AlSr Master Alloy, AlSr10, AlSr15, AlSr20, Strontium Modifier Alloy, Sr Grain Modifier, 7446-09-5, 7429-90-5, 7439-89-6

AlSr Master Alloy, AlSr10, AlSr15, AlSr20, Strontium Modifier Alloy, Sr Grain Modifier, 7446-09-5, 7429-90-5, 7439-89-6

ALUMINUM STRONTIUM (AlSr) MASTER ALLOY

AlSr Grain Modifier / Eutectic Silicon Modifier

CAS Numbers: 7429-90-5 (Al), 7446-09-5 (Sr), 7440-21-3 (Si), 7439-89-6 (Fe)

1. IDENTIFICATION

Note: The alloy itself does not have a dedicated CAS number; the constituent elements are used for identification.

2. STANDARD GRADES & COMPOSITIONS

Typical Specifications:

3. PHYSICAL PROPERTIES

4. CHEMICAL PROPERTIES

Key Intermetallic Phase:

Modification Mechanism:

5. MODIFICATION EFFECT ON AlSi ALLOYS

Visual Comparison:

Unmodified (Acicular):     Modified (Fibrous):
     |                         ~
    /|\                       /~~\
   / | \                     /~~~~\
  /  |  \                   /~~~~~~\
     |                         ~
(Needle-like silicon)    (Spheroidal silicon)

6. APPLICATIONS

6.1. Aluminum-Silicon Casting Alloys (Primary Use)

6.2. Automotive Industry

6.3. Aerospace Industry

6.4. General Casting

7. TYPICAL ADDITION RATES

Formula:

Addition rate (kg/ton) = (Target Sr ppm × 1000) / (% Sr in master alloy × 10,000)
Simplified: Addition (kg/ton) = Target Sr (ppm) / (% Sr in master alloy × 10)
Example: Target Sr = 150 ppm, Master alloy = AlSr10 (10% Sr)
Addition = 150 / (10 × 10) = 150 / 100 = 1.5 kg/ton

Typical Addition Ranges:

8. FADING (LOSS OF MODIFICATION)

Fading Rate Estimate:

9. ADVANTAGES OF AlSr

10. COMPARISON WITH OTHER MODIFIERS

Selection Guide:

11. STORAGE & HANDLING

Handling Notes:

• AlSr is moisture-sensitive. Do not open packages until ready to use.

• Pre-heat the master alloy to 100-150°C before addition to remove moisture.

• Add Sr as late as possible in the casting process to minimize fading.

12. SAFETY & HEALTH INFORMATION

GHS Classification (for the alloy – bulk solid)

Notes:

• The solid master alloy is not classified as hazardous under normal handling conditions.

• Strontium is highly reactive with water; avoid contact with moisture.

• Fine dust (from grinding) may be combustible.

• Fumes from melting may cause respiratory irritation.

First Aid Measures

Personal Protective Equipment (PPE) for Handling/Melting

13. ENVIRONMENTAL INFORMATION

14. TRANSPORT INFORMATION

15. OTHER MASTER ALLOYS (For Reference)

16. SECTORAL COMPATIBILITY

17. OTHER NAMES & SYNONYMS

18. SUMMARY

Aluminum Strontium (AlSr) Master Alloy is a eutectic silicon modifier for aluminum-silicon casting alloys. It transforms acicular (needle-like) silicon into fibrous/spheroidal morphology, significantly improving ductility, strength, and fatigue resistance.

Key Features:

Standard Grades:

Main Application Areas:

Key Advantages:

• Improved ductility – 5-15% elongation (vs 1-3% unmodified)

• Higher strength – 20-40% increase in tensile strength

• Better fatigue resistance – Essential for dynamic applications

• Enhanced machinability – Reduced tool wear

• Superior pressure tightness – Critical for hydraulic components

19. IMPORTANT NOTES

1. Fading (Loss of Modification): Strontium modification fades over time (typically 30-60 minutes) due to reaction with oxygen, hydrogen, and other impurities. Add Sr as late as possible in the casting process and minimize holding time.

2. Moisture Sensitivity: Strontium is highly reactive with moisture. AlSr master alloy must be stored in sealed, dry packaging. Pre-heat the master alloy to 100-150°C before addition to remove any surface moisture.

3. Selection of Sr Level: AlSr10 is the most common grade for general applications. AlSr15 and AlSr20 are used when smaller addition volumes are desired (e.g., automated addition systems). Higher Sr grades reduce the amount of master alloy added, minimizing temperature drop.

4. Recovery Rate: Strontium recovery is typically 70-90% depending on addition method, temperature, and melt condition. Proper addition technique (submerged addition, no surface oxidation) improves recovery.

5. Over-Modification: Unlike sodium, strontium does not cause over-modification. Even at higher addition rates, the structure remains modified (no detrimental effects). However, excessive Sr can increase porosity.

6. Comparison with Sodium (Na): Sodium provides stronger modification but fades very rapidly (10-20 minutes). Sodium is suitable only for HPDC with very short cycle times. Strontium is preferred for LPDC, gravity die casting, and sand casting where longer holding times are required.

7. Antimony (Sb) for Long Holding Times: For holding times exceeding 2 hours, antimony-modified alloys (AlSb) are used because Sb does not fade. However, Sb coarsens (rather than modifies) the silicon, providing less improvement in ductility.

8. Effect on Porosity: Strontium increases hydrogen solubility in aluminum, which can increase gas porosity if not properly degassed. Ensure adequate degassing (rotary degassing with argon or nitrogen) when using Sr modification.

9. Compatibility with Grain Refiners: AlSr can be used together with AlTiB or AlTiC grain refiners. No negative interactions. Add grain refiner first, then Sr modifier, to maximize effectiveness.

10. Quality Testing: The effectiveness of Sr modification can be verified by metallographic examination (microstructure) or thermal analysis. Properly modified alloys show a characteristic eutectic arrest temperature of 555-565°C (vs. 575-585°C for unmodified).

Important Disclaimer: This Technical Data Sheet (TDS) is for informational purposes only. For complete safety, handling, storage, and regulatory compliance information, always refer to the official Safety Data Sheet (SDS) provided by the manufacturer/supplier.