ASTM Grade 23 (UNS R56401) ELI grade titanium alloy extruded tubes - Damage tolerance design optimization
ASTM Grade 23 (UNS R56401) is the ELI (Extra Low Interstitial) version of Grade 5, corresponding to the Chinese TC4 ELI grade. Chemical composition: Al 5.5%~6.5%,V 3.5%~4.5%,Fe≤0.25%,O≤0.13%,C≤0.08%,N≤0.03%,H≤0.0125%,Ti Surplus. The reduction of interstitial elements significantly improves fracture toughness and low-temperature plasticity.
Complete mechanical performance indicators:
·Tensile strength (Rm): ≥ 828 MPa (typical value about 850~900 MPa)
·Yield strength (Rp0.2): ≥ 759 MPa (typical value about 780-840 MPa)
·Post fracture elongation (A): ≥ 10% (gauge length 50mm, typical value about 14-18%)
·Shrinkage rate of cross-section (Z): ≥ 15%
·Hardness (HRC): Approximately 30-34
·Density: 4.43 g/cm 3
·Elastic modulus: approximately 113 GPa
Damage tolerance performance (compared to Grade 5):
·Fracture toughness (K_IC): ≥ 75 MPa · m 1/2 (Grade 5 is about 65-75, an increase of about 10-15%)
·Stress corrosion cracking threshold (K_ISCC): ≥ 55 MPa · m 1/2 (Grade 5 approximately 45~55)
·Fatigue crack propagation rate (da/dN, Δ K=20 MPa · m 1/2, R=0.1): ≤ 2.5 × 10 ?? mm/cycle (Grade 5 approximately 4.0 × 10 ??)
·Room temperature impact toughness (Charpy V-type): ≥ 20 J/cm 2 (Grade 5 approximately 15-18)
ASTM Grade 23ELI titanium alloy extruded tube ,Low temperature performance:
·-Tensile strength at 196 ℃: ≥ 1200 MPa
·-Yield strength at 196 ℃: ≥ 1100 MPa
·-Elongation at 196 ℃: ≥ 8%
·-Impact toughness at 196 ℃: ≥ 25 J/cm 2
ASTM Grade 23ELI titanium alloy extruded tube.Physical properties:
·Phase transition point (β transus): approximately 975-990 ℃ (slightly lower than Grade 5)
·Thermal conductivity (20 ℃): 6.7 W/(m · K)
·Linear expansion coefficient (20~400 ℃): 9.1 × 10
Grade 23 extruded tubes are significantly superior to the standard Grade 5 in terms of fracture toughness, fatigue crack propagation resistance, and low-temperature impact toughness, making them particularly suitable for aerospace structural components and low-temperature service environments dominated by damage tolerance design concepts. Its preparation process is basically the same as Grade 5, but it has stricter requirements for raw material purity and melting process control to avoid contamination of interstitial elements during the melting process. In the aerospace grade titanium tube standard system, AMS 4944 and other standards specifically specify the technical requirements for ELI grade titanium tubes. Grade 23 extruded tubes are mainly used in critical structural components of aircraft, low-temperature pipelines of ships, deep-sea equipment, and low-temperature containers of superconducting magnets, which have strict requirements for fracture toughness.
