| 摘要: | 近年來，環保意識抬頭以及鋁合金本身具備優異的比強度，使得其在航太、汽車……等需要高結構性能的領域中應用越來越廣泛。然而隨著這些領域對元件形狀的需求日益複雜，傳統製造已無法滿足其要求。積層製造因其特殊的工法，能夠製作出複雜的幾何結構，逐漸成為理想的選擇，但因鋁合金在積層製造中熱裂紋以及粗大柱狀晶⋯⋯等挑戰需要克服，故本研究主要探討利用雷射粉床熔融（LPBF）技術製備7075鋁合金的微觀結構變化及熱處理對其性能的影響。
研究中使用參雜1.5 wt.%的TiC奈米顆粒7075鋁合金粉末進行LPBF製程。樣品的微觀結構顯示，添加TiC奈米顆粒可顯著細化晶粒，平均晶粒尺寸降低至1–2 μm，並成功抑制了柱狀晶的形成，有效改善了材料的力學性能顯微結構表現。
此外經過T6熱處理後，樣品的孔隙率普遍上升，從平均2.22%的孔隙率成長到平均36.84%，成因可能是由於封閉氣體的膨脹及微空隙的體積擴張所致。除了孔隙率提升，晶粒大小也變得粗大，平均約為1.54 um粗化到58.12 μm，但與未添加TiC奈米顆粒的7075鋁合金相比，TiC仍對晶粒的粗化具有一定的抑制作用，顯示出在熱處理過程中對晶粒的穩定性有所影響。另外在機械性質表現在經過熱處理後，硬度顯著提升，平均提升幅度為30%至50%。
綜上所述，本研究透過使用LPBF列印與T6熱處理後7075鋁合金微觀結構與機械性質的分析，建立了材料在積層製造下的行為特徵與機制理解。雖然孔隙增多與晶粒粗化不可避免，但材料整體性能仍具可調控潛力，為7075鋁合金未來應用於積層製程提供重要技術基石。;In recent years, with the rising environmental awareness and the excellent specific strength of aluminum alloys, their applications in high-performance structural fields such as aerospace and automotive have become increasingly widespread. However, as the demand for component shapes in these fields becomes more complex, traditional manufacturing methods can no longer meet these requirements. Additive manufacturing, with its unique process, allows for the production of complex geometric structures and has gradually become an ideal choice. Therefore, this study primarily investigates the microstructural changes of 7075 aluminum alloy fabricated using Laser Powder Bed Fusion (LPBF) technology and the impact of heat treatment on its performance.
In this study, 1.5 wt.% of TiC nanoparticles were added to the 7075 aluminum alloy powder to improve the uniformity of its microstructure and to inhibit the formation of thermal cracks during the melting process. After the LPBF process, the microstructure of the samples showed that the addition of TiC nanoparticles significantly refined the grain size, reducing the average grain size to 1–2 μm, and successfully suppressed the formation of columnar grains, which effectively improved the mechanical properties and microstructural performance of the material.
Furthermore, T6 heat treatment was applied to the samples. After heat treatment, the porosity of the samples generally increased, rising from an average of 2.22% to an average of 36.84%. This increase was likely caused by the expansion of trapped gas and the volumetric expansion of microvoids. In addition to the increased porosity, the grain size also grew significantly, from an average of 1.54 μm to 58.12 μm. However, compared to the 7075 aluminum alloy without TiC nanoparticles, the TiC still had a certain inhibitory effect on grain coarsening, indicating that TiC nanoparticles contributed to the stability of the grains during the heat treatment process. Ultimately, after heat treatment, the hardness of the 7075 aluminum alloy significantly increased, with an average increase of 30% to 50%.
The results of this study provide an effective process strategy. By adding TiC nanoparticles and applying heat treatment, the microstructure of 7075 aluminum alloy fabricated using LPBF was significantly improved, providing technical guidance and reference for the future application of aluminum alloys in additive manufacturing. |
