| 摘要: | 本研究藉由微結構觀察與機械性質測試，探討以不同尺寸(直徑:2mm、4mm，分別以L、H表示之)的聚苯乙烯(PS)球所製備之17-4PH不鏽鋼空心球、壁厚(180μm、250μm，分別以l、h表示之)與熱處理(燒結態、固溶(ST)態、時效(AGL)態)對其多孔預型體壓縮性質之影響。
結果顯示，由H-PS球製備之大孔洞(H=4mm)、薄球壁(l)180μm之燒結態(AS)多孔預型體(代號：Hl-AS)，微結構係由板狀麻田散鐵(硬度為Hv341)、與條狀δ-肥粒鐵(硬度為Hv213)所組成，經壓縮測試，得悉其平台應力、與單位能量吸收分別為32MPa、13.6 J/g。經1050oC*1hr固溶處理後(代號：Hl-ST)，銅原子回溶至基地，由光學顯微鏡觀察微結構仍為板狀麻田散鐵、與條狀δ-肥粒鐵所組成，其硬度分別為Hv308與Hv208。
施以520oC*4hr時效處理後(代號:Hl-AGL)，富銅相(ε-Cu)在基地中析出，由光學顯微鏡觀察微結構仍為板狀麻田散鐵、與條狀δ-肥粒鐵所組成，其硬度分別為Hv383與Hv215，顯示麻田散鐵硬度較燒結態大幅提高，其平台應力〖(σ〗_pl)與單位能量吸收分別提高為58MPa、與24.2J/g。δ-肥粒鐵之硬度在各種條件下並無顯著變化。大孔洞(H=4mm)、厚球壁(h)250μm之燒結態多孔預型體(Hh-AS)、小孔洞(L=2mm)、薄球壁(l)180μm之 (Ll-AS)、與大孔洞(L=4mm)、厚球壁(h)250μm之(Lh-AS) 之預型體之機械性質皆有相同之傾向。
L-PS球製備之小孔洞(L=2mm)預型體燒結態與時效處理狀態，皆隨著壁厚(180μm、250μm)增加，其密度、平台應力皆獲得提升，燒結態預型體因壁厚的增加，其平台應力(σ_pl)由59MPa提升至91MPa，但單位能量吸收值(W)由24.1(J/g)下降至19.1(J/g)。H-PS球預型體則壓縮性質都獲得提升。
相同壁厚(180μm、250μm)與熱處理條件下，空心球尺寸越小，其平台應力越高。研究發現，具高壁厚(250μm)、小孔洞 (L-PS球)之預型體，經520oC時效處理後具有最佳壓縮性質，其平台應力(σ_pl)、與單位能量吸收值(W)，分別為141MPa、與33.9(J/g)。
;The effects of different pore sizes, wall thickness, and heat treatment on the compressive properties of 17-4PH stainless steel hollow spheres preform were investigated.
The results show that the porous preform made from H-PS spheres with large pores (H=4mm), thin wall (l=180μm), and sintered state (AS) exhibits a microstructure composed of plate-like martensite (with a hardness of Hv341) and lath-shaped δ-ferrite (with a hardness of Hv213). Compression testing reveals a plateau stress of 32MPa and an energy absorption capacity of 13.6 J/g. After solution treatment at 1050°C for 1 hour, copper atoms are re-dissolved into the matrix, and the microstructure still consists of plate-like martensite and lath-shaped δ-ferrite, with hardness of Hv308 and Hv208, respectively.
Upon aging treatment at 520°C for 4 hours, copper-rich phase (ε-Cu) precipitates in the matrix. The microstructure observed under an optical microscope remains as plate-like martensite and lath-shaped δ-ferrite, with hardness values of Hv383 and Hv215, respectively. It indicates a significant increase in the hardness of martensite compared to the sintered state, resulting in an increased plateau stress〖(σ〗_pl) of 58MPa and an energy absorption capacity of 24.2J/g. The hardness of δ-ferrite shows no significant change under various conditions. The mechanical properties of the porous preforms, including Hh-AS (large pores, h=250μm), Ll-AS (small pores, l=180μm), and Lh-AS (large pores, h=250μm), exhibit similar trends.
For L-PS sphere-prepared preforms, both the sintered state and aged state show increased density and plateau stress as the wall thickness (180μm, 250μm) increases. In the sintered state, the increase in wall thickness leads to an increase in plateau stress (σ_pl) from 59MPa to 91MPa, but the energy absorption capacity (W) decreases from 24.1 J/g to 19.1 J/g. The H-PS sphere-prepared preforms show improved compressive properties.
Under the same wall thickness (180μm, 250μm) and heat treatment conditions, smaller hollow sphere sizes result in higher plateau stress. It is found that preform with high wall thickness (250μm) and small pores (L-PS spheres), after aging treatment at 520°C, exhibit the best compressive properties with a plateau stress (σpl) of 141MPa and an energy absorption capacity (W) of 33.9 J/g. |
