Abstract
Laser surface melting (LSM) pre-treatment was conducted before large area electron beam (LAEB) treatment in an attempt to eliminate the cracking of the amorphous layer. In our previous work, LAEB treatment successfully generated an amorphous layer on a cast polycrystalline Al–Co–Ce glass forming alloy. However, cracking was found and was associated with large and brittle Al8Co2Ce phase in the bulk material. Results show that prior LSM treatment in this present work can effectively refine the microstructure of as-cast material, decreasing the particle size and particle spacing of Al8Co2Ce phase. This decrease in the microstructural length scale greatly reduced the results of cracking of the amorphous layer. The LAEB pulse number required for the homogenisation and amorphisation of treated layer was also decreased for the laser pre-treated sample compared to as-cast material.
Highlights
Amorphous metallic alloys are capable of exhibiting attractive mechanical and chemical properties, especially corrosion resistance compared to the crystalline form of the same material
Laser treated material was cut into ~5 mm ×5 mm×4 mm pieces for the Large-area electron beam (LAEB) treatment with different number of pulses. 2.2 Laser surface treatment A YLR–2000SM ytterbium fibre laser (IPG laser, GmbH, Germany) with a wavelength of 1070 nm and a Gaussian (TEM00) beam profile was operated in the continuous wave mode at a power of 2 kW throughout this work
From a combination of the energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) results, the bright white phase 1 is identified as Al11Ce3, the darkest region 2 is the eutectic consisting of two phases attributed as Al and Al11Ce3
Summary
Amorphous metallic alloys are capable of exhibiting attractive mechanical and chemical properties, especially corrosion resistance compared to the crystalline form of the same material. The Al-TM (transition metal)-RE (rare earth) family of amorphous alloys is promising for corrosion resistant applications [1]. Laser surface melting can produce cooling rates of ~ 105 K s-1 but electron beam surface melting can achieve even higher cooling rates, typically of the order of 108-109 K s-1 [3]. These processes have generated amorphous phases in various Al-, Zr- and Cubased alloys [4,5,6]. The aim of the work reported here was to investigate whether a prior laser surface treatment stage could refine the microstructure of as-cast Al-Co-Ce alloy and eliminate the occurrence of this cracking
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