What Are the Density, Strength, and Physical Properties of Gr4 Titanium Foil?

In industrial material selection, Gr4 titanium foil (Grade 4 Titanium Foil) is often categorized as one of the higher-strength grades among commercially pure titanium. Its density is about 4.51 g/cm³, and its annealed tensile strength per ASTM B265 has a lower limit of 550 MPa. Compared with Gr1 and Gr2, Gr4 offers higher strength but correspondingly reduced ductility. Based on standard requirements and public engineering data, this article organizes the physical properties, mechanical properties, processing effects, and typical application boundaries of Gr4 titanium foil as a reference for engineers and purchasing personnel.

Cluster link: For the grade-level overview, see Grade 4 titanium overview.

1. Basic Physical Property Parameters and Applicable Scope of Gr4 Titanium Foil

The physical properties of Gr4 titanium foil are influenced by impurity elements such as oxygen and iron, as well as the actual processing condition. The typical density is 4.51 g/cm³, about 60% of steel. In lightweighting scenarios, structural weight can be reduced, but stiffness must be checked against the elastic modulus. Its melting point is about 1668℃, but “long-term service temperature ≤350℃” is an engineering experience range and does not mean that creep or oxidation will not occur during long-term use at 350℃. Verification based on atmosphere and stress level is required when approaching the upper limit. The resistivity is about 0.55–0.60 μΩ·m, making it a material with low electrical conductivity and relatively high resistance compared with copper and aluminum. Its non-magnetic nature suits equipment sensitive to magnetic fields, but its low electrical conductivity makes it unsuitable as an efficient electromagnetic shielding wrapping material. In terms of composition, Gr4 controls the upper limits of oxygen, iron, and other elements per ASTM B265; it should not be defined solely by “titanium purity of not less than 99.0%.” Its higher strength is precisely associated with the higher allowable oxygen and iron content.

Table 1: Typical physical properties and composition notes of Gr4 titanium foil

2. Annealed Mechanical Properties of Gr4 Titanium Foil and Notes on Thin-Gauge Elongation

The mechanical properties of Gr4 titanium foil must be distinguished by condition. Per the annealed requirements of ASTM B265, Gr4 has a tensile strength of ≥550 MPa, a yield strength of ≥483 MPa, and an elongation of ≥15%. These values are the standard lower limits for the annealed condition and do not apply to all thicknesses and conditions.

Higher strength can be obtained in the cold-worked condition, but elongation decreases. ASTM B265 does not provide unified lower limits for cold-worked tensile properties; these must be confirmed per the ordering specification. The mechanical property requirements of ASTM B265 should be understood in combination with product thickness, specimen size, and the test methods specified in the standard. For conventional sizes, Grade 4 annealed minimum tensile strength is 550 MPa, 0.2% yield strength is 483 MPa, and elongation is 15%. For ultra-thin foil such as 0.02 mm, specimen preparation, gripping method, size effects, and edge quality all have a significant influence on tensile results; therefore, directly applying the 15% elongation of conventional thickness as the guaranteed value for all ultra-thin foil is not recommended. Tensile testing of thin gauges is affected by size effects and surface condition, and elongation should be confirmed by measurement or mutual agreement.

Table 2: Annealed mechanical properties of Gr4 titanium foil (per ASTM B265, conventional thickness)

3. Typical Property Differences Between Gr4 and Gr1/Gr2 Titanium Foil

From Gr1 to Gr4, strength increases while ductility decreases. The strength differences originate primarily from the increased levels of elements such as oxygen, nitrogen, and iron, which raise the resistance to lattice deformation, rather than from added alloying elements. Table 3 lists the standard lower limits and typical yield strength ranges. The yield strength ranges are typical ranges, not the ASTM B265 acceptance upper/lower limits.

Table 3: Comparison of Gr1 / Gr2 / Gr4 titanium foil properties

*Typical range, not the ASTM B265 acceptance upper/lower limits.

In terms of the cost-performance trade-off, Gr4 approaches the strength of certain low-alloy titanium materials at lower cost, making it suitable for applications that do not require the full property set of an alloy grade but have higher strength requirements.

4. Effects of Cold Rolling, Annealing, and Surface Treatment on Gr4 Titanium Foil Properties

(1) Synergistic Effects of Cold Rolling and Intermediate Annealing

Multi-pass cold rolling precisely controls thickness and introduces stored deformation energy, but intermediate annealing is required between passes to avoid cracking caused by excessive hardening. The final grain size depends on the cold-rolling reduction and the annealing temperature and time: a larger reduction and lower annealing temperature yield finer grains with higher strength but lower elongation; conversely, grains coarsen, strength decreases, and elongation recovers.

(2) Effect of Annealing Schedule on Strength and Elongation

Gr4 is typically annealed at about 600–760℃, requiring vacuum or an inert atmosphere to prevent surface hydrogen absorption and oxidation. The purpose of annealing is to eliminate cold-work residual stress and induce recrystallization, adjusting the dislocation density and grain size to the target range. An excessive annealing temperature or extended hold time causes grain coarsening, with decreasing tensile and yield strength and increasing elongation; an insufficient temperature may retain cold-worked microstructure, resulting in inadequate elongation and increased anisotropy. Equipment temperature control accuracy can improve batch consistency, but the key is the match between temperature and speed, rather than a single upper temperature limit.

(3) Surface Treatment

Grinding should be avoided for ultra-thin foil. Ultrasonic cleaning, degreasing, and necessary chemical cleaning are recommended to remove oil and surface adsorbates, improving interfacial adhesion for coating, welding, or lamination. When surface roughness requirements exist, they can be controlled through roll surface condition and annealing atmosphere rather than mechanical grinding, which would thin the material.

5. Typical Applications and Material-Selection Notes for Gr4 Titanium Foil

(1) Chemical and Marine Engineering

Gr4 titanium foil can be used in chloride-containing, seawater, and oxidizing acid environments for sealing gaskets, linings, electrode claddings, and electrochemical components. Its corrosion resistance depends on the surface passive film; it may corrode rapidly in strong reducing acid environments, and corrosion verification should be performed before material selection.

(2) Aerospace and Precision Manufacturing

It can be used for non-primary-load honeycomb core materials, thermal/insulation sealing gaskets, and thin-wall support layers. Owing to foil thickness limitations, it should not be described as a primary load-bearing structure or the main pressure-bearing lining of deep-sea pressure vessels. The lightweighting advantage is genuine, but design review must incorporate stiffness, fatigue, and joining processes.

(3) New Energy and Electronics

The non-magnetic nature of Gr4 titanium foil suits magnetically sensitive sensor packaging and chemical power electrode substrates. Its low electrical conductivity makes it unsuitable as an efficient electromagnetic shielding material; in current-collector applications, contact resistance and the welding window should be addressed. The 0.02 mm ultra-thin gauge suits roll-to-roll processing, but mechanical properties must be validated for the actual thickness and condition.

6. Conclusion

Gr4 titanium foil is a higher-strength grade within commercially pure titanium, providing a practical engineering balance among density, corrosion resistance, non-magnetic behavior, and processability. Mechanical properties should be based on the annealed requirements of the standard, with the differences between the cold-worked condition and thin gauges distinguished. Material selection should be validated against the specific thickness, condition, and service environment, rather than relying only on nominal parameters.

FAQ

(1) Q1: What is the density of Gr4 titanium foil?

The density of Gr4 titanium foil is about 4.5 g/cm³, commonly taken as approximately 4.51 g/cm³ in engineering calculations, about 60% of steel. The weight-saving effect should be assessed comprehensively in combination with stiffness design.

(2) Q2: How large is the strength difference between Gr4 and Gr2?

Per the minimum tensile strength requirements of ASTM B265, Gr4 is 550 MPa and Gr2 is 345 MPa, a difference of 205 MPa between the two standard lower limits. Actual material strength is also affected by thickness, processing condition, and batch variation.

(3) Q3: Is Gr4 titanium foil stable at high temperatures?

Gr4 has a melting point of about 1668℃, but the melting point cannot be used as the basis for long-term service temperature. For long-term service environments at several hundred degrees Celsius, actual stress, atmosphere, oxidation, and creep behavior should be evaluated.

Contact Us

For further information on the sizes, tolerances, delivery conditions, and quality documents of Gr4 titanium foil, contact Titanium Valley. Depending on order requirements, products in thicknesses of 0.02–1.0 mm and widths up to 680 mm can be supplied, along with material certificates. Email: sales@titaniumvalleys.com

References

1. [1] Zhang Xiyan, Zhao Yongqing, Bai Chenguang. Titanium Alloys and Their Applications [M]. Beijing: Chemical Industry Press, 2005.
2. [2] Wang Jinyou, Ge Zhiming, Zhou Yanbang. Titanium Alloys for Aviation [M]. Shanghai: Shanghai Scientific & Technical Publishers, 1985.
3. [3] Huang Boyun, Li Chenggong, Shi Likai, et al. China Materials Engineering Canon: Volume 4, Nonferrous Metals Materials Engineering [M]. Beijing: Chemical Industry Press, 2006.
4. American Society for Testing and Materials. ASTM B265/B265M-20a Standard Specification for Titanium and Titanium Alloy Strip, Sheet, and Foil [S]. West Conshohocken, Pennsylvania, USA: ASTM International, 2020.