工艺参数对铝合金摩擦挤压增材组织及性能的影响

采用6061-T651铝合金圆棒进行摩擦挤压增材制造(friction extrusion additive manufacturing,FEAM)工艺实验研究,探讨和分析不同主轴转速对单道双层增材试样的增材成形、组织特征和力学性能的影响规律。结果表明:对给定横向移动速度300 mm/min,采用主轴转速为600 r/min和800 r/min均能获得完全致密无任何内部缺陷、厚度分别为2 mm和4 mm的单道双层增材试样,增材整体由细小等轴晶粒组成,增材层间实现冶金连接;800 r/min下工具轴肩的摩擦挤压作用降低,增材层间结合界面呈平直状,塑化金属流动不充分,沉积层宽度较窄、表面成形更粗糙;600 r/min下结合界面经历的塑性变形和热循环更为显著,晶粒细化至6.0μm,但增材界面区软化程度较严重,硬度仅为增材棒料母材的52.7%~56.2%,而800 r/min下界面区的硬度能够达到母材的56.0%~61.3%;在600 r/min和800 r/min下,增材试样均具有优良的综合力学性能,抗拉强度分别达到增材棒料母材6061-T651的66%和70%,而断后伸长率明显较高,分别为母材的212%和169%;与目前其他增材工艺力学性能比较均具有明显的优势。

Effects of process parameters on microstructure and properties of aluminum alloy fabricated by friction extrusion additive manufacturing

The friction extrusion additive manufacturing (FEAM) process of aluminum 6061-T651 cylindrical bar was successfully achieved by using independently developed solid-state friction extrusion additive equipment. The forming characteristics, microstructure features and mechanical properties of the final specimen obtained under different rotational speeds were comparatively analysed and discussed. The results show that for a given transverse movement speed of 300 mm/min, a fully dense single-channel double-layer specimen with thickness of 2 mm and 4 mm without any internal defects can be obtained by using the rotational speed of 600 r/min and 800 r/min respectively. The final specimen achieved under the higher rotational speed presents a flat interface, a narrower deposition layer, and a rougher surface because the effects of friction and extrusion experienced by the rotational shoulder are weakened during the deposition process. The plastic deformation and thermal cycle experienced by the bonding interface under 600 r/min are more significant than those under 800 r/min, and the grains are refined to 6.0 μm. The softening degree of the interface obtained under 600 r/min is more serious, and the hardness in this region is only 52.7%-56.2% of the value of the as-received feed rod, while this value can reach 56.0%-61.3% of the hardness of the base material. The final specimen attains a good comprehensive mechanical property. The ultimate tensile strength of the final specimen obtained under rotational speeds of 600 and 800 r/min can reach 66% and 70% of the value of the as-received feed rod respectively, while the percentage elongation after the break can reach 212% and 169% of the value of the base material respectively. The tensile properties of 6061 aluminum alloy prepared in this paper have obvious advantages compared with those of other Al-Mg-Si alloys fabricated by other well-developed additive manufacturing processes.