Solidification cracking (SC) of 2024 high-strength aluminium alloy during fusion welding or additive manufacturing has been a long-term issue. In this work, crack-free weld could be obtained using a Zr-core-Al-shell wire (ZCASW filler material, a novel filler) coupled with an oscillating laser-arc hybrid welding process, and we investigated the solidification cracking susceptibility (SCS) and cracking behavior of AA2024 weld fabricated with different filler materials. The cracking inhibition mechanism of the weld fabricated with ZCASW filler material was elucidated by combined experiments and phase-field simulation. The results show that the effectiveness of filler materials in reducing the SC gradually improves in the order of ER2319 filler material < ER4043 filler material < ZCASW filler material. The main cracking (when using the ER2319 filler material) branches and the micro cracking branches interact with each other to produce cracking coalescence, which aggravates the cracking propagation. The formation of the Al3Zr phase (when using the ZCASW filler material) promotes heterogeneous nucleation of α-Al, thereby resulting in finer and equiaxed non-dendrite structures, which shortens the liquid phase channels and decreases cracking susceptibility index |dT/d(fs)1/2| (T is temperature and fs is solidification fraction) at final solidification. A higher proportion (7.65 % area fraction) of inter-dendrite phase with spherical distribution state, a shorter (8.6 mm liquid channel length) inter-dendrite phase coupled with round non-dendrite structure (6 µm dendrite size) effectively inhibit the SC. The present study can be a useful database for welding and additive manufacturing of AA2024.

中文翻译：

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基于 Zr-core-Al-shell 线材的 2024 Al 合金在振荡激光-电弧混合焊接过程中的凝固开裂抑制机制


2024 高强度铝合金在熔焊或增材制造过程中的凝固开裂 （SC） 一直是一个长期问题。在这项工作中，使用 Zr-core-Al-shell 线（ZCASW 填充材料，一种新型填充材料）结合振荡激光-电弧混合焊接工艺可以获得无裂纹焊缝，我们研究了用不同填充材料制造的 AA2024 焊缝的凝固开裂敏感性 （SCS） 和开裂行为。通过结合实验和相场模拟，阐明了 ZCASW 填充材料焊缝的开裂抑制机制。结果表明，填充材料降低SC的有效性依次为ER2319填充材料< ER4043填充材料< ZCASW填充材料。主开裂（使用 ER2319 填充材料时）支枝和微开裂支枝相互相互作用产生开裂聚结，从而加剧开裂扩展。Al3Zr 相的形成（当使用 ZCASW 填充材料时）促进了 α-Al 的异质成核，从而产生更细和等轴的非枝晶结构，从而缩短了液相通道并降低了开裂敏感性指数 |dT/d（fs）1/2|（T 是温度，fs 是凝固分数）。具有球形分布状态的较高比例（7.65% 面积分数）的枝晶间相、较短（8.6 mm 液道长度）的枝晶间相与圆形非枝晶结构（6 μm 枝晶尺寸）相结合，可有效抑制 SC。本研究可为 AA2024 的焊接和增材制造提供有用的数据库。