Aluminium bronze is copper alloyed with 6–13% aluminium, and it is the strongest and most corrosion-resistant of the common copper alloy families. The aluminium forms a tenacious, self-healing alumina film that outperforms the oxide on any brass or tin bronze — outstanding in seawater at high velocity, resistant to non-oxidising acids, and highly resistant to erosion and cavitation. Below about 8% aluminium the alloy is single-phase alpha: formable, weldable, and not hardenable. Above about 9.4% a beta phase appears and the alloy becomes quench hardenable like a steel — stronger, hot forgeable, and progressively harder as the aluminium climbs. C61900 reaches 1048 MPa. Two grades, C61300 and C61400, are ASTM F468 and F467 certified fastener alloys carrying two to three times the yield of a brass bolt. All of them are non-sparking and non-magnetic, with no beryllium handling regime.
Try adjusting your search criteria or contact us for custom alloys.
Aluminium sets the phase structure, and the structure sets everything else. Below roughly 8% aluminium the alloy is single-phase alpha: ductile, cold formable, readily welded, and not hardenable by heat treatment — strength comes from cold work alone. Above roughly 9.4% aluminium a beta phase is stable at temperature and the alloy becomes alpha-beta: much stronger, superb in hot forging and extrusion, and — uniquely among the common copper alloys — quench hardenable like a steel. C61000, C61300 and C61400 are alpha; C61900, C62300, C62400, C62500 and the cast C95400 are alpha-beta.
The catch is the eutectoid, and it is the reason heat treatment matters here more than on any other copper alloy. On slow cooling through about 565 °C the beta phase decomposes to alpha plus gamma-2 (γ₂, Cu₉Al₄), a hard brittle intermetallic that embrittles the alloy and corrodes preferentially. Rapid cooling from the beta field suppresses it; a subsequent temper anneal then develops a fine, controlled structure with good strength and good corrosion behaviour. For C95400 the published cycle is solution treat at 871–913 °C for one hour, water quench, then temper anneal at 621–663 °C — the TQ50 condition, which lifts the specified minimum from 517 to 621 MPa and hardness from 150 to 190 HB. Specify the heat-treated condition on the order, not just the alloy number.
Dealuminification is the failure mode to design against. Aluminium is selectively leached out, leaving a porous copper-rich residue that keeps the original shape of the part — the same deceptive failure that makes dezincification dangerous in brass. Attack concentrates on the gamma-2 phase and on continuous beta networks, so it is a structural problem, not simply a compositional one. There are three defences: stay single phase below about 8% aluminium, which is why C61300 and C61400 are the grades for long-life seawater tube and fastening; control the heat treatment, quenching and temper annealing to suppress gamma-2; or add nickel, which at around 4% suppresses the eutectoid outright and is the entire reason the nickel aluminium bronzes exist as a separate family.
What the alumina film buys you, and where it stops. The film is thin, tenacious and self-healing, and far more stable than the cuprous oxide on a brass. It gives outstanding resistance in seawater and brackish water at high flow velocity, good resistance to non-oxidising acids — dilute sulphuric, hydrochloric and phosphoric — excellent erosion, cavitation and impingement resistance, and high resistance to biofouling. Aluminium bronze is also non-sparking and essentially non-magnetic, which makes it a safety-tool material alongside beryllium copper but without the beryllium particulate controls, and it holds useful strength at elevated temperature. The limits: oxidising acids, notably nitric, attack it; ammonia and amines can cause stress-corrosion cracking; and sulphide-polluted stagnant seawater degrades the film.
Two grades here are certified fastener alloys, and they are the strongest copper-alloy bolting in the ASTM nonferrous standards. ASTM F468 and F467 list C61300 as Cu 613 and C61400 as Cu 614. Cu 613 is specified at 552–758 MPa tensile with 345 MPa minimum yield to 13 mm; Cu 614 at 517–758 MPa with 241 MPa minimum yield in all sizes; both at 70–95 HRB and 30% minimum elongation. A naval brass bolt to Cu 464, for comparison, is specified at 345 MPa with 103 MPa minimum yield. The other six grades are supplied to their mill product standards — ASTM B150, B169, B124, B283, B111, B315, B148 and B505 as applicable — with thread conformance to the relevant ASME or ISO standard.
Aluminium bronze is tough, strongly work hardening and abrasive — the most demanding of the common copper alloys to cut. CDA machinability ratings here run from 20 for the alpha grades C61000 and C61400 and the 13% alloy C62500, through 30 for C61300, to 50 for the forging grades C62300 and C62400 and 60 for the cast C95400. None approaches a leaded brass, and no leaded aluminium bronze exists — lead and aluminium together make the alloy hot short. What works is rigid setups and heavy, uninterrupted cuts, because the alloy work hardens severely if the tool dwells; positive rake with a keen, well-supported edge; reduced surface speed with generous feed rather than the reverse; carbide tooling and flood coolant throughout. On the forming side, the alpha grades cold form and the alpha-beta grades hot forge — C62400 and C62500 are rated Excellent for hot forming and Poor or Not Recommended for cold working.
All composition and machinability data from the Copper Development Association alloy records. Aluminium and iron figures are read directly from the individual grade pages. Machinability is on the CDA scale where C36000 free-cutting brass = 100.
| Grade | Designation | Family | Aluminium % | Iron % | Structure | Machinability | Chosen For |
|---|---|---|---|---|---|---|---|
| C61000 | Aluminium Bronze 8% Al | Alpha | 6.0–8.5 | 0.50 max | Single-phase alpha | 20 | Welding and wear overlay; 15% IACS — highest here |
| C61300 | Tin-Modified Aluminium Bronze | Alpha | 6.0–7.5 | 2.0–3.0 | Single-phase alpha | 30 | ASTM F468 Cu 613 bolting; condenser tube |
| C61400 | Iron Aluminium Bronze | Alpha | 6.0–8.0 | 1.5–3.5 | Single-phase alpha | 20 | ASTM F468 Cu 614; the family workhorse |
| C61900 | Heat-Treatable Strip | Alpha-beta | 8.5–10.0 | 3.0–4.5 | Alpha-beta | — | 1048 MPa — springs and contacts |
| C62300 | Aluminium Bronze, 9% | Alpha-beta | 8.5–10.0 | 2.0–4.0 | Alpha-beta | 50 | Hot forging with the best wrought machinability |
| C62400 | Aluminium Bronze, 11% | Alpha-beta | 10.0–11.5 | 2.0–4.5 | Alpha-beta | 50 | Hot forging; bushings and wear parts |
| C62500 | High-Aluminium Bronze, 13% | Alpha-beta | 12.5–13.5 | 3.5–5.5 | Alpha-beta | 20 | Wear, bearing and die material; 1% elongation |
| C95400 | Cast Aluminium Bronze | Cast | 10.0–11.5 | 3.0–5.0 | Cast alpha-beta | 60 | The standard casting alloy; CAST, quench hardenable |
Read the aluminium column first; it tells you the structure and almost everything else. The three alpha grades at 6–8.5% aluminium are the formable, weldable, dealuminification-resistant choices, and the two marked ones are the ASTM F468 and F467 certified fastener alloys Cu 613 and Cu 614. From 8.5% upward the alloys are alpha-beta and quench hardenable: C61900 exploits that hardest, reaching 1048 MPa in the HR10 temper — the highest figure on this hub and in beryllium copper territory for spring duty, without the beryllium handling regime. C62300 and C62400 are the hot forging grades and carry the best machinability of the wrought family at 50. C62500 at 13% aluminium is a wear and die material rather than a structural one — 1% elongation is not a misprint. C95400 is a cast alloy, available only as castings and cast bar; it is the standard general-purpose aluminium bronze casting and the easiest alloy here to machine. Iron matters more than its small percentage suggests — it refines the grain and raises strength, which is why C61400 outperforms C61000 at a similar aluminium level. Note finally that CDA register no common alloy name for five of these eight grades; the designations shown are descriptive, and the UNS number is the authoritative identifier on drawings and orders.
We are committed to delivering zero-defect aluminium bronze fasteners and components. All products undergo rigorous testing including PMI (Positive Material Identification), chemical analysis with aluminium, iron and nickel certified explicitly — aluminium sets the phase structure and therefore the heat-treatability and dealuminification behaviour — heat-treatment certification to the specified cycle, mechanical and hardness verification against the condition and section supplied, microstructural examination for gamma-2 and continuous beta where required, dimensional inspection and full traceability with EN 10204 3.1 certification.
Exotic Alloy exports aluminium bronze rod, bar, plate, tube, forgings, castings, fasteners and machined components to marine, offshore, desalination, power generation, chemical process, pump and valve clients worldwide. Our dedicated logistics team ensures secure export packaging and timely deliveries by sea and air freight with full customs documentation support.