Advanced Analysis of Aluminum Alloys with Handheld LIBS

In comparison with X-ray technology, aluminum alloy sorting and chemical analysis can be performed comprehensively and rapidly using handheld laser-induced breakdown spectroscopy (LIBS).

LIBS offers analysis of lighter elements on a par with spark-OES technology, but unlike OES, is available in a handheld form factor.

SciAps offers the Z LIBS Analyzer (Figure 1), which consists of a wide range high-resolution spectrometer and patented on-board argon purge for a 10x improvement in accurate, high-speed laser shot cleaning to avoid surface effects.

The sophisticated spectrometer is a key component, as it provides better resolution for a wider range of elements than simple sorting LIBS analyzers can offer, including lithium (Li) and sodium (Na). The performance and functionality of this handheld device is comparable to mobile or benchtop OES devices.

The Z LIBS Analyzer

Figure 1. The Z LIBS Analyzer

The Z LIBS Analyzer can be used for:

  • Rapid magnesium measurements
  • Trace lithium analysis
  • Measurement of low concentrations of contaminant beryllium (Be)
  • Low concentration, accurate iron measurements for increasing scrap value

Beryllium (Be)

Beryllium is added to aluminum alloys composed of magnesium in order to minimize oxidation at elevated temperatures. Also, beryllium is harmful to health, especially upon inhaling of fine Be particles. Therefore, it is critical to know about the existence and concentration of Be.

Figure 2 depicts the response curve for the Z-200 for the maximum 3 second test. As shown in this figure, the 3-sigma detection limit is roughly 10 ppm, and the relative standard deviation (repeatability) is below 10% at 20ppm, which means 20 ± 2ppm.

Unlike other HH LIBS units that measure beryllium, the SciAps Z is capable of measuring trace amounts of Be down to 10 ppm, thanks to the power of the laser and the argon purge capability.

Response curve for low concentrations of Be in various aluminum alloys from < 10ppm up to 40ppm.

Figure 2. Response curve for low concentrations of Be in various aluminum alloys from < 10ppm up to 40ppm.

Low % Iron Analysis

Aluminum scrap is more valuable for most foundries if the material with less than 0.2% iron - or even less than 0.1% iron - can be sorted and separated. The use of low iron scrap feed in the manufacture of some aluminum products reduces the amount of virgin raw material required, and ultimately lowers production costs.

The rastered laser and the argon purge available in the Z analyzer allows measurement of less than 1% of Fe in aluminum alloys. Averaging of multiple test locations is highly critical, as iron clustering is seen in some cases. If reference standards in the target concentration range are used, the Z is capable of quantifying Fe content down to 0.05%.

The LIBZ Z-200 fills a unique role in the aluminum manufacturing and producer’s analytical testing requirements.

Figure 3. The LIBZ Z-200 fills a unique role in the aluminum manufacturing and producer’s analytical testing requirements.

Rapid, Accurate Mg Measurements from 0.02 – 6%

Many aluminum alloys are only differentiated by the variations in Mg concentration. In terms of sorting, there is a strong correlation between the value of the material and Mg percentage - for instance, 356/357, 2024/2014, 3003/3005.

Mg can be very precisely and accurately measured using the Z LIBS analyzer. Also, the sensitivity and speed of the Z for Mg measurements is superior to HHXRF - the Z matches benchtop and mobile OES in terms of analytical performance on Mg.

The Z LIBS analyzer is factory configured with several calibration curves in order to cover the concentration range of 0.02-0.5%, 0.5-1.5% and greater than 1.5%. Users have the ability to produce their own curves on proprietary materials whenever required.

Calibration curve showing the low concentration regime of Mg values. The measured values were generated using multiple Mg calibration curves typically from 0 – 1% and 1-6%.

Figure 4. Calibration curve showing the low concentration regime of Mg values. The measured values were generated using multiple Mg calibration curves typically from 0 – 1% and 1-6%.

Trace and Alloying Lithium Analysis

The argon purge and the broad spectral range of 190 – 615 nm enable the Z-200 to produce outstanding results for lithium measurements (based on the lithium spectral line at 610.39 nm).

Using the Z, lithium measurements can be rapidly and accurately obtained for the latest aerospace alloys, such as 2195, as well as trace lithium measurements.

The high intensities attained offer a lithium detection limit in the range of 50 – 100 ppm (0.005 – 0.01%). It is also possible to modify the Z platform with a third spectrometer (Z-300), which extends the range for measuring the brighter 670.8nm line if it is necessary to have detection limits in the 10ppm range (Figure 5). It is possible to upgrade any Z-200 to the Z-300 whenever needed.

Trace level lithium analysis with the Z-200.

Figure 5. Trace level lithium analysis with the Z-200.

Conclusion

The LIBZ Z-200 plays a unique role in the aluminum production and manufacturer’s analytical testing requirements. The Z provides fast, accurate analysis for a myriad of aluminum alloy applications comparable to benchtop argon-based spark OES units.

However, the Z is offered in a 4lb handheld form factor which is unavailable for OES, providing the portability of handheld XRF. This combination of portability and range of analysis is a unique feature of the Z LIBS Analyzer.

This information has been sourced, reviewed and adapted from materials provided by SciAps, Inc.

For more information on this source, please visit SciAps, Inc.

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