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In-situ formation of particle reinforced Aluminium matrix composites by laser powder bed fusion of Fe2O3/AlSi12 powder mixture using laser melting/remelting strategy
Journal of Materials Processing Technology ( IF 6.3 ) Pub Date : 2021-09-08 , DOI: 10.1016/j.jmatprotec.2021.117357
Qimin Shi 1, 2 , Raya Mertens 1 , Sasan Dadbakhsh 1, 3 , Guichuan Li 4 , Shoufeng Yang 1, 5
Affiliation  

In-situ preparation of particle reinforced Al matrix composites (PRAMCs) by laser powder bed fusion (LPBF) is a promising strategy to strengthen Al-based alloys. The laser-driven thermite reaction can be a practical mechanism to in-situ synthesise PRAMCs. However, the introduction of elements oxygen by adding Fe2O3 makes the powder mixture highly sensitive to form porosity and Al2O3 film during LPBF, bringing challenges to prepare dense materials. This work develops an LPBF processing strategy combined with consecutive high-energy laser melting scanning and low-energy laser remelting scanning to prepare dense PRAMCs from Fe2O3/AlSi12 powder mixture. A high relative density (98.2 ± 0.55 %) was successfully obtained by optimising laser melting (Emelting) and remelting energy density (Eremelting) to Emelting = 35 J/mm2 and Eremelting = 5 J/mm2. Results reveal the necessity to increase Emelting to improve metal liquid’s spreading/wetting by breaking up Al2O3 films surrounding molten pools; however, the high-energy laser melting produced much porosity. Low-energy laser remelting could close the resulting internal pores, backfill open gaps and smoothen solidified surfaces. Although with two-times laser scanning, the microstructure still shows fine cellular Si networks with Al grains inside (grain size 370 nm) and in-situ nano-precipitates (Al2O3, Si and Al-Fe(-Si) intermetallics). Finally, the fine microstructure, nano-structured dispersion strengthening and high-level densification strengthen the prepared in-situ PRAMCs, reaching yield strength of 426 ± 4 MPa and tensile strength of 473 ± 6 MPa. Furthermore, the results can provide valuable information to process other powder mixtures with severe porosity/oxide-film formation potential considering the evidenced contribution of laser melting/remelting strategy to densify material and obtain good mechanical properties during LPBF.



中文翻译:

使用激光熔化/重熔策略,通过激光粉末床熔化 Fe2O3/AlSi12 粉末混合物原位形成颗粒增强铝基复合材料

通过激光粉末床融合(LPBF)原位制备颗粒增强铝基复合材料(PRAMCs)是增强铝基合金的一种很有前景的策略。激光驱动的铝热反应可以成为原位合成 PRAMC 的实用机制。然而,通过添加Fe 2 O 3引入元素氧使得粉末混合物在LPBF过程中对形成孔隙和Al 2 O 3薄膜高度敏感,给制备致密材料带来挑战。这项工作开发了一种 LPBF 处理策略,结合连续的高能激光熔化扫描和低能激光重熔扫描,从 Fe 2 O 3制备致密的 PRAMCs/AlSi12 粉末混合物。通过将激光熔化(E熔化)和重熔能量密度(E重熔)优化为E熔化= 35 J/mm 2E重熔= 5 J/mm 2,成功获得了高相对密度 (98.2 ± 0.55%) 。结果表明有必要通过分解 Al 2 O 3来增加E熔化以改善金属液体的铺展/润湿围绕熔池的薄膜;然而,高能激光熔化产生了很多孔隙。低能激光重熔可以关闭由此产生的内部孔隙,回填开放的间隙并平滑凝固的表面。尽管进行了两次激光扫描,微观结构仍然显示出精细的蜂窝状硅网络,内部有 Al 晶粒(晶粒尺寸 370 nm)和原位纳米沉淀物(Al 2 O 3、Si 和 Al-Fe(-Si) 金属间化合物)。最后,精细的微观结构、纳米结构的弥散强化和高水平的致密化增强了制备的原位 PRAMC,屈服强度达到 426±4 MPa,拉伸强度达到 473±6 MPa。此外,考虑到激光熔化/重熔策略对在 LPBF 过程中致密化材料和获得良好机械性能的明显贡献,结果可以为处理具有严重孔隙率/氧化膜形成潜力的其他粉末混合物提供有价值的信息。

更新日期:2021-09-12
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