Overview
ISO 20032:2013 specifies a standardized tensile test method for evaluating the tensile properties of metallic superplastic materials that display fine-grained superplasticity without significant work‑hardening or dynamic microstructure evolution. The test uses flat-form test pieces (S‑type or R‑type) strained at a constant cross‑head velocity and is performed without an extensometer. Key outputs include superplastic elongation (A), flow stress (σf), and the strain‑rate sensitivity exponent (m‑value) - parameters essential for superplastic forming and materials characterization.
Key Topics and Requirements
- Scope: Intended for fine‑grained superplastic metals tested at elevated temperatures using constant cross‑head velocity; extensometer-free measurements on flat specimens.
- Test pieces: Two specimen geometries are defined:
- S‑type (suitable for lower total strains; gauge and parallel‑side portions specified).
- R‑type (suitable for high‑strain testing since strain concentrates in a central arc‑shaped R portion).
- Dimensional tolerances align with ISO 6892‑1.
- Apparatus:
- Testing machine must conform to ISO 7500‑1 and provide constant cross‑head velocity.
- Clamping devices must resist plastic deformation at test temperature and apply only axial load (minimal pre‑tension to maintain straightness).
- Furnace with controlled, uniform temperature over the gauge length; allowable temperature stability varies with temperature bands (tight tolerances at moderate temperatures, agreed limits at extremes).
- Thermometry via thermocouple per IEC 60584 (or equivalent) to measure specimen temperature accurately.
- Controlled atmosphere considerations and pressure compensation for force readings if applicable.
- Procedure highlights:
- Clamping method to avoid off‑axis loads.
- Temperature measurement directly on the test piece.
- Dimensional measurement after testing for elongation and section area changes.
- Methods to determine m‑value and flow stress, including procedures specific to the R‑type specimen.
Applications and Users
- Who uses ISO 20032: materials engineers, metallurgists, test lab personnel, quality managers, and researchers involved in:
- Superplastic forming process development (aerospace, automotive, precision forming).
- Material selection and qualification for high‑temperature forming.
- R&D on fine‑grained alloys and superplastic behavior.
- Practical benefits: enables reproducible evaluation of superplastic capacity, strain‑rate sensitivity, and flow behavior needed for forming simulations, process optimization, and specification compliance.
Related Standards
Keywords: ISO 20032:2013, tensile properties, metallic superplastic materials, fine‑grained superplasticity, superplastic elongation, m‑value, constant cross‑head velocity, S‑type test piece, R‑type test piece, elevated temperature testing.