次重铸拉伸试验样品。该合金在石墨坩埚中通过电加热熔化，并比较了四种情况：新合金以及铸了两次、三次和四次的合金（n = 4）。铸造后，对时效硬化的样品以0.5毫米/分钟的伸长率加载直至破坏，并记录应力 - 应变曲线。通过单向方差分析对样品组的屈服强度、抗拉强度和伸长率值进行分析，随后进行学生 - 纽曼 - 基尔斯多重范围检验。重铸后屈服强度和伸长率出现显著下降（P <.01），尽管抗拉强度没有显著差异（P >.05）。扫描电子显微镜检查表明，铸造缺陷的数量随着重熔而增加，并且它们的存在主导了拉伸断裂过程。合金机械性能随重熔的变化归因于这些铸造缺陷。
