Aluminum 6160: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Alloy 6160 is a member of the 6xxx series aluminum alloys (Al-Mg-Si family) characterized by precipitation hardening through Mg2Si formation. Its principal alloying elements are silicon and magnesium, typically balanced to promote controllable age hardening and good extrudability.

The strengthening mechanism for 6160 is heat-treatable precipitation hardening; it attains useful strength through solution treatment, quenching and artificial aging rather than by work-hardening. Typical traits include moderate-to-high strength for the 6xxx family, good corrosion resistance in many atmospheres, favorable weldability with appropriate fillers, and reasonable cold formability depending on temper.

6160 finds use in structural extrusions, automotive trim and subcomponents, railway and architectural profiles, and niche aerospace fittings where a balance of extrudability, machinability and age-hardenable strength is required. Engineers choose 6160 when a compromise of extrudability and predictable precipitation response is needed over alloys that emphasize either maximum strength (7xxx series) or maximum formability/conductivity (1xxx series).

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (>20%)	Excellent	Excellent	Fully annealed, maximum ductility for forming
H111	Low-Moderate	High	Very Good	Very Good	Slightly cold-worked, limited property control
H14	Moderate	Moderate	Good	Very Good	Single-step strain-hardened, no heat treatment
T4	Moderate	Moderate-High	Good	Very Good	Solution heat-treated and naturally aged
T5	Moderate-High	Moderate	Good	Very Good	Cooled from shaping and artificial aged
T6	High	Moderate (8–15%)	Fair to Good	Good	Solution heat-treated and artificially aged
T61 / T651	High	Moderate	Fair to Good	Good	Stress-relieved after quench (T651) for structural parts

Temper significantly alters the balance between strength and ductility in 6160; annealed O-temper offers the best formability for deep drawing and complex bends while T6 provides peak static strength for structural applications. Aging schedules (T5 vs T6) change precipitate size and distribution, which in turn affect fatigue resistance, HAZ response during welding and resistance to stress-corrosion cracking.

Chemical Composition

Element	% Range	Notes
Si	0.6–1.0	Controls Mg2Si precipitation; improves fluidity and extrudability
Fe	0.15 max	Impurity element; high Fe forms intermetallics that reduce ductility
Mn	0.05 max	Minor, helps control grain structure if present
Mg	0.45–0.9	Combines with Si to form strengthening Mg2Si precipitates
Cu	0.05–0.25	Small additions can raise strength but may reduce corrosion resistance
Zn	0.2 max	Typically low; higher Zn not intended for 6160
Cr	0.1 max	Trace levels help control grain structure and recrystallization
Ti	0.1 max	Grain refiner when intentionally added
Others (each)	0.05 max	Residuals and trace elements kept low; total others limited

The Si/Mg ratio and absolute amounts determine the precipitation kinetics and the achievable peak strength after artificial aging. Trace additions and residuals control grain size, recrystallization behavior, and the tendency to form coarse intermetallics that can act as fatigue initiation sites.

Mechanical Properties

In tensile behavior 6160 demonstrates classic precipitation hardened response: low strength and high elongation in annealed condition and elevated tensile and yield strengths after artificial aging. Yield strength in peak-aged conditions typically approaches a large fraction of ultimate tensile strength, with moderate work-hardening capacity; elongation reduces as precipitate volume fraction increases. Fatigue performance is strongly influenced by surface finish, heat treatment state and the presence of casting/extrusion defects; properly aged extrusions show good high-cycle fatigue properties for aluminum structural applications.

Thickness affects both quench effectiveness and precipitation uniformity; thicker sections can be under-aged in central regions after typical quench schedules, leading to lower strengths and lower fatigue life compared with thin-walled extrusions. Hardness correlates well with tensile strength in 6160 and serves as a practical shop-floor proxy for aging condition; Vickers or Brinell hardness ranges are useful to confirm aging rather than relying solely on time-temperature cycles.

Property	O/Annealed	Key Temper (e.g., T6)	Notes
Tensile Strength	~100–140 MPa	~240–290 MPa	T6 yields significantly higher UTS due to Mg2Si precipitation
Yield Strength	~50–90 MPa	~210–260 MPa	Pronounced increase after solution + artificial aging
Elongation	>20%	~8–15%	Ductility reduced in peak-aged states, still adequate for many structural parts
Hardness (HB)	~30–45 HB	~65–95 HB	Hardness increases in direct proportion to aging response

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for wrought aluminum alloys
Melting Range	555–650 °C	Solidus-liquidus interval influenced by alloying; avoid overheating during processing
Thermal Conductivity	~160–180 W/m·K	Good thermal transport relative to steels; useful for heat-dissipating components
Electrical Conductivity	~30–40 % IACS	Lower than pure aluminum due to alloying; acceptable for structural conductors not optimized for conductivity
Specific Heat	~0.90 kJ/kg·K	Typical for Al alloys; important for thermal mass considerations
Thermal Expansion	~23–24 µm/m·K (20–100°C)	Relatively high coefficient; differential expansion must be considered in assemblies

The combination of low density and good thermal conductivity makes 6160 attractive where weight-sensitive thermal management is required. The alloy’s melting range and thermal expansion behavior dictate process windows for brazing, welding and thermal cycling design.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6.0 mm	Thin sections age uniformly; good surface finish	O, T4, T5, T6	Used for light panels and trim
Plate	6–25 mm	Thicker sections can suffer quench delays and underaging	O, T6 (after suitable quench)	Structural plates for moderate loads
Extrusion	Wall thickness 1–20 mm; complex profiles	Excellent age response; extruded microstructure affects properties	O, T4, T5, T6, T651	Primary form for 6160; widely used in architectural and transport sectors
Tube	OD ranges from small to several hundred mm	Welding and heat treatment affect wall properties	O, T6	Seamless or welded tubes for structural and architectural use
Bar/Rod	Diameters up to 200 mm	Similar age response to extrusions; machinability adequate	O, T6	Used for machined components and fastening elements

Extrusions are the dominant product form for 6160, leveraging its designed chemistry for good press flow and controlled precipitation during post-extrusion aging. Plate and thicker sections require tailored quench practices and sometimes thicker-section aging strategies to avoid underaged cores and variable properties across the cross-section.

Equivalent Grades

Standard	Grade	Region	Notes
AA	6160	USA	Primary designation in Aluminum Association listings
EN AW	6160	Europe	Often listed as EN AW‑6160; chemical and mechanical limits vary slightly by standard
JIS	A6160 (approx.)	Japan	Local standards may list 6160 or provide nearest alternatives such as A6xxx family equivalents
GB/T	6160 (approx.)	China	Chinese designations may align to 6xxx family; check exact spec for mechanical limits

Direct cross-references between regions require checking specific standard texts because temper definitions, permitted impurity levels and mechanical-property acceptance criteria can vary. Where a formal equivalent is not available, engineers commonly substitute nearby 6xxx alloys such as 6063 or 6061 after validation testing.

Corrosion Resistance

Alloy 6160 exhibits good general atmospheric corrosion resistance characteristic of Al‑Mg‑Si alloys, forming a stable oxide film that protects from uniform attack. In industrial or mildly polluted atmospheres the oxide remains protective, but in chloride-rich marine environments the pitting susceptibility increases, particularly at welds, machined surfaces and in the presence of tensile residual stresses.

Stress corrosion cracking risk is relatively low compared with high-strength 7xxx series alloys, but can appear in peak-aged tempers under combined tensile stress and corrosive chloride exposure; design should avoid triaxial tensile restraint in aggressive environments. Galvanic interaction favors protecting aluminum when coupled to more noble metals; in assemblies with steel or copper, electrical isolation or compatible coatings are recommended to prevent accelerated galvanic corrosion.

Compared with 5xxx (Al-Mg) alloys, 6160 typically has slightly lower corrosion resistance in pure chloride environments due to the presence of silicon and the precipitation microstructure, but it generally outperforms many heat-treatable alloys in balanced performance when corrosion protection is combined with moderate strength needs.

Fabrication Properties

Weldability

6160 is readily welded by TIG and MIG processes when appropriate filler alloys and joint design are used; common fillers include Al‑Si (e.g., 4043) and Al‑Mg‑Si (e.g., 5356 variants) depending on service requirements. Welding causes HAZ softening through dissolution and coarsening of strengthening precipitates, so post-weld heat treatment or design for allowable reduced local strength is often required. Hot-cracking risk is low but may rise with high copper contents or poor joint fit-up, so control of weld parameters and cleanliness is important.

Machinability

As a naturally age-hardenable alloy, 6160 machines reasonably well in solution-treated and mild tempers; machinability ratings are moderate compared with free-cutting wrought alloys. Carbide tooling with positive rake and effective chip breaking is recommended; moderate to high cutting speeds and feeds produce good surface finish, but the temper and degree of age hardening will strongly influence tool life. Coolant and chip evacuation are important to avoid built-up edge and surface tearing.

Formability

The best formability is achieved in O, T4 or H111 conditions where ductility is highest; minimum bend radii typically range from 2–4× material thickness depending on part geometry and tooling. Cold working in H‑tempers is possible but reduces the potential peak age-hardened strength; for complex forming followed by strength requirement, a route of forming in O or T4 followed by solution treatment or artificial aging may be specified.

Heat Treatment Behavior

6160 is a heat-treatable alloy that responds to solution treatment, quenching and artificial aging to develop strength through Mg2Si precipitation. Typical solution treatment temperatures are in the 520–550 °C range to dissolve Mg and Si into solid solution; quenching must be sufficiently rapid to retain solute for subsequent age hardening.

Artificial aging for T5/T6 conditions is commonly performed at 150–190 °C for times from several hours to achieve peak hardness and strength; lower temperature aging yields higher toughness and better stress-corrosion resistance at the expense of peak strength. T651 variants include stress-relief stretching or thermal straightening after quench to stabilize dimensional features and reduce residual stresses prior to aging.

High-Temperature Performance

As temperature rises, 6160 shows a reduction in yield and tensile strength due to precipitate coarsening and reduced matrix strength; practical continuous-service temperature limits are often set below 120 °C for load-bearing applications. Short-term exposure to higher temperatures (150–200 °C) will accelerate overaging and reduce mechanical properties, so designs intended for elevated-temperature service should be validated with targeted aging cycles and creep testing.

Oxidation is minimal for aluminum at moderate temperatures, but the degradation of mechanical properties in the heat-affected zone after welding and in thermally cycled components must be accounted for, particularly where dimensional stability and fatigue life are critical.

Applications

Industry	Example Component	Why 6160 Is Used
Automotive	Structural extruded rails, trim and subframes	Good extrudability and age-hardening for moderate strength and lightweighting
Marine	Architectural railings and structural profiles	Balanced corrosion resistance and formability for fabricated structures
Aerospace	Secondary fittings and non-critical brackets	Favorable strength-to-weight and good machinability for complex parts
Electronics	Chassis and heat-dissipating profiles	Thermal conductivity combined with extrudable complex cross-sections

6160 is favored in applications where complex extruded profiles are required with predictable age-hardening behavior and good machinability for secondary operations. Its balance of properties makes it a common choice for transport and architectural sectors where moderate strength and good corrosion performance are required.

Selection Insights

Use 6160 when extrudability and controlled precipitation hardening are priorities and when the design calls for moderate-to-high strength after aging without the very high strength or SCC susceptibility of 7xxx alloys. Compared with commercially pure aluminum (1100), 6160 sacrifices some electrical and thermal conductivity and formability to gain substantially higher strength and better structural utility. Compared with work-hardened alloys such as 3003 or 5052, 6160 provides higher peak strength via heat treatment while retaining comparable corrosion resistance in many atmospheres, though forming in 3003/5052 can be easier for complex deep draws.

When compared with common 6xxx alloys like 6061 or 6063, 6160 is selected where specific extrusion flow or slightly different aging response is desired; it may offer better extrudability or different mechanical balance for certain profile geometries even if its peak strength is similar or marginally lower. Consider material availability, finish requirements and qualification constraints as deciding factors alongside mechanical trade-offs during alloy selection.

Closing Summary

Alloy 6160 remains a relevant and practical Al‑Mg‑Si alloy for engineered extrusions and machined structural parts where a balance of extrudability, predictable precipitation hardening and adequate corrosion resistance is required. Its versatility across tempers and productive heat-treatment response make it a useful option for designers targeting weight reduction and manufacturable complex profiles.