Alloy ML8
Designation
| Name |
The value |
| Designation GOST Cyrillic |
МЛ8 |
| Designation GOST Latin |
ML8 |
| Transliteration |
ML8 |
| The chemical elements |
CuЛ8 |
Description
Alloy ML8 is used: for the manufacture of castings loaded parts with maximum operating temperature +150 °C — long +200 °C — short-term.
Note
Alloy system Mg-Zn-Zr.
Doping with zirconium refines the grain, reduces the temperature interval of crystallization and, therefore, improves mechanical and casting properties. Additional doping with cadmium increases the strength and improves technological properties. ML8 alloy doped with cadmium (0,2−0,8%), has high mechanical properties (superior to that of ML5 alloy for yield strength, almost 2 times). High and homogeneous mechanical properties allow to cast from this alloy of highly complex castings, working in conditions of static and alternating loads (brackets, rocking, beads, drums, wheels, etc.).
Compared with the alloys of the system Mg-Al-Zn alloy has several advantages. It possess higher strength characteristics. Refinement of the structure with the introduction of Zirconia reduces the sensitivity of the alloy to the thickness of the cross section of the casting. Due to the smaller grain size in castings microregion less than in the casting of alloys МЛ4 or ML5.
Standards
| Name |
Code |
Standards |
| Non-ferrous metals, including rare metals, and their alloys |
В51 |
GOST 2856-79 |
| Thermal and thermochemical treatment of metals |
В04 |
OST 1 90121-90 |
| Castings from non-ferrous metals and alloys |
В84 |
OST 1 90200-75, OST 1 90248-77 |
| Test methods. Packaging. Marking |
В59 |
OST 1 90360-85 |
Chemical composition
| Standard |
Si |
Ni |
Fe |
Cu |
Al |
Zn |
Zr |
Mg |
Be |
Cd |
| GOST 2856-79 |
≤0.03 |
≤0.005 |
≤0.01 |
≤0.03 |
≤0.02 |
5.5-6.6 |
0.7-1.1 |
The rest |
≤0.001 |
0.2-0.8 |
Mg is the basis.
According to GOST 2856-79, the content of other impurities is ≤ 0.12%, the sum of the impurities being determined is 0.20%.
Mechanical characteristics
| Section, mm |
sT|s0,2, MPa |
σB, MPa |
d5, % |
| Casting in sand, shell, investment casting and plaster mold and chill casting GOST 2856-79. Mode Kzt61: Homogenization + annealing in water + aging |
|
≥175 |
≥275 |
≥4 |
| Casting in sand, shell, investment casting and plaster mold and chill casting GOST 2856-79. T6 mode: Homogenization + annealing at air + aging |
|
≥170 |
≥265 |
≥4 |
| Casting forming OST 1 90200-75. In the delivery condition specified in the casting method, delivery condition and strength class KP |
|
≥186 |
≥275 |
≥4 |
|
≥196 |
≥284 |
≥6 |
|
≥177 |
≥255 |
≥2.5 |
|
≥177 |
≥255 |
≥3 |
|
≥167 |
≥235 |
≥2.5 |
Description mechanical marks
| Name |
Description |
| Section |
Section |
| sT|s0,2 |
Yield strength or limit of proportionality with a tolerance for residual deformation of 0.2% |
| σB |
Limit short-term strength |
| d5 |
Elongation after rupture |
Physical characteristics
| Temperature |
Е, ГПа |
r, кг/м3 |
l, Вт/(м · °С) |
С, Дж/(кг · °С) |
| 20 |
43 |
1820 |
1205 |
10048 |
A description of the physical symbols
| Name |
Description |
| Е |
The normal elasticity modulus |
| r |
Density |
| l |
Coefficient of thermal conductivity |
| R |
UD. the resistivity |
Technological properties
| Name |
The value |
| Features of heat treatment |
According to OST 1 90121-90 to improve the mechanical properties (σв, σ0,2) casting in the ground, shell molding, gravity die casting, investment casting and plaster mold apply heat treatment by mode T6 - Quenching by blowing air at 490±5 °C (Step heat to 420±5 °C (exposure 1-2 hours), heating to 490±5 °C (delay of 5-7 h)) + Aging at 165±5 °C (aging 18-24 h) or at 150±5 °C (extract 42-48 h), air cooling. In this case the plastic properties decrease. A noticeable increase in the values of σв, σ0,2 is achieved in the hardening of the casting by blowing air. To maximize the mechanical properties of the alloy (σв, σ0,2) mode is applied Kzt61 - Quenching in warm water (80-90 °C) with 490±5 °C (Step heat to 420±5 °C (exposure 1-2 hours), heating to 490±5 °C (delay of 5-7 h)) + Aging at 165±5 °C (delay of 18-24 hours), air cooling. To improve the mechanical properties (σв, σ0,2) also applied heat treatment regime T62 - Quenching by blowing air at 490±5 °C (Step heat to 420±5 °C (exposure 1-2 hours), heating to 490±5 °C (delay of 5-7 h)) + two-step Aging at 130±5 °C (aging 6-8 h) + at 185±5 °C (delay of 2-4 h), air cooling. |
