1.1 这些测试方法为决定是否存在双重晶粒度提供了简单的指导。试验方法将双重晶粒尺寸分为两个不同类别中的一个，然后分为这些类别中的特定类型，并为每种类型的晶粒尺寸表征提供系统。 1.2 单位- 以国际单位制表示的数值应视为标准。本标准不包括其他计量单位。 1.3 本标准可能涉及危险材料、操作和设备。本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 由于某些金属和合金的热机械加工历史，它们可能会出现双重晶粒尺寸。为了将机械性能与冶金特征进行比较，或出于规范目的，能够表征此类材料的晶粒度可能很重要。将平均晶粒度值分配给双重晶粒度试样并不能充分表征该试样的外观，甚至可能歪曲其外观。例如，平均两个明显不同的晶粒尺寸可能会导致报告的尺寸实际上并不存在于样本中的任何地方。 5.2 这些试验方法可应用于含有两种或两种以上明显不同尺寸的随机混合晶粒（以下称为随机双重晶粒尺寸）的试样或产品。随机双相晶粒度的例子包括: 晶粒细小得多、晶粒尺寸分布极宽、晶粒尺寸双峰分布的基体中的孤立粗晶粒。 5.3 这些测试方法也可应用于含有两种或两种以上明显不同尺寸的晶粒，但以拓扑变化模式分布的试样或产品（以下称为拓扑双相晶粒尺寸）。拓扑双相晶粒度的例子包括:晶粒度在产品截面上的系统变化、项链结构、带状结构以及临界应变选定区域的发芽晶粒生长。 5.4 这些试验方法可应用于试样或产品，无论其再结晶状态如何。 5.5 因为这些测试方法描述了与单一对数正态粒度分布的偏差 模式 晶粒度的变化，样品的总交叉- 部分必须进行评估。 5.6 这些测试方法仅限于在单个抛光和蚀刻冶金样品中可识别的双重晶粒尺寸。如果怀疑产品中的双重晶粒尺寸过大，无法作为单个样品进行抛光和蚀刻，则应将宏观蚀刻视为评估的第一步。如果可能的话，应将整个宏观蚀刻截面用作估计不同晶粒尺寸所占面积分数的基础。如果随后需要进行显微镜检查，则必须采集单个样本，以估计整个产品横截面的面积分数，并确定代表整个横截面的晶粒尺寸。 5.7 这些试验方法适用于双相晶粒 尺寸。 双重晶粒 结构 （例如，多相合金）在晶粒尺寸上不一定是双重的，因此不是这些方法的主题。 然而，这里描述的用于面积分数估计的测试方法可以用于描述双相晶粒结构。

1.1 These test methods provide simple guidelines for deciding whether a duplex grain size exists. The test methods separate duplex grain sizes into one of two distinct classes, then into specific types within those classes, and provide systems for grain size characterization of each type. 1.2 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Duplex grain size may occur in some metals and alloys as a result of their thermomechanical processing history. For comparison of mechanical properties with metallurgical features, or for specification purposes, it may be important to be able to characterize grain size in such materials. Assigning an average grain size value to a duplex grain size specimen does not adequately characterize the appearance of that specimen, and may even misrepresent its appearance. For example, averaging two distinctly different grain sizes may result in reporting a size that does not actually exist anywhere in the specimen. 5.2 These test methods may be applied to specimens or products containing randomly intermingled grains of two or more significantly different sizes (henceforth referred to as random duplex grain size). Examples of random duplex grain sizes include: isolated coarse grains in a matrix of much finer grains, extremely wide distributions of grain sizes, and bimodal distributions of grain size. 5.3 These test methods may also be applied to specimens or products containing grains of two or more significantly different sizes, but distributed in topologically varying patterns (henceforth referred to as topological duplex grain sizes). Examples of topological duplex grain sizes include: systematic variation of grain size across the section of a product, necklace structures, banded structures, and germinative grain growth in selected areas of critical strain. 5.4 These test methods may be applied to specimens or products regardless of their state of recrystallization. 5.5 Because these test methods describe deviations from a single, log-normal distribution of grain sizes, and characterize patterns of variation in grain size, the total specimen cross-section must be evaluated. 5.6 These test methods are limited to duplex grain sizes as identifiable within a single polished and etched metallurgical specimen. If duplex grain size is suspected in a product too large to be polished and etched as a single specimen, macroetching should be considered as a first step in evaluation. The entire macroetched cross-section should be used as a basis for estimating area fractions occupied by distinct grain sizes, if possible. If microscopic examination is subsequently necessary, individual specimens must be taken to allow estimation of area fractions for the entire product cross-section, and to allow determination of grain sizes representing the entire cross-section as well. 5.7 These test methods are intended to be applied to duplex grain sizes. Duplex grain structures (for example, multiphase alloys) are not necessarily duplex in grain size, and as such are not the subject of these methods. However, the test methods described here for area fraction estimation may be of use in describing duplex grain structures.