Alloy Comparator

Compare two alloys side by side — mechanical properties, ratings, composition, and best use cases.

Finder

How to Use

  1. 1
    Select Two or More Alloys to Compare

    Search for alloys by name, UNS number, or composition — for example, 316L stainless steel vs. 2205 duplex — and add them to the comparison queue.

  2. 2
    Choose Properties of Interest

    Select the mechanical, thermal, electrical, or corrosion properties you need to evaluate, such as tensile strength, thermal conductivity, or pitting resistance equivalent number (PREN).

  3. 3
    Review the Side-by-Side Table

    Examine the normalized comparison table, where color coding highlights the best-performing alloy for each property, enabling rapid identification of trade-offs between candidates.

About

Alloy selection often comes down to understanding subtle but critical differences between grades that appear superficially similar. The AlloyFYI comparator provides a structured, data-driven way to evaluate these differences across mechanical, thermal, corrosion, and physical properties simultaneously. Rather than toggling between multiple datasheet PDFs, engineers can see every relevant property side by side, with the best value for each property highlighted to accelerate decision-making.

The tool is particularly valuable for substitution analysis — determining whether a more readily available or less expensive alloy can replace a specified material without compromising performance. Supply chain disruptions have made material substitution a recurring engineering challenge, and systematic property comparison with gap analysis reveals exactly where a candidate substitute falls short and by how much. The comparator also supports design optimization: when two alloys both meet minimum requirements, the engineer can quantify which provides the larger performance margin, informing risk management decisions in safety-critical applications such as pressure vessels, structural aerospace components, and medical devices.

FAQ

How is the pitting resistance equivalent number (PREN) calculated?
PREN = %Cr + 3.3×%Mo + 16×%N. This empirical formula predicts resistance to pitting and crevice corrosion in chloride-containing environments. Austenitic 316L has a PREN around 24, duplex 2205 reaches approximately 35, and super-duplex 2507 exceeds 40. A higher PREN indicates better resistance to localized corrosion, though it is a guide rather than an absolute guarantee; temperature and pH strongly influence actual performance in service.
What is the difference between 304 and 316 stainless steel?
Both are austenitic stainless steels with similar mechanical properties, but 316 contains 2–3% molybdenum, which raises its PREN from approximately 18 (304) to 24–26 (316). This molybdenum addition substantially improves resistance to pitting in chloride environments such as seawater, swimming pool water, and many chemical processing media. 316L is the low-carbon variant with carbon ≤0.03%, reducing sensitization risk during welding. In non-chloride environments where corrosion is not a concern, 304 is almost always the economical choice.
How do I compare aluminum alloy tempers, such as T6 vs. T651?
The T6 temper designates solution heat treatment followed by artificial aging. T651 adds a controlled stretching operation between solution treatment and aging to relieve residual stresses and improve dimensional stability. The mechanical properties (yield and tensile strength, elongation) are essentially identical; the distinction matters for precision-machined parts where residual stress relief is critical to prevent distortion. Always specify the correct temper when ordering plate or bar to avoid unexpected part movement during or after machining.
Can I compare alloys across different material families, like steel vs. aluminum?
Yes. The comparator supports cross-family comparison and automatically normalizes properties where direct comparison is meaningful — for example, specific strength (σ_y/ρ) rather than absolute yield strength, and specific stiffness (E/ρ) rather than elastic modulus. These normalized indices enable direct comparison of the structural efficiency of an aluminum alloy versus a high-strength steel for a weight-critical application. Cost-per-unit-strength indices can also be displayed when cost data is available.
What does 'minimum' vs. 'typical' property values mean in the comparator?
Minimum guaranteed values are the lower bounds specified in material standards (ASTM, AMS, EN) that every compliant heat or lot must meet; they are used for structural design calculations with appropriate safety factors. Typical values represent the statistical mean of large production datasets and are useful for estimating expected performance but should not be used as design allowables without knockdown factors. For critical applications, consult MMPDS (Metallic Materials Properties Development and Standardization) or equivalent authoritative databases for statistically derived design allowables (A-basis or B-basis values).
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