The dynamic behaviour of thermally driven segregation of Cr to the surface of WCrY smart alloy is studied with low energy ion scattering (LEIS). Sputtering the WCrY sample with 500 eV ${\mathrm{D}}_2^{+}$ ions at room temperature results in preferential removal of the lighter alloy constituents and causes an almost pure W surface layer. At elevated temperatures above 700 K the segregation of Cr atoms towards the surface sets in and prevents the formation of a pure W layer. The simultaneous heating and sputtering of the sample leads to a surface state which reflects the balance between sputter removal and segregation flux, and deviates from the equilibrium due to thermally driven segregation. Stopping the sputter ion beam allows the system to relax and develop toward the segregation equilibrium. The time constants for the temporal changes of W and Cr surface coverage are obtained from a series of LEIS measurements. The segregation enthalpy is determined from the time constants obtained for various sample temperatures.

利用低能离子散射（LEIS）研究了Cr热驱动偏析到WCrY智能合金表面的动力学行为。用500 eV溅射WCrY样品${\mathrm{d}}_2^{+}$室温下的离子会优先去除较轻的合金成分，并导致几乎纯净的W表面层。在高于700 K的高温下，Cr原子向表面的偏析进入并阻止了纯W层的形成。样品的同时加热和溅射导致表面状态，该状态反映了溅射去除和偏析通量之间的平衡，并且由于热驱动偏析而偏离了平衡。停止溅射离子束可使系统松弛并朝着偏析平衡发展。W和Cr表面覆盖率随时间变化的时间常数是从一系列LEIS测量获得的。根据不同样品温度获得的时间常数确定离析焓。