ASTM E112 PDF

More E The grain size of specimens with two phases, or a phase and a constituent, can be measured using a combination of two methods, a measurement of the volume fraction of the phase and an intercept or planimetric count see Section The test methods may also be used for any structures having appearances similar to those of the metallic structures shown in the comparison charts. The three basic procedures for grain size estimation are: 4. The precision of the method is a function of the number of grains counted. An accurate count does require marking off of the grains as they are counted.

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A number in parentheses indicates the year of last reapproval. This standard has been approved for use by agencies of the U.

Department of Defense. INTRODUCTIONThese test methods of determination of average grain size in metallic materials are primarilymeasuring procedures and, because of their purely geometric basis, are independent of the metal oralloy concerned. In fact, the basic procedures may also be used for the estimation of average grain,crystal, or cell size in nonmetallic materials. The comparison method may be used if the structure ofthe material approaches the appearance of one of the standard comparison charts.

The intercept andplanimetric methods are always applicable for determining average grain size. However, thecomparison charts cannot be used for measurement of individual grains. These test methods may also be applied to nonmetallicmaterials with structures having appearances similar to those ofthe metallic structures shown in the comparison charts. Thesetest methods apply chiefly to single phase grain structures butthey can be applied to determine the average size of a particulartype of grain structure in a multiphase or multiconstituentspecimen.

These distributions areapproximately log normal. These test methods do not covermethods to characterize the nature of these distributions. Characterization of grain size in specimens with duplex grainsize distributions is described in Test Methods E Mea-surement of individual, very coarse grains in a fine grainedmatrix is described in Test Methods E Determination of spatial grain size, that is, measurement of thesize of the three-dimensional grains in the specimen volume, isbeyond the scope of these test methods.

Utilization of semi-automatic digitizingtablets or automatic image analyzers to measure grain size isdescribed in Test Methods E Equivalent inch-pound values, whenlisted, are in parentheses and may be approximate.

It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Current edition approved Oct. Published February Originallyapproved in Last previous edition approved as E — Referenced Documents2. To obtain the number per square milli-metre at 1X, multiply by Significance and Use4.

The grainsize of specimens with two phases, or a phase and aconstituent, can be measured using a combination of twomethods, a measurement of the volume fraction of the phaseand an intercept or planimetric count see Section The testmethods may also be used for any structures having appear-ances similar to those of the metallic structures shown in thecomparison charts.

The three basic procedures for grain sizeestimation are Repeatability and reproducibility of comparison chart ratingsare generally 61 grain size number.

The precision ofthe method is a function of the number of grains counted. Aprecision of Results are free of bias andrepeatability and reproducibility are less than An accurate count does require marking off of the grainsas they are counted. The precision of the method is a functionof the number of intercepts or intersections counted. A preci-sion of better than Results are free of bias;repeatability and reproducibility are less than Because an accurate count can be made without need ofmarking off intercepts or intersections, the intercept method isfaster than the planimetric method for the same level ofprecision.

For higher degrees of accuracy in determiningaverage grain size, the intercept or planimetric procedures maybe used. The intercept procedure is particularly useful forstructures consisting of elongated grains see Section Partially recrystallizedwrought alloys and lightly to moderately cold-worked materialmay be considered as consisting of non-equiaxed grains, if agrain size measurement is necessary.

Because they show a distri-bution of grain dimensions, ranging from very small to verylarge, depending on the relationship of the planar section andthe three-dimensional array of grains, the charts are notapplicable to measurement of individual grains. Generalities of Application5. A metal structure is an aggregate of three-dimensional crystals of varying sizes and shapes.

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The grain size of specimens with two phases, or a phase and a constituent, can be measured using a combination of two methods, a measurement of the volume fraction of the phase and an intercept or planimetric count see Section The test methods may also be used for any structures having appearances similar to those of the metallic structures shown in the comparison charts. The three basic procedures for grain size estimation are: 4. The precision of the method is a function of the number of grains counted.

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Metalografia: Tamanho de Grão ASTM E112

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