For high-temperature environments, as in future fusion reactors, the use of tungsten materials has been sincerely discussed in the last decade. Although severe cold-rolling of tungsten leads to significant improvements in mechanical properties, the fine-grained microstructure of such tungsten material has to be stabilized. For that, the use of potassium-doping (K-doping) in tungsten sheets is investigated in our ongoing study. In this work, we compare mechanical properties of warm- and cold-rolled sheets of pure tungsten and K-doped tungsten (for five different degree of deformation respectively) by means of fracture toughness tests and tensile tests.

Fracture toughness and brittle-to-ductile transition temperatures ($T_{\text{BDT}}$) are assessed, showing a slightly lower transition temperature for the cold-rolled K-doped sheets (lower than −100 °C for the 50 µm thick foil). The better performance of the K-doped sheet is related to its finer grain size. The thickest K-doped sheet shows a much higher $T_{\text{BDT}}$ than its pure tungsten counterpart. This is presumably caused by the presence of several tens of micrometre thick bands, containing only low angle boundaries, in the microstructure of the K-doped sheet.

Tensile tests reveal an outstanding yield strength of 2860 MPa and an ultimate tensile strength of 2970 MPa for the thinnest K-doped sheet with similar, but slightly lower values for the pure tungsten counterpart. Both thinnest sheets show a drastic increase in ultimate tensile strength in correlation to their mean grain size, much higher than expected by a Hall-Petch relation. This deviation has been observed for the microhardness as well and is assumed to be caused by an extraordinary increase in the density of dislocations.

Our results indicate that no disadvantages in tensile strength and brittle-to-ductile transition are to be expected compared to pure tungsten, when K-doped tungsten is used to inhibit recrystallization in high-temperature environments.

对于高温环境，如在未来的聚变反应堆中，在过去的十年中已经对钨材料的使用进行了认真的讨论。尽管钨的严格冷轧导致机械性能的显着改善，但必须稳定这种钨材料的细晶粒组织。为此，我们正在进行的研究研究了在钨片中使用钾掺杂（K掺杂）的情况。在这项工作中，我们通过断裂韧性测试和拉伸测试比较了纯钨和掺K钨的热轧和冷轧薄板的机械性能（分别针对五个不同的变形程度）。

断裂韧性和脆性至韧性转变温度（${Ť}_{\text{电信发展局}}$）进行了评估，结果表明冷轧K掺杂薄板的转变温度略低（对于50 µm厚的箔，其转变温度低于-100°C）。掺钾片材的更好性能与其更细的晶粒尺寸有关。最厚的K掺杂薄层显示出更高的厚度${Ť}_{\text{电信发展局}}$而不是纯钨。据推测，这是由于在掺杂K的薄板的微观结构中存在仅包含低角度边界的几十微米厚的条带引起的。

拉伸试验表明，对于最薄的掺K薄板，屈服强度为2860 MPa，极限抗拉强度为2970 MPa，与纯钨相当，但值略低。两种最薄的片材均显示出与其平均晶粒尺寸相关的极限抗拉强度的急剧增加，远高于霍尔-皮奇关系的预期。还已经观察到该显微硬度的偏差，并且被认为是由位错密度的极大增加引起的。

我们的结果表明，当使用掺K的钨抑制高温环境下的再结晶时，与纯钨相比，抗张强度和脆性至韧性转变没有任何不利之处。