17-4 PH Stainless vs Ti-6Al-4V (Grade 5)
17-4 PH stainless and Ti-6Al-4V (Grade 5) are both high-strength alloys, but they balance cost, weight, and biocompatibility differently. 17-4 PH is a precipitation-hardening stainless reaching high hardness and ~1070 MPa tensile at lower cost. Ti-6Al-4V offers comparable strength at roughly half the density, with outstanding corrosion resistance and biocompatibility for aerospace and medical use. Weight and biocompatibility versus cost frames the decision.
The verdict
Choose 17-4 PH stainless for high strength and hardness at lower cost when weight is not critical. Choose Ti-6Al-4V when you need half the density, the best strength-to-weight, top corrosion resistance, or biocompatibility for medical and aerospace parts. Stainless for affordable strength; titanium for lightweight, corrosion, and implants.
Side-by-side data
| Property | 17-4 PH Stainless | Ti-6Al-4V (Grade 5) |
|---|---|---|
| Category | Stainless Steel | Titanium |
| Density (g/cm³) | 7.8 | 4.43 |
| Tensile strength (MPa) | 1070 | 1000 |
| Yield strength (MPa) | 1000 | 910 |
| Elongation (%) | 10 | 14 |
| Hardness | 38 HRC | 36 HRC |
| Max service temp (°C) | 300 | 400 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 18 | 6.7 |
| Typically used for | High-strength corrosion-resistant parts | Aerospace & medical — best strength-to-weight |
Which should you choose?
Choose 17-4 PH Stainless when…
- Cost matters — 17-4 PH is ~4/5 versus Ti-6Al-4V at ~5/5
- High hardness is needed via age hardening (~38 HRC) for wear and strength
- Very high strength is required — tensile ~1070 MPa, comparable to titanium
- Weight is not the dominant constraint (17-4 is ~7.8 g/cm3, dense)
- Good corrosion resistance (4.0/5) in general and marine environments suffices
- You want a heat-treatable stainless with adjustable strength via aging conditions
Choose Ti-6Al-4V (Grade 5) when…
- Weight is critical — titanium is ~4.43 g/cm3, roughly half 17-4 PH's ~7.8
- Best-in-class strength-to-weight is the goal — ~1000 MPa tensile at low density
- Biocompatibility is required for implants and surgical components
- Maximum corrosion resistance is needed — Ti rates 5/5 vs 17-4's 4.0/5
- Aerospace structures demand light, strong, fatigue-resistant parts
- The higher cost (~5/5) is justified by weight, corrosion, or medical requirements
Key differences that matter
- Ti-6Al-4V is ~half the density of 17-4 PH (~4.43 vs ~7.8 g/cm3) — major weight savings
- Both reach very high strength (~1000-1070 MPa tensile), so strength-to-weight favors titanium
- 17-4 PH gains strength and hardness (~38 HRC) through precipitation (age) hardening
- Titanium leads on corrosion resistance (5/5 vs 4.0/5) and is biocompatible for implants
- 17-4 PH is cheaper (~4/5 vs ~5/5) — a meaningful saving where weight is not critical
- Both are difficult to machine; titanium is especially demanding (1.5/5)
- Choice: 17-4 for affordable hardness/strength, titanium for light weight, corrosion, biocompatibility
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Which is stronger, 17-4 PH or Ti-6Al-4V?
On absolute tensile they are close — 17-4 PH ~1070 MPa versus Ti-6Al-4V ~1000 MPa. But titanium achieves that strength at roughly half the density, so its strength-to-weight is far superior. If raw strength at a given size is all that matters and weight is irrelevant, 17-4 edges ahead; for strength per unit mass, titanium wins decisively.
Why choose titanium if 17-4 PH is cheaper?
Three reasons titanium justifies its higher cost: weight (about half the density), corrosion resistance (5/5 versus 4.0/5), and biocompatibility for medical implants. In aerospace and surgical applications those properties are non-negotiable. Where weight, corrosion, and biocompatibility are not critical, 17-4 PH's lower cost (~4/5 vs ~5/5) makes it the more economical strong alloy.
Is 17-4 PH biocompatible like titanium?
Not to the same degree. Ti-6Al-4V is the established choice for long-term implants because of its excellent biocompatibility and corrosion resistance in the body. 17-4 PH is used in some surgical instruments but is generally not preferred for permanent implants. For implantable medical devices, titanium is the standard; 17-4 suits reusable instruments and tooling.
How does age hardening affect 17-4 PH?
17-4 PH is precipitation-hardening: a relatively low-temperature aging treatment (such as H900) forms strengthening precipitates that raise hardness to about 38 HRC and tensile to ~1070 MPa. Different aging conditions trade strength for toughness, giving design flexibility. This heat-treat response lets a single alloy be tuned to the strength and hardness a part requires.
Which is harder to machine?
Both are challenging, but Ti-6Al-4V is harder, at 1.5/5 versus 17-4 PH's 2.0/5. Titanium's low thermal conductivity concentrates heat at the cutting edge and it work-hardens, demanding slow speeds, sharp rigid tooling, and flood coolant. 17-4 PH is also tough on tools, particularly after aging. Neither machines quickly, which adds to part cost.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.