The XRD patterns of the samples before and after the HCPEB irradiations are shown in Figure 1.
Figures 2(b) and 2(c) show the typical cross-sectional micrograph of the etched samples after 5 and 10 pulses of the HCPEB irradiation, respectively.
Similar results were also observed in D2 steel [9, 15] HSS S6-5-2 steel , and M50 steel  irradiated by the multiple pulses of the HCPEB irradiation.
It is reasonably believed that the formation of the twins in the preformed martensite plates was mainly resulted from the high applied stresses and the strain rate due to the rapid heating and cooling caused by HCPEB irradiation .
In conclusion, HCPEB irradiations provide an effective method for fabricating surface nanostructure.
As shown in Figure 3(b), the surfaces of [Mg.sub.67][Zn.sub.30][Y.sub.3] quasicrystal alloys are repeatedly melted and solidified owing to multiple HCPEB treatments (two pulses).
The weight loss of the Al-17.5Si and the [Mg.sub.67][Zn.sub.30][Y.sub.3] quasicrystal alloys was determined before and after the HCPEB treatment.
The nano primary Si phase in the hypereutectic Al-17.5 Si alloy is formed during the rapid solidification of the HCPEB treatment.
This study demonstrates that the surface nanocrystallization of the primary Si phase in hypereutectic Al17.5Si alloy and quasicrystal phase ([Mg.sub.3][Zn.sub.6]Y) in quasicrystal alloy ([Mg.sub.67][Zn.sub.30][Y.sub.3]) is induced by HCPEB irradiation.