Alloy ML8

Designation

Name	The value
Designation GOST Cyrillic	МЛ8
Designation GOST Latin	ML8
Transliteration	ML8
By 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, 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 90200-75, OST 1 90248-77
Test methods. Packing. 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	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 properties

Section, mm	s_T\|s_0,2, MPa	σ_U, 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
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	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.