拉伸试验测试金属韧性的不确定性：中温脆性和应变速率脆性

摘要

International Standard, ISO 6892-2, Metallic Materials-Tensile Testing: Method of Test at Elevated Temperature maintained that the strain rate variations and test temperature variations can induce the measurement uncertainty of mechanical properties in tensile testing, which will imperil the reliability of tension tests. In this paper, the measurement uncertainties of shrinkage rate or elongation rate in tensile testing cross-section, intermediate temperature embrittlement and strain rate embrittlement are first described experimentally. Second, the fundamental results on the microscopic theory of elastic deformation in metals are briefly mentioned. Then the phenomena of the measurement uncertainties are explained based on the microscopic theory. It is expounded that the elastic deformation of tension tests induces the impurities to segregate to grain boundaries and the relative embrittlement which produces the measurement uncertainties of reduction in area. This work gives a theoretical basis for correcting the present standard method of tension testing to avoid the measurement uncertainty of reduction in area.%金属高温拉伸试验国际技术标准ISO 6892-2-2011认定，拉伸试验的拉伸温度或应变速率的改变会引起拉伸试验测试力学性能结果的不确定性，危及到拉伸试验技术的可靠性。本文综述了拉伸试验测试断面收缩率或延伸率的不确定性：中温脆性和应变速率脆性的实验现象和特征，简述了多晶金属弹性变形微观理论的基本结果，以此微观理论解释了上述两种测试不确定性的试验现象，阐明了这两种测试不确定性是拉伸试验弹性变形阶段杂质晶界偏聚，脆化了晶界引起的。为修正金属拉伸试验技术标准，避免断面收缩率测试的不确定性提供了理论基础。