1.1 这些测试方法为确定是否存在双重粒度提供了简单的指导。试验方法将双重粒度分为两个不同类别中的一个，然后在这些类别中分为特定类型，并为每种类型的粒度表征提供系统。 1.2 单位- 以国际单位制表示的数值应视为标准值。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。本标准的用户有责任在使用前咨询适当的安全和健康实践，并确定监管限制的适用性。 ====意义和用途====== 5.1 由于热机械加工历史，某些金属和合金中可能出现双重晶粒尺寸。为了将机械性能与冶金特征进行比较，或出于规范目的，能够表征此类材料中的晶粒尺寸可能很重要。将平均晶粒度值指定给双晶粒度试样并不能充分表征该试样的外观，甚至可能会歪曲其外观。例如，平均两种明显不同的晶粒尺寸可能导致报告的尺寸实际上不存在于试样中的任何地方。 5.2 这些试验方法可适用于含有两种或两种以上显著不同尺寸的随机混合颗粒（以下称为随机双颗粒尺寸）的试样或产品。 随机双重晶粒尺寸的示例包括:更细晶粒基质中的孤立粗晶粒、极宽的晶粒尺寸分布和双峰晶粒尺寸分布。 5.3 这些试验方法也可适用于含有两种或两种以上显著不同尺寸颗粒，但以拓扑变化模式分布的样品或产品（以下称为拓扑双重晶粒尺寸）。拓扑双重晶粒尺寸的示例包括:产品截面上晶粒尺寸的系统变化、项链结构、带状结构和选定临界应变区域内的发芽晶粒生长。 5.4 这些试验方法可适用于试样或产品，无论其再结晶状态如何。 5.5 因为这些测试方法描述了粒径的单对数正态分布的偏差，并对其进行了表征 模式 对于晶粒尺寸的变化，必须评估试样的总截面。 5.6 这些试验方法仅限于在单个抛光和蚀刻冶金试样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太大，无法作为单个试样进行抛光和蚀刻，则应将宏观蚀刻视为评估的第一步。如有可能，应将整个宏观蚀刻横截面用作估算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，以估计整个产品交叉的面积分数- 并允许确定代表整个横截面的晶粒尺寸。 5.7 这些试验方法旨在应用于双相晶粒 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，此处描述的面积分数估计测试方法可用于描述双重晶粒结构。

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 associated with its use. It is the responsibility of the user of this standard to consult appropriate safety and health practices and determine the applicability of regulatory limitations prior to its use. ====== 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.