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Aluminum-Magnesium Alloy Composition

Release time:

Jul 21,2026

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Aluminum-Magnesium Alloy Composition Adjustment: Dilution and Charge Calculation Guide

In aluminum-magnesium alloy production, chemical composition control is not simply “adding materials according to a recipe.” During melting, the final chemistry is affected by raw material composition, furnace analysis, master alloy additions, burn-off, dilution, and impurities introduced by each charge material.

The photos show a typical aluminum alloy charge calculation case: when one alloying element is too high, the melt must first be diluted; when other elements become lower after dilution, they must be corrected with magnesium ingot or aluminum-based master alloys.

For buyers of aluminum-magnesium alloy plates, bars, tubes, foils, profiles, or CNC machined parts, this matters because stable material performance starts with controlled chemistry.

Quick Answer: How Is Aluminum-Magnesium Alloy Composition Adjusted?

The usual workflow is:

Step	Purpose	Common Method
Furnace analysis	Check actual melt composition	Rapid chemical or spectrometric analysis
Element too high	Reduce the percentage	Dilute with pure aluminum or low-content charge
Element too low	Bring it back to target	Add Mg ingot or Al-based master alloy
Impurity check	Confirm Fe and Si remain within limits	Calculate impurity introduced by all charges
Final verification	Confirm the melt meets standard	Re-sample and analyze before casting

The key rule is: dilute the over-limit element first, then recalculate additions for elements lowered by dilution.

What Is Dilution in Aluminum Alloy Melting?

Dilution is used when an alloying element is higher than the target range. Instead of adding more alloying elements immediately, the melt is blended with pure aluminum or low-content charge material to bring the over-limit element down.

A common formula is:

X = (b - a)Q / a

Where:

Symbol	Meaning
X	Dilution amount, kg
Q	Original melt weight, kg
a	Target content of the element, %
b	Actual furnace analysis value, %

This formula is suitable when the diluting material contains little or none of the over-limit element.

Example: 2A12 Aluminum Alloy Charge Adjustment

The case in the photos uses 9000 kg of 2A12 aluminum alloy melt. The rapid analysis results show:

Element	Target Content / %	Furnace Analysis / %	Decision
Cu	4.50	4.95	Too high, dilute first
Mg	1.50	1.50	Will drop after dilution, needs correction
Mn	0.70	0.60	Low, needs addition
Ti	0.05	0.05	Will drop after dilution, needs correction
Fe	≤0.45	0.30	Within limit, verify after additions
Si	≤0.35	0.25	Within limit, verify after additions

Because Cu is too high, calculate the required dilution amount:

X = [(4.95 - 4.50) × 9000] / 4.50 = 900 kg

So, about 900 kg of dilution charge is needed to reduce Cu toward the target content.

Why Add Mg, Mn, and Ti After Dilution?

After adding 900 kg of dilution material, the total melt weight increases. Cu is reduced, but Mg, Mn, and Ti are also diluted. That means the alloy may no longer meet the required target for these elements.

The example uses:

Charge Material	Main Purpose
Al-Ti master alloy	Add Ti
Al-Mn master alloy	Add Mn
Mg99.80 magnesium ingot	Add Mg
99.60 aluminum ingot	Main dilution material

The calculated additions are:

Addition	Required Amount
Al-Ti master alloy	about 11 kg
Al-Mn master alloy	about 153 kg
Mg ingot	about 13.5 kg
Aluminum ingot	about 722.5 kg

Total:

11 + 153 + 13.5 + 722.5 = 900 kg

This means the same 900 kg dilution plan is not only pure aluminum. It includes the necessary master alloys and magnesium addition to restore the full target chemistry.

Why Fe and Si Must Be Checked

Fe and Si are common impurities in aluminum alloy production. Even if the original melt is within specification, master alloys and aluminum ingots may introduce additional Fe and Si.

In the example:

Material	Fe / %	Si / %
Original melt	0.30	0.25
Al-Ti master alloy	0.60	0.40
Al-Mn master alloy	0.50	0.40
Aluminum ingot	0.25	0.18

After calculation, Fe and Si remain below the 2A12 alloy limits. That confirms the charge plan is acceptable.

This step is important. Many charge mistakes do not come from the main alloying elements, but from ignoring impurities brought in by master alloys or return scrap.

What This Means for Aluminum-Magnesium Alloy Buyers

If you are buying aluminum-magnesium alloy materials, do not only ask whether the supplier has stock. Ask whether the chemistry, temper, and inspection documents match your application.

A good RFQ should include:

RFQ Information	Why It Matters
Alloy grade	AZ31B, AZ91D, 5052, 5083, 2A12, etc.
Product form	Plate, sheet, bar, tube, foil, profile, billet, machined part
Dimensions	Thickness, diameter, length, tolerance
Temper	O, H, T condition, or project-specific requirement
Standard	GB, ASTM, AMS, EN, or customer standard
Quantity	Affects stock, production route, and quote
Inspection	Chemical composition, mechanical properties, SGS, RoHS
Processing	Cutting, CNC machining, drilling, milling, surface treatment
Application	Aerospace, automotive, electronics, lightweight structures

If Mg content, Fe/Si limits, tensile strength, elongation, or machining behavior matters to your project, provide those requirements at the quote stage.

Common Mistakes in Alloy Charge Control

Avoid these mistakes:

correcting low elements before diluting over-limit elements
ignoring Mg burn-off during melting
assuming master alloy is impurity-free
calculating only Cu, Mg, Mn, Ti and ignoring Fe/Si
using return scrap without chemistry verification
failing to re-test after additions
quoting aluminum-magnesium alloy products without confirming standard and temper

Good composition control is not only a production issue. It directly affects procurement reliability, machining stability, and final product performance.

Final Recommendation

The example from the photos shows a practical composition adjustment logic: Cu is too high, so the melt is diluted first; Mg, Mn, and Ti are then corrected; Fe and Si are finally checked to confirm they remain within specification.

For aluminum-magnesium alloy buyers, this is also a useful supplier evaluation point. A reliable supplier should be able to discuss alloy grade, chemical composition, temper, inspection reports, processing route, and delivery requirements before quoting.

When requesting a quote, send the alloy grade, product form, dimensions, quantity, standard, inspection needs, and application. That gives the supplier enough information to recommend the right aluminum-magnesium alloy material and avoid performance mismatch later.