UNS C95400 Aluminum Bronze — Properties, Composition & Casting Guide

Introduction

UNS C95400 aluminum bronze is the highest-strength cast copper alloy most engineers will ever specify — combining tensile strength up to 655 MPa, excellent seawater corrosion resistance, and proven wear performance in a single castable material. Marine engineers, pump designers, and heavy-equipment OEMs have relied on C95400 for decades because it survives where softer bronzes fail and machines more predictably than most high-strength alternatives.

This guide delivers exact composition limits, as-cast and heat-treated mechanical values, foundry process parameters, and the cost logic that tells you exactly when C95400 is worth the premium — and when it isn’t. Read to the end and you’ll know which alloy condition to specify, which casting route to call out, and which competitor alloys genuinely outperform it in specific scenarios.

C95400 vs C95500 vs C93200 — Quick Comparison

Material selection decisions live or die on the comparison. Here’s how C95400 stacks up against its two closest rivals before anything else.

C95400 wins when you need the strength-corrosion combination at lower cost than C95500 and with better performance than C93200 can deliver. C93200 fails in seawater. C95500 outperforms in extreme marine duty but costs more and machines harder. C95400 owns the space between them.

UNS C95400 Composition — Alloy Chemistry Breakdown

C95400 is a copper-aluminum-iron alloy. Aluminum does the heavy lifting — it drives strength, hardness, and the protective oxide film that makes this alloy exceptional in corrosive service.

The critical detail most engineers miss: aluminum content sitting at 10.0% vs 11.5% produces measurable differences in heat treatment response. At the high end of the Al range, the alloy responds more strongly to solution treatment — yielding harder, stronger parts.

Always request the mill certificate and cross-reference Al content against your target mechanical properties. C95400 contains no lead — making it fully RoHS-compliant and suitable for potable water systems where C93200 is disqualified.

UNS C95400 Mechanical Properties — As-Cast and Heat-Treated Values

C95400 is unique among common cast bronzes because heat treatment materially changes its performance. Specify the condition on your drawing — not just the alloy.

Mechanical Properties

Physical Properties

Note the narrow solidus-liquidus gap of just 11 °C — this alloy solidifies fast. That tightens your foundry process window considerably compared to tin bronzes.

C95400 Casting Process — Sand, Centrifugal & Continuous Cast Guide

C95400 is a high-performance casting alloy — not a forgiving one. Casting quality determines whether you get 586 MPa or a scrap part.

Sand Casting handles large, complex geometries like valve bodies, pump casings, and structural hardware. It’s the most flexible route for one-off and low-volume parts.

The penalty is higher internal porosity risk. C95400 has high shrinkage during solidification — sand cast parts require aggressive risering and feeding design to avoid internal voids on heavy sections.

Centrifugal Casting is the preferred route for bushings, sleeves, and cylindrical wear components. The centrifugal force produces a denser, more uniform structure with fewer discontinuities than conventional gravity casting.

Specify centrifugal casting whenever your bushing bore diameter exceeds 50 mm and roundness tolerance matters. The process-driven grain refinement adds measurable wear life.

Continuous Casting suits bar, tube, and plate stock for machined-from-solid components. It delivers the most consistent cross-sectional properties and eliminates casting defects in the working zone entirely.

Use it for wear strips, slide plates, and guide rails where consistent hardness across the full cross-section drives service life.

Critical foundry parameters to specify:

C95400 has high drossing tendency — aluminum oxidizes aggressively at melt temperature. Require inert atmosphere or cover flux during melting and transfer.

Dross inclusions in aluminum bronze don’t just reduce strength — they become initiation sites for corrosion pitting in service.

Pouring temperature must stay within a tight window above the 1038 °C liquidus. Excessive superheat above ~1100 °C accelerates dross formation and compositional drift in aluminum content.

Require ceramic filtration in the gating system on any pressure-containing part. Request radiographic testing (RT) to ASTM E272 for valve bodies and pump casings — shrinkage in C95400 reads as irregular, jagged voids distinctly different from the smooth hydrogen porosity in tin bronzes.

UNS C95400 Heat Treatment — Solution, Quench & Stress Relief Guide

Heat treatment is not optional for C95400 in demanding service. It’s the process step that separates a 586 MPa casting from a 655 MPa component.

Stress Relief at 315 °C (600 °F) removes residual casting stress without changing bulk mechanical properties. Apply it to all as-cast parts before finish machining to prevent dimensional shift during material removal.

Solution Treatment followed by Water Quench targets the TQ50 condition — the heat-treated designation used in ASTM specifications. Solution treat at 870–913 °C (1600–1675 °F), hold for section-thickness-dependent time, then quench immediately into water.

This dissolves the corrosion-sensitive β-phase and locks in a more uniform microstructure. The result: +69 MPa on UTS, +89 MPa on yield strength, and significantly improved resistance to selective phase corrosion (dealuminification).

Annealing at 621–663 °C (1150–1225 °F) softens over-hardened material and improves ductility where formability or toughness matters more than peak strength. Use it when downstream forming operations follow casting.

The specification mistake that causes field failures: ordering C95400 “as-cast” for seawater service. The as-cast microstructure retains β-phase at grain boundaries — precisely the phase that dealuminifies in marine crevice conditions. Always specify TQ50 condition for submerged or intermittently wetted marine hardware.

C95400 Machinability, Joining & Surface Finishing

Machinability is moderate — significantly harder to cut than C93200 leaded bronze, roughly comparable to other high-strength copper alloys. C95400 work-hardens under the cutting tool if feed rates drop too low.

Use carbide tooling with positive rake geometry. Target surface speeds of 90–150 m/min for turning, with continuous feed and generous flood coolant.

Never dwell — rubbing without cutting builds a work-hardened layer that destroys tool life on the next pass. Final machining after heat treatment is the rule for precision bearing bores.

Joining by gas-shielded arc welding (GTAW or GMAW) is acceptable when necessary. Use ERCuAl-A2 filler wire and preheat to 150–200 °C to reduce cracking risk in heavy sections.

Oxyacetylene welding is not recommended — the flame atmosphere promotes aluminum oxide contamination in the weld pool. Post-weld stress relief at 315 °C is required to restore corrosion resistance in the heat-affected zone.

Surface Finishing for bearing applications requires honing to Ra 0.4–0.8 µm for reliable lubricant film formation. C95400’s 170 HB hardness means it holds this finish under load better than tin bronze alternatives.

For marine hardware, no additional coating is typically required — the natural Al₂O₃ film provides the corrosion barrier. Mechanical polishing to Ra ≤ 1.6 µm improves film quality on submerged surfaces exposed to high-velocity flow.

C95400 Corrosion Resistance — Marine, Seawater & Industrial Performance

C95400 builds its own corrosion protection. The aluminum content spontaneously forms a dense Al₂O₃ oxide film that passivates the surface — similar in concept to how stainless steel relies on its chromium oxide layer.

In static or low-velocity seawater, C95400 delivers corrosion rates below 0.025 mm/year — among the lowest of any cast copper alloy. This is why it dominates marine pump and valve specifications where C90300 tin bronze starts to show limits.

Where C95400 genuinely outperforms C90300: high-velocity seawater above 2–3 m/s. C90300 suffers erosion-corrosion at those flow rates. C95400’s harder surface and tougher oxide film resist impingement attack that strips tin bronze surfaces in months.

Where C95400 shows vulnerability: dealuminification in poorly heat-treated castings. As-cast C95400 retains β-phase at grain boundaries — in stagnant seawater, crevices, or shielded areas, that phase corrodes preferentially, leaving a copper-rich sponge with no structural integrity.

The fix is mandatory. Specify TQ50 heat treatment for all marine submerged or crevice-exposed components — no exceptions. Galvanic compatibility also requires attention: C95400 is noble, and coupling it to aluminum alloys or carbon steel without isolation accelerates corrosion of the less noble metal.

C95400 Cost & Decision Logic — When the Premium Pays Off

C95400 costs more than C90300 tin bronze and significantly more than C93200 leaded bronze. The question isn’t whether it’s expensive — it’s whether the service life math justifies the upfront delta.

C95400 makes economic sense when at least two of these conditions apply:

The part operates under high mechanical load (PV value above ~1.75 MPa·m/s) where C90300’s 300 MPa UTS is insufficient margin. Undersized bronze in a bearing doesn’t fail gradually — it fails suddenly and takes the shaft with it.

The part is exposed to seawater or process water at flow velocities above ~2 m/s. C90300 degrades under erosion-corrosion at those speeds. The replacement cost of a corroded impeller at a 6-month service interval far exceeds the alloy premium at procurement.

The part requires heat treatment to meet a strength specification. If you’re already paying for TQ50 processing, the incremental cost of C95400 over C90300 compresses significantly in total part cost.

When to stay with C90300 instead: moderate-load bushings and fittings in low-velocity water service. C90300 at 320 MPa UTS handles most pump bushing PV values below 1.5 MPa·m/s without issue — and it costs less, machines faster, and casts more easily.

When to step up to C95500 instead: propeller hubs, offshore structural components, and parts exposed to cavitation damage. C95500’s higher nickel content pushes seawater corrosion resistance and strength beyond what C95400 delivers — justified for safety-critical components where failure consequences are severe.

Quick decision rule: heavy load + wet service = C95400. Moderate load + wet service = C90300. Extreme load + offshore marine = C95500. Economy + dry service = C93200.

UNS C95400 Applications — Pumps, Bearings, Marine & Gears

C95400 earns its place in applications where two or more failure modes are simultaneously active. Each category below exploits a different combination of the alloy’s properties.

Pump Impellers and Casings — the combination of erosion-corrosion resistance and high strength makes C95400 the default specification for seawater pump internals. The Al₂O₃ film resists cavitation damage that destroys tin bronze impellers in high-head pump configurations.

Heavy-Duty Bearings and Bushings — plain bearings, sleeve bushings, and thrust washers under high load and slow speed. C95400’s anti-galling behavior at 170 HB hardness provides seizure resistance that softer bronzes cannot match under boundary lubrication conditions.

Marine and Offshore Hardware — shipboard through-hull fittings, propulsion system components, and deck hardware in continuous seawater exposure. Specify TQ50 condition without exception for submerged hardware — as-cast C95400 in seawater is a warranty claim waiting to happen.

Worm Gears and Transmission Components — C95400 pairs well against hardened steel worm shafts in high-load gear sets. Its ~170 HB hardness combined with galling resistance supports higher contact stress than C90300’s ~70 HB allows.

Wear Strips, Slide Plates and Guide Rails — continuous friction applications under abrasive or contaminated contact. The combination of hardness and low seizure tendency produces predictable, measurable wear rates that allow planned maintenance intervals — eliminating unscheduled downtime from unpredictable failure.

Power Generation and Industrial Fittings — turbine components, high-load structural supports, and industrial connectors in elevated temperature service. C95400’s thermal conductivity of 58.7 W/m·K and modulus of 107 GPa provide dimensional stability under cyclic thermal and mechanical loading that eliminates fatigue cracking seen in lower-strength alternatives.

UNS C95400 FAQs — Properties, Heat Treatment & Material Selection

Is UNS C95400 the same as 954 bronze?

Yes — “954 bronze,” “C954,” “CDA 954,” and “UNS C95400” all refer to the same aluminum bronze alloy family. The UNS designation is the authoritative reference for procurement and material certification.

Is C95400 magnetic?

Effectively no — magnetic permeability runs at ~1.27 as-cast and ~1.2 in TQ50 condition. For practical engineering purposes it is non-magnetic. Minor responses can appear near welds or heavily deformed zones but are negligible in service.

Can C95400 be welded?

Yes, with correct procedure. Use GTAW or GMAW with ERCuAl-A2 filler, preheat to 150–200 °C, and follow with stress relief at 315 °C. Oxyacetylene welding is not recommended. Post-weld heat treatment is mandatory for any seawater-exposed weld joint — unrelieved welds are susceptible to stress corrosion.

Is C95400 suitable for seawater service?

Yes — with the correct heat treatment condition. Specify TQ50 for all submerged and crevice-exposed marine components. As-cast C95400 in seawater risks dealuminification at grain boundaries. Heat-treated C95400 in seawater delivers service life measured in years, not months.

What is the main weakness of C95400?

Sensitivity to microstructure quality. As-cast or improperly heat-treated C95400 retains β-phase at grain boundaries — the phase most vulnerable to selective corrosion in marine environments. The alloy’s strength is not the risk; foundry and heat treatment process control is.

C95400 vs C90300 — which is better for marine pump impellers?

C95400. Flow velocities above ~2 m/s in seawater cause erosion-corrosion that C90300 cannot resist long-term. C95400’s harder surface and protective oxide film sustain impeller geometry and wall thickness through multi-year service intervals.

What casting process produces the best C95400 bushing?

Centrifugal casting. The process produces denser, more uniform microstructure with fewer internal discontinuities than sand casting — directly translating to longer wear life in high-load bushing applications. Specify centrifugal cast and TQ50 heat treatment together for maximum performance.

Does C95400 require heat treatment to meet ASTM B505 minimums?

No — the 586 MPa UTS and 221 MPa yield minimums are achievable as-cast under ASTM B505. Heat treatment (TQ50) pushes those values to 655 MPa and 310 MPa respectively. For seawater service, specify TQ50 regardless of strength requirements — the microstructural improvement is the primary driver, not the strength increment.

The Conclusion on UNS C95400 Aluminum Bronze

C95400 sits at the top of the cast copper alloy performance pyramid for one straightforward reason — it handles the load cases, corrosion environments, and service conditions that eliminate every other option from the candidate list. It’s harder to cast than tin bronze, more demanding to machine than leaded bronze, and more expensive than both.

Every one of those trade-offs is intentional. When you need a part that runs hard, runs wet, and runs for years without intervention, C95400 is not a compromise — it’s the specification.