Bulk Analysis of Cast and Wrought Aluminum Alloys

Importance of Bulk Analysis in Aluminum Alloys

Aluminum alloys are widely used in automotive, aerospace and construction due to their high strength-to-weight ratio, corrosion resistance and desirable mechanical properties. Accurate bulk compositional analysis is essential to ensure alloy grades meet specifications, control production costs and guarantee final product performance.

Objectives and Study Overview

This application note demonstrates the use of glow discharge spectroscopy (GDS) for rapid, routine determination of major and minor alloying elements in both cast and wrought aluminum alloys. Key goals include validating linear calibration over wide concentration ranges, evaluating analytical precision and assessing throughput in a production environment.

Methodology and Instrumentation

The analyses were performed on LECO GDS500A, a CCD-based glow discharge system. Sample surfaces were prepared by wet grinding with a 320-grit silicon carbide disk or by lathe/milling to a finish of 1.6 E-3 mm. A polisher accessory (LECO VP) was used when needed. Certified reference materials and factory-installed calibrations (from Alcoa, Alcan, MBH, NIST, ARMI) provided working curves. Homogeneous set-up standards enabled drift correction.

Main Results and Discussion

Calibration curves for silicon, magnesium and chromium exhibited excellent linearity across high, mid and low concentrations typical of cast (Si up to 27%) and wrought (<1.5% Si) alloys. Repeated analyses of various standards (e.g., Alcoa SS-356-ME, MBH 55XG28J5-P, NIST 1240B) showed relative standard deviations below 5% for most elements and deviations from certified values under 3%. The “analyze all in one spot” mode enabled three sequential burns in 90 seconds without sample repositioning, significantly improving throughput.

Benefits and Practical Applications

• Robust, linear quantification of multiple elements in a single analysis
• Reduced surface interference due to uniform sputtering
• High sample throughput with multi-burn capability
• Minimal operator skill required for sample preparation

Future Trends and Potential Uses

Emerging developments may include integration of GDS into automated production lines, extended dynamic ranges for trace element detection, coupling with data analytics for real-time process control and portable glow discharge instruments for field verification.

Conclusion

Glow discharge spectroscopy using the LECO GDS500A provides fast, accurate and reproducible bulk compositional data for both cast and wrought aluminum alloys. Its linear calibration performance, low spectral interferences and high throughput make it an ideal tool for quality assurance, alloy verification and cost management in industrial settings.

References

• Alcoa certified standards SS-356-ME, SS-383-T, SS-6061-EN
• MBH reference material 55XG28J5-P
• NIST standards 1240B (3004) and 1259 (7075)