Aluminum 4A30: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

4A30 is a 4xxx-series aluminum alloy, placing it within the silicon-rich family of aluminium materials that emphasize improved castability, reduced thermal expansion and enhanced weldability compared with many other series. The 4xxx designation signals that silicon is the principal alloying element, often supplemented by modest additions of magnesium, manganese and trace elements to tailor strength, ductility and fabrication behavior.

Major alloying elements in 4A30 typically include silicon as the primary additive, with controlled levels of iron, manganese and small magnesium and copper fractions. Silicon contributes to improved fluidity and thermal stability, manganese refines grain structure and mitigates hot tearing, and magnesium provides modest solid-solution strengthening and improved strain hardening in some tempers.

4A30 is primarily strengthened by a combination of solid-solution effects and work-hardening rather than by classic age-hardening processes, which makes it effectively non-heat-treatable for large strength gains. The alloy offers a blend of moderate strength, good corrosion resistance in atmospheric environments, favorable weldability with silicon-bearing fillers, and reasonable formability in annealed conditions, making it a versatile choice for many fabricated components.

Typical industries that use 4A30 include automotive body and trim manufacture, structural components in transport and marine applications, general industrial fabrications, and some thermal management parts where a balance of conductivity and mechanical performance is required. Engineers select 4A30 when the design requires moderate strength combined with good weldability and formability, particularly where silicon’s benefits (reduced thermal distortion, better casting/extrusion quality) outweigh the need for peak age-hardened strength.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed condition for maximum ductility
H12	Low-Mid	Moderate	Good	Excellent	Partial strain-hardened, limited drawing
H14	Mid	Moderate	Fair	Excellent	Moderate work-hardening for added strength
H16	Mid-High	Lower	Fair	Good	Higher strain hardening, reduced stretch formability
H24	Mid-High	Low-Moderate	Fair	Good	Strain-hardened then thermally stabilized
T4 (limited response)	Mid	Moderate	Good	Excellent	Solution treated and naturally aged; limited precipitation response
T5 (if applicable)	Mid-High	Lower	Fair	Good	Cooled from hot working then artificial aging; modest gains possible
T6 (rare for 4xxx)	Mid-High	Lower	Poor-Fair	Variable	Artificially aged after solutioning; not all 4A30 chemistries develop strong T6 response

The temper selected for 4A30 has a pronounced effect on formability and strength. Annealed (O) condition maximizes elongation and bending performance, while H-series tempers use cold work to raise strength at the expense of ductility and stretch formability.

Heat treatments such as T4 or T5 produce only modest precipitation strengthening in silicon-rich alloys like 4A30 compared with classic 6xxx alloys, so tempering is typically employed to balance residual stresses and dimensional stability rather than to achieve large strength increases.

Chemical Composition

Element	% Range	Notes
Si	0.7 – 1.3	Primary alloying element; improves fluidity, reduces thermal expansion, influences welding characteristics
Fe	0.2 – 0.7	Impurity/strengthener; forms intermetallics that can reduce ductility when high
Mn	0.3 – 0.9	Grain refiner and strengthener via dispersoids and subgrain formation
Mg	0.2 – 0.8	Provides modest solid-solution strengthening and improves work-hardening response
Cu	0.05 – 0.25	Small additions raise strength but can reduce corrosion resistance if excessive
Zn	0.05 – 0.25	Typically kept low to avoid susceptibility to stress-corrosion cracking
Cr	0.02 – 0.2	Microalloying to control recrystallization and grain structure
Ti	0.02 – 0.12	Used in small amounts as grain refiner particularly for cast/extruded products
Others (each)	0.01 – 0.05	Trace impurities and intentional microalloying tailored by mill

The chemistry of 4A30 is deliberately balanced to exploit silicon’s beneficial effects while avoiding high levels of iron and copper that can form brittle intermetallic phases. Silicon and magnesium together can enable modest precipitation phenomena but do not produce the same T6-ageable response as 6xxx alloys unless the composition and thermal processing are specifically optimized.

Control of manganese and trace chromium/titanium is critical to achieve a fine, stable grain structure during hot working and subsequent cold forming, which improves toughness, reduces anisotropy and limits hot-cracking in welding and extrusion operations.

Mechanical Properties

Tensile behaviour of 4A30 is characterized by a moderate ultimate tensile strength with a ductile fracture mode in the annealed condition and a progressively higher yield as work-hardening is imposed. Yield-to-tensile ratios are typically favourable for energy-absorbing structures, with elongation declining as strength increases through H-series tempers. Thickness and processing history strongly influence tensile values; thin sheet often exhibits higher apparent yield due to cold rolling.

Hardness trends mirror tensile data: annealed material exhibits low Brinell or Vickers hardness, while H-temper and artificially aged conditions show measurable increases. Fatigue performance is generally good for components with smooth surface finishes and conservative design stress levels, but fatigue life can be reduced by surface defects, welding HAZ heterogeneity, and coarse intermetallic particles.

Thickness affects both ductility and strength: thinner sections are easier to cold-form and can achieve higher work-hardened strengths through rolling, whereas thicker components retain more as-cast/extruded microstructural heterogeneity and show slightly lower ductility. Welding leads to localized HAZ softening or heterogeneity that should be considered in fatigue-critical designs.

Property	O/Annealed	Key Temper (e.g., H14/T5)	Notes
Tensile Strength	~80 – 140 MPa	~160 – 260 MPa	Wide ranges depend on thickness, cold work and specific batch chemistry
Yield Strength	~35 – 70 MPa	~120 – 200 MPa	Yield rises sharply with work-hardening; lower in annealed condition
Elongation	~25 – 35%	~6 – 18%	Ductility decreases as strength increases; H-tempered ranges variable with processing
Hardness (HB)	~20 – 45 HB	~50 – 95 HB	Hardness correlates with cold work and any artificial aging performed

Values above are indicative engineering ranges established from typical production and should be refined by material test certificates and mill data for critical component design.

Physical Properties

Property	Value	Notes
Density	2.68 g/cm³	Typical for aluminium-silicon alloys; useful for mass and stiffness calculations
Melting Range	~555 – 640 °C	Silicon lowers the solidus slightly versus pure Al; melting interval depends on Si content
Thermal Conductivity	~120 – 170 W/m·K	Lower than pure aluminium but still favorable for heat-sinking compared with many alloys
Electrical Conductivity	~25 – 45 % IACS	Silicon and other solutes reduce conductivity versus pure Al; acceptable for many bus/thermal applications
Specific Heat	~880 – 920 J/kg·K	Typical for aluminium alloys; used for transient thermal modeling
Thermal Expansion	~22 – 24 µm/m·K (20–200 °C)	Slightly reduced by silicon compared with 1xxx alloys, beneficial for dimensional stability

The physical properties make 4A30 attractive where a balance of thermal transport and dimensional stability is required, for example in heat exchangers or welded assemblies that experience moderate thermal gradients. Thermal conductivity remains high relative to steels but is reduced from pure aluminium due to alloying; this is often an acceptable trade-off when increased mechanical or processing performance is required.

The moderate melting range and silicon content also improve casting and brazing characteristics for certain processing routes, while the electrical conductivity reduction should be considered when designing current-carrying components.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3 – 6 mm	Good formability in O; higher strength in H14/H16	O, H12, H14	Widely used for panels and formed parts; thin gauges cold-roll well
Plate	6 – 50 mm	Lower ductility in thick sections; variation through thickness	O, H24	Heavy sections used for structural members, may require annealing after processing
Extrusion	Wall thicknesses 1 – 20 mm	Good dimensional stability; controllable properties	O, T5, H12	Silicon assists extrudability and reduces hot-tear risk
Tube	Diameters 6 – 200 mm	Similar to sheet/pipe; cold drawing raises strength	O, H14	Used for structural tubing and heat-exchanger cores
Bar/Rod	Diameters up to 200 mm	Strength increases with cold drawing or rolling	H14, H16	Used where machined parts require moderate strength

Sheets and extrusions are the most common product forms for 4A30 and are often supplied in coils or cut lengths for stamping and forming operations. Plate and heavy sections can require additional thermal/mechanical processing to homogenize properties through thickness, especially when the forged or cast feedstock contains casting-derived intermetallics.

Extrusion benefits from silicon’s effect on fluidity, enabling complex profiles with fewer defects; however, post-extrusion straightening and stress-relief are common to minimize residual distortion prior to final fabrication.

Equivalent Grades

Standard	Grade	Region	Notes
AA	4A30	USA	Designation used in mill literature; not a direct AIAG-recognized AA number in all catalogs
EN AW	~AlSi1MgMn	Europe	Approximate chemistry corresponds to low-silicon Al-Si-Mg-Mn wrought grades; check EN alloy tables for precise matches
JIS	A###	Japan	Japanese standards may list comparable low-silicon wrought alloy compositions under different labels
GB/T	4A30	China	Domestic Chinese designation; use GB/T certificates to confirm composition and mechanical requirements

Direct one-to-one equivalents are not always available because regional standards may distribute alloying elements differently and define tempers with different testing methods. Engineers should cross-reference mill certificates and perform property comparisons—particularly for tensile, corrosion and weldability parameters—before substituting alloys between standards.

When exact equivalence is required for qualification, request certified composition and mechanical test reports from the supplier and, if necessary, perform application-specific testing for corrosion or fatigue-critical parts.

Corrosion Resistance

4A30 typically exhibits good atmospheric corrosion resistance due to the presence of silicon and modest magnesium that together form a stable oxide and slow general corrosion rates. In industrial and rural atmospheres the alloy performs comparably to other 4xxx-series alloys, with long-term durability when painted or anodized appropriately.

Marine exposure represents a more aggressive environment; 4A30 resists uniform corrosion reasonably well but is susceptible to localized pitting and crevice corrosion in stagnant seawater or chloride-rich conditions. Protective coatings, cathodic isolation and design to avoid crevices are standard mitigations in marine applications.

Stress corrosion cracking (SCC) susceptibility is generally lower than high-strength copper- or zinc-rich alloys, but SCC risk increases with higher tensile stresses and the presence of certain impurities. Galvanic interactions with dissimilar metals—especially steels and copper alloys—must be minimized by insulating layers or sacrificial anodes to prevent accelerated local attack where direct contact occurs.

Compared with 3xxx (Mn) and 5xxx (Mg) families, 4A30 trades some absolute corrosion resistance for better thermal stability and welding performance. It is typically preferred where weldability and dimensional stability under thermal cycling are valued over maximal seawater endurance.

Fabrication Properties

Weldability
4A30 welds well using TIG (GTAW) and MIG (GMAW) processes because silicon reduces the solidification range and helps avoid hot-cracking. Standard silicon-bearing filler metals such as ER4043 or ER4047 are recommended to match chemistry and reduce cracking risk and porosity. Weld heat-affected zones (HAZ) can exhibit softening in higher-strength tempers; joint design and post-weld stabilization may be required for tight-tolerance fabrications.

Machinability
Machinability of 4A30 is moderate and generally better than high-strength aluminum alloys that contain significant copper or zinc. Carbide tooling with robust coatings (TiAlN or TiN) and moderate to high spindle speeds with ample coolant produce good surface finishes. Chip control is usually acceptable but can be impacted by intermetallic particles; optimizing feeds to avoid built-up edge and ensuring sharp tooling improves productivity.

Formability
In the annealed O temper, 4A30 has excellent bendability and deep-drawing characteristics, allowing tight bend radii and complex stamped geometries. Cold-working into H-tempers increases strength but reduces formability; recommended minimum internal bend radii depend on thickness and temper but often fall in the 1–3× thickness range for O temper and increase for H-series. Warm forming may expand formability windows for thicker sections where springback control is necessary.

Heat Treatment Behavior

4A30 is effectively a non-fully-heat-treatable alloy: large precipitation-hardening responses comparable to 6xxx or 2xxx series are not typical unless the composition is specifically optimized for Mg-Si precipitation. Solution treatment followed by quenching (T4) can provide some microstructural homogenization and modest natural aging, but artificial aging (T5/T6) produces only limited additional strength in most 4A30 chemistries.

When heat treatment is used, solution temperatures are usually in the 510–540 °C range followed by rapid quenching to retain solute in supersaturated solid solution; artificial aging in the 150–200 °C range may produce moderate increases in hardness and strength. For engineering practice, heat treatment is primarily used to relieve stresses after forming or welding, or to stabilize properties rather than to obtain large strength jumps.

For non-heat-treatable production, work hardening and controlled annealing are the primary tools. Annealing at approximately 300–400 °C (or per mill guidelines) restores ductility and homogenizes microstructure; partial anneals can be used to achieve specific H tempers with intermediate strength and ductility.

High-Temperature Performance

Mechanical properties of 4A30 decline with increasing temperature, with appreciable reductions above ~100–150 °C and significant strength loss approaching 250–300 °C. Long-term elevated-temperature exposure encourages coarsening of dispersoids and intermetallic particles that reduce yield strength and increase creep susceptibility in load-bearing parts.

Oxidation resistance at elevated temperatures is generally good because aluminum forms a protective alumina layer; however, silicon-rich alloys can form mixed oxide layers that affect emissivity and surface characteristics. Welding near high-temperature service zones can produce HAZ softening and residual-stress concentrations that accelerate creep and fatigue damage.

For applications requiring continuous operation at moderately high temperatures or under thermal cycling, derating factors should be applied and selection can favor more heat-resistant alloys (e.g., certain 2xxx or 7xxx series) if mechanical retention is critical. 4A30 remains suitable for intermittent high-temperature exposure where thermal conductivity and dimensional stability are more important than retained high strength.

Applications

Industry	Example Component	Why 4A30 Is Used
Automotive	Body panels, inner structural members	Good formability in O temper, weldability and controlled thermal expansion
Marine	Superstructure panels, moderate-load brackets	Reasonable corrosion resistance and weldability with coatings
Aerospace	Secondary fittings, fairings	Favorable strength-to-weight and thermal stability for non-primary structures
Electronics	Heat spreaders, housings	Combined thermal conductivity and fabrication ease
General Industry	Heat exchangers, piping and ductwork	Silicon aids extrusion performance and thermal behavior

4A30 is frequently selected for components that require a balance of formability, weldability and reasonable mechanical performance without the complexity of age-hardening processing. Its utility in extruded profiles and sheet applications makes it a cost-effective choice for mid-duty structural and thermal-management parts.

Selection Insights

When choosing 4A30, prioritize it where weldability, thermal stability and good forming in the annealed condition are important and where only moderate strength is required. Its silicon content reduces thermal distortion and improves extrusion and welding behavior compared with low-silicon alloys.

Compared with commercially pure aluminium (1100), 4A30 trades some electrical conductivity and maximum malleability for higher strength and better dimensional stability under thermal cycling. Compared with work-hardened alloys such as 3003 or 5052, 4A30 offers similar or slightly improved thermal stability and weldability with comparable mid-range strength dependent on temper and processing. Compared with common heat-treatable alloys like 6061 or 6063, 4A30 typically delivers lower peak age-hardened strength but can be preferred where superior weld fluidity, lower thermal expansion and easier extrusion/forming are prioritized over maximum tensile capacity.

Select 4A30 when component geometry, welding requirements and processing economics outweigh the need for the highest possible strength, and always verify supplier mill certificates and perform application-level testing for corrosion or fatigue-critical designs.

Closing Summary

4A30 remains relevant as a mid-performance aluminium alloy that balances formability, weldability and thermal behavior for a wide range of fabricated parts. Its silicon-based chemistry and controlled microalloying make it a practical, economical choice for engineers needing stable dimensional performance and reliable fabrication characteristics rather than maximum age-hardened strength.