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孔隙形状和尺寸调控对3D打印多孔钨相关性能的影响

Influence on mechanical properties of 3D printing porous tungsten by control shape and size of porous

  • 摘要: 本文设计正方体和三棱锥两种孔隙形状的多孔钨。经有限元分析发现,正方体和三棱锥骨架单元分别承受点、线和面载荷时,受力不均匀。当骨架单元分别承受面和线载荷时,受到支撑的棱柱处应力较小,没有支撑的棱柱处应力较大,并引起了较大的变形量。当骨架单元承受点载荷时,其应力和变形量均在加载处最大。采用选区激光熔化(SLM)技术制备两种孔结构的高孔隙率多孔钨,探讨孔隙形状和尺寸对其力学性能的影响。结果表明,两种多孔钨的宏观形貌与其设计结构无明显差别,由于骨架棱柱(边)上易悬垂和粘粉导致孔隙率较设计值有所降低。预设孔隙率为50%和80%的正方体多孔钨抗拉强度分别为127.4 MPa和55.8 MPa,抗压强度分别为667.1 MPa和213 MPa,冲击韧性分别为6.7641 J/cm2和4.4924 J/cm2,硬度值相差不大。预设相同孔隙率的三棱锥多孔钨抗压强度分别为231.1 MPa和65.3 MPa,冲击韧性均为2.03J/cm2,硬度与正方体骨架相同。正方体和三棱锥多孔钨的拉伸和压缩断口形貌均呈现出典型的准解理脆性断裂特征。

     

    Abstract: In this paper, porous tungsten with two pore shapes, cube and triangular pyramid, were designed. The finite element analysis shows that when point, line, and surface loads are applied respectively, the stress on the cube and triangular pyramid skeleton units is uneven. When the skeleton unit is subjected to plane and line loads respectively, the stress at the supported struts is relatively small, while the stress at the unsupported struts is relatively large, causing a large amount of deformation. When the skeleton unit is subjected to a point load, its stress and deformation are both maximum at the loading point. Two types of porous tungsten with high porosity were fabricated by selective laser melting (SLM) technique, and the effects of pore shape and size on mechanical properties were investigated. The results show that the macrostructure of both these skeleton structure is not significantly different from the designed structure. Because of the hanging and sticky powders on the struts, the porosity is lower than the designed value. The tensile strength of cube skeleton with 50% and 80% porosity is 127.4 MPa and 55.8 MPa, the compressive strength is 667.1 MPa and 213 MPa, the impact toughness is 6.7641 J·cm-2 and 4.4924 J·cm-2, respectively. In addition, both have similar hardness. The compressive strength of the triangular pyramid skeleton with the same designed porosity is 231.1 MPa and 65.3 MPa, the impact toughness is 2.03 J·cm-2, and has the same hardness as the cube skeleton. The tensile and compressive fracture morphology of cube and triangular porous tungsten shows typical quasi-cleavage brittle fracture.

     

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