1. Why Material Selection Matters
Material selection directly affects mechanical performance, machining cost, surface treatment options, and service life. Wrong material choice can lead to insufficient strength, machining difficulties, excessive cost, or failure to meet environmental requirements.
2. Detailed Comparison of Four Common Materials
Stainless Steel
Common grades: 304, 316, 316L, 17-4PH, 420, 440C
Properties: Density 7.93 g/cm³; tensile strength ~520MPa (304) to 1000MPa+ (17-4PH); excellent corrosion resistance, with 316 superior to 304 for chloride environments.
Machining: Severe work hardening, high cutting forces, poor thermal conductivity. Use YG-class carbide or dedicated stainless steel tools at low speed and high feed with ample coolant.
Surface treatments: Electropolishing, passivation, sandblasting, PVD coating
Applications: Food machinery, medical devices, chemical equipment, marine engineering, valves, precision shafts
Aluminum Alloy
Common grades: 6061-T6, 7075-T6, 5052, 2024
Properties: Density 2.7 g/cm³ (1/3 of steel); tensile strength ~310MPa (6061-T6) to 570MPa (7075-T6); good corrosion resistance.
Machining: Excellent machinability, low cutting forces, high-speed machining possible. High thermal expansion requires heat control during finishing. Use diamond or polished carbide tools at high RPM.
Surface treatments: Anodizing (clear/black/color), hard anodizing, chemical oxidation, sandblasting, brushing, plating, powder coating
Applications: Aerospace structures, automotive parts, electronics enclosures, heat sinks, automation equipment, sports equipment
Copper & Copper Alloys
Common grades: Brass H62/H59, Copper T2, Tin bronze QSn6.5-0.1, Beryllium copper QBe2
Properties: Density 8.5-8.9 g/cm³; excellent electrical and thermal conductivity; brass ~380MPa tensile, beryllium copper up to 1250MPa after aging.
Machining: Pure copper is soft and gummy with work hardening; brass H59 has excellent free-machining; beryllium copper is machined in solution-annealed state then age-hardened.
Surface treatments: Plating (Ni/Cr/Au/Ag), passivation, chemical polishing, black oxide
Applications: Electrical terminals, connectors, heat sinks, valves, bearing bushings, spring contacts
Titanium Alloy
Common grades: TC4 (Ti-6Al-4V), TA1/TA2 (pure titanium), Ti-6Al-4V ELI (medical grade)
Properties: Density 4.5 g/cm³; tensile strength ~900MPa (TC4); exceptional strength-to-weight ratio; excellent corrosion resistance; biocompatible; works at 600°C.
Machining: Notoriously difficult-to-machine. Extremely poor thermal conductivity (1/6 of steel), high cutting temperatures; low elastic modulus causes springback and vibration; high chemical reactivity accelerates tool wear. Use YG carbide tools, low speed, high feed, high-pressure coolant.
Surface treatments: Anodizing (various colors), micro-arc oxidation, sandblasting, PVD coating
Applications: Aerospace structures, medical implants (bone screws/joints), chemical equipment, racing parts, high-end bicycles, watch cases