Aluminum 5450: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

5450 is a member of the 5xxx series aluminum alloys, a family characterized by magnesium as the principal alloying addition. The 5xxx series are non-heat-treatable alloys whose elevated strength derives primarily from solid-solution strengthening by Mg and from strain hardening where applicable.

Major alloying elements in 5450 are magnesium (nominally in the mid-to-high single digits by weight) with controlled manganese, iron and trace amounts of Cu, Si, Zn and Cr to tailor strength, grain structure and corrosion behavior. The strengthening mechanism is non-heat-treatable: strength is obtained from Mg in solid solution and by mechanical cold working; artificial aging is not used to increase peak strength.

Key traits of 5450 include a combination of moderately high strength for a non-heat-treatable alloy, good general corrosion resistance (especially in atmospheric and mildly marine environments), very good weldability using typical aluminum filler metals, and good formability in annealed conditions. These characteristics make 5450 attractive for structural applications where strength-to-weight, corrosion resistance and weldability must be balanced.

Typical industries using alloys of this class include shipbuilding and marine structures, automotive and transportation components, pressure vessels, and certain aerospace secondary structures. Engineers choose 5450 over other alloys when a higher as-fabricated strength and superior weld/paint performance are needed without the cost and distortion penalties of heat-treated alloys.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed, best for forming and deep drawing
H111	Low–Moderate	High	Very Good	Very Good	Slight, unspecified strain hardening; retains good formability
H14	Moderate	Moderate	Good	Very Good	Half-hard; common for sheet applications requiring modest strength
H22	Moderate	Moderate	Good	Very Good	Strain-hardened and stabilized by thermal treatment for improved stability
H32	Moderate–High	Moderate	Fair	Very Good	Strain-hardened and stabilized; widely used for structural sheet
H34	High	Lower	Fair–Poor	Very Good	Full hard condition used where high stiffness and lower ductility accepted

The temper chosen for 5450 strongly affects both mechanical and forming behavior; annealed O temper maximizes ductility and enables complex forming while H‑tempers trade ductility for higher yield and tensile values. Stability during processing, including resistance to stress relaxation and temper changes in the heat-affected zone when welding, is influenced by the specific H‑designation and any stabilization treatments applied.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.40	Deoxidizer and strength trade-off; kept low to preserve corrosion resistance
Fe	≤ 0.50	Impurity element; higher Fe can form intermetallics affecting formability
Mn	0.2–1.0	Refines grain structure and improves strength and resistance to recrystallization
Mg	3.5–5.5	Primary strengthening element; controls solid-solution strengthening and corrosion behavior
Cu	≤ 0.25	Small additions increase strength but can reduce corrosion resistance at higher levels
Zn	≤ 0.25	Kept low to minimize susceptibility to galvanic and localized corrosion
Cr	0.05–0.25	Controls grain structure and improves resistance to grain boundary corrosion
Ti	≤ 0.15	Grain refiner for cast or extrusion feedstock; typically residual in wrought alloys
Others	Balance Al, trace impurities	Minor additions and residuals are controlled to meet mechanical and corrosion targets

The alloy chemistry is tuned so Mg provides the primary strength mechanism while Mn and small amounts of Cr control grain size, recrystallization behavior and toughness. Low levels of Si, Fe and Cu are maintained to prevent brittle intermetallic particles and to preserve formability and corrosion resistance. The exact composition window will vary between suppliers and standards but the influence of Mg and Mn is central to 5450 performance.

Mechanical Properties

The tensile behavior of 5450 is strongly temper-dependent. In annealed condition it exhibits relatively low yield and tensile strength but high uniform elongation suitable for severe forming operations. In strain-hardened tempers the yield strength increases substantially while total elongation declines, producing useful stiffness for structural components.

Yield strength and tensile strength are a function of both Mg content and cold work; typical H‑tempers used for structural sheet deliver significantly higher yield than annealed material but will show characteristic yield point phenomena and limited work-hardening capacity in subsequent forming. Hardness follows the same trend, rising with increasing cold work and stabilizing with any thermal stabilization process.

Fatigue performance of 5450 benefits from a clean microstructure and proper control of surface condition; fatigue strength is higher in strain‑hardened tempers but is sensitive to welds and notches that introduce local stress concentrations. Thickness effects are important: thinner gauges are more readily strain-hardened during fabrication and will display higher strength but lower through-thickness ductility and different residual stress profiles after welding.

Property	O/Annealed	Key Temper (e.g., H32/H34)	Notes
Tensile Strength	~180–260 MPa (range typical for alloy family)	~260–360 MPa (depends on cold work level)	Values vary with gauge, temper and manufacturer; quoted as typical engineering ranges
Yield Strength	~60–150 MPa	~150–320 MPa	Yield increases substantially with cold work; H‑temper designation controls stability
Elongation	~20–35%	~8–18%	Annealed condition yields highest elongation; H‑tempers reduce ductility
Hardness	HB 30–55	HB 60–120	Hardness scales with cold work and reflects strain-hardening history

Physical Properties

Property	Value	Notes
Density	~2.66 g/cm³	Typical for Al‑Mg alloys; slightly higher than high‑purity aluminum due to alloying
Melting Range	~570–650 °C	Solidus–liquidus range depends on exact composition and minor constituents
Thermal Conductivity	~120–160 W/m·K	Lower than pure Al but still good for thermal dissipation in structural components
Electrical Conductivity	~30–40 % IACS	Reduced relative to pure Al due to Mg and alloying; impacts EMI and conductor applications
Specific Heat	~880–910 J/kg·K	Close to pure aluminum; useful for thermal mass calculations
Thermal Expansion	~23–24 µm/m·K (20–100 °C)	Similar to most commercial aluminum alloys; important for thermal mismatch calculations

The physical property set places 5450 among aluminum alloys that offer a favorable strength‑to‑weight ratio while retaining useful thermal and electrical conductivity. Designers should account for the relatively high coefficient of thermal expansion when joining to dissimilar materials and consider the thermal conductivity reduction relative to pure aluminum for heat sink or thermal management applications. Density and specific heat are beneficial for lightweight structures where thermal inertia is also required.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6 mm	Good in H‑tempers; annealed for deep draw	O, H14, H32, H34	Most common form; used for panels and formed components
Plate	6–150 mm	Strength decreases with increasing thickness for same temper	O, H111, H32 (limited)	Thicker sections require control of cast/rolled feedstock and heat treatment history
Extrusion	Profiles up to large cross-sections	Strength depends on cooling & subsequent cold work	O (for forming), H112 (some stability)	Used for structural members and frames; alloy must be adjusted for extrusion feedstock
Tube	Diameter and wall per application	Welded or seamless; mechanical properties influenced by processing	O, H32	Common in mechanical applications and fluid handling; welds alter local properties
Bar/Rod	Diameters up to 200 mm	Work hardening produces high strengths in drawn rod	O, H14, H34	Used for machined components, fasteners and parts requiring higher stiffness

Product form selection affects microstructure, strength uniformity and fabrication steps. Sheet and plate are rolled and may receive post‑rolling annealing or stabilization to tune properties, whereas extrusions and forged shapes require careful control of billet composition and thermal history to avoid surface oxides and ensure dimensional stability. Weldability and post‑weld properties are influenced by the form — thicker plate often shows greater HAZ softening potential and may require post‑weld mechanical or thermal stabilization.

Equivalent Grades

Standard	Grade	Region	Notes
AA	5450	USA	Wrought alloy designation in the American system
EN AW	5450	Europe	Common European designation; chemical and mechanical requirements can vary by spec
JIS	A5450 (approx.)	Japan	Local standards may reference similar Al‑Mg alloy families with regional allowances
GB/T	5450 (approx.)	China	Chinese standards provide equivalent compositions but check local spec sheets for exact ranges

Direct one‑to‑one equivalence between standards can be approximate because regional standards often allow different tolerances for impurities, mechanical property testing and product forms. Engineers must compare full chemical and mechanical tables in the relevant specifications and verify vendor mill certificates for plate or sheet to ensure interchangeability for critical applications.

Corrosion Resistance

5450 displays good general atmospheric corrosion resistance due to the protective aluminum oxide and the alloying balance that resists pitting. In marine and chloride-bearing environments it is generally robust, especially when protected by coatings or anodizing, but localized attack can occur at welds, fastener sites or scratches if the surface is not properly treated.

Stress corrosion cracking (SCC) susceptibility is influenced by Mg content and temper; alloys in the 5xxx family with Mg above approximately 3.5% can exhibit SCC in high-tensile or sensitized tempers under sustained tensile stress in corrosive environments. Welding introduces a softened HAZ in many cold-worked tempers, which can reduce local corrosion resistance and mechanical performance if not accounted for.

Galvanic interactions follow typical aluminum behavior: 5450 is anodic to stainless steels and copper alloys, so design should avoid direct contact without insulating materials or sacrificial protection. Compared to 6xxx and 7xxx series, 5450 tends to offer better general corrosion resistance and weldability but lower ultimate strength than peak-aged 6xxx or 7xxx alloys; compared with 3xxx series it provides significantly higher strength with similar or slightly reduced formability.

Fabrication Properties

Weldability

5450 is well suited to common fusion welding processes such as MIG (GMAW) and TIG (GTAW), showing good melt‑pool behavior and low hot‑cracking tendency when proper filler and parameters are used. Typical filler alloys for welded 5xxx family members include ER5183 and ER5356, chosen for matching strength, corrosion behavior and to control hydrogen pickup; ER5356 is often preferred for esthetic joints and anodized surfaces. Heat‑affected zone softening is a practical issue in strain‑hardened tempers and designers should consider joint design, pre/post‑weld mechanical stabilization and potential post‑weld strengthening strategies.

Machinability

Machinability of 5450 is moderate to fair; like many Al‑Mg alloys it can be gummy and produces continuous chips unless chip breakers or interruption strategies are used. Carbide tooling with positive rake and sharp geometries is recommended, together with moderate cutting speeds and liberal flood coolant to avoid built‑up edge and to manage heat. Surface finish and dimensional accuracy are generally good when appropriate feeds and tooling materials are selected for the alloy’s ductility.

Formability

Forming is best performed in the annealed (O) temper where minimum bend radii and deep drawing operations are achievable. In H‑tempers bend radii must be increased and forming operations should account for reduced elongation and springback behavior; typical minimum internal bend radii for H14–H32 tempers are on the order of 1–2× material thickness depending on tooling and part geometry. If significant forming is required after welding or cold working, an intermediate anneal can restore ductility but must be specified into the process flow.

Heat Treatment Behavior

5450 is a non-heat-treatable alloy; mechanical properties are not appreciably increased by classical solution treatment and artificial aging. Strengthening is accomplished by solid-solution Mg and by cold working where practical. Annealing (full softening to O) is performed by heating to appropriate temperatures to reduce residual stresses and restore ductility; specific anneal cycles depend on thickness and product form.

Thermal stabilization (e.g., controlled low-temperature overaging or mild thermal exposures) may be applied to stabilize H‑tempers against strain aging and to reduce the degree of softening in service or during welding. Attempts to apply T‑type heat treatments (designed for precipitation-hardening alloys) will not produce the peak strengths seen in 6xxx or 7xxx alloys for 5450 and are therefore not used as a strengthening route.

High-Temperature Performance

As with most aluminum alloys, 5450 shows progressive strength loss with increasing temperature; continuous service is typically limited to well below 200 °C to avoid significant reductions in yield strength and creep resistance. For many structural applications a conservative upper service temperature is chosen in the 100–150 °C range to maintain adequate mechanical margins.

Oxidation at elevated temperatures is limited by the protective alumina scale, but long exposures at elevated temperature can alter microstructure near grain boundaries and accelerate localized corrosion phenomena in aggressive environments. The weld heat-affected zone and previously cold-worked regions are particularly sensitive to thermal excursions and should be evaluated for property degradation under the expected service thermal profile.

Applications

Industry	Example Component	Why 5450 Is Used
Automotive & Transportation	Structural reinforcements, crash management components	Combination of higher as-fabricated strength and good weldability for welded assemblies
Marine	Hull panels, deck structures, brackets	Good corrosion resistance in seawater environments and high rivet/weld compatibility
Aerospace (secondary)	Fittings, access panels, floor system elements	Favorable strength-to-weight and good fabrication properties for non-primary structures
Pressure Vessels & Tanks	Tank shells, fittings	Strength and ductility balance with good weldability for welded pressure parts
Electronics & Thermal Management	Brackets, housings with heat spreading needs	Adequate thermal conductivity with higher mechanical strength than pure Al

5450 is selected for components where higher strength than conventional work‑hardened alloys is required without the schedule impact and distortion risks of precipitation‑hardening heat treatments. Its balanced property set enables welded, formed and machined parts across many transportation and marine applications.

Selection Insights

For engineers selecting materials, 5450 is a pragmatic choice when moderate-to-high strength, excellent weldability and good corrosion resistance are prioritized over maximal conductivity or ultimate heat-treatable strengths. Compared with commercially pure aluminum such as 1100, 5450 trades off electrical/thermal conductivity and ease of forming for much higher yield and tensile strength.

Compared with work‑hardened alloys like 3003 or 5052, 5450 typically offers significantly higher static strength while keeping comparable corrosion resistance; the trade-off is lower formability in cold‑worked tempers and potentially higher material cost. Compared with heat‑treatable alloys such as 6061 or 6063, 5450 will not reach peak aged strengths but is frequently preferred when superior weldability, lower distortion risk and better marine corrosion performance are more important than maximum achievable tensile strength.

Use 5450 when design priorities favor welded fabrication, corrosion robustness in atmospheric/marine settings, and a higher baseline strength that can be adjusted via temper and cold work rather than by heat treatment.

Closing Summary

5450 remains relevant as a robust 5xxx‑series aluminum offering a compelling balance of strength, corrosion resistance and fabrication friendliness for welded and formed structural applications. Its non‑heat‑treatable nature simplifies production and inspection, making it an efficient choice where reproducible as‑fabricated mechanical performance and service durability are required.