1. 介绍
Cast aluminum and cast iron are two of the most widely used casting materials in industry.
Both offer routes to produce complex net-shape components, but they differ fundamentally in density, 刚性, strength modes, 热行为, 铸造方法, corrosion resistance and lifecycle cost.
Selecting between them is a trade-off among weight, 刚性, 戴阻力, 可加工性, cost and operating environment.
This article compares the two across technical axes and provides actionable data and selection guidance.
2. What is cast aluminum?
铸造铝 refers to components produced by pouring molten aluminum (or aluminum alloy) into a mould and letting it solidify into the final or near-final geometry.
Because aluminum has a relatively low melting point, good fluidity in alloyed form, and a low density, cast aluminum is a preferred choice where complex geometry, 轻的, thermal conductivity or corrosion resistance are important.
Casting routes for aluminum include high-pressure die casting, low-pressure and gravity permanent-mold casting, 沙子铸造, and investment (失去蜡) 铸件; each route gives different limits on wall thickness, 表面饰面, dimensional accuracy and mechanical properties.
特征
- 轻的: density ≈ 2.6–2.8 g/cm³ (通常 2.70 g/cm³).
- Low elastic modulus: Young’s modulus ≈ 69–72 GPa (≈ 69 GPa typical).
- 良好的导热率: alloys vary but often 100–200 W·m⁻¹·K⁻¹; pure aluminium is ~237 W·m⁻¹·K⁻¹.
- 良好的耐腐蚀性: forms a stable oxide film; behaviour improved with anodizing or coatings.
- Ductile fracture behavior: many cast Al alloys are reasonably ductile (取决于合金和热处理).
- Easily machined: comparatively low cutting forces and good machinability for many alloys.
- 可回收: aluminium is highly recyclable with relatively low energy to remelt versus primary production.
Common aluminum alloys (typical cast families)
| Alloy family (typical name) | Representative grades / trade names | Key alloying elements (wt％) | 热处理? | 典型的应用 |
| al-是的 (通用) | A356 / AlSi7 | Si ≈ 6–8; Mg ≈ 0.2–0.5 | 经常 (T6 available) | Structural housings, 泵主体, general automotive castings |
| Al–Si–Mg (结构, 热处理) | A356-T6, A357 | Si ≈ 6–7; Mg ≈ 0.3–0.6 | 是的 (T5/T6) | 悬架组件, 车轮, 传输外壳 |
| Die-casting Al–Si–Cu / al-是的 | A380, ADC12, A383 | Si ≈ 8–13; Cu ≈ 1–4; Fe controlled | 有限的 (mostly as-cast or semi-aged) | Thin-wall housings, 连接器, consumer enclosures |
Al -Andi (engine & elevated-T alloys) |
合金 319 | Si ~6–8; Cu ~3–4; Mg small | 是的 (解决方案 + 老化) | 气缸盖, 活塞 (with liners), engine hardware |
| High-Si / hypereutectic alloys | al-是的 (10–20% Si) | Si 10–20; minor Mg/Cu | Somewhat (有限的) | 活塞, wear surfaces, low-expansion components |
| Al–Si–Sn / bearing alloys | Al–Si–Sn bearing variants | Si moderate; sn (±Pb) as solid lubricants | Typically no (soft as-cast) | Plain bearings, 衬套, sliding surfaces |
| Specialty high-strength cast Al | Al–Zn–Mg variants (limited cast use) | Zn, 毫克, small Cu additions | 是的 (age-hardenable) | High-strength structural parts (niche/aerospace) |
3. What is cast iron?
铸铁 is a family of iron-carbon alloys produced by pouring molten metal into molds and allowing it to solidify.
What distinguishes cast irons from steels is their relatively 高碳含量 (通常 >2.0 wt％c) and the presence of graphitic carbon in the as-cast microstructure.
The carbon commonly occurs as graphite (in several morphologies) or as iron carbide (水泥岩) depending on alloy chemistry and solidification conditions.
That graphite — and the matrix that surrounds it — controls the mechanical behavior, machinability and application space of the various cast-iron types.
Cast irons are the workhorses of heavy, wear-resistant and vibration-sensitive applications because they are economical to cast in large or complex shapes, offer excellent damping, and can be tailored through chemistry and post-casting heat treatment (例如。, 东部回火) to a wide range of properties.
关键功能
- Graphite morphology controls properties. The shape, size and distribution of graphite (flake, spheroidal, compacted) dominate tensile ductility, 韧性, stiffness and machinability:
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- Flaky (灰色的) 石墨 produces good machinability and damping but lower tensile strength and notch sensitivity.
- 球体 (nodular/ductile) 石墨 yields much higher tensile strength and ductility.
- Compacted graphite (CGI) is intermediate — better strength and thermal fatigue resistance than gray iron while retaining good damping.
- 出色的振动阻尼. Graphite nodules/flakes interrupt elastic wave propagation, so cast irons are preferred for machine-tool frames, engine blocks and housings where damping suppresses noise and vibration.
- Good compressive strength and wear resistance. Especially in pearlitic and white irons; suitable for heavy-duty bearings, rollers and wear parts.
- Relatively brittle in tension (一些成绩). Gray iron is notch sensitive and shows low elongation; ductile iron improves toughness significantly but still behaves differently from steels.
- Economical for large/complex castings. Sand casting and shell molding are well established; 收缩, feeding and directional solidification are managed with standard foundry techniques.
- Wide design envelope via post-solidification treatment. Through heat treatments (标准化, 退火, 东部回火) 和合金 (在, Cr, 莫),
cast irons can be tailored from very hard wear grades to tough structural grades (例如。, ADI—Austempered Ductile Iron). - Good thermal stability in many grades. Some cast irons preserve dimensional stability and strength at elevated temperatures better than aluminum alloys.
Common cast-iron types
Below is a practical summary of the major cast-iron families, typical chemistry trends, microstructure and representative properties / 申请.
| 类型 | 典型成分 (大约. wt％) | Key microstructure feature | Representative mechanical behavior | 典型的应用 |
| 灰色铸铁 (GJL / Classed per ASTM A48) | C ~3.0–3.8; Si ~1.5–3.0; Mn ≤0.5; s & P controlled | Graphite flakes in ferrite/pearlite matrix | Tensile strength broadly ~150–350 MPa (varies by class); 低伸长 (<1–3％); excellent damping; moderate hardness | 发动机块, 制动鼓, 泵外壳, 机器基础 |
| 公爵 (结节) 铁 (GJS / ASTM A536) | C ~3.2–3.8; Si ~1.8–2.8; Mg ~0.03–0.06 (nodularizing), trace Ce/RE | Spheroidal graphite nodules in ferrite/pearlite | High tensile strength and ductility; common grades like 60–40–18 (60 ksi UTS ≈ 414 MPA, 40 ksi YS ≈ 276 MPA, 18% 伸长) | 齿轮外壳, 曲轴, safety-critical structural castings |
| 压实石墨铁 (CGI) (GJV) | C ~3.2–3.6; Si ~1.8–2.6; trace Mg/RE | 袖珍的 (vermicular) 石墨 — intermediate between flakes and spheroids | Better tensile strength and thermal fatigue resistance than gray iron, with good damping; UTS in intermediate range | 柴油发动机块, 排气组件, heavy-duty cylinder blocks |
| White iron | C ~2.6–3.6; Si low (<1.0); high cooling rates | 水泥岩 / ledeburite (碳化物) — essentially no graphite | 非常高的硬度 (often HB several hundred), excellent abrasive wear resistance; 低韧性 | Crushers, 穿盘子, shot-blast liners, severe abrasion environments |
Malleable iron |
Initially white iron composition; 热处理 | Cast as white iron then 退火 to temper carbon into irregular aggregates (temper carbon) | Combines improved ductility/toughness vs. 灰铁; 中等力量 | Small castings requiring ductility (配件, 括号) |
| 奥斯特延延延性铁 (阿迪) | Ductile iron base + controlled austempering heat treatment | Spheroidal graphite in ausferritic matrix (bainitic ferrite + stabilized austenite) | Exceptional strength-to-ductility ratio: UTS from ~600 to >1000 MPA with useful elongation (3–10% depending on grade); 极好的抗疲劳性 | High-performance drivetrain, 悬架组件, 重型机械 |
| Alloyed cast irons (例如。, Ni-resist, high-Cr irons) | Base with significant Ni, Cr, Mo additions | Matrix tailored to resist heat/corrosion; graphite may be present or suppressed | Specialized corrosion/oxidation resistance, or high-temperature strength | Pump components for corrosive fluids, 阀体, high-temp wear parts |
4. 机械性能比较
Numbers are presented as practical, foundry-level 典型的范围 (not guaranteed minima/maxima) because actual values depend strongly on exact chemistry, casting route, 截面大小, 和热处理.
Typical mechanical property ranges — representative cast aluminum vs cast iron grades
| 材料 / 年级 (typical designation) | 密度 (g·cm⁻³) | Young’s modulus (GPA) | 抗拉强度, UTS (MPA) | 产生强度 (MPA) | 伸长 (一个, %) | 硬度 (布里尔, HB) | 典型的应用 |
| A356-T6 (Al–Si–Mg, heat-treated cast aluminum) | 2.68–2.72 | 68–72 | 200 - 320 | 150 - 260 | 5 - 12 | 60 - 110 | Structural housings, 轮毂, 传输外壳 |
| A380 / ADC12 (common die-casting Al–Si family, 铸造) | 2.70–2.78 | 68–72 | 160 - 280 | 100 - 220 | 1 - 6 | 70 - 130 | Thin-wall housings, consumer parts, 连接器 (压铸) |
| Hypereutectic Al–Si (活塞 / low-expansion alloys) | 2.70–2.78 | 68–72 | 150 - 260 | 100 - 220 | 1 - 6 | 80 - 140 | 活塞, 滑动组件, low-expansion parts |
| 灰色铸铁 (typical ASTM A48 Class 30) | 6.9–7.3 | 100–140 | ≈207 (≈30 ksi) | - (no distinct yield) | <1 - 3 | 140 - 260 | 发动机块, 机器框架, 制动鼓 |
| 灰色铸铁 (ASTM A48 Class 40) | 6.9–7.3 | 100–140 | ≈276 (≈40 ksi) | - | <1 - 3 | 160 - 260 | Heavier duty housings, 泵主体 |
| 公爵 (结节) iron — 60–40–18 (ASTM A536) | 7.0–7.3 | 160–180 | ≈414 (60 KSI) | ≈276 (40 KSI) | 〜18 | 160 - 260 | 齿轮外壳, crank components, 结构铸件 |
| 压实石墨铁 (CGI) (典型范围) | 7.0–7.3 | 140–170 | 350 - 500 | 200 - 380 | 2 - 8 | 180 - 300 | 柴油发动机块, 排气组件 (high thermal fatigue resistance) |
| 白色的 / high-Cr wear iron (wear grades) | 7.0–7.3 | 160–200 | low tensile / 脆 | - | <1 - 2 | >300 - 700 | Crushers, wear liners, shot-blast components |
5. Thermal and Casting Process Considerations
Melting and solidification behavior
- Melting point / 液体: aluminium alloys melt in the 〜550–650°C 范围 (pure aluminium 660.3 °C).
Cast iron solidifies at higher temperatures (~1150–1250 °C depending on composition) and forms graphite or cementite based on composition and cooling rate. - 导热率: aluminum alloys typically conduct heat significantly better than cast iron (often 2–4× higher), which affects mold cooling, solidification speed and chill behavior.
- Solidification shrinkage: typical linear shrinkage for aluminum alloys ~1.3–1.6%; gray cast iron shrinkage is smaller (〜0.5–1.0％), though micro- and macro-shrinkage depend on section thickness and feeding.
Casting methods & typical use
- 投掷 铝: commonly produced by 压铸 (高压), 永久模具, 低压, 和 沙子铸造.
Die casting yields excellent surface finish and thin-wall capability; sand casting handles large, 重的, or complex parts with lower tooling cost. - 铸铁: 通常 沙子铸造 (green-sand, 壳) 和 迷失的泡沫/壳 for complex shapes.
Ductile iron castings are commonly sand-cast. Cast iron tolerates large sections and heavy castings well.
尺寸公差 & 表面饰面
- Die-cast aluminum: best dimensional capability of cast routes — typical tolerances in the range ±0.1–0.5 mm for many dimensions (depends on size), surface finish Ra often 0.8–3.2 µm 铸造.
- Permanent-mold aluminum: tolerances ±0.25–1.0 mm, surface finish better than sand casting.
- Sand-cast iron: coarser tolerances, typically ±0.5–3.0 mm depending on size and finish; surface finish rougher, Ra often 6–25 µm as-cast unless machined.
- Wall thickness capability: die-cast aluminum can produce thin walls (<2 毫米) economically;
cast iron typically requires thicker sections to avoid defects and to feed shrinkage, though modern molding can achieve moderate thin sections for small parts.
Machinability and secondary operations
- 铝 machines easily at higher speeds and lower forces; tooling life is good; machining allowances are modest for die-cast parts.
- 铸铁 machines differently — gray iron is relatively easy to machine due to graphite acting as chip breaker and lubricant;
ductile iron is harder and requires different tooling; cast iron cutting often results in brittle chips and requires appropriate tool grades.
6. Corrosion Resistance and Operating Environments
- 铸造铝: naturally corrosion-resistant due to stable oxide film; performs well in atmospheric, mildly corrosive and marine environments if appropriate alloy/coating is chosen.
Anodizing and paint systems further improve surface durability and appearance. - 铸铁: ferrous material prone to rust (氧化) in wet environments; 需要保护涂料 (油漆, 电镀), cathodic protection or alloying for corrosion resistance.
在某些应用中 (发动机块), cast iron performs acceptably because of oil protection and controlled environments. - High-temperature performance: 铸铁 (especially gray and ductile) retains strength at elevated temperatures better than aluminum.
Aluminum’s strength drops rapidly as temperature increases above ~150–200 °C, limiting its use in hot-engine or exhaust-exposed components unless special alloys or cooling are used.
7. Advantages of Cast Aluminum vs Cast Iron
Cast aluminum advantages
- Weight savings: ~62.5% lighter for equivalent volume than cast iron — critical in transportation for fuel economy.
- 高热电导率: 更好的散热 (helpful for heat exchangers, cylinder heads in automotive after appropriate design).
- 良好的耐腐蚀性 铸造; optionally anodizable for enhanced protection and aesthetics.
- Thin-wall and complex thin-feature capability (尤其是铸造) — enables consolidated parts and cost savings upstream.
- Favorable recyclability and lower mass-related shipping costs.
Cast iron advantages
- Higher stiffness and damping: good for structures requiring rigidity and vibration control (机床基库, 泵外壳).
- Superior wear resistance and tribological properties: pearlitic and white irons excel in abrasive/wear environments.
- Higher compressive strength and thermal stability at elevated temperatures — used for heavy-duty engine blocks, 气缸衬里, and brake rotors.
- Typically lower raw material cost per kg and robust casting behavior for very large sections.
8. Limitations of Cast Aluminum vs Cast Iron
Cast aluminum limitations
- Lower stiffness: requires larger cross-sections or ribs to achieve equivalent stiffness — can reduce some weight advantages.
- Lower high-temperature strength: aluminum loses yield strength at elevated temperatures faster than iron.
- Less wear resistance: plain cast aluminum is softer; requires surface treatments (努力阳极氧化, 涂料) for wear-critical surfaces.
- Porosity and gas-related defects: aluminium is prone to gas porosity and shrinkage defects if melt and casting practice are not controlled.
Cast iron limitations
- 重的: higher density increases part mass — negative for weight-sensitive applications.
- Brittle tensile behavior: gray iron shows low tensile ductility and is prone to brittle fracture under impact; design must account for notch sensitivity.
- Corrodes if unprotected: requires coatings or corrosion management.
- Lower thermal conductivity than Al (slower heat dissipation); may require cooling design adjustments.
9. Cast Aluminum vs Cast Iron: Differences Comparison
| 属性 | 铸造铝 (例如。, A356-T6, A380) | 铸铁 (灰色的, 公爵) | Practical implication |
| 密度 | ~2.6–2.8 g·cm⁻³ | ~6.8–7.3 g·cm⁻³ | Aluminum is ~60–63% lighter — huge benefit for weight-sensitive designs. |
| Elastic modulus (e) | ≈ 69–72 GPa | ≈ 100–170 GPa | Iron is 1.5–2.5× stiffer; aluminum needs more material/ ribs to match stiffness. |
| 抗拉强度 (典型的) | A356-T6: ~200–320 MPa; A380: ~160–280 MPa | 灰色的: ~150–300 MPa; 公爵: ~350–700 MPa | Ductile iron outperforms Al in strength and ductility; some Al alloys approach lower-end iron strengths. |
| 产生强度 | ~150–260 MPa (A356-T6) | 灰色的: no clear yield; 公爵: ~200–300 MPa | Use ductile iron when distinct yield behavior and higher static strength needed. |
| 伸长 (延性) | ~5–12% (A356-T6) or 1–6% (die-cast) | 灰色的: <1–3％; 公爵: ~10–20% | Ductile iron and heat-treated Al offer good ductility; gray iron is brittle in tension. |
| 硬度 / 穿 | HB ≈ 60–130 (alloy dependent) | HB ≈ 140–260 (灰色的); >300 (white/pearlitic) | 铁, especially pearlitic/white grades, best for abrasive wear. Aluminum requires coatings/inserts for wear. |
| 导热率 | ~80–180 W·m⁻¹·K⁻¹ (alloy dependent) | ~30–60 W·m⁻¹·K⁻¹ | Aluminum preferred for heat-dissipation parts (散热器, 住房). |
| 热稳定性 / high-T strength | Strength drops quickly above ~150–200 °C | Better high-temperature strength retention | Use iron for elevated-temperature load bearing. |
| 减震 / 振动 | 一般 | 出色的 (特别是灰铁) | Iron preferred for machine frames, bases and components where vibration damping matters. |
| 可铸性 / thin-wall capability | 出色的 (压铸; 薄壁 <2 mm possible) | Limited — better for thicker sections | Aluminum enables consolidated, lightweight thin-walled parts; iron better for heavy sections. |
表面饰面 & 公差 (铸造) |
Die cast: fine finish, 严格的公差 | Sand cast: 更粗糙, wider tolerances | Die casting lowers post-machining; sand cast iron often requires more machining. |
| 可加工性 | Easy, high removal rates; low tool wear | Gray iron machines well (graphite aids chip formation); ductile iron harder on tools | Aluminum reduces machining cycle times; iron may need tougher tooling but gray irons cut cleanly. |
| 耐腐蚀性 | 良好 (protective oxide); further improved by anodize/coatings | Poor in wet/chloride environments without protection | Aluminum often needs less corrosion protection; iron must be painted/plated or alloyed. |
| 回收 | 出色的; remelting energy lower per kg than primary | 出色的; highly recyclable | Both have strong scrap value; aluminum energy savings per kg large vs primary production. |
| Typical cost considerations | Higher $/kg but lower mass may reduce system cost; die-casting tooling high | Lower $/kg; sand casting tooling low for low volumes | Select based on part mass, volume and required finishing. |
| 典型的应用 | 汽车住房, 散热器, 轻巧的结构部分 | 发动机块, 机器基础, 穿零件, heavy housings | Match material to functional priorities — weight vs stiffness/wear. |
Selection guidance (practical rules of thumb)
- Choose cast aluminum when: mass reduction, thermal dissipation, corrosion resistance and thin-wall feature consolidation are primary drivers (例如。, automotive body components, 散热器, lightweight housings).
Use aluminum die casting for high volumes and thin-walled, feature-rich parts; use A356-T6 when higher structural performance and post-heat treatment are required. - Choose cast iron when: 刚性, 减震, wear resistance or elevated service temperatures are paramount (例如。, 机床基库, 制动组件, heavy duty housings, abrasive wear liners).
Select ductile iron for structural parts that require toughness and some tensile ductility.
Use gray iron when damping and machinability (for heavy machining operations) are important and tensile ductility is less critical. - When in doubt, evaluate system-level tradeoffs: a heavier iron part may be cheaper per kg but increase downstream costs (燃料消耗, 处理, 安装);
反过来, aluminum can reduce system mass but may require larger sections or inserts to achieve stiffness/wear life targets — run a part-level mass, stiffness and cost comparison.
10. 结论
Cast aluminum vs cast iron are complementary materials, each excelling in scenarios where their unique properties align with application requirements.
Aluminum castings dominates lightweight, high-efficiency sectors (automotive EVs, 航天, 消费电子产品) thanks to its strength-to-weight ratio, 导热率, and complex castability. </span>
Cast iron remains irreplaceable in heavy-duty, cost-sensitive applications (机床, construction pipes, traditional engines) due to its wear resistance, 振动阻尼, and low cost.</span>
常见问题解答
How much lighter is a cast aluminum part than the same volume cast iron part?
Typical densities: aluminum ~2.7 g/cm³ vs cast iron ~7.2 g/cm³. For equal component volume, 铝是 关于 62.5% 打火机 (IE。, same-volume aluminum mass = 37.5% of cast iron mass).
Can aluminum replace cast iron in engine blocks?
Aluminum is used extensively for modern engine blocks and cylinder heads to save weight.
Replacing iron requires careful design for stiffness, 热膨胀, cylinder liner strategies (例如。, cast-in liners, iron sleeves) and attention to fatigue and wear.
For high-load or high-temperature applications, cast iron or special aluminum alloys/designs may be preferred.
Which is cheaper: cast aluminum or cast iron?
On a per-kilogram basis, iron tends to be cheaper; on a per-part basis the answer depends on volume, 工具 (die-casting dies are expensive), machining time, and the weight-driven system costs (例如。, fuel consumption in vehicles).
用于大量的, die-cast aluminum may be economical despite higher material cost.
Which material resists wear better?
铸铁 (particularly pearlitic or white iron) generally exhibits superior wear resistance compared with as-cast aluminum.
Aluminum can be surface-treated or coated for wear applications but rarely matches hardened iron without added processes.
Does cast aluminum rust?
Aluminum does not rust like iron; it forms an oxide layer that protects it from further corrosion. Under some conditions (氯化物暴露, 电耦合) aluminum can corrode and may require coatings or cathodic protection.
