Zinc die-casting alloys

The material. Zinc is a bluish-white metal with a low melting point (420°C). The slang in French for a bar or pub is le zinc; bar counters in France used to be clad in zinc—many still are—to protect them from the ravages of wine and beer. Bar surfaces have complex shapes: a flat top, curved profiles, rounded or profiled edges. These two sentences say much about zinc; it is ductile; it is hygienic; it survives exposure to acids (wine), to alkalis (cleaning fluids), and to misuse (upset customers). These remain among the reasons it is still used today. Another is the "castability" of zinc alloys; their low melting point and fluidity give them a leading place in die casting.

Composition

Zn + 3-30% Al, typically, often with

up to 3% Cu.

General properties

Density

4950

– 7000

kg/m3

Price

*3.09

– 3.4

USD/kg

Mechanical properties

Young’s modulus

68

– 100

GPa

Yield strength (elastic limit)

80

– 450

MPa

Tensile strength

135

– 510

MPa

Compressive strength

80

– 450

MPa

Elongation

1

– 30

%

Hardness—Vickers

55

– 160

HV

Fatigue strength at 107 cycles

*20

– 160

MPa

Fracture toughness

*10

– 70

MPa. m1/2

Thermal properties

Melting point

375

– 492

°C

Maximum service temperature

*80

– 110

°C

Thermal conductor or insulator?

Good conductor

Thermal conductivity

100

– 130

W/m. K

Specific heat capacity

405

– 535

J/kg. K

Thermal expansion coefficient

23

– 28

p, strain/°C

Electrical properties

Electrical conductor or insulator?

Good conductor

Electrical resistivity

5.4

– 7.2

puhm. cm

Zinc die castings are cheap, have high surface finish, and can be complex in shape. On the left, a corkscrew; everything except the screw itself is die-cast zinc alloy. On the right, a carburetor body.

Ecoproperties: material

Annual world production

9.7 x 106

– 1.0 x 107

tonne/yr

Reserves

2.18 x 108

– 2.21 x 108

tonne

Embodied energy, primary production

70

– 75

MJ/kg

CO2 footprint, primary production

3.7

– 4

kg/kg

Water usage

*160

– 521

l/kg

Eco-indicator

3000

– 3400

millipoints/kg

Ecoproperties: processing

Casting energy

*1.09

– 1.32

MJ/kg

Casting CO2

*0.065

– 0.08

kg/kg

Recycling

Embodied energy, recycling

12.6

– 13.5

MJ/kg

CO2 footprint, recycling

0.66

– 0.72

kg/kg

Recycle fraction in current supply

20

– 25

%

Typical uses. Die castings; automotive parts and tools; gears; house­hold goods; office equipment; building hardware; padlocks; toys; business machines; sound reproduction equipment; hydraulic valves; pneumatic valves; soldering; handles; gears; automotive components.