7075 Alüminyum Nedir?
7075, çinko, magnezyum ve bakır üzerine kurulu bir 7xxx serisi alaşımdır; burada MgZn₂ çökeltisi ana mukavemetlendirme fazıdır; çökelme sertleşmesi yoluyla, diğer hiçbir yaygın dövme alüminyumun eşleşemediği bir mukavemet seviyesine ulaşır ve bu da onu yüksek yük, ağırlık açısından kritik yapılar için kendi sınıfına yerleştirir. Bu en yüksek mukavemet, alaşımın kazanmak için tasarlandığı ödündür — ancak mukavemeti sağlayan aynı çinko açısından zengin, bakır içeren kimya, 7075'i aynı zamanda daha az korozyona dayanıklı ve füzyon yöntemleriyle pratikte kaynaklanamaz hale getirir.
The cost of that strength shows up in service: in humid, marine, or chloride environments, peak-aged 7075 can crack under sustained tensile load — a failure mode called stress-corrosion cracking (SCC) that no coating fully eliminates. 7075 answers that risk with a deliberately overaged temper, T73, which gives up a slice of peak strength to make the alloy reliable where corrosion and long service life decide the build — and whether T73 or its stress-relieved cousin T7351 is your call is the decision the next section explains.
Understanding the T73 Temper
“T73” means the material is solution heat-treated, quenched, then overaged through a two-stage artificial aging process. The alloy is heated to dissolve the Zn/Mg/Cu into solid solution, quenched to trap them supersaturated, then aged in two steps — a higher-temperature stage that coarsens the precipitates, followed by a lower-temperature stabilization. Overaging deliberately carries the material past peak strength so the grain-boundary precipitates grow coarse and electrochemically inactive, which cuts the driving force for intergranular SCC. The step that defines T73 is that second, overaging stage — it is what separates T73 from the peak-aged T6.
What the user gives up is ~12–15% of T6’s strength (UTS 505 vs 572 MPa; yield 435 vs 503 MPa), but what they get back is decisive: SCC resistance jumps from moderate (T6) to Excellent, salt-spray life runs roughly 1500–2000 h versus T6’s 500–1000 h, fracture toughness rises to about 28–33 MPa·√m versus ~20–24 for T6, and elongation improves so the material is less brittle and more damage-tolerant. For any part that lives in corrosion or carries cyclic load, that trade is almost always worth it.
T73 itself is içermediği stress-relieved, so a heavily machined T73 plate can still move as material is removed. That gap is why the “51” variant exists: T7351 adds a 1.5–3% stretch after quenching, combining the overaged corrosion resistance of T73 with the machining stability of T651. T7351 is the aerospace standard for thick, machined plates — it is the call when you need both corrosion resistance and dimensional stability after CNC work.
| Element | Tipik aralık (7075) |
|---|---|
| Çinko (Zn) | 5.1–6.1% |
| Magnezyum (Mg) | 2.1–2.9% |
| Bakır (Cu) | 1.2–2.0% |
| Krom (Cr) | 0.18–0.28% |
| Silisyum (Si) | Maks. %0,40 |
| Demir (Fe) | Maks. %0,50 |
| Manganez (Mn) | Maks. %0,30 |
| Titanyum (Ti) | Maks. %0,20 |
| Alüminyum (Al) | Denge |
The chemistry is identical to every other 7075 temper — the difference is entirely in the heat treatment, not the mix. Zinc provides the primary strengthening, copper adds hardness, and chromium improves SCC resistance; T73 simply manipulates the precipitate structure so the copper-driven corrosion susceptibility no longer controls the part’s life.
How T73 Differs from T6
T6 is peak-aged in a single artificial-aging step (~120 °C) to reach maximum strength, with only moderate SCC resistance. T73 runs the extra overaging stage, accepting ~12–15% lower UTS and yield to make the alloy SCC-resistant and tougher. The composition is the same; only the heat treatment differs. When corrosion is in the picture and the part must survive a long service life, T73 wins; when strength is everything and the environment is dry and controlled, T6 holds the advantage. For the peak-strength, stress-relieved side of the family, see our 7075-T651 complete guide.
7075-T73 Mechanical Properties
7075-T73 trades a slice of peak strength for corrosion and toughness — the numbers below are typical for plate, sheet, and bar.
| Mülkiyet | 7075-T73 | 7075-T6 (reference) |
|---|---|---|
| Yoğunluk | 2,81 g/cm³ | 2,81 g/cm³ |
| Çekme mukavemeti | ~505 MPa (73 ksi) | ~572 MPa (83 ksi) |
| Akma mukavemeti (%0,2 ofset) | ~435 MPa (63 ksi) | ~503 MPa (73 ksi) |
| Kopma uzaması | 13% | 11% |
| Yorulma mukavemeti | ~130–150 MPa | ~160 MPa |
| Brinell sertliği | ~135 HB | ~150 HB |
| Elastik (Young) modülü | ~71,7 GPa | ~71,7 GPa |
| Kesme mukavemeti | ~290 MPa | ~331 MPa |
| Fracture toughness (KIC) | ~28–33 MPa·√m | ~20–24 MPa·√m |
| Termal iletkenlik | ~130 W/m-K | ~130 W/m-K |
| Elektriksel iletkenlik | ~33–40% IACS | ~ IACS |
| Termal genleşme katsayısı | 23 µm/m·K | 23 µm/m·K |
The ~435 MPa yield is the number that matters most: about 15% below T6’s 503, but still roughly 2.4× the yield of 6061-T6 and well above any 6xxx grade. What you buy with that reduction is fracture toughness (~28–33 versus ~20–24 MPa·√m) and SCC resistance that is Excellent rather than moderate, so a T73 part tolerates cracks and corrosion far better than T6. Density, modulus, and thermal expansion are alloy-level properties and identical across every 7075 temper — only strength and corrosion behavior move with heat treatment. For the cross-alloy picture, see our 6061 vs 7075 karşılaştırma rehberimize.
Where 7075-T73 Is Used
7075-T73 earns its place wherever SCC, fracture toughness, or long service life decide the build — and where the user can accept ~15% less strength than T6 to get there. It owns the corrosion-exposed, damage-tolerant end of the 7075 range that T6 and T651 leave to dry, protected, strength-critical roles.
Aerospace Structures in Corrosive or Cyclic Service
Wing skins and planks, fuselage frames, bulkheads, landing-gear components, and helicopter rotor parts use T73 because the overaged structure resists SCC and crack growth over decades of flight. These are high-value, hard-to-inspect structures where a single corrosion-driven crack is unacceptable, so the toughness and SCC margin of T73 are worth more than the lost peak strength. For machined thick plate in these roles, T7351 is the usual specification.
Marine, Offshore, and Humid-Environment Hardware
Ship and boat structures, offshore platform brackets, marine-aircraft components, and coastal infrastructure use T73 because Excellent SCC and exfoliation resistance survive chloride exposure that would crack T6. T73 (or T7351 for machined parts) is chosen over T6 precisely because the environment is wet — the strength T6 gives up is the price of staying intact. Beyond aerospace and marine, T73 appears in high-performance sporting goods and automotive parts where both strength and corrosion resistance are required.
T73 vs Other 7075 Tempers — How to Choose
7075-T73 is the overaged, corrosion-first option; the other tempers trade strength for different priorities (machining stability, peak strength, or formability).
| Temper | İşlem | Çekme Dayanımı (MPa) | Akma Mukavemeti (MPa) | SCC direnci | İçin en iyisi | Kaçının |
|---|---|---|---|---|---|---|
| T73 | Solution + overage (no stretch) | ~505 | ~435 | Mükemmel | Corrosive, marine, long-service structures | Tight-tolerance machined thick plate (no stress relief) |
| T7351 | Çözelti + çekme + aşırı yaşlandırma | ~505 | ~435 | Mükemmel | Corrosive + precision-machined plate | En yüksek mukavemet gereklidir |
| T651 | Solution + stretch + peak age | ~572 | ~503 | Orta düzeyde | Dry, protected, precision-machined plate | Nemli, deniz veya klorür maruziyeti |
| T6 | Solution + peak age | ~572 | ~503 | Orta düzeyde | Maximum strength, dry/controlled environment | Corrosion or cyclic-load service |
| O | Tavlanmış | ~250 | ~110 | İyi | Şekillendirme, kesme, zorlu bükümler | Her türlü yük taşıma kullanımı |
When T73 Is the Right Call
Choose T73 when the part faces sustained humidity, salt spray, or chloride and cannot be fully protected by coating — you trade ~12–15% yield for SCC resistance that is orders of magnitude better and a salt-spray life roughly 2–3× that of T6. Choose T73 when the part carries cyclic load or must tolerate crack growth over a long service life (airframe, landing gear) — the higher fracture toughness and damage tolerance matter more than peak strength.
Başka Bir Temper Ne Zaman Daha Uygundur?
Step up to T7351 when the part is machined from thick plate ve sees corrosion — you keep T73’s SCC resistance plus the stretch step that stops it warping during CNC. Keep T6 or T651 when the environment is dry and protected and strength or machining stability leads the decision — T73 would only cost you strength you do not need to give up. For any part that must be fusion-welded or formed with tight radii, leave 7075 entirely: 6061-T6 welds and forms far better (see our 6061-T6 tam kılavuzu), ve O temperi şiddetli şekillendirmeye uygun tek 7075 durumudur.
Working with 7075-T73 — What You Need to Know
- İşleme. T73 machines well — its slightly softer surface means a touch less tool wear than T6, and overaging lowers residual stress so it holds tolerance through the cut. Use sharp carbide tooling and good coolant flow; expect clean finishes for mold, fixture, and airframe work, with better dimensional stability than unstress-relieved T6.
- Kaynak. 7075 is not recommended for fusion welding — arc processes cause hot cracking, soften the weld zone by 40–50%, and leave residual stress that invites SCC in service. For structural joints, design for riveting, bolting, or adhesive bonding; friction stir welding (FSW) can retain most base strength for non-critical seams, but a fusion-welded 7075 load path should not return to service.
- Korozyon koruması. T73 already carries Excellent SCC and exfoliation resistance, so it needs less supplemental protection than T6 — but in severe marine service still specify anodizing (Type II or III), chromate conversion coating (Alodine), cladding, or paint. T73 is the temper to choose when coating alone cannot be trusted to carry the corrosion risk.
- Şekillendirilebilirlik. T73 has poor formability and cracks under tight-radius bends; form in the O temper, then heat-treat the finished shape to T73 after shaping — do not expect to form T73 directly. The overaged condition is fixed by the heat treatment, not by cold work.
Artılar ve Sınırlamalar Bir Bakışta
| Boyut | Avantaj | Sınırlama |
|---|---|---|
| Dayanım-ağırlık oranı | High (~435 MPa yield, ~2.4× 6061-T6) | ~15% below T6/T651 peak |
| SCC direnci | Excellent (salt spray 1500–2000 h) | Still needs coating in extreme marine |
| Fracture toughness | ~28–33 MPa·√m, tolerant of cracks | — |
| Talaşlı İmalat | Good; lower residual stress than T6 | Not stress-relieved unless specified T7351 |
| Korozyon | Excellent exfoliation + SCC | Gives up peak strength to get it |
| Kaynaklanabilirlik | Kritik olmayan bağlantılar için FSW uygulanabilir | Füzyon kaynağı önerilmez |
| Stok Durumu | Stocked as plate, sheet, bar, tube | İnce cidar ve özel ekstrüzyonlar daha az yaygındır |
Sonuç
The trade-off is clear: 7075-T73 gives up ~12–15% of T6’s peak strength to deliver Excellent stress-corrosion cracking resistance, higher fracture toughness, and better damage tolerance — the right call whenever corrosion, cyclic load, or long service life decide the build, and the wrong call in dry, strength-critical roles where T6 or T651 wins. Choose T73 or T7351 when chloride or humidity is in the picture; choose T6 or T651 when the environment is controlled and peak strength or machining stability leads the decision.
At Linsy Alüminyum, we stock 7075-T73 in plate, sheet, bar, and tube, with T7351 and other 7075 tempers (T6, T651) available across forms. Every order ships with a Mill Test Certificate, and SGS composition, mechanical, and ultrasonic (thick-plate) reports are available on request. Our team reviews your drawing, flags SCC risk before you over-specify, and recommends T73 versus T7351 based on whether the part is machined. Çizimi ve gereksinimleri gönderin, size bir sınıf uygunluk incelemesi ve teklif döndüreceğiz.
Sıkça Sorulan Sorular
Is 7075-T73 weaker than T6?
Yes, by about 12–15% — UTS drops from ~572 to ~505 MPa and yield from ~503 to ~435 MPa. What you gain is SCC resistance (Excellent versus moderate), fracture toughness (~28–33 versus ~20–24 MPa·√m), and better damage tolerance, so for any corrosive or long-life part the lower strength is the right trade.
7075-T73 vs T7351: which should I choose?
Both carry the same overaged corrosion resistance; T7351 adds a 1.5–3% stress-relief stretch. Choose T7351 when the part is CNC-machined from thick plate, because the stretch keeps it from warping as material is removed. Choose plain T73 when forming or finishing is light and machining stability is not the deciding factor.
Can 7075-T73 be welded?
Füzyon kaynağı ile değil. Ark işlemleri sıcak çatlamaya neden olur, kaynak bölgesini –50 yumuşatır ve serviste SCC riski bırakır, bu nedenle yapısal 7075 bağlantıları perçinlenir, cıvatalanır veya yapıştırılır. Sürtünme karıştırma kaynağı kritik olmayan dikişler için çalışabilir ve temel mukavemetin çoğunu korur, ancak füzyon kaynaklı bir 7075 yük yolu servise dönmemelidir.
Is 7075-T73 good for marine or outdoor use?
Yes — it is the preferred 7075 temper for marine, offshore, and coastal service because of its Excellent SCC and exfoliation resistance in chloride. It still benefits from anodizing, Alodine, or paint in severe exposure, but unlike T6 it is specified specifically because coating alone cannot be trusted to carry the risk.
Does Linsy stock 7075-T73, and what is the lead time?
Yes. Stock plate, sheet, bar, and tube ship from inventory; non-stock sizes and tempers (including T7351) run on custom production with a typical lead time of 10–60 days depending on alloy, dimensions, and processing. Linsy supports low-MOQ custom production, so mixed-spec or harder-to-find 7075 orders rarely block a project.
