ASTM-B49:09(R2021) pdf free download – Standard Practice for Micrometer Bend Test for Ductility of Electrodeposits.
NOTE 1—For convenience, an ordinary hexavalent chromium electroplating solution can be used for preparing the basis metal.
NOTE 2—As an alternative basis metal, a piece of cold-rolled steel of any convenient size, such as 100 by 150 mm. shall be properly cleaned. rinsed, acid dipped. rinsed and electroplated with approximately 7.5 iim of nickel. After rinsing, the specimen shall be cleaned anodically for approximately 15 seconds in a hot alkaline cleaner, rinsed, acid dipped in approximately 1 N sulfuric acid (approximately 27 inL of concentrated sulturic acid added to approximately 900 mL of cold water, mixed, and diluted with cold water to I L), rinsed, and immediately placed in the electroplating solution of the metal to be tested.
6.3 The panel size should be selected based upon the solution volume to be used in order to maintain the additives within 85 % of their original concentrations. Additions to the test solution shall not be made since they can alter the original composition.
6.4 Cut off the edges of the panel with a power or hand shear, or by any convenient method that permits ready separation of the foil from the basis metal.
6.5 Using a pair of sharp scissors, cut three or more test specimens from the center of the foil, at least 6 mm wide (hut not to exceed the width of the micrometer jaws) by at least 50 mm in length.
7. Procedure
7.1 Measure the thickness of the test foil with the micrometer at the point of bending. Bend the test foil in the shape of a “U” with the side of the foil that was against the basis metal facing inward in the “U.” Place the bent foil between the jaws of the micrometer so that as the jaws are closed, the bend remains between the jaws and is in complete contact with them throughout the procedure (See Note 3). Close the micrometer jaws slowly until the foil cracks (See Note 4). Use an average of three or more foil tests. Record the micrometer reading as 2R and the thickness of the foil as determined by the micrometer as T.
NOTE 3—If any of the bent part of the foil is outside of the micrometer jaws the force may not he uniformly distributed, which could lead to misleading results.
NOTE 4—With foils of a ductility of 70 % or greater it is helpful to examine the foil at low magnification (lOx) while it is still in the micrometer.
7.2 At times, no single crack may develop over the convex surface. If jagged cracks or a series of shorter cracks develop (excluding edges), they signify failure. If no cracks develop, the maximum ductility values are obtained.