The temperature driven segregation of Cr to the surface of the tungsten-based WCrY alloy is analysed with low energy ion scattering of He⁺ ions with an energy of 1 keV in the temperature range from room temperature to 1000 K. Due to the high surface sensitivity, these measurements probe only the composition of the outermost monolayer. The surface concentration of Cr increases slightly when the temperature of the sample is increased up to 700 K and exhibits a much stronger increase when the sample temperature is further raised. The segregation enthalpy for Cr is obtained from the Langmuir-McLean relation and amounts to 0.7 eV. The surface concentration of Y shows a similar behaviour to the Cr concentration. The temperature thresholds between slow and accelerated surface density increases for Cr and Y are nearly the same. At a temperature of 1000 K the low energy ion scattering detects almost no W on the surface. The modified surface composition due to the segregated species, i.e. the mixed Cr/Y layer, stays stable during cool-down of the sample. Preferential sputtering is investigated using ion bombardment of 250 eV D atoms, resulting in an increase of the W surface density at room temperature. This effect is counteracted at elevated temperatures where segregation replenishes the lighter elements on the surface and prevents the formation of an all-W surface layer. The flux of segregating Cr atoms towards the surface is evaluated from the equilibrium between sputter erosion and segregation.

利用He ^+的低能离子散射分析了Cr在钨基WCrY合金表面的温度驱动偏析在室温至1000 K的温度范围内，离子的能量为1 keV。由于表面灵敏度高，这些测量仅探测最外层单分子层的组成。当样品温度升高到700 K时，Cr的表面浓度会略有增加，而当样品温度进一步升高时，Cr的表面浓度会表现出更强的增加。Cr的偏析焓是从Langmuir-McLean关系获得的，等于0.7 eV。Y的表面浓度显示出与Cr浓度相似的行为。Cr和Y在缓慢和加速表面密度增加之间的温度阈值几乎相同。在1000 K的温度下，低能离子散射几乎检测不到表面上的W。由于分离的物种（即 Cr / Y混合层在样品冷却期间保持稳定。使用250 eV D原子的离子轰击研究了优先溅射，从而导致了室温下W表面密度的增加。在偏析会补充表面上较轻的元素并防止形成全钨表面层的高温下，这种作用会抵消。从溅射腐蚀和偏析之间的平衡来评估Cr原子向表面的通量。在偏析会补充表面上较轻的元素并防止形成全钨表面层的高温下，这种作用会抵消。从溅射腐蚀和偏析之间的平衡来评估Cr原子向表面的通量。在偏析会补充表面上较轻的元素并防止形成全钨表面层的高温下，这种作用会抵消。从溅射腐蚀和偏析之间的平衡来评估Cr原子向表面的通量。