Alloy МЛ4
Designation
| Name |
The value |
| Designation GOST Cyrillic |
МЛ4 |
| Designation GOST Latin |
ML4 |
| Transliteration |
ML4 |
| The chemical elements |
CuЛ4 |
Description
Alloy МЛ4 used: for the manufacture of parts of engines and other units operating in conditions of high corrosion resistance, static and dynamic loads with maximum operating temperature +150 °C — long, +250 °C — short; parts operating in conditions of high corrosion resistance, static and dynamic loads (buildings appliances, buildings tools, handwheels, etc.). The alloy used for cathodic protection in shipbuilding.
Note
Alloy system Mg-Al-Zn.
МЛ4 alloy has good corrosion resistance and limited weldability. He is prone to the formation of microremote, has a high brittleness and a significant shrinkage. For these reasons, it is not recommended for chill casting and pressure casting. The primary method of alloy casting in sand molds.
Aluminum and zinc increase the mechanical properties of the alloy (and the effect of aluminum effect is stronger than zinc) and manganese improves corrosion resistance. To reduce oxidation, the alloy is injected beryllium (0.002% when casting in sand molds and the mold and to 0.01% when casting under pressure).
The alloy can strengthen its positions heat treatment — quenching and aging.
The alloy has a broader crystallization range than alloys based on aluminum, therefore has a low castability. Due to the large interval of crystallization of the alloy is prone to hot cracks.
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 90248-77 |
Chemical composition
| Standard |
Mn |
Si |
Ni |
Fe |
Cu |
Al |
Zn |
Zr |
Mg |
Be |
| GOST 2856-79 |
0.15-0.5 |
≤0.25 |
≤0.01 |
≤0.06 |
≤0.1 |
5-7 |
2-3.5 |
≤0.002 |
The rest |
≤0.002 |
Mg is the basis.
According to GOST 2856-79, the content of other impurities is ≤ 0.10%, the sum of the impurities to be determined is 0.50%. With a simultaneous content of beryllium and zirconium, the mass fraction of beryllium should not exceed 0.0015%.
Mechanical characteristics
| Section, mm |
sT|s0,2, MPa |
σB, MPa |
d5, % |
| Casting in sand molds, shell molds and in the mold without heat treatment according to GOST 2856-79 |
|
≥80 |
≥160 |
≥3 |
| Casting in sand mold, shell mold and shell mold according to GOST 2856-79. Mode T4: Homogenization + annealing in air |
|
≥80 |
≥220 |
≥5 |
| Casting in sand mold, shell mold and shell mold according to GOST 2856-79. T6 mode: Homogenization + annealing at air + aging |
|
≥100 |
≥225 |
≥2 |
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 |
1830 |
795 |
10467 |
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 casting in the ground and the shell molds following the recommended modes of heat treatment: T2 (to reduce internal stresses) - Annealing at 350±5 °C (delay 2-3 hours), air cooling. For a significant increase in mechanical properties of the alloy (σв, δ, EA), heat treatment is performed on taimu T4 Annealing in air of 380±5 °C (extract 8-16 h). Due to the low rate of diffusion processes as the cooling medium is usually a calm air. To improve the mechanical properties of the cooled castings may be conducted by blowing of air. To improve the mechanical properties (σв, σ0,2) applied heat treatment by mode T6 - Tempering air with 380±5 °C (extract 8-16 h) and Aging at 175±5 °C (delay of 12-16 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. |
