GMNA GMN11021 PDF

Note: Nothing in this standard supersedes applicable laws and regulations unless specific exemption has been obtained.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.

Purpose. The standard described herein measures the potential for aluminum to experience permanent growth due to metallurgical instability. Aluminum parts often operate at temperatures that facilitate phase transformation and precipitation of supersaturated alloying elements. These metallurgical changes may be accompanied by volumetric expansion. Background on this phenomenon is given in Appendix A. Results of a benchmark study are presented in Appendix B.

Foreword. Summary of test method: Three (3) groups of five right-circular cylinders with pre-measured end-to-end lengths are heated at 250°C for, respectively, 1, 10, and 100 h. After cooling to ambient temperature, each sample is remeasured with the change in length converted into % growth. Average and mean + 3 sigma growth is plotted against log time. The largest mean + 3 sigma growth is defined as "permanent growth potential" for the material and rated per Section 9 against a maximum allowance.

Applicability. Aluminum alloys.