Alloy МЛ4

Designation

Name	The value
Designation GOST Cyrillic	МЛ4
Designation GOST Latin	ML4
Transliteration	ML4
By 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, and their alloys	В51	GOST 2856-79
Thermal and thermochemical treatment of metals	В04	OST 1 90121-90
Castings, 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	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 properties

Section, mm	s_T\|s_0,2, MPa	σ_U, 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
s_T\|s_0,2	Yield strength or limit of proportionality with a tolerance for residual deformation of 0.2%
σ_U	Limit short-term strength
d₅	Elongation after rupture

Physical characteristics

Temperature	Е, HPa	r, kg/m³	l, W/(m · °C)	С, J/(kg · °C)
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.