Common alloy grades and classifications of magnesium alloy castings
Magnesium alloy castings can be divided into Mg-Al-Zn series (AZ series), Mg-Al-Mn series (AM series), Mg-Zn-Ca series (ZC series), Mg-Re-Zr series (rare earth magnesium alloys, such as WE series) according to the alloy element system. The following are the most commonly used grades and their performance characteristics in the industry:
1. Mg-Al-Zn series (AZ series)
Features: Contains aluminum (Al) and zinc (Zn) elements, excellent casting performance, balanced strength and corrosion resistance, and is the most commonly used magnesium alloy casting system.
1. AZ91D
Composition: Al 8.5~9.5%, Zn 0.45~0.9%, Mn ≥0.17%, and the balance is Mg.
Performance characteristics:
High strength: tensile strength can reach 200~220 MPa, yield strength is about 100 MPa, suitable for structural parts with medium loads.
Good corrosion resistance: Due to the high Al content, a dense Al₂O₃ oxide film is easily formed on the surface, and the salt spray resistance is better than pure magnesium (about 100~200 hours), but surface treatment is still required to improve protection.
Casting processability: Excellent fluidity, suitable for complex thin-walled parts (minimum wall thickness can be up to 1.5 mm), widely used in sand casting, metal mold casting and high-pressure die casting.
Typical applications: automotive gearbox housing, steering column bracket, motorcycle engine cylinder, power tool housing.
2. AZ31B
Composition: Al 2.5~3.5%, Zn 0.6~1.4%, Mn ≥0.2%, balance Mg.
Performance characteristics:
Medium strength: tensile strength of about 170 MPa, good plasticity (elongation 8~12%), suitable for parts requiring a certain toughness.
Excellent weldability: can be connected by TIG and MIG welding, often used for structural parts that require post-processing or assembly.
Weak corrosion resistance: Al content is low, and surface treatment (such as anodizing) protection is required.
Typical applications: bicycle frames, 3C product middle frames, medical device brackets.
2. Mg-Al-Mn series (AM series)
Features: Contains aluminum (Al) and manganese (Mn), no Zn element, better corrosion resistance and weldability than AZ series, higher plasticity.
1. AM60B
Composition: Al 5.6~6.4%, Mn ≥0.28%, balance Mg (no Zn).
Performance characteristics:
High toughness and impact resistance: elongation can reach 8~10%, tensile strength is about 180 MPa, yield strength is about 85 MPa, suitable for scenes with dynamic loads or impacts.
Excellent corrosion resistance: Because Mn forms high melting point compounds (such as MnFe₂Al₈) with impurities such as Fe and Ni, the tendency of intergranular corrosion is reduced, and the salt spray resistance is about 30% higher than that of AZ91D (about 150~250 hours).
Casting processability: The fluidity is slightly lower than that of AZ91D, but the tendency of hot cracking is small. It is suitable for sand casting and metal casting. High-pressure die casting is not recommended (easy to stick to the mold).
Typical applications: automobile wheels, airbag housings, ski bindings, and aerospace interiors.
2. AM50A
Composition: Al 4.5~5.3%, Mn ≥0.28%, and the balance is Mg.
Performance characteristics:
Lower Al content: Plasticity is further improved (elongation can reach 12%), but strength is slightly reduced (tensile strength is about 160 MPa).
Excellent weldability and corrosion resistance: suitable for scenes that require frequent welding or contact with corrosive media (such as bathroom hardware, marine equipment accessories).
Typical applications: weldable structural parts, corrosion-resistant valve parts.
3. Other commonly used alloy grades
1. Mg-Zn-Ca system (ZC63)
Composition: Zn 5.5~6.5%, Ca 2.5~3.5%, balance Mg.
Performance characteristics:
Outstanding high temperature performance: The tensile strength retention rate at 150~200℃ is more than 70%, which is better than the AZ/AM series.
Biocompatibility: The Ca element gives it degradable properties and is used in the medical field (such as absorbable bone nails).
Typical applications: engine heat-resistant parts, biomedical implants.
2. Rare earth magnesium alloy (WE43, WE54)
Composition: Contains rare earth elements (such as Y, Nd) and Zr, such as WE43 contains Y 2.9~3.5%, Nd 0.4~1.0%, Zr 0.4~1.0%.
Performance characteristics:
Ultra-high heat resistance: The tensile strength can reach 180 MPa at 250℃, and it has excellent oxidation resistance and is used for aerospace engine parts.
Strong creep resistance: It is not easy to deform under high temperature and high pressure, and is suitable for turbocharger housings and missile compartments.
Typical applications: aircraft engine casings, spacecraft structural parts.
Selection logic:
If high strength + high casting accuracy (such as thin-walled complex parts) is required, select AZ91D, but matching surface treatment (such as electroplating or micro-arc oxidation) is required to improve corrosion resistance.
If you need impact resistance + corrosion resistance + weldability (such as dynamic loads or parts that need to be processed later), choose AM60B, which is suitable for medium and large parts of sand casting.
Summary
The selection of magnesium alloy casting grades should focus on the five core dimensions of strength, toughness, corrosion resistance, operating temperature, and casting process. AZ91D and AM60B, as the most mainstream commercial grades, dominate the "high-strength casting" and "high-toughness corrosion resistance" scenarios respectively, while rare earth magnesium alloys, Zn-Ca series, etc. play an irreplaceable role in special fields (such as high temperature and medical treatment). With the surge in demand for lightweight in industries such as new energy vehicles and aerospace, high-performance magnesium alloy castings and their alloy systems will continue to iterate and upgrade.
Common alloy grades and classifications of magnesium alloy castings
Magnesium alloy castings can be divided into Mg-Al-Zn series (AZ series), Mg-Al-Mn series (AM series), Mg-Zn-Ca series (ZC series), Mg-Re-Zr series (rare earth magnesium alloys, such as WE series) according to the alloy element system. The following are the most commonly used grades and their performance characteristics in the industry:
1. Mg-Al-Zn series (AZ series)
Features: Contains aluminum (Al) and zinc (Zn) elements, excellent casting performance, balanced strength and corrosion resistance, and is the most commonly used magnesium alloy casting system.
1. AZ91D
Composition: Al 8.5~9.5%, Zn 0.45~0.9%, Mn ≥0.17%, and the balance is Mg.
Performance characteristics:
High strength: tensile strength can reach 200~220 MPa, yield strength is about 100 MPa, suitable for structural parts with medium loads.
Good corrosion resistance: Due to the high Al content, a dense Al₂O₃ oxide film is easily formed on the surface, and the salt spray resistance is better than pure magnesium (about 100~200 hours), but surface treatment is still required to improve protection.
Casting processability: Excellent fluidity, suitable for complex thin-walled parts (minimum wall thickness can be up to 1.5 mm), widely used in sand casting, metal mold casting and high-pressure die casting.
Typical applications: automotive gearbox housing, steering column bracket, motorcycle engine cylinder, power tool housing.
2. AZ31B
Composition: Al 2.5~3.5%, Zn 0.6~1.4%, Mn ≥0.2%, balance Mg.
Performance characteristics:
Medium strength: tensile strength of about 170 MPa, good plasticity (elongation 8~12%), suitable for parts requiring a certain toughness.
Excellent weldability: can be connected by TIG and MIG welding, often used for structural parts that require post-processing or assembly.
Weak corrosion resistance: Al content is low, and surface treatment (such as anodizing) protection is required.
Typical applications: bicycle frames, 3C product middle frames, medical device brackets.
2. Mg-Al-Mn series (AM series)
Features: Contains aluminum (Al) and manganese (Mn), no Zn element, better corrosion resistance and weldability than AZ series, higher plasticity.
1. AM60B
Composition: Al 5.6~6.4%, Mn ≥0.28%, balance Mg (no Zn).
Performance characteristics:
High toughness and impact resistance: elongation can reach 8~10%, tensile strength is about 180 MPa, yield strength is about 85 MPa, suitable for scenes with dynamic loads or impacts.
Excellent corrosion resistance: Because Mn forms high melting point compounds (such as MnFe₂Al₈) with impurities such as Fe and Ni, the tendency of intergranular corrosion is reduced, and the salt spray resistance is about 30% higher than that of AZ91D (about 150~250 hours).
Casting processability: The fluidity is slightly lower than that of AZ91D, but the tendency of hot cracking is small. It is suitable for sand casting and metal casting. High-pressure die casting is not recommended (easy to stick to the mold).
Typical applications: automobile wheels, airbag housings, ski bindings, and aerospace interiors.
2. AM50A
Composition: Al 4.5~5.3%, Mn ≥0.28%, and the balance is Mg.
Performance characteristics:
Lower Al content: Plasticity is further improved (elongation can reach 12%), but strength is slightly reduced (tensile strength is about 160 MPa).
Excellent weldability and corrosion resistance: suitable for scenes that require frequent welding or contact with corrosive media (such as bathroom hardware, marine equipment accessories).
Typical applications: weldable structural parts, corrosion-resistant valve parts.
3. Other commonly used alloy grades
1. Mg-Zn-Ca system (ZC63)
Composition: Zn 5.5~6.5%, Ca 2.5~3.5%, balance Mg.
Performance characteristics:
Outstanding high temperature performance: The tensile strength retention rate at 150~200℃ is more than 70%, which is better than the AZ/AM series.
Biocompatibility: The Ca element gives it degradable properties and is used in the medical field (such as absorbable bone nails).
Typical applications: engine heat-resistant parts, biomedical implants.
2. Rare earth magnesium alloy (WE43, WE54)
Composition: Contains rare earth elements (such as Y, Nd) and Zr, such as WE43 contains Y 2.9~3.5%, Nd 0.4~1.0%, Zr 0.4~1.0%.
Performance characteristics:
Ultra-high heat resistance: The tensile strength can reach 180 MPa at 250℃, and it has excellent oxidation resistance and is used for aerospace engine parts.
Strong creep resistance: It is not easy to deform under high temperature and high pressure, and is suitable for turbocharger housings and missile compartments.
Typical applications: aircraft engine casings, spacecraft structural parts.
Selection logic:
If high strength + high casting accuracy (such as thin-walled complex parts) is required, select AZ91D, but matching surface treatment (such as electroplating or micro-arc oxidation) is required to improve corrosion resistance.
If you need impact resistance + corrosion resistance + weldability (such as dynamic loads or parts that need to be processed later), choose AM60B, which is suitable for medium and large parts of sand casting.
Summary
The selection of magnesium alloy casting grades should focus on the five core dimensions of strength, toughness, corrosion resistance, operating temperature, and casting process. AZ91D and AM60B, as the most mainstream commercial grades, dominate the "high-strength casting" and "high-toughness corrosion resistance" scenarios respectively, while rare earth magnesium alloys, Zn-Ca series, etc. play an irreplaceable role in special fields (such as high temperature and medical treatment). With the surge in demand for lightweight in industries such as new energy vehicles and aerospace, high-performance magnesium alloy castings and their alloy systems will continue to iterate and upgrade.
