冲击加载条件下化学气相沉积高纯钨的塑性变形机制

Plastic Deformation Mechanism of High Pure Tungsten Prepared by CVD Method at High Strain Rate

摘要:

采用较低温度下的化学气相沉积技术制备了高纯钨，利用分离式HOPKINSON压杆装置对制备的高纯钨和商用粉末烧结纯钨进行应变率为1000／s～2000／s的冲击加载，对冲击后的样品进行了变形机制对比分析。结果表明：在冲击载荷作用下粉末烧结纯钨变形机制以滑移和品界滑动为主，析化学气相沉积纯钨则是孪生变形起到很大的作用：临近孪生间的交互作用会产生2种类型的穿晶断裂，这是化学气相沉积纯钨致脆的原因：在低于10^3／s应变率量级化学气相沉积纯钨不会发生绝热剪切，难以与钨合金一样通过绝热翦切变形提高其塑性变形能力。

Abstract:

High pure tungsten (W, 99.99%) were prepared by chemical vapor deposition (CVD), then high pure tungsten and polycrystalline tungsten prepared by powder metallurgy (PM) process were impacted using Split Hopkinson Bar (SHB) over a narrow range of strain rates, 1000 s-1~2000 s-1. The deformation mechanisms were analyzed by optical microscope (OM). The results show that the main deformation mechanisms of the polycrystalline tungsten prepared by Powder Metallurgy Process are slip and grain-boundary slide, while those of high pure tungsten are slip, twinning deformation and grain-boundary slide. The interaction between the neighbouring twinnings may induce two kinds of intergranular cracks, which is the key reason of the high pure tungsten em-brittleness. The adiabatic shear band (ASB) is not found for the high pure tungsten under the strain rate in this paper e.g. lower than 103 s-1, so the plastic deformation ability of the high pure tungsten can not be improved as that of tungsten heavy alloy (WHA).