ZL27 Zinc Alloy
Hot chamber pressure diecasting Zinc alloy.
ZL27 is a high aluminium content zinc alloy that conforms to BS EN 1774 and is one of a family of versatile high grade zinc alloys manufactured by Brock Metal.
Application
ZL 27 is a zinc alloy containing 27% aluminium. It has exceptionally high strength and excellent bearing properties. Originally this alloy was envisaged for use in the sand and gravity diecasting industries but, has subsequently found a niche market as a pressure diecasting alloy using cold chamber diecasting machines. ZL 27 has a wide freezing range which is ideally suited to thin wall castings with small section changes. This alloy also has excellent machining characteristics, good corrosion resistance and will accept a variety of decorative and protective surface finishes.
It should be specified where high strength is important, as the alloy will compete with moderately high strength materials that cannot be cast using high-pressure diecasting. ZL 27 offers the extended tool life applicable to zinc alloys which, when combined with its higher strength and hardness makes the alloy an automatic choice when aluminium alloys are unable to meet the service conditions anticipated.
When designing a stressed component using ZL27 further reference should be made to the alloys properties, at elevated temperatures, after natural or artificial ageing and the alloys creep properties.
| Alloy Designation | ZnAl27Cu2 | Colour code | White + violet. |
|---|---|---|---|
| Short designation | ZL 27 | Alloy Number. | ZL2720 |
| Chemical composition of Ingots. | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Al | Cu | Mg | Pb | Cd | Sn | Fe | Ni | Si | |
| Minimum | 25.5 | 2.0 | 0.012 | ||||||
| Maximum | 28.0 | 2.5 | 0.03 | 0.005 | 0.005 | 0.002 | 0.07 | -- | 0.07 |
| MECHANICAL PROPERTIES | ||
|---|---|---|
| Supplied in diecast form. | As Cast | Aged |
| Tensile strength | 426 MPa | 360 MPa |
| Yield strength | 371 MPa | 317 MPa |
| Impact strength | 5 Joules | 2.2 joules |
| Elongation 50mm | 2.5% | 3% |
| Shear strength | 296 MPa | 234 MPa |
| Compressive yield strength | 385 MPa | 288 MPa |
| Fatigue Strength | 145 MPa | -- |
| Hardness BHN 500Kg | 122 max | 100 max |
| PHYSICAL PROPERTIES | |
|---|---|
| Melting range | 376 - 484° C |
| Density | 5.0 g / cm3 |
| Coefficient of Thermal expansion | 26 um/m0 C |
| Thermal Conductivity | 125.5 W/m0 C |
| Electrical Conductivity | 29.7 % IACS |
| Electrical Resistivity | 5.8 u ohm-cm at 200 C |
