Significance and Use

This practice is used to assess the nature and extent of banding or orientation of microstructures of metals and other materials where deformation and processing produce a banded or oriented condition.

Banded or oriented microstructures can arise in single phase, two phase or multiphase metals and materials. The appearance of the orientation or banding is influenced by processing factors such as the solidification rate, the extent of segregation, the degree of hot or cold working, the nature of the deformation process used, the heat treatments, and so forth.

Microstructural banding or orientation influence the uniformity of mechanical properties determined in various test directions with respect to the deformation direction.

The stereological methods can be applied to measure the nature and extent of microstructural banding or orientation for any metal or material. The microindentation hardness test procedure should only be used to determine the difference in hardness in banded heat-treated metals, chiefly steels.

Isolated segregation may also be present in an otherwise reasonably homogeneous microstructure. Stereological methods are not suitable for measuring individual features, instead use standard measurement procedures to define the feature size. The microindentation hardness method may be used for such structures.

Results from these test methods may be used to qualify material for shipment in accordance with guidelines agreed upon between purchaser and manufacturer, for comparison of different manufacturing processes or process variations, or to provide data for structure-property-behavior studies.

1. Scope

1.1 This practice describes a procedure to qualitatively describe the nature of banded or oriented microstructures based on the morphological appearance of the microstructure.

1.2 This practice describes stereological procedures for quantitative measurement of the degree of microstructural banding or orientation.

Note 1 Although stereological measurement methods are used to assess the degree of banding or alignment, the measurements are only made on planes parallel to the deformation direction (that is, a longitudinal plane) and the three-dimensional characteristics of the banding or alignment are not evaluated.

1.3 This practice describes a microindentation hardness test procedure for assessing the magnitude of the hardness differences present in banded heat-treated steels. For fully martensitic carbon and alloy steels (0.10-0.65 %C), in the as-quenched condition, the carbon content of the matrix and segregate may be estimated from the microindentation hardness values.

1.4 This standard does not cover chemical analytical methods for evaluating banded structures.

1.5 This practice deals only with the recommended test methods and nothing in it should be construed as defining or establishing limits of acceptability.

1.6 The measured values are stated in SI units, which are regarded as standard. Equivalent inch-pound values, when listed, are in parentheses and may be approximate.

1.7 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

A370 Test Methods and Definitions for Mechanical Testing of Steel Products

A572/A572M Specification for High-Strength Low-Alloy Columbium-Vanadium Structural Steel

A588/A588M Specification for High-Strength Low-Alloy Structural Steel, up to 50 ksi [345 MPa] Minimum Yield Point, with Atmospheric Corrosion Resistance

E3 Guide for Preparation of Metallographic Specimens

E7 Terminology Relating to Metallography

E140 Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness, and Scleroscope Hardness

E384 Test Method for Knoop and Vickers Hardness of Materials

E407 Practice for Microetching Metals and Alloys

E562 Test Method for Determining Volume Fraction by Systematic Manual Point Count

E883 Guide for Reflected-Light Photomicrography

Keywords

anisotropy index; banding; feature interceptions; feature intersections; microindention hardness; orientation; steel; stereology;

ICS Code

ICS Number Code 07.030 (Physics. Chemistry)

DOI: 10.1520/E1268-01R07

ASTM International is a member of CrossRef.

ASTM E1268