Direct Forming of 3-D Sandwich Parts by Fused Deposition Method Using Double Nozzle

利用熔融旋压沉积法中熔融和凝固的特征凝固顺序，结合材料熔点的差异，可实现由不同金属材料组成的夹芯件的直接成形，无需进行粘接热处理。本文作为FSD方法的一个应用，利用双喷嘴型FSD装置，研究了由内外金属材料组成的双相管件的直接成形条件。采用Al-4mass%Cu合金和Cu-20mass%Sn合金作为双相管铸件的内、外材料。铝铜合金熔体堆积形成外管后，铜锡合金熔体沉积在与外管侧面接触的铝铜合金管内。改变内外管开始沉积的时间间隔t，利用OM、SEM和TEM观察了纵截面上的微观组织。对于较小的Δt，低熔点的外管发生熔化，对于较大的Δt，观察到内外管之间的界面结合不足。在适当的时间间隔Δt=196s的情况下，实现了完全的界面结合和双管成形，其中在管的外侧和内侧观察到两个界面。在Al-Cu-Sn三元相图中，界面附近的微观结构由复杂的相组成。结果表明，采用双喷嘴FSD法，在不进行粘接热处理的情况下，在内外管开始沉积之间设置适当的时间间隔，可以实现直接成形。

By applying a characteristic solidification sequence of melting and solidification in the Fused Spinning Deposition method and the difference in melting point of materials, direct forming of sandwich parts consisting of different metallic materials is expected to be available without bonding heat-treatment. In the present work, as an application of the FSD method, the conditions for direct forming of duplex tube castings consisting of inner and outer metallic materials were examined using a double nozzle type FSD apparatus. Al-4mass%Cu alloy and Cu-20mass%Sn alloy were used as outer and inner materials of duplex tube castings. After piling up the Al-Cu alloy melt to form the outer tube, the Cu-Sn alloy melt was deposited inside the Al-Cu alloy tube in contact with the side surface of the outer tube. Changing the time interval t between the start of deposition of outer and inner tubes, the microstructures on the vertical section were observed using OM, SEM and TEM. For smaller Δt, melting-down of the outer tube with low melting point occurred and, for greater Δt, insufficient interface bonding between the outer and inner tubes was observed. In the case of an adequate time interval, Δt=196s, complete interface bonding and duplex tube shaping were achieved, where two interfaces were observed on the outer and inner tube sides. The microstructures near the interfaces consisted of complex phases appeared in the Al-Cu-Sn ternary phase diagram. It was demonstrated from the results obtained that direct forming is possible by setting a suitable time interval between the start of deposition of outer and inner tubes without bonding heat-treatment by the FSD method using double nozzles.