GB/T 5168-2020Microstructure and macrostructure examination for titanium and titanium alloys (English PDF)

Foreword

This Standard is drafted in accordance with the rules given in GB/T 1.1-2009.

This Standard replaces GB/T 5168-2008 "Microstructure and macrostructure examination for alpha-beta titanium alloys".

Compared with GB/T 5168-2008, in addition to editorial changes, the main technical changes of this Standard are as follows:

- ADD the elements "Principle", "Reagents", and "Apparatus" (see Clause 3, Clause 4, and Clause 5);

- Modify the requirements for preparation of macrostructure sample (see 6.1;

2.1 of the 2008 edition);

- ADD the requirements for heat treatment of samples during macro-beta-spot and macro-grain size examination (see 6.2.2);

- Modify the composition of macrostructure corrosive agent (see Table 2;

2.2.1 of the 2008 edition);

- Modify the requirements for preparation of microstructure sample (see 7.2;

3.1 of the 2008 edition);

- Modify the composition of microstructure corrosive agent (see Table 3; 3.1.3 of the 2008 edition);

- ADD "Determination of common defect structures" (see Clause 8);

- ADD "Metallographs of typical macrostructures and microstructures of titanium and titanium alloys"; delete Appendix A the 2008 edition "Personal and apparatus protection" (see Appendix A; Appendix A of the 2008 edition);

- Modify the content of Appendix B; CHANGE from "Typical pictures of macrostructures" to "Metallographs of typical metallurgical defects of titanium and titanium alloys" (see Appendix B; Appendix B of the 2008 edition);

- Modify the content of Appendix C; CHANGE from "Typical pictures of microstructures" to "Metallographs of typical processing defects of titanium and titanium alloys" (see Appendix C; Appendix C of the 2008 edition);

1 Scope

This Standard specifies the microstructure and macrostructure examination for alpha-type, alpha-beta-type, beta-type titanium and titanium alloys.

This Standard applies to the microstructure and macrostructure examination for titanium and titanium alloys.

2 Normative references

The following documents are indispensable for the application of this document.

For the dated references, only the editions with the dates indicated are applicable to this document. For the undated references, the latest edition (including all the amendments) are applicable to this document.

GB/T 6394 Metal - Methods for estimating the average grain size

GB/T 6611 Terminology and metallographs for titanium and titanium alloys

GB/T 13298 Inspection methods of microstructure for metals

YB/T 4377 Electrolytic polishing method of metallic specimens

3 Principle

Low magnification (macrostructure) examination is to select the appropriate corrosive agent to show the macrostructure of titanium and titanium alloy samples; use a magnifying glass no more than 20 times or visually check the morphological characteristics. High magnification (microstructure) examination is to select the appropriate corrosive agent to reveal the microstructure of titanium and titanium alloy samples; use the microscope to analyze and identify the microstructure characteristics of titanium and titanium alloy materials.

4 Reagents

Unless otherwise stated, the reagents used in the test are chemically pure.

4.1 Ammonium bifluoride (rho=1.52 g/cm³).

4.2 Hydrofluoric acid (rho=1.15 g/mL).

4.3 Nitric acid (rho=1.40 g/mL).

4.4 Hydrochloric acid (rho=1.19 g/mL).

4.5 Hydrogen peroxide (rho=1.10 g/mL).

4.6 Glacial acetic acid (rho=1.05 g/mL).

4.7 Glycerol (glycerin) (rho=1.3 g/mL).

5 Apparatus

5.1 Microstructure and macrostructure examination related equipment includes sample preparation equipment (metallographic cutting machine, inlay machine, grinding-polishing machine, electrolytic polishing corrosion equipment, etc.), metallographic microscope, and photographic system, etc. It shall all meet the relevant safety and technical requirements.

5.2 The metallographic grinding-polishing machine shall be equipped with water inlet and drainage channels; or select fully-automatic sample preparation equipment.

5.3 The metallographic microscope shall be qualified by measurement calibration. The photographic system shall ensure the traceability of the image size. If there is a scale in the eyepiece, the micrometer shall be used for calibration. The micrometer shall be subject to verification according to the measurement requirements.

6 Macrostructure examination

7 Microstructure examination

7.1.2 Recommended sample size: The area of the surface to be examined is less than 400 mm². The height is preferably 15 mm~20 mm.

7.1.3 According to different examination purposes, select a reasonable surface to be examined and clearly mark. Longitudinal section is selected for the surface to be examined of the structure of extruded or rolled pipe. Transverse section, which is perpendicular to the main deformation direction, is selected for the surface to be examined of the structure of other processed products.

7.6.2 Choose different magnifications from low to high for structure observation.

According to product technical requirements or sample structures, choose the appropriate magnification.

7.6.3 Observe the full range of the surface to be examined of the sample.

According to the test purposes or product technical requirements, select a representative field of view to judge the results.

7.6.5 The measurement of the primary alpha-phase content is carried out in accordance with the provisions of Appendix E.

7.6.6 The measurement of the size of the strip alpha-phase is carried out in accordance with the provisions of Appendix F.

8 Determination of common defect structures of titanium and titanium alloys

Appendix F (Normative) Method for measuring the size of strip alpha-phase