AZ91D vs AM60B -Strength vs Crash Safety

AZ91D and AM60B are both 34% lighter than aluminum. Both provide inherent EMI shielding. But their mechanical properties diverge in ways that are decisive for specific applications -and choosing AZ91D for a safety-critical automotive structure is a functional safety failure.

---

The Composition Difference

Element	AZ91D	AM60B	Effect
Aluminum (Al)	8.3-8.7%	5.5-6.5%	Higher Al = more Mg17Al12 intermetallic -stronger but more brittle
Zinc (Zn)	0.35-1.0%	0.22% max	Minor
Manganese (Mn)	0.15% min	0.24% min	Minor
Impurities (Fe, Ni, Cu)	Strictly controlled	Strictly controlled	Same corrosion protection

---

Properties

Property	AZ91D	AM60B	Preferred
Tensile strength	230 MPa	220 MPa	AZ91D +5%
Yield strength	160 MPa	130 MPa	AZ91D +23%
Elongation	3%	8%	AM60B +167%
Impact strength (Charpy)	4 J	20 J	AM60B 5x higher
Fatigue strength	70 MPa	97 MPa	AM60B +38%
Corrosion resistance	Better (higher Al)	Good	AZ91D slightly better

---

Why the Impact Difference Is Not Just a Number

AZ91D fractures at 3% elongation. AM60B deforms to 8% before fracture. Under crash loading, this is the difference between controlled energy absorption and brittle fragmentation.

Automotive safety logic:

• A steering wheel armature must deform progressively under head impact -absorbing energy, maintaining airbag geometry, not fracturing into sharp fragments
• A seat frame must maintain occupant restraint through the crash pulse
• An instrument panel beam must absorb energy without becoming a projectile

AZ91D's 4 J impact strength makes it unsuitable for these applications regardless of its higher static tensile strength. AM60B's 20 J and 8% elongation are what safety regulations require.

Euro NCAP, IIHS, and FMVSS crashworthiness testing has validated AM60B-based steering wheel armatures, seat frames, and IP crossbeams in production vehicles since the mid-1990s.

---

Decision Guide

Application	AZ91D	AM60B
Electronics chassis (laptop, tablet)	Yes	-
Camera and instrument bodies	Yes	-
Power tool housings	Yes	-
Automotive steering wheel armature	-	Yes
Automotive seat frame	-	Yes
Instrument panel cross-car beam	-	Yes
Non-safety automotive brackets	Yes	Yes
Telecom enclosures	Yes	-

---

Cost and Availability

AZ91D and AM60B are similarly priced -the difference in aluminum content is small enough that material cost premium is negligible (<2%). Both are available from major magnesium alloy suppliers globally. The choice is purely technical.

---

Magnesium alloy selection: yaoqingpu1983@gmail.com | +86 138 1403 4409