Aluminum constitutes approximately 8 wt% of the earth’s crust. As a metal it was first produced on an industrial scale in 1854. Aluminum metal is characterized by a low melting point (660 ºC) and a very low density (2.7 g/ cm3). Its high strength to weight ratio makes it an ideal construction material for the aviation and space industry. Many applications are also based on its high electrical and thermal conductivity and its resistance to corrosion. To change its properties it can be easily alloyed with other metals.
Accurate and fast elemental analysis during the production process of aluminum and its base materials is a critical requirement. The Axios FAST is ideally suited for many applications where speed and accuracy are factors of prime importance. This application note demonstrates the performance of the Axios FAST XRF spectrometer for the analysis of Al-Si and Al-Mg alloys.
Measurements were performed using an Axios FAST simultaneous X-ray fluorescence spectrometer equipped with a 4 kW Rh SST-mAX X-ray tube, set at 60 kV/66 mA for optimal measurement conditions. A 300 µm brass tube filter and a brass beam- stop were mounted. Further it was equipped with:
- Rh reference plate with 37 mm opening
- Fixed channels for Mg, Si, Ti, Mn, Fe, Ni, and Zn
- A focusing goniometer with beam attenuator was used to analyze Al. This goniometer is suitable for the elemental range Al-Fe.
Fixed channels and both goniometers run simultaneously, ensuring a minimum measuring time.
Sample preparation International standards for Al-Si alloys (CKD 236 - 241) and Al-Mg alloys (CKD 242-246) were used to set up the calibration. The samples were milled on a Herzog lathe type HAF/2. Prior to measurement they were cleaned with ethanol. A sample holder with a 37 mm aperture was used for the measurements.
Proven reliability - best quality and speed
Axios FAST, our high-end simultaneous X-ray spectrometer, is the first choice for fast analytical control in demanding industries.
Combining the revolutionary 4 kW SST-mAX X-ray tube with Zeta technology, advanced counting electronics and well-proven features developed over several generations of industry-standard spectrometers, the Axios FAST ensures faster than ever sample processing, together with outstanding operational reliability. To extend the analysis flexibility, the instrument can be fitted with up to four programmable goniometers, giving additional flexibility to a dedicated fixed channel configuration.
For the lighter elements, which determine overall measuring times, the Axios FAST employs so- called “Hi-Per” channels. Initially developed for high-performance analysis in the semiconductor industry, these feature synthetic multilayer monochromators and a reduced optical path length to increase sensitivities.
An application was created with which the X-ray intensities for nine elements in eleven aluminum standards were measured. Al was measured on the focusing goniometer. However, usually Al will not be measured for this application because it can be determined by difference. Calibration was performed using the theoretical alphas and Fundamental
Parameters (FP) regression models incorporated in the SuperQ software package. FP allows for the analysis of elements with wide concentration ranges with a single program, thus saving both on the time to set up and maintain numerous calibrations, as well as on the number of standards required. During the calibration two line-overlap corrections were determined using the multiple regression functionality of the SuperQ software. No other empirical corrections were applied.
For a full simultaneous spectrometer, the analysis speed is usually determined by the element with the lowest sensitivity (Mg in this case) and/or the lowest concentration. Despite the short counting time of 10 seconds, excellent results are obtained for all elements, including Al measured with the focusing goniometer. Table 1 gives an overview of the elements with their concentration range, their respective values for the ‘root mean square’ (RMS) error, for K and for the lower limit of detection (LLD) based on a 100 second counting time. The values for RMS and K are absolute and relative indications, respectively, of the magnitude of the differences between the measured and the supplied chemical concentration.
A lower value for K indicates a more accurate calibration. Since the RMS value relates to the whole concentration range, a better estimate for the absolute error of a specific element with a known concentration can be obtained by using a formula based on the K value:
For example, error estimates for Si determinations of 1.0 and 10.0 wt% based on the calibration details in Table 1 (where K = 0.030) would be 0.030 wt% and 0.095 wt% respectively.
Table 1. Values for ‘K’, ‘RMS’ and ‘LLD’ for wide-range aluminum alloys
The Axios FAST is perfectly suited for analyzing an extended range of concentrations for various types of aluminum alloys within one analytical program. A high accuracy of analysis is achieved within a total counting time of 10 seconds.