Question about tensile testing

No reference materials are accredited by ISO 17025. The laboratory must determine the reference material/specimen criteria for any standard methods used,  and ensure these are complied with. I cannot comment specifically on a sector requirement.

For more information, have a look at

The article: What does ISO 17025:2017 require for laboratory measurement equipment and related procedures? at https://advisera.com/17025academy/blog/2019/07/25/iso-17025-measurement-requirements-of-the-standard/
The ISO 17025 toolkit document template: Equipment and Calibration Procedure at https://advisera.com/17025academy/documentation/equipment-and-calibration-procedure/
The ILAC P10:07/2020 ILAC Policy on Metrological Traceability of Measurement Results  available from https://ilac.org/publications-and-resources/