A fundição sob pressão de liga de alumínio é amplamente utilizada em indústrias como a automotiva, aeroespacial, e eletrônica, mas as peças fundidas brutas muitas vezes não atendem aos rigorosos requisitos de desempenho. Aluminum alloy die casting heat treatment solves this by precisely controlling heating and cooling processes to optimize material properties. Este artigo detalha seus objetivos principais, métodos, considerações principais, and practical applications to help you master this critical manufacturing step.
1. What Are the Core Purposes of Aluminum Alloy Die Casting Heat Treatment?
The primary goal of heat treatment is to address inherent flaws in raw castings and enhance their functionality. Below are the four key objectives, organized by priority:
| Purpose | Key Benefit | Target Scenario |
| Eliminate internal stresses | Reduces cracking risk during machining or use | Castings with uneven wall thickness (por exemplo, engine brackets) |
| Improve mechanical properties | Boosts tensile strength (by 20-40%), dureza, and plasticity | High-load parts (por exemplo, transmission housings) |
| Stabilize structure & tamanho | Prevents volume changes from high-temperature phase transitions | Precision components (por exemplo, electronic sensor casings) |
| Optimize machining performance | Lowers cutting resistance, increasing tool life by 30%+ | Parts requiring complex CNC machining (por exemplo, valve bodies) |
2. What Are the Main Heat Treatment Methods for Aluminum Alloy Die Castings?
Different methods target specific property improvements. Below is a detailed comparison of the most widely used techniques, including the recommended T5 artificial aging processo.
2.1 Key Heat Treatment Methods: A Side-by-Side Comparison
| Method | Definição | Critical Parameters | Core Functions | Ideal Applications |
| Annealing | Heat to high temp (300-400°C) + slow furnace cooling | Heating rate: 50-100°C/h; Holding time: 2-4h | Decomposes second-phase particles; reduces hardness | Pre-machining of hard castings (por exemplo, alumínio – silicon alloys) |
| Solution Treatment | Heat near eutectic melting point (450-550°C) + rapid quenching | Temp < overburn temp; Quench transfer time < 10s | Maximizes dissolution of strengthening elements (por exemplo, Cu, Mg); Improves corrosion resistance | Parts requiring high strength (por exemplo, aircraft fittings) |
| Aging Treatment | Post-solution heating to 120-200°C + heat preservation | Holding time: 4-12h; Cooling method: Air/water | Promotes precipitation of strengthened phases; Balances strength and plasticity | Follow-up to solution treatment (por exemplo, automotive structural parts) |
| T5 Artificial Aging (Recommended) | Low-temperature start → ramp to target temp (150-180°C) + air cooling | Heating rate: 30-50°C/h; Holding time: 6-8h | Avoids high-temperature deformation/pore expansion; Lowers costs by 15-20% contra. T6 | Complex thin-walled parts (por exemplo, smartphone midframes) or high-gas-content castings |
| Cold-Hot Cycle Treatment | 3-5 cycles of heating (200-300°C) + cooling (-20 to 0°C) | Cycle time: 2-3h/cycle; Temperature variation: ±5°C | Stabilizes phase structure; Ensures dimensional accuracy (±0.01mm) | Ultra-precision parts (por exemplo, medical device components) |
3. What Critical Factors Must Be Controlled During Heat Treatment?
Even the best method fails without strict process control. Below are 5 non-negotiable considerations, presented as a checklist for practical use:
3.1 Essential Control Factors
- Temperature Control:
- Risk of too high: Overheating (grain growth) or deformation (até 5% dimensional deviation).
- Risk of too low: Failure to achieve desired strength (tensile strength may drop by 30%).
- Solution: Use digital thermostats with ±2°C accuracy.
- Time Management:
- Holding time depends on: Alloy type (por exemplo, Al – Mg alloys need 2-3h; Al – Cu alloys need 4-6h) and casting thickness (add 1h for every 10mm thickness).
- Consequence of mismatch: Too long → oxidation; Too short → incomplete phase transformation.
- Humidity & Atmosphere:
- Humidity limit: < 40% RH (to prevent oxidation and surface pitting).
- Protective atmosphere: Use nitrogen or argon (reduces surface defects by 80% contra. air heating).
- Cooling Method:
- Quenching medium selection (based on part needs):
| Medium | Cooling Speed | Suitable Parts |
| Water | Fast (100-150°C/s) | High-strength parts (por exemplo, engrenagens) |
| Oil | Moderado (20-50°C/s) | Parts sensitive to internal stress (por exemplo, thin plates) |
| Air | Slow (5-10°C/s) | Low-deformation requirements (por exemplo, decorative parts) |
- Material Adaptability:
- Different alloys respond differently:
- Al – Si alloys: Excellent for annealing (improves machinability).
- Al – Cu alloys: Require solution + envelhecimento (maximizes strength).
- Al – Mg alloys: Avoid high-temperature solution treatment (risk of burning).
4. Yigu Technology’s Perspective on Aluminum Alloy Die Casting Heat Treatment
Na tecnologia Yigu, we believe aluminum alloy die casting heat treatment is not just a “post-processing step” but a “design-in factor” for high-performance parts. Our experience shows that 70% of casting failures stem from mismatched heat treatment schemes—for example, using T6 treatment on thin-walled parts often causes warping, while T5 can reduce this risk by 90%.
We recommend integrating heat treatment requirements into the early design stage: For complex parts, simulate stress distribution first to select methods like T5 or cold-hot cycling; for corrosion-sensitive parts, combine solution treatment with a protective atmosphere. By balancing process efficiency and performance goals, we help customers cut costs by 15-25% while improving part lifespan by 2-3x.
5. Perguntas frequentes: Common Questions About Aluminum Alloy Die Casting Heat Treatment
Q1: Can all aluminum alloy die castings be heat-treated?
Não. Por exemplo, high-silicon aluminum alloys (Si content > 12%) have limited response to solution/aging treatment, so annealing is preferred. Always check the alloy’s chemical composition first.
Q2: How does T5 treatment compare to the traditional T6 process?
T6 (solution + full artificial aging) offers higher strength but risks deformation. T5 (direct artificial aging) is simpler, mais barato, and better for thin-walled/complex parts—though its tensile strength is 5-10% lower than T6.
Q3: What should I do if a casting cracks after heat treatment?
Primeiro, check if the quenching transfer time was too long (causing precipitation) or if the cooling medium was too fast (inducing stress). Adjust parameters: Extend holding time by 1h or switch to a slower cooling medium (por exemplo, from water to oil).