Magnesium Alloy Comparison Overview

Choosing between AM60B and AZ91D is one of the most critical decisions in magnesium die casting. Each alloy offers distinct advantages and limitations. This guide helps you select the optimal alloy for your application.

Side-by-Side Comparison

Mechanical Properties

Processing Characteristics

Temperature Performance

AM60B Alloy: In-Depth Analysis

Strengths

Superior Castability

• Wider freezing range (easier to control)
• Reduced hot tearing and porosity
• Better feeding in thick sections
• More forgiving process parameters

Excellent Ductility

• 5-10% elongation (vs. 3-5% for AZ91D)
• Better impact resistance
• More reliable in dynamic applications
• Lower risk of catastrophic failure

Lower Process Difficulty

• More stable during solidification
• Less sensitive to temperature variations
• Reduced scrap rates (typically 5-8% vs. 10-15%)
• Faster learning curve for operators

Limitations

Temperature Restrictions

• Yield strength drops rapidly above 100°C
• Not suitable for hot engine components
• Limited to ambient/moderate temperature use

Cost

• 10-15% premium vs. AZ91D
• Justified by lower scrap and faster cycles
• Better for high-volume, cost-sensitive production

Best Applications

• Automotive seat frames and structural components
• Electronic device housings
• Power tool bodies
• Complex thin-wall components
• Parts requiring high ductility

AZ91D Alloy: In-Depth Analysis

Strengths

High-Temperature Performance

• Maintains strength to 150°C+
• Suitable for engine compartment applications
• Good thermal stability
• Better creep resistance

Established Standards

• Decades of field history
• Well-understood processing
• Industry acceptance (especially automotive)
• Extensive supplier base

Superior Rigidity

• 35% higher yield strength than AM60B
• Less deflection under load
• Better for structural applications
• Excellent for high-stress components

Limitations

Castability Challenges

• Narrower freezing range (requires tight control)
• Susceptible to hot cracking
• More difficult feeding
• Higher scrap rates

Lower Ductility

• 3-5% elongation only
• Brittleness risk in impact scenarios
• Less forgiving under stress
• May require thicker walls for durability

Process Demands

• Stricter temperature control (±5°C)
• More sophisticated mold cooling required
• Trained operators essential
• Higher defect rates with poor control

Best Applications

• Engine cylinder head castings
• Transmission housings
• High-temperature bearing supports
• High-stress structural brackets
• Automotive suspension components

Selection Decision Matrix

Cost-Benefit Analysis

Material Cost Comparison (per kg)

• AM60B ingot: $4-5
• AZ91D ingot: $3.50-4

Process Cost Impact

AM60B Advantage

• Lower scrap rate: -$0.05/part
• Shorter cycle time: -$0.02/part
• Less operator expertise: -$0.03/part
• Better first-pass quality: -$0.04/part

Total AM60B advantage: ~$0.14/part on high-volume (even with material premium)

Total Cost of Ownership

For 1 million parts/year:

• AM60B: $4.40/part all-in
• AZ91D: $4.80/part all-in (for similar quality)

Industry Trends

Shift Toward AM60B

• 65% of new automotive programs specify AM60B
• Suppliers investing in AM60B capacity
• Industry momentum toward ease of processing

AZ91D Persistence

• Still dominant in high-temperature applications
• Legacy programs (engine blocks, housings)
• Proven field reliability
• Specialized equipment investment

Quality and Certification

ISO 12508:2009 Standards

• Both alloys covered
• Tensile and yield requirements
• Elongation specifications
• Hardness ranges defined

Industry Specifications

• ASTM B94 (magnesium castings)
• Automotive: IATF 16949 compliance
• Aerospace: AS9100 certification needed

Conclusion

Choose AM60B if:

• Applications are ambient-temperature
• Complex thin-wall geometry required
• Cost efficiency and ease important
• High-volume production planned
• First-pass quality priority

Choose AZ91D if:

• High-temperature performance needed (>100°C)
• Rigidity and strength critical
• Established automotive platforms
• Long-term thermal stability required
• Industry standard compliance essential

The trend is clearly moving toward AM60B for most applications due to superior castability and lower total cost of ownership. However, AZ91D remains essential for high-temperature engine applications and structural components.

Related Articles:

• Magnesium Casting Fundamentals
• Material Selection Guide