| 摘要: | 本研究利用粉末燒結技術，以球形PS作為空間支架，製作出具有相同孔隙率(50%)、不同孔徑(2、3、4 mm)排列之17-4PH不鏽鋼多孔合金。藉以探討時效處理和孔徑梯度排列對其微結構和壓縮性質之影響。
結果顯示，燒結後，多孔17-4PH之微結構為板狀麻田散鐵和肥粒鐵，經(480、520、560°C)時效處理後，微結構除板狀麻田散鐵和肥粒鐵，並觀察到ε-Cu析出相析出於基地中，能有效地提高硬度、平台應力(σPL )和吸收能量(W)。隨著時效溫度升高至620°C，微結構為針狀麻田散鐵、肥粒鐵、沃斯田鐵及ε-Cu析出相，沃斯田鐵的形成與ε-Cu的粗化使合金硬度、平台應力和吸收能量降低，但延性上升，應力應變曲線變得平滑，應力下降比(R)降低。
另外，孔隙率、孔徑大小和孔徑梯度排列是影響壓縮性質的重要參數。在相同孔隙率下，孔徑小(2 mm)之多孔合金因孔洞數量多，有更多的孔壁分擔負荷以提高強度，導致小孔徑多孔合金比孔徑大者，具有較高之平台應力、吸收能量。而具有孔徑梯度排列之合金，其平台應力雖然略低於孔徑隨機分布之多孔合金，但不同的破裂形式造成孔徑梯度排列有更好的理想能量吸收效率(68.5%)。此外，多層的孔徑梯度排列則比少層的梯度排列有更平滑的壓縮應力應變曲線。
;In this study, 17-4PH stainless steel metal foams with the same porosity (50%) and different pore size (2, 3, 4 mm) were produced by using powder sinter technology and adding spherical space holder(Styrofoam Ball). The effects of aging process and gradient arrangement on 17-4PH steel foams were investigated by microstructure observation and compression test.
As a result of this study, the microstructure of the 17-4PH foams after sintering is mainly composed of lath martensite and δ-ferrite. After aging treatment, ε-Cu precipitates precipitated in matrix, thereby effectively increasing the plateau stress (σPL) and energy absorption (W). As the aging temperature increases (620°C), formation of austenite and coarsening of ε-cu make the hardness of the alloy decrease, but the ductility increases, the stress-strain curve becomes smoother, and the stress drop ratio (R) decreases.
In addition, porosity, pore size and pore gradient arrangement are important parameters affecting the compressive properties. At the same porosity, the porous alloy with small pore diameter (2 mm) has more pores than the porous alloy with large pore diameter (4 mm), and there are more pore walls to share the load to increase the strength, so the compression properties of small pore diameter are better than those of large pore diameter. Besides, the plateau stress of the alloy with gradient pore size arrangement is slightly lower than that of the alloy with random pore size arrangement, but the different fracture forms cause the pore size gradient arrangement to have a better ideal energy absorption efficiency (68.5%). In addition, the gradient arrangement of multilayer pore size has a smoother compressive stress-strain curve than the gradient arrangement of few layers. |
