Both materials are viable.
- Weight: cast aluminum is ~2.7 g/cm³ vs cast iron ~7.2 g/cm³ (≈2.7× lighter).
- Strength: cast iron wins in compressive and high-stiffness applications; cast aluminum (e.g., AlSi10Mg-T6 ≈ 230 MPa yield) is competitive in tensile/weight-critical parts. Cast aluminum wins for weight, heat spreading, corrosion resistance, and thin-wall, high-volume parts (HPDC).
- Thermal: aluminum has higher conductivity (≈150–200 W/m·K) and higher specific heat, so it ramps temperature faster and spreads heat better (heat sinks, housings).
- Corrosion: aluminum forms a stable oxide; cast iron requires coatings and is prone to rust in wet or marine environments.
- Temperature window: cast iron keeps strength at higher temperatures; most Al castings lose yield above ~150–200 °C unless specially alloyed.
- Cost: raw iron is cheaper, but die casting (aluminum) may beat sand-cast iron on cycle time/near-net-shape in volume. Cast iron wins for stiffness (high E), vibration damping, compressive loads, and high-temperature duty at low raw-material cost.
Pick by load case + temperature + environment + volume/tolerance.
👉 Rule of thumb: choose cast aluminum when weight, corrosion resistance, or heat dissipation matters; choose cast iron for high-stiffness, high-temperature, or heavy compressive loads at low material cost.
Cast Aluminum vs Cast Iron comparison (room temp)
| Property | Cast Aluminum (e.g., A380, AlSi10Mg) | Cast Iron (grey/ductile) | Design meaning |
|---|---|---|---|
| Density | ~2.7 g/cm³ | ~7.2 g/cm³ | Al is ≈2.7× lighter → easier handling, lower freight |
| Tensile | ~150–250 MPa (AlSi10Mg-T6 ≈ 280–320 MPa UTS) | Grey: ~150–300 MPa; Ductile: ~420–600 MPa | Iron can reach higher UTS (grade-dependent) |
| Yield | A380 ≈ ~170 MPa; AlSi10Mg-T6 ≈ ~230 MPa | Ductile ≈ ~240–420 MPa (grade-dependent) | Verify spec + heat treatment |
| Modulus E | ~70 GPa | Grey: ~110–130 GPa; Ductile: ~160–170 GPa | Iron is much stiffer → less deflection |
| Thermal k | ~150–200 W/m·K | ~40–60 W/m·K | Al spreads heat → heat sinks, housings |
| Specific heat | ~0.90 kJ/kg·K | ~0.45 kJ/kg·K | Al heats/cools faster per kg |
| Corrosion | Good (oxide; anodize/coat) | Poor uncoated (rust) | Outdoor/marine favors Al + coating |
| Melting point | ~560–630 °C | ~1150–1200 °C | Iron retains strength at heat |
| Damping | Low–med | High (grey iron) | Iron calms vibration (machine bases) |
| Typical wall | HPDC 1–2.5 mm | Sand/shell 3–10 mm+ | Geometry guides process |
| Cost at volume | High tooling, low part cost | Modest tooling, slower cycle | Volume decides |
Cast Aluminum vs Cast Iron Industry & application (both can be “right”)
| Industry → Subsector | Cast Aluminum often chosen when… | Cast Iron often chosen when… | Why / Notes |
|---|---|---|---|
| Automotive/EV → inverter boxes, motor housings | Weight, heat spreading, corrosion | Blocks, brake carriers, hubs | Duty temp + stiffness drive pick |
| Industrial machinery → gearboxes, covers | Manual handling, outdoor corrosion | Machine beds, frames, fixtures | Iron’s modulus & damping |
| Power electronics → heat sinks | High k + thin fins | Heat soak near furnaces | Thermal profile |
| Rail / off-highway → boxes, covers | Weight/corrosion | Wheels, bogie parts, brakes | Hot compressive loads |
| HVAC / Pumps → impellers, fan housings | Thin blades, corrosion | Pressure bodies | Pressure & wall |
| Marine → housings, deck gear | Corrosion (with coat/anodize) | Winches, anchors | Salt vs brute force |
| Medical / Lab → carts, housings | Light + clean finishes | Counterweights | Portability vs stability |
| Aerospace/Drone → gimbals, mounts | Ultra-light, complex | Ground fixtures | Geometry vs damping |
Decision memo: Both materials can meet spec; we select by load case, temperature, environment, volume/tolerance, and finish.
Aluminum Cast Processing Methods
- HPDC (High-Pressure Die Casting)
Thin walls (≈1–5 mm), very good repeatability, complex ribs/bosses, inserts, fast cycle. Tooling cost high, part cost low at volume. Vacuum die casting + controlled fill reduces porosity and improves fatigue & leak-tightness. - Squeeze casting / High-integrity HPDC
Combines pressure solidification with slow fill; lower porosity, better mechanicals (approaches permanent-mold), good for structural brackets. - Permanent mold (gravity die)
Walls ≈3–8 mm, lower porosity than sand/HPDC as-cast, stable dimensions; can T6 (e.g., AlSi10Mg-T6). - Sand casting
Flexible for larger parts, moderate tooling cost, slower cycle; porosity and surface roughness higher than permanent-mold/HPDC unless tightly controlled. - Semi-solid / Thixoforming (less common but powerful)
Near-wrought properties, tight walls, excellent fill at lower gate speeds; tooling similar to die casting.
Cast iron Processing Methods
- Green sand / No-bake
Most common; large size freedom; good for thick sections and compressive duty. - Shell mold
Better surface & accuracy than green sand; thinner walls feasible. - Ductile-iron heat treatment
Grades (e.g., 60-40-18, 80-55-06) tune strength/ductility; austempering (ADI) lifts wear/fatigue. - Lost foam / Investment (niche)
Used for complex shapes when machining cost offsets casting cost.
Aluminum Surface protection & finishing
- Anodize Type II (sulfuric): decorative, corrosion resistance, dyable; good for housings.
- Anodize Type III (hardcoat): wear-resistant ~25–50 µm; good for sliding/contact surfaces.
- Conversion coating (trivalent chromate/“chemfilm”): paint base, electrical bonding.
- Powder coat / E-coat / Wet paint: outdoor durability; choose UV-stable systems.
- Shot-blast + powder: hides minor cosmetic porosity; uniform matte.
- Sealing & thread inserts: specify helicoils/keenserts for repeated assembly.
Cast iron Surface protection & finishing
- Zinc-rich epoxy primer + polyurethane topcoat: outdoor heavy-duty standard.
- Phosphate + paint: improved paint adhesion.
- Thermal spray (Zn/Al) + seal: marine & splash zones.
- Oil/alkyd shop coats: indoor/rust-control during transport.
- Enamel/porcelain (cookware, chemical): chemical and cleanability benefits.
Practical note: for salt fog or fertilizers, aluminum + powder/anodize outlasts uncoated iron; iron must be coated to avoid rust bleed.
Cast Aluminum vs Cast Iron Typical data ranges
| Property | Cast Aluminum (A380 / AlSi10Mg-T6) | Cast Iron (Grey / Ductile) |
|---|---|---|
| Density | ~2.7 g/cm³ | ~7.2 g/cm³ |
| Yield strength | A380 ~170 MPa; AlSi10Mg-T6 ~230 MPa | Grey: n/a in tension (brittle); Ductile: ~240–420 MPa |
| Tensile strength | AlSi10Mg-T6 ~280–320 MPa | Grey: ~150–300 MPa; Ductile: ~420–600 MPa |
| Elongation | 2–8% (alloy/temper-dependent) | Grey 1–3%; Ductile 10–18% |
| Modulus E | ~70 GPa | Grey ~110–130 GPa; Ductile ~160–170 GPa |
| Hardness (HBW) | ~70–110 | Grey ~150–220; Ductile ~170–240 |
| Thermal conductivity | ~150–200 W/m·K | ~40–60 W/m·K |
| Specific heat | ~0.90 kJ/kg·K | ~0.45 kJ/kg·K |
| CTE (20–100 °C) | ~21–24 µm/m·K | ~10–12 µm/m·K |
| Melting range | ~560–630 °C | ~1150–1200 °C |
Temperature note: many Al casting alloys lose ~10–30% of yield by 100–150 °C; iron retains strength better at heat.
Inspection Checklist for Buyer’s
Material & performance
- Material + grade + heat treatment (AlSi10Mg-T6, A380 HPDC, Ductile iron 60-40-18).
- Operating temperature + environment (salt/fertilizer/chemicals).
- Structural driver: stiffness/buckling vs strength/fatigue; allowable deflection.
- Leak-tightness (pressure/medium/time) & NDT (X-ray/CT/dye/pressure-decay).
Geometry & process
- Annual volume + wall-thickness range; preferred process (HPDC / sand / permanent-mold).
- Draft (HPDC 0.5–1°, sand 1–2°), min radii, parting/gating constraints.
- Machining datums, flatness/position tolerances, threads & tool access.
Finish & compliance
- Finish stack (anodize type, powder/paint spec), color/gloss, masked areas.
- Standards: aluminum ASTM B179 / B26/B108; iron ASTM A48 / A536 (or regional).
- Docs: PPAP/FAI, CoC, MTR, RoHS/REACH, IMDS (if automotive).
Logistics
- Target weight & packaging (VCI/desiccant), corrosion protection, pallet spec.
Cast Aluminum vs Cast Iron Optional process-selection table
| Volume / Geometry | Thin-wall, complex | Medium wall | Heavy/thick section |
|---|---|---|---|
| Low volume | Sand Al / Sand Iron | Sand Al / Sand Iron | Sand Iron |
| Mid volume | Permanent-mold Al / Shell Iron | Permanent-mold Al / Sand Iron | Sand Iron |
| High volume | HPDC Al | HPDC Al / Permanent-mold Al | Shell/au |
Send your drawing—get a material + process proposal, weight estimate, porosity plan, and an indicative quote within 24 hours.
