GB/T 3246.2-2026Inspection methods for the structure of wrought aluminium and aluminium alloy products - Part 2: Inspection method for macrostructure (English PDF)

1 Scope

This document describes methods for examining the macrostructure of aluminum and aluminum alloy products.

This document applies to the macrostructure examination of aluminum and aluminum alloy ingots (or billets), plates, strips, foils, tubes, rods, profiles, wires, forgings, and their processed products, as well as cast aluminum alloy products.

2 Normative references

The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies to this document; for undated references, the latest edition (including all amendments) applies.

GB/T 6682 Water for analytical laboratory use - Specification and test methods

GB/T 8005 (all parts) Aluminium and aluminium alloy - Terms and definitions

GB/T 8170 Rules of rounding off for numerical values & expression and judgement of limiting values

GB/T 22638.1-2016 Test methods for aluminium and aluminium alloy foils - Part 1: Determination of thickness

GB/T 26492 (all parts) Defects for wrought aluminium and aluminium alloys ingots and products

GB/T 43139-2023 Density testing of cast aluminum alloy liquid reduced pressure solidification samples

3 Terms and definitions

The terms and definitions defined in GB/T 8005 (all parts) and GB/T 26492 (all parts), as well as the following terms and definitions, apply to this document.

4 Overview of method

Examine and analyze grains and defects within the material microstructure (cast structure, deformation structure, etc.) visually or with the aid of a magnifying glass; evaluate and characterize features such as grain size, porosity, inclusions, cracks, coarse grain rings, poor weld bonding, laps (folds), irregular flow lines, segregation layers, delamination, billet transition zones.

5 Reagents

Warning - The inorganic acids used in the analysis are corrosive to the human body; testing personnel shall wear personal protective equipment to avoid direct exposure that could cause skin burns.

Unless otherwise specified, use only reagents confirmed to be of chemically pure grade and water conforming to Grade 3 requirements as specified in GB/T 6682.

5.1 Extra-strong mixed acid. Mix hydrofluoric acid (rho = 1.15 g/mL), nitric acid (rho = 1.40 g/mL), hydrochloric acid (rho = 1.19 g/mL) in a volume ratio of 1.5.15; mix thoroughly.

5.2 Strong mixed acid A. Mix hydrofluoric acid (rho = 1.15 g/mL), nitric acid (rho = 1.40 g/mL), hydrochloric acid (rho = 1.19 g/mL), water in a volume ratio of (1+5+15+42); mix thoroughly.

5.3 Strong mixed acid B. Mix hydrofluoric acid (rho = 1.15 g/mL), nitric acid (rho = 1.40 g/mL), hydrochloric acid (rho = 1.19 g/mL), water in a volume ratio of (3+3+9+5); mix thoroughly.

Note: Strong mixed acid B is also known as Tucker's reagent.

5.4 High-concentration mixed acid. Mix hydrofluoric acid (rho = 1.15 g/mL), nitric acid (rho = 1.40 g/mL), hydrochloric acid (rho = 1.19 g/mL), water in a volume ratio of (2+1+1+76); mix thoroughly.

5.5 Nitric acid, which has a concentration range of (1+4) ~ (1+3).

5.6 Sodium hydroxide solution A (80 g/L ~ 120 g/L).

5.7 Sodium hydroxide solution B (150 g/L ~ 250 g/L).

6 Specimen

Where the product standard or order specifies requirements for macrostructure sampling and specimen preparation, proceed in accordance with those specifications.

In the absence of such specifications, conduct sampling and specimen preparation as prescribed in Table 1. […]