From Material to Component 

Material selection depends not only on performance parameters but also on the ability to be processed into required components efficiently and reliably. This chapter provides an in-depth analysis of the process characteristics of magnesium alloys, titanium alloys, carbon fiber, and aluminum alloys in forming, joining, thermal stability, and composite applications, revealing the manufacturing path from "ideal material" to "practical part."

Chapter 3: Comprehensive Analysis of Structure and Manufacturing Characteristics: The Leap from Material to Component

By  Lei Zhang

Content

Chapter 3 |  Comprehensive Analysis of Structure and Manufacturing Characteristics: The Leap from Material to Component

• 3.1 Forming and Processing: Process Determines Productivity

• 3.2 Welding, Joining, and Surface Treatment: The Art of Functional Processing

• 3.3 Thermal Expansion and Structural Stability: The Survival Code in Extreme Environments

• 3.4  Metal + Carbon Fiber Hybrid Structures: The Next-Generation Answer for Lightweighting

•3.5 References

3.1 Forming and Processing: Process Determines Productivity

Magnesium Alloys: The "Speed King" of Die Casting
In its molten state at 640–680°C, magnesium alloy exhibits excellent fluidity, making it an ideal material for thin-wall die casting. Taking AZ91D as an example, its minimum wall thickness can be die-cast to 0.6mm, with a production cycle shortened by 40–60% compared to traditional metals. In electronic device housing manufacturing, magnesium alloy die casting enables laptop housings to be controlled at 0.8mm thickness, and automotive transmission housings achieve  35% weight reduction, making it a preferred choice combining lightweight and efficiency.

Titanium Alloys: The "Noble Material" of High-Difficulty Machining
The low thermal conductivity of titanium alloys (e.g., TC4 is only 6.7 W/m·K) causes cutting heat to dissipate poorly, resulting in tool wear rates 10–20 times higher than for steel, with traditional machining material utilization rates as low as 10%. However, near-net-shape technologies like powder metallurgy and additive manufacturing have increased utilization rates to over 90%. For instance, an electron beam wire feed deposition (EBF³) manufactured 2319 aluminum alloy sample achieved a density of 99.3%, with grain size less than 10μm. After T6 heat treatment, its strength increased to 400–500 MPa, demonstrating the great potential of additive manufacturing for difficult-to-machine materials.

Carbon Fiber: From "Handicraft" to "Automated Technology"
Carbon fiber manufacturing is transitioning from traditional manual layup (cycle time 2–4 h/m²) to automated fiber placement/tape laying (AFP/ATL), improving efficiency by 5–8 times. Resin Transfer Molding (RTM) is suitable for medium-volume production, achieving fiber volume fractions of 50–60%. The global carbon fiber market size is projected to grow with a CAGR of about 6%, where aerospace remains the largest application field.

Aluminum Alloys: The "All-Rounder" of Industrialization
Aluminum alloys support full-process manufacturing including extrusion, forging, stamping, and casting. Cutting speeds with high-speed steel tools reach 200–400 m/min, die-casting cycles are 20–60 seconds, and extrusion speeds are 1–5 m/min. The 2xxx series alloys (e.g., 2014, 2024) offer high strength and excellent machinability, while the 5xxx series (e.g., 5052) are known for corrosion resistance and weldability, making them foundational materials for the aerospace and automotive industries.

3.2 Welding, Joining, and Surface Treatment: The Art of Functional Processing

Welding Performance Comparison of Four Materials

Temperature's Impact on Strength: The Test of Heat and Cold

• Low-Temperature Performance:

  • Titanium alloy TC4 maintains impact energy >25J at -196°C, with no low-temperature brittleness.

  • Aluminum alloy 2024-T3 strength increases by 10–15% at -50°C.

• High-Temperature Performance:

  • Titanium alloy retains >80% strength at 500°C, suitable for aero-engine compressor blades.

  • Aluminum alloy strength drops to 50% of room temperature strength at 200°C.

Creep and Fatigue: Challenges of Time and Cycles

• Creep Strain Ranking (1000 hours):

  1. Carbon Fiber: <0.01%

  2. Titanium Alloy (at 500°C): <0.2%

  3. Aluminum Alloy (at 200°C): 1–2%

  4. Magnesium Alloy (at 25°C): 0.5–1%

• Fatigue Strength Ratio (Fatigue Limit/Tensile Strength):

• • Titanium Alloy TC4: 0.5–0.6

  • Carbon Fiber (T300/Epoxy): 0.6–0.7

  • Aluminum Alloy 2024-T3: 0.35–0.45

3.4 Metal + Carbon Fiber Hybrid Structures: The Next-Generation Answer for Lightweighting

Value of Hybrid Structures: Complementing Weaknesses, Integrating Strengths

• Carbon Fiber Weaknesses: Low interlaminar shear strength (30–80 MPa), poor impact resistance (CAI=180–250 MPa).

• Metal Weaknesses: Low specific strength, susceptibility to fatigue cracking.

Empirical Experience: In early Boeing 787 tests, the annual corrosion depth at contact points between the carbon fiber fuselage and aluminum alloy reached 0.3mm. This was subsequently resolved by switching to titanium alloy fasteners and fiberglass isolation layers.

Chapter 3 Key Takeaways Summary

1. Processing Difficulty Ranking: Aluminum Alloy < Magnesium Alloy < Carbon Fiber < Titanium Alloy. Additive manufacturing significantly improves material utilization, e.g., 2319 aluminum alloy achieving 99.3% density.

2. Joining Technology Trend: Adhesive bonding + mechanical fastening becoming mainstream for hybrid structures, requiring focused attention on galvanic corrosion and thermal mismatch stress.

3. Thermal Stability Comparison: Carbon fiber axial CTE is near zero, suitable for high-precision structures; Titanium alloy performs best at high temperatures (>80% strength retention at 500°C).

4. Hybrid Structure Design Key: Requires systematic solutions like gradient materials, flexible adhesive layers, and isolation layers to address interface problems.

5. Future Trends: Smart hybrid structures (e.g., with embedded fiber optic sensors) and 4D printing technology (e.g., shape memory polymers + carbon fiber) will drive the birth of next-generation lightweight components.

 3.5 References

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