A413 is the near-eutectic aluminum-silicon casting alloy, holding 11.0 to 13.0% silicon with copper capped at 1.0% maximum. Sitting beside the 12.6% aluminum-silicon eutectic gives it the narrowest freezing range of the production die casting alloys, 574 to 582 °C, and from that single fact follow its three defining properties: the best fluidity, excellent pressure tightness and the highest thermal conductivity of the four grades we cast at 121 W/m·K.
A413 is the near-eutectic aluminum-silicon casting alloy, holding 11.0 to 13.0% silicon with copper capped at 1.0% maximum. Sitting beside the 12.6% aluminum-silicon eutectic gives it the narrowest freezing range of the production die casting alloys, 574 to 582 °C, and from that single fact follow its three defining properties: the best fluidity, excellent pressure tightness and the highest thermal conductivity of the four grades we cast at 121 W/m·K.
A413 is the alloy to specify when the casting has to move heat or hold pressure. Freezing over an 8 °C range rather than A380's 55 °C means the metal stays liquid until late and then solidifies almost all at once, so there is far less of the interdendritic shrinkage that becomes a leak path. The same behaviour fills long thin fins that A380 would freeze short, which is why cast LED and power electronics heat sinks are usually A413.
The costs are strength and machining. As cast it reaches 296 MPa tensile and 145 MPa yield, the lowest of the four, with 2.5% elongation against 3.5% for the others. More importantly the silicon that makes it fill also makes it abrasive: machinability is rated fair, and heavily machined parts need polycrystalline diamond tooling rather than carbide. Specify A413 where thermal or sealing performance is the requirement, and A380 or A360 where it is not.
| ASTM designation | A413 / 413.0 (ASTM B85, UNS A04130) |
|---|---|
| Equivalent grades | ADC1 (JIS), EN AC-44300, YL102 (GB) |
| Chemical designation | AlSi12, AlSi12(Fe) in EN 1706 |
| Ultimate tensile strength | 296 MPa (43 ksi) |
| Yield strength (0.2% offset) | 145 MPa (21 ksi) |
| Elongation in 50 mm | 2.5% |
| Brinell hardness | 80 HB |
| Silicon content | 11.0-13.0% |
| Copper content | 1.0% max |
| Density | 2.66 g/cm³ |
| Thermal conductivity | 121 W/m·K, the highest of the four production grades |
| Melting range | 574-582 °C, an 8 °C freezing range |
A413 is an aluminum-silicon die casting alloy standardised in ASTM B85 as alloy 413.0, with the UNS number A04130 and the chemical designation AlSi12. Unlike A380 and ADC12 it carries no deliberate copper addition and unlike A360 no deliberate magnesium addition, so silicon is effectively the only alloying element. In the Aluminum Association system that places it in the 4xx.x series rather than the 3xx.x series the other three grades occupy.
Everything distinctive about the alloy follows from where that silicon level sits. The aluminum-silicon eutectic occurs at 12.6% silicon and 577 °C, the composition at which the alloy freezes in a single reaction at essentially one temperature instead of pasting through a mushy range. A413 at 11.0 to 13.0% silicon brackets that point, so a production melt freezes between 574 and 582 °C, a span of roughly 8 °C against 55 °C for A380.
A narrow freezing range is worth more in a die casting than it sounds. Metal that stays fluid until the last moment travels further into thin sections before it stalls, and metal that solidifies all at once leaves fewer interconnected shrinkage channels behind. Those two consequences are the reason A413 fills fin arrays other alloys cannot and passes leak tests other alloys fail.
The composition below is the ASTM B85 specification for alloy 413.0. Only one limit really defines the alloy: silicon between 11.0 and 13.0%. Copper at 1.0% maximum and magnesium at 0.10% maximum are residual allowances rather than additions, which is why A413 keeps good corrosion resistance and high conductivity instead of trading them for strength.
| Element | Min % | Max % | Function in the alloy |
|---|---|---|---|
| Silicon (Si) | 11.0 | 13.0 | Brackets the 12.6% eutectic, giving the narrowest freezing range, best fluidity and lowest shrinkage of the production grades |
| Copper (Cu) | — | 1.0 | Residual only. Keeping it low preserves thermal conductivity and corrosion resistance at the cost of strength |
| Iron (Fe) | — | 2.0 | Prevents soldering to the die; we hold 0.7 to 1.1% in the furnace because iron needles cut the already low ductility |
| Magnesium (Mg) | — | 0.10 | Restricted. Mg2Si would add yield strength but would also depress conductivity and raise hot tearing risk |
| Manganese (Mn) | — | 0.35 | Converts needle-shaped iron phases into a rounded, less damaging morphology |
| Nickel (Ni) | — | 0.50 | Residual from secondary feedstock; slightly improves elevated-temperature stability |
| Zinc (Zn) | — | 0.50 | Held far tighter than A380's 3.0% allowance, because zinc degrades corrosion resistance |
| Tin (Sn) | — | 0.15 | Tightly limited; tin depresses strength and corrosion performance |
| Others, total | — | 0.25 | Combined residual allowance, half that permitted in A380 |
| Aluminum (Al) | Balance | Balance | Base metal, typically 86 to 88% of the alloy |
Where a drawing specifies EN AC-44300 rather than A413, note that the EN grade caps copper at 0.10% against the ASTM grade's 1.0%. That difference is not academic on a conductivity-critical part, so we buy ingot to the EN chemistry and certify against EN 1706 rather than substituting standard A413. Every ingot lot is spectrometer verified before it enters the melt.
Two numbers in this table carry the alloy. Thermal conductivity of 121 W/m·K is 26% above A380 and ADC12 at 96 W/m·K, and 7% above A360 at 113 W/m·K, which makes A413 the best conductor of the production grades. The 8 °C freezing range is the other, and it is what delivers the pressure tightness and fin filling that the conductivity figure alone would not.
The numbers to design around rather than celebrate are 145 MPa yield strength and 2.5% elongation, both the lowest of the four grades. A413 tolerates stress concentrations worse than A380 does, so every internal corner needs a generous radius and abrupt section changes have to be designed out rather than accepted.
| Property | Value | Notes |
|---|---|---|
| Ultimate tensile strength | 296 MPa (43 ksi) | Separately cast test bar, as-cast condition |
| Yield strength (0.2% offset) | 145 MPa (21 ksi) | The lowest of the four production grades; size structural features accordingly |
| Elongation in 50 mm | 2.5% | Below the 3.5% of the other three grades, so radius every internal corner |
| Shear strength | 170 MPa (25 ksi) | Relevant to fastener bosses and cover flanges |
| Fatigue strength | 131 MPa (19 ksi) | R.R. Moore rotating beam, 5 × 10⁸ cycles |
| Modulus of elasticity | 71 GPa | Stiffness comes from section geometry, not the alloy |
| Brinell hardness | 80 HB | 500 kg load, 10 mm ball; equal to A380 despite lower strength |
| Density | 2.66 g/cm³ | Lighter than A380 at 2.74, heavier than A360 at 2.63 |
| Melting range | 574-582 °C | An 8 °C freezing range against A380's 55 °C; the source of the fluidity and pressure tightness |
| Thermal conductivity | 121 W/m·K | The highest of the production grades, 26% above A380 and ADC12 |
| Coefficient of thermal expansion | 20.4 µm/m·°C | The lowest of the four, measured 20 to 100 °C; high silicon restrains expansion |
| Electrical conductivity | 31% IACS | The highest of the four, because copper is essentially absent |
Typical as-cast values on separately cast test bars, consistent with the master alloy comparison used across this site. Properties in a real casting vary with wall thickness and local solidification rate.
A cast heat sink has to do two things that pull in different directions: conduct heat from the mounting face out to the fin tips, and actually exist as a fin array fine enough to present the surface area the thermal budget needs. A413 is the only production die casting alloy that is best in class at both.
Conduction is the straightforward half. At 121 W/m·K the alloy moves roughly a quarter more heat than A380 or ADC12 for identical geometry. On a fin array that matters most at the tips, because fin efficiency falls as conductivity drops and the outer portion of a long fin on a poorly conducting alloy contributes very little surface area in practice.
Filling is the half that decides whether the design is manufacturable at all. A fin is a long, thin, dead-ended flow path with a high surface-area-to-volume ratio, so the metal entering it loses heat quickly and has one chance to reach the tip. The near-eutectic composition keeps A413 fluid right down to 582 °C, which is what lets it complete fins that A380 freezes short. Where a fin array has to go finer than A413 will fill, the honest answer is a bonded or extruded fin assembly rather than a thinner casting.
| Fin parameter | Comfortable | Achievable with review | Notes |
|---|---|---|---|
| Fin thickness at base | 2.0 to 2.5 mm | 1.5 mm | Below 1.5 mm, fill becomes gate-position dependent and scrap climbs |
| Fin thickness at tip | 1.2 to 1.5 mm | 1.0 mm | Taper is structural as well as thermal; it is what lets the fin release |
| Fin height | Up to 25 mm | 40 mm | Tall fins need the gate feeding the base of the array, not the perimeter |
| Fin pitch (gap between fins) | 4 to 6 mm | 3 mm | Narrow gaps make the die core fragile and slow the cycle |
| Height to gap ratio | Up to 6:1 | 8:1 | The single most reliable predictor of whether an array will fill |
| Draft angle on fin faces | 2 to 3° | 1.5° | Less draft risks dragging the fin and scoring the die core |
| Base plate thickness | 4 to 6 mm | 3 mm | Has to spread heat laterally before it reaches the fins |
These are the ranges we quote without qualification on A413. A fin array outside them is not automatically rejected, but it needs a mold flow simulation before tooling is cut, and we will tell you if the geometry is better served by an extrusion.
A413 and A360 are the two grades we rate excellent for pressure tightness, and they get there by different routes. A360 removes copper so there are no low-melting copper-rich eutectics to freeze last. A413 compresses the whole freezing event into 8 °C so there is barely a mushy stage during which interconnected shrinkage can form. For a part whose only job is to hold pressure, A413 is marginally the safer metallurgy.
Alloy choice is necessary and not sufficient. Leak paths are designed in long before they are cast: an isolated thick boss that freezes after everything around it, a sealing face positioned where the last metal arrives, or a wall that steps from 5 mm to 2 mm with no transition. We review for those during DFM, position gates and overflows so the final freezing happens in an overflow rather than in a sealing land, and apply vacuum assist where the geometry requires it.
Where a design genuinely leaves no better option, vacuum impregnation seals residual microporosity. It is a legitimate production process and we offer it, but it is a remedy rather than a plan, and a part that needs impregnation on every unit usually has a geometry problem worth fixing in the tool.
A413's machinability is rated fair, the lowest of the four grades, and this is the constraint that most often decides against it. The reason is physical rather than metallurgical. Silicon in an aluminum-silicon alloy is present as hard primary and eutectic particles distributed through a soft matrix, and at 11 to 13% silicon there are a great many of them. Those particles abrade the cutting edge continuously, so carbide tooling that would run for hours in A380 wears visibly in a fraction of that time.
The answer is tooling rather than acceptance. Polycrystalline diamond inserts last roughly ten to twenty times longer than carbide in this alloy and hold a cleaner edge, which keeps bore size stable through a production lot instead of drifting as the tool wears. PCD costs more per insert and pays for itself quickly on any part with real machining content. Where only a few features are cut, coated carbide at reduced surface speed with generous coolant is still workable.
The design consequence is worth stating plainly: do not specify A413 for a part that will be heavily machined unless the thermal or sealing requirement demands it. A housing that needs a bored bearing seat, a faced mounting plane and twenty tapped holes is cheaper and more accurate in A380. A heat sink that needs a flat, lapped contact face and four clearance holes is a perfect A413 part.
121 W/m·K against 113 for A360 and 96 for both A380 and ADC12. On a casting that doubles as the heat sink, that margin is frequently what lets cast fins replace a separate bonded or extruded thermal assembly, removing an interface, a bond line and an assembly operation.
Sitting at the eutectic keeps the metal liquid until 582 °C, so it reaches the tips of long fins and the ends of thin dead-ended sections that A380 freezes short. Geometry that is marginal in other alloys is routine in A413.
An 8 °C freezing range leaves far less interdendritic shrinkage than A380's 55 °C, so fewer parts fail a leak test after machining opens a sealing face. For pressure boundaries and sealed enclosures this raises first-pass yield enough to matter commercially.
Eutectic solidification means less volumetric contraction and more uniform contraction across the part, so large flat sections stay flatter and the die shrinkage factor is more predictable on a first tool.
With copper capped at 1.0% maximum there are far fewer Al2Cu particles to drive galvanic pitting than in A380's 3.0 to 4.0%. A413 rates good rather than fair, which matters on outdoor luminaires and enclosures where a coating scratch would otherwise become a corrosion site.
20.4 µm/m·°C, the lowest of the four, because silicon expands less than aluminum. On a part clamped to a PCB, a ceramic substrate or a steel frame across a wide temperature range, that reduces the differential movement the joint has to absorb.
Machinability is fair, the lowest of the four. High silicon content abrades carbide quickly, so parts with real machining content need polycrystalline diamond inserts to hold size through a lot. Heavily machined parts are cheaper and more accurate in A380.
296 MPa tensile and 145 MPa yield, against 324 and 159 for A380. Where a part is sized against load rather than heat, A413 needs more section to carry the same force, which gives back some of the thermal and weight advantage.
2.5% elongation against 3.5% for the other three grades. A413 is less forgiving of stress concentrations, so sharp internal corners, abrupt section changes and unradiused rib roots are more likely to initiate cracks under shock or vibration loading.
Like every high pressure die casting alloy, A413 cannot take a conventional T6 treatment, because entrapped gas expands and blisters the surface at solution temperature. With magnesium restricted to 0.10% there is little precipitation response to recover anyway, so design to as-cast properties.
Silicon does not anodize, so 11 to 13% of the surface stays as unconverted particles in the film. The result is a dark grey, visibly non-uniform finish. Where appearance matters, powder coat instead and accept that anodizing is a functional rather than cosmetic option on this alloy.
Relative cost is moderate against A380's lowest, from cleaner ingot requirements and from the tooling cost of machining it. Specify A413 because the part needs its conductivity or its sealing behaviour, not as a general upgrade.
Against A380 the exchange is clear. A413 gives up tensile strength, yield strength, ductility and machinability, and gains 26% more thermal conductivity, markedly better fluidity, excellent pressure tightness and better corrosion resistance. If the part does not need heat or sealing performance, A380 is the better commercial answer and we will say so on the quotation.
Against A360 the comparison is closer and comes down to what else the part does. A360 conducts 113 W/m·K against A413's 121, which is a 7% difference rather than a decisive one, and in exchange A360 offers 170 MPa yield against 145, 3.5% elongation against 2.5% and good machinability against fair. For a housing that both dissipates heat and carries mounting loads with machined interfaces, A360 is usually the better balance. For a dedicated heat sink or a pure pressure boundary, A413 wins.
Against ADC12 the question is only ever thin walls. ADC12 at 9.6 to 12.0% silicon fills nearly as well and machines better, so it is the right answer for thin-wall enclosures and covers. A413 is worth the machining penalty only when conductivity or pressure tightness is the point of the part.
| Property | A380 (AlSi8Cu3Fe) | ADC12 (A383) | A360 (AlSi10Mg) | A413 (AlSi12) |
|---|---|---|---|---|
| Ultimate tensile strength | 324 MPa (47 ksi) | 310 MPa (45 ksi) | 317 MPa (46 ksi) | 296 MPa (43 ksi) |
| Yield strength (0.2%) | 159 MPa (23 ksi) | 150 MPa (22 ksi) | 170 MPa (25 ksi) | 145 MPa (21 ksi) |
| Elongation in 50 mm | 3.5% | 3.5% | 3.5% | 2.5% |
| Brinell hardness | 80 HB | 75 HB | 75 HB | 80 HB |
| Silicon content | 7.5-9.5% | 9.6-12.0% | 9.0-10.0% | 11.0-13.0% |
| Copper content | 3.0-4.0% | 1.5-3.5% | 0.6% max | 1.0% max |
| Density | 2.74 g/cm³ | 2.70 g/cm³ | 2.63 g/cm³ | 2.66 g/cm³ |
| Thermal conductivity | 96 W/m·K | 96 W/m·K | 113 W/m·K | 121 W/m·K |
| Castability | Excellent | Excellent | Very good | Excellent |
| Corrosion resistance | Fair | Fair | Good | Good |
| Machinability | Very good | Good | Good | Fair |
| Pressure tightness | Good | Good | Excellent | Excellent |
| Relative cost | Lowest | Low | Moderate | Moderate |
Properties are typical as-cast values measured on separately cast test bars and will vary with wall thickness, gating and section geometry. Request a material certificate for lot-specific values.
They are close equivalents written to different standards. A413 is the ASTM B85 grade, AlSi12 is its chemical designation, ADC1 is the JIS H 5302 equivalent, EN AC-44300 (AlSi12(Fe)) is the EN 1706 die casting grade and YL102 is the Chinese GB grade. All are near-eutectic aluminum-silicon alloys with 11 to 13% silicon and no deliberate copper or magnesium. The one difference worth checking is copper: EN AC-44300 caps it at 0.10% while ASTM A413 permits up to 1.0%, which is measurable on a conductivity-critical part. If your drawing names the EN grade we buy ingot to the EN chemistry and certify against EN 1706.
Not usually, and the distinction matters for machining. The aluminum-silicon eutectic sits at 12.6% silicon, and A413's specified range of 11.0 to 13.0% brackets it, so a typical production melt at 11.5 to 12.5% silicon is slightly hypoeutectic to essentially eutectic. True hypereutectic alloys are the 390 series at 16 to 18% silicon, which contain large primary silicon crystals and are used for cylinder bores and wear surfaces. Those alloys are far more abrasive than A413 and require diamond tooling absolutely rather than preferentially. A413 is best described as a near-eutectic alloy.
Because A380 contains 3.0 to 4.0% copper and A413 contains at most 1.0%. Alloying elements dissolved in the aluminum matrix scatter the free electrons that carry heat through a metal, and copper in solid solution is particularly effective at it. Removing the copper addition leaves a cleaner matrix, which lifts thermal conductivity from 96 W/m·K to 121 W/m·K, a 26% improvement, and electrical conductivity from 23% to 31% IACS. The silicon itself is present mostly as discrete particles rather than in solution, so it costs less conductivity than its 11 to 13% share would suggest.
Yes, relative to the other die casting alloys, and it is the main reason to think twice about specifying it. Machinability is rated fair against A380's very good. The 11 to 13% silicon exists as hard particles that abrade cutting edges continuously, so carbide tooling wears fast enough that bore sizes drift through a production lot. The practical answer is polycrystalline diamond tooling, which lasts roughly ten to twenty times longer and holds size, plus flood coolant and moderated surface speed. If a part needs heavy machining and has no thermal or sealing requirement, specify A380 instead.
A413 if the part is essentially a heat sink, A360 if it is a housing that also sheds heat. A413 conducts 121 W/m·K against A360's 113, only a 7% edge, but its near-eutectic fluidity fills finer and taller fin arrays, which usually buys more real thermal performance than the conductivity difference does. A360 counters with 170 MPa yield against 145, 3.5% elongation against 2.5% and good machinability against fair. So a finned LED housing with a lapped contact face and a few clearance holes is an A413 part, while a motor housing with cast fins, a bored bearing seat and twenty tapped holes is an A360 part.
Yes, and along with A360 it is one of the two grades we rate excellent for it. The 8 °C freezing range means the alloy solidifies almost all at once rather than pasting through a long mushy stage, which leaves far less of the interconnected interdendritic shrinkage that becomes a leak path when machining opens a sealing face. Alloy choice alone is not enough: the design needs uniform walls with no isolated thick sections, gating arranged so the last metal to freeze ends up in an overflow rather than a sealing land, and vacuum assist where the geometry demands it. We leak test to your specified pressure and offer vacuum impregnation where a design leaves no better option.
Powder coating works well and is what we recommend. The as-cast surface at Ra 1.6 to 3.2 µm takes a chromate conversion pretreatment and powder cures to any RAL colour with good adhesion, and on a heat sink the coating also raises surface emissivity, which slightly improves radiative heat transfer. Anodizing is possible but cosmetically poor on this alloy: silicon does not anodize, so at 11 to 13% silicon a large fraction of the surface remains as unconverted particles and the film comes out dark grey and visibly uneven. Treat anodizing on A413 as a functional hardness option rather than a finish.
Send your 2D drawing and 3D model with the thermal budget or sealing pressure the part has to meet. We will confirm whether A413 is the right grade against A360, flag any fin geometry that needs mold flow simulation, quote piece price and tooling, and return a written DFM report.