Material Selection

Systematic approach to choosing materials:

Requirements Definition:

Mechanical Requirements:
- Strength (yield, ultimate)
- Stiffness (modulus)
- Fatigue life
- Impact resistance
- Hardness
- Wear resistance

Environmental Requirements:
- Corrosion resistance
- Temperature range
- Chemical exposure
- UV resistance
- Humidity

Physical Requirements:
- Weight constraints
- Dimensional stability
- Thermal conductivity
- Electrical properties
- Appearance

Manufacturing Requirements:
- Formability
- Machinability
- Weldability
- Available forms
- Surface finish capability

Selection Process:

Step 1: Define Function
- What does the part do?
- Critical performance criteria
- Failure modes to prevent

Step 2: Identify Constraints
- Must-have requirements
- Go/no-go screening
- Eliminate non-starters

Step 3: Rank Criteria
- Relative importance
- Weighted factors
- Trade-off priorities

Step 4: Screen Materials
- Material databases
- Property charts
- Eliminate unsuitable options

Step 5: Evaluate Candidates
- Detailed comparison
- Cost analysis
- Risk assessment
- Prototype if needed

Step 6: Select and Validate
- Final selection
- Testing if required
- Specification documentation

Selection Tools:

Material Databases:
- MatWeb
- ASM materials databases
- Manufacturer data
- Standards (ASTM, SAE)

Ashby Charts:
- Property vs property plots
- Visual screening
- Trade-off visualization
- CES Selector software

Cost Analysis:
- Raw material cost
- Processing cost
- Total manufactured cost
- Life cycle cost

Understanding material families:

Steels:

Carbon Steel:
- Lowest cost
- Good strength
- Easily welded
- Corrosion protection needed

Alloy Steels:
- Enhanced properties
- Higher strength
- Better hardenability
- More expensive

Stainless Steels:
- Corrosion resistance
- Higher cost
- Various grades
- Appearance option

Tool Steels:
- Wear resistance
- Hardness
- Specialized applications
- Heat treatment required

Aluminum Alloys:

1xxx (Pure):
- High corrosion resistance
- Excellent formability
- Low strength
- Electrical applications

2xxx (Cu):
- High strength
- Poor corrosion resistance
- Aerospace
- Heat treatable

5xxx (Mg):
- Good corrosion resistance
- Weldable
- Marine applications
- Work hardenable

6xxx (Mg-Si):
- Good formability
- Heat treatable
- Extrusions
- General structural

7xxx (Zn):
- Highest strength
- Aerospace
- Poor weldability
- Heat treatable

Other Metals:

Titanium:
- High strength-to-weight
- Excellent corrosion resistance
- High cost
- Aerospace, medical

Copper Alloys:
- Electrical/thermal conductivity
- Corrosion resistance
- Formability
- Higher cost than steel

Nickel Alloys:
- High temperature
- Corrosion resistance
- Very expensive
- Specialized applications

Non-Metals:

Plastics:
- Low cost
- Light weight
- Corrosion immunity
- Lower strength/stiffness

Composites:
- High strength-to-weight
- Directional properties
- Complex manufacturing
- Aerospace, sports, wind energy

Ceramics:
- High hardness
- Temperature resistance
- Brittle
- Specialized applications

Matching materials to applications:

Structural Applications:

Considerations:
- Load magnitude and type
- Safety factors
- Fatigue requirements
- Cost constraints

Common Choices:
- Carbon steel (general)
- HSLA steel (weight reduction)
- Aluminum 6061 (light weight)
- Stainless where corrosion matters

Corrosion Environments:

Considerations:
- Chemical exposure
- Temperature
- Galvanic coupling
- Life expectancy

Options:
- Stainless steel (austenitic for most)
- Aluminum (many environments)
- Coatings on steel
- Plastics where suitable

High Temperature:

Considerations:
- Service temperature
- Strength at temperature
- Oxidation resistance
- Creep behavior

Materials:
- Nickel alloys (highest temp)
- Stainless steels
- Tool steels
- Ceramics

Wear Applications:

Considerations:
- Wear mechanism
- Lubrication
- Mating surface
- Life requirements

Options:
- Hardened steel
- Tool steels
- Hard coatings
- Ceramics

Manufacturing Impact:

Machining:
- Free-machining grades
- Avoid very hard materials
- Consider material cost vs machining time

Welding:
- Weldability ratings
- Preheat requirements
- Filler compatibility
- Post-weld treatment

Forming:
- Formability ratings
- Bend radius limits
- Work hardening behavior
- Heat treatment after forming

Cost Considerations:

Material Cost:
- Raw material price
- Volatility
- Availability
- Scrap value

Processing Cost:
- Machining difficulty
- Welding complexity
- Heat treatment
- Surface finishing

Life Cycle:
- Durability
- Maintenance
- Replacement frequency
- Disposal/recycling

Using material selection skills:

Career Roles:

Design Engineer:
Select materials for products:
- Performance optimization
- Cost reduction
- Manufacturing integration
- $70,000-$100,000

Materials Engineer:
Material expertise:
- Selection and specification
- Failure analysis
- Process development
- $75,000-$110,000

Quality Engineer:
Material verification:
- Incoming inspection
- Testing programs
- Supplier quality
- $65,000-$95,000

Manufacturing Engineer:
Material processing:
- Manufacturing compatibility
- Process optimization
- Cost reduction
- $70,000-$100,000

Skills Development:

Knowledge Base:
- Material properties
- Processing effects
- Application requirements
- Cost factors

Tools:
- Material databases
- Selection software
- Property testing
- Failure analysis

Experience:
- Application history
- Failure lessons
- Industry knowledge
- Supplier relationships

Resources:

References:
- ASM Handbooks
- Material standards (ASTM, SAE)
- Manufacturer technical data
- Trade publications

Training:
- ASM courses
- University short courses
- Industry seminars
- On-the-job learning

Industries:

All manufacturing relies on material selection:
- Aerospace (critical performance)
- Automotive (cost and performance)
- Medical (biocompatibility)
- Energy (extreme environments)
- Consumer products (cost focus)

Material selection expertise supports engineering and quality careers.