Study on the Behavior of a Surface Oxide Layer during hot Consolidation and Extrusion of Splat-Quenched Aluminum Alloy Tapes.

近年来，粉末冶金(P/M)技术与快速凝固(RS)技术相结合，既能提高材料的高温力学性能，又能提高材料的低密度-高模数，近年来受到了广泛的关注。然而，铝带在凝固和热加工过程中，当不完全破碎或分布不均匀时，铝带表面会产生氧化层，从而影响粉末冶金制品的力学性能，特别是延展性。本研究的目的是阐明铝铬锆合金和铝锂锆两种快淬态合金在热固结和挤压过程中表面氧化层的行为，一种是铝铬锆合金，另一种是锂含量高于普通I/M合金的铝锂合金。一种是实验室空气，另一种是干式Ar，以改变氧化和水合程度。用光学显微镜、透射电子显微镜、扫描电子显微镜、选区电子衍射仪和X射线衍射仪等手段对这些带材在真空中进行热压，然后以1：20或1：18的挤压比热挤压制成线材。这些带材在真空中热挤压后，氧化层仍然残留在原有的带材边界区域，热挤压后，氧化层被分解成薄膜碎片。在热压坯料中，氧化层仍然留在原有的带材边界区域，热挤压后，氧化层被分解成薄膜碎片。结果表明，Al-Cr-Zr和Al-Li-Zr合金的塑性有很大的不同，在Al-Cr-Zr合金中，充分的热挤压可以提高塑性，但对于Al-Li-Zr合金则不是这样，因为它可能需要完全避免表面氧化物的形成。

In recent years, a powder metallurgy (P/M) method combined with rapid solidification (RS) techniques have attracted considerable attention, because this process could improve elevated temperature mechanical properties and also low density-high modulus. However, aluminum tapes inherently exhibit a surface oxide layer, which affects detrimentally mechanical properties and particularly ductility of P/M products when incompletely broken up or nonuniformly distributed during consolidations and hot working.The object of this study is to clarify the behavior of surface oxide layer during hot consolidation and extrusion of splat-quenched two kinds of alloys, one is Al-Cr-Zr alloys and the other is Al-Li-Zr containing higher concentration of Li than that in an ordinary I/M alloy.In splat-quenching techniques, molten droplets were injected into two kinds of atomospheres, one is experimental laboratory air and the other is dry argon to change the degree of oxidation and hydration.The microstructures of these tapes in the conditions of as-splat as well as heat treated by means of optical, transmission and scanning electron microscopy, selected area electron diffraction and X-ray.The tapes were hot pressed in a vacuum to produce billete, and hot pressed billete were subsequently hot extruded to make wires by extrusion ratio 1 : 20 or 1 : 18.In the hot pressed billets , oxide layers still remains on the prior tape boundary area, and after hot extrusion, the oxide layer were broken up into film fragments.However, the ductility was concluded to be quite different between Al-Cr-Zr and Al-Li-Zr alloys.In the case of Al-Cr-Zr alloys, the ductility was improved by the sufficient hot extrusion, but it was not the case for Al-Li-Zr where it may be necessary to avoid completely a formation of oxide surface layers.