La, Ce, Nd and Pr quantification in Mg-Zn-Zr-RE alloys using CF LIBS

abstract

English

Magnesium alloys are starting to be widely used in automotive, airline and space industry due to their low specific mass and good mechanical properties. Alloying them with different REE’s can decrease grain size, increase structure homogeneity, corrosion resistance, mechanical properties, creep resistance and much more. Recently the research of biodegradable Mg alloys with addition of La, Ce and Nd proved their effect on corrosion resistance1. LIBS spectroscopy was already used for the identification2, detection3 and quantification4 of REE’s content in different samples. For plasma generation the Nd:YAG laser operating at 266 nm and 532 nm was used. The measured spectra were recorded by two spectrometers: broadband Mechelle spectrometer (230 nm – 975 nm, Andor Technology) equipped with iCCD camera (iStar DH743, Andor Technology) and a high resolution THR 1500 spectrometer (JobinYvon), coupled with the same iCCD camera for the separation of closed REE’s spectral lines. The measurements were taken in the vacuum chamber under Ar atmosphere at different low pressures (starting from 1330 Pa) and in open air at atmospheric pressure. The spectra were recorded in different gate dealys: from 100 ns to 7 µs depending on the pressure. Gate width was always set to the same value as the gate delay. Electron density was determined using Stark broadening of H alpha spectral line at 656.23 nm from residual gas and the electron temperature from Saha-Boltzmann plot of Zr I-II spectral lines. We measured the elemental composition of both ZE10 and ZE41 alloys. While the bulk material of the alloy is composed of substitutional solid solution δ (Zn in Mg), the REE’s and Zn are mostly found in small inclusions distributed heterogeneously. The average content of Mg, Zr, Zn and REE’s(La, Ce, Nd, Pr) was determined using CF LIBS method by scanning accumulations over the sample surface. For the CF LIBS quantification the multiple Mg I-II, Zn I, Zr I-II, La II, Ce II, Nd II, Pr II lines were used. Obtained values were compared to the EDS sample analysis.

Mg alloys, ZE10, ZE41, REE detection, CF-LIBS

VEIS, S.; PLAVČAN, J.; HORŇÁČKOVÁ, M.; DOLEŽAL, P.; VEIS, P.

14. 9. 2015