Bulk Analysis of Cast and Wrought Aluminum Alloys (GDS900)

Importance of the Topic

Aluminum alloys are widely used in industries ranging from aerospace to automotive due to their high strength-to-weight ratio, corrosion resistance, thermal and electrical conductivity. Accurate, rapid and reliable elemental analysis of both cast and wrought aluminum grades is critical for quality control, material verification and research and development.

Study Objectives and Overview

This application note presents a bulk analysis method for cast and wrought aluminum alloys using the LECO GDS900 glow discharge atomic emission spectrometer (AES). Key goals include demonstrating linear calibration across major and minor alloying elements, evaluating precision and accuracy on representative alloy standards, and highlighting throughput improvements.

Methodology and Instrumentation

The analytical workflow comprises:

• Instrumentation Used: LECO GDS900 atomic emission spectrometer with CCD-based detection and glow discharge source
• Sample Preparation: Wet grinding of solid samples on a 320-grit silicon carbide disk or lathe/milling to a 1.6×10⁻³ mm surface finish; optional polisher (LECO PX) for consistent surface quality
• Glow Discharge Conditions: Plasma excitation removes surface contamination and exposes fresh substrate for analysis; neutral atomic emission lines dominate spectra, minimizing spectral interferences
• Calibration: Factory-installed aluminum calibration using certified reference materials (CRM) and reference materials (RM) from Alcoa, Alcan, MBH, NIST; drift correction via homogeneous setup standards (SUS)
• Analysis Cycle: Single burn in 70 s or three sequential burns in 90 s without sample dropping, leveraging continuous sputtering for rapid repeat analyses

Key Results and Discussion

Calibration curves for silicon, magnesium, iron and chromium demonstrated excellent linearity across low, mid and high concentration ranges typical of aluminum alloys. Precision tests on wrought alloy 1080 and cast alloys 380, SS-356, and wrought alloys 6061, 7075 yielded relative standard deviations below 3% for most elements. Average values closely matched certified concentrations, confirming both accuracy and repeatability of the GDS900 method. Multi-burn analysis provided consistent results with negligible matrix effects due to the glow discharge excitation away from the immediate surface.

Benefits and Practical Applications

This method offers:

• High throughput: up to three analyses in 90 s without repositioning samples
• Minimal spectral interferences: simplified glow discharge spectra reduce cleanup complexity
• Robust calibration stability: CCD detection ensures reproducible performance in production environments
• Versatility: applicable to a wide range of ferrous and nonferrous materials beyond aluminum

Future Trends and Opportunities

Advancements may include automation of sample handling, expanded libraries of CRM/RM for emerging alloys, integration with laboratory information management systems (LIMS), and coupling with surface mapping techniques for localized compositional analysis. Further research on extending detection limits for trace elements could open new applications in nanomaterials and advanced alloy development.

Conclusion

The LECO GDS900 glow discharge AES provides a fast, accurate and reliable solution for bulk elemental analysis of cast and wrought aluminum alloys. Its linear calibration, low interferences, and high throughput make it well suited for industrial quality control and research laboratories.

References

• LECO Corporation. Bulk Analysis of Cast and Wrought Aluminum Alloys. Application Note, Form No. 203-821-575, Rev. 2, 2019.