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钨合金中钾的掺杂会引入大量的缺陷, 如尺寸几十纳米的钾泡、高密度的位错以及微米量级的晶粒带来的晶界等, 这些缺陷的浓度和分布直接影响合金的服役性能. 本文运用正电子湮没谱学方法研究钾掺杂钨合金中的缺陷信息, 首先模拟计算了合金中各种缺陷的正电子湮没寿命, 发现钾的嵌入对空位团、位错、晶界等缺陷的寿命影响很小; 然后测量了不同钾含量掺杂钨合金样品的正电子湮没寿命谱, 建立三态捕获模型, 发现样品中有高的位错密度和低的空位团簇浓度, 验证了钾对位错的钉扎作用, 阐述了在钾泡形成初期是钾元素与空位团簇结合并逐渐长大的过程; 最后使用慢正电子多普勒展宽谱技术表征了样品中缺陷随深度的均匀分布和大量存在, 通过扩散长度的比较肯定了钾泡、晶界等缺陷的存在.Tungsten alloy is known as a promising plasma-facing material (PFM) in IETR because of high strength, high-temperature stability, low sputtering erosion, low tritium retention, etc. However, tungsten has some disadvantages, such as high ductile-brittle transition temperature, low temperature brittleness, and radiation embrittlement. For the severe environment of PFM, various techniques have been adopted to improve W-based materials, among which the potassium doping is an effective bubble strengthening method, it can bring in nano-sized K bubbles, and enhance the toughness and strength, thermal shock performance, irradiation resistance of the materials. The K bubbles, which can pin grain boundaries (GBs) and dislocations, are the most characteristic defects in W-K alloy and have been widely reported. However, little attention is paid to other defects such as vacancies, GBs and dislocations. In fact, high-density dislocations exist in W-K alloy and vacancies play a considerable role in forming the K bubbles. Thus, positron annihilation technique (including the positron annihilation lifetime spectrum and slow positron beam Doppler broadening spectrum), which is a useful technique for detecting defects in solids, can be used to study these defects in W-K alloy samples. The positron lifetime of potassium bulk is about 376 ps and the positron lifetime of tungsten bulk is about 110 ps. But by simulating positron lifetime of defects in tungsten, it is found that potassium atoms in tungsten lattice do not exhibit the characteristic positron lifetime. Therefore, potassium is not considered in analyzing positron annihilation lifetime spectra of W-K alloy samples with different potassium content (46, 82, 122, 144 ppm). Three-state capture model is established in this paper, the dislocation density and vacancy cluster concentration of these samples are obtained. From the results, the dislocation densities in all samples are very high, but vacancy cluster concentrations are relatively low, and the vacancy cluster concentration in the sample with 82 ppm potassium content is the lowest in all samples. The behavior of potassium atoms in the sintering process is also discussed. Then the slow positron beam Doppler broadening spectra of W-K alloy samples and pure tungsten samples are measured and the obtained data are fitted by VEPFIT. It is noted that the defects in W-K alloy samples are much more than those in pure tungsten sample, and are distributed homogeneously with depth. The positron diffusion length information simultaneously obtained is compared with these values computed by dislocation density and vacancy cluster concentration, confirming the positrons trapped by potassium bubbles and grain boundaries are existent.
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编号 Σ GB plane GB type Rotation axis Angle/(°) W-GB-1 5 $ \langle 210 \rangle $ twist z(001) 53.15 W-GB-2 13 $ \langle 510 \rangle $ twist z(001) 22.61 W-GB-3 5 $ \{0\bar1 5\} $ tilt x(100) 22.61 W-GB-4 13 $ \{0\bar15\} $ tilt x(100) 53.15 编号 Slip plane(z) Burgers vector[b] Dislocation line[y] Dislocation type b-yAngle/(°) W-DL-1 $ (\bar101) $ (111)/2 $ (\bar 12\bar 1) $ EDGE 90 W-DL-2 $ (\bar101) $ (111)/2 (111) SCREW 0 W-DL-3 $ (\bar101) $ (111)/2 (010) MIX 54.73 
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编号 Intact/ps Vac.1/ps Vac.9/ps K1/ps K9/ps W-GB-1 116.6 198.2 297.4 110.6 108.4 W-GB-2 117.9 198.0 297.2 116.4 111.7 W-GB-3 135.2 204.8 304.4 142.3 144.1 W-GB-4 142.2 198.0 317.3 141.0 144.6 W-DL-1 133.9 160.3 309.7 133.9 134.2 W-DL-2 106.5 194.7 324.0 104.7 105.8 W-DL-3 123.4 158.0 315.4 123.4 123.4 下载:
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钾含量/ppm 编号 ${\tau _{{\rm{1, }}\exp }}$/ps ${I_{1, \exp }}$/% ${\tau _{{\rm{2, }}\exp }}$/ps ${I_{2, \exp }}$/% 平均寿命${\tau _{{\rm{av}}}}$/ps 捕获率$\kappa $/ns–1 计算体寿命$\tau _{\rm{1}}^{{\rm{cal}}}$/ps 46 A1 123.4 74.62 296.2 25.38 167.3 1.1999 97.2 82 B1 123.3 75.68 305.1 24.32 167.5 1.1752 97.4 122 C1 140.1 72.42 332.6 27.58 193.2 1.1395 97.7 144 D1 143.2 77.07 328.3 22.93 185.6 0.9028 100.1 下载:
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钾含量/ppm 编号 位错捕获率${\kappa _1}$/ps–1 空位团簇捕获率${\kappa _2}$/ps–1 位错密度${C_{{\rm{dis}}}}$/1010cm2 空位团簇浓度${C_{{\rm{cl}}}}$/10–7 46 A1 0.00912 0.00505 0.8289 1.515 82 B1 0.00895 0.00474 0.8136 1.424 122 C1 0.03359 0.01511 3.0534 4.538 144 D1 0.04400 0.01489 3.9991 4.470 下载:
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钾含量/ppm 编号 第一层厚度/nm 第一层S1 第二层S2 46 A2 10 0.4521 0.4424 82 B2 11 0.4520 0.4406 122 C2 13 0.4521 0.4455 0 PMW 10 0.4050 0.3880 下载:
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钾含量/ppm 编号 寿命谱$L_{{\rm{ +, eff}}}^{{\rm{cal}}}$/nm 编号 第一层$L_{ +, {\rm{eff}}}^1$/nm 第二层$L_{ +, {\rm{eff}}}^2$/nm 46 A1 77.59 A2 2.73 ± 0.89 59.75 ± 9.96 82 B1 78.39 B2 4.98 ± 1.06 58.61 ± 7.86 122 C1 49.22 C2 1.65 ± 1.56 37.44 ± 7.72 0 PMW 6.50 ± 0.29 109.32 ± 5.46 下载:
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