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）方法与快速凝固（RS）技术相结合，因其可以改善高温力学性能和低密度高模量而受到广泛关注。然而，铝带表面固有地呈现出一层氧化层，当铝带在固结和热加工过程中不完全破裂或不均匀分布时，氧化层会对粉末冶金产品的机械性能和延展性产生不利影响。本研究的目的是阐明两种合金，一种是Al-Cr-Zr合金，另一种是Li含量高于普通I/M合金的Al-Li-Zr合金，其表面氧化层在热固结和挤压过程中的行为。在溅射淬火技术中，将熔滴注入两种大气中，一种是实验室空气，另一种是干燥氩气，以改变氧化和水化的程度。通过光学、透射和扫描电子显微镜、选定区域电子衍射和x射线等手段，研究了这些带在溅射和热处理条件下的微观结构。将带材在真空中进行热压生产坯料，热压后的坯料按1:20或1:18的挤出比例进行热挤压制成线材。在热压坯料中，氧化层仍然保留在先前的带边界区域，经过热挤压后，氧化层被分解成薄膜碎片。Al-Cr-Zr合金与Al-Li-Zr合金的塑性差异较大。在Al-Cr-Zr合金的情况下，通过充分的热挤压可以提高延展性，但对于Al-Li-Zr合金则不是这样，因为它可能需要完全避免氧化表面层的形成。

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.