Mechanical behavior and strengthening mechanisms in ultrafine grain precipitation-strengthened aluminum alloy
Mechanical behavior and strengthening mechanisms in ultrafine grain precipitation-strengthened aluminum alloy
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DOI：
10.1016/j.actamat.2013.09.042
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发表时间：
2014-01-01
期刊：
影响因子：
9.4
通讯作者：
Schoenung, Julie M.
中科院分区：
文献类型：
--
作者：
Ma, Kaka;Wen, Haiming;Schoenung, Julie M.
为了深入了解复杂的沉淀强化合金体系中析出现象、晶粒度和力学行为之间的关系，本研究选择常用的铝合金Al 7075合金作为模型体系。采用低温球磨、脱气、热等静压、挤压、热处理等工艺制备了超细晶(UFG)块体材料。分析了材料的力学性能和显微组织，并直接与粗晶(CG)材料进行了比较。利用三维原子探针层析技术研究了挤压UFG材料中金属间化合物和氧化物分散体的形成。在每个相同的条件下，UFG 7075表现出比CG 7075合金更高的强度。经T6回火后，UFG7075的屈服强度(YS)和极限抗拉强度(UTS)分别达到了734和774 Mpa，比CG等效件提高了120 Mpa。挤压态UFG 7075的强度(YS：583 Mpa，UTS：631 Mpa)甚至高于商用7075-T6。更重要的是，首次定量地建立了这一复杂的沉淀强化体系在每种材料中的强化机制，考虑了晶界、位错、固溶、析出和氧化物弥散强化的贡献。挤压态UFG-T6和UFG-T6的强度增量分别为472和414 Mpa，晶界强化是主要机制，强度增量估计为242 Mpa。(C)2013 Acta Materialia Inc.由Elsevier Ltd.出版。保留所有权利。
To provide insight into the relationships between precipitation phenomena, grain size and mechanical behavior in a complex precipitation-strengthened alloy system, Al 7075 alloy, a commonly used aluminum alloy, was selected as a model system in the present study. Ultrafine-grained (UFG) bulk materials were fabricated through cryomilling, degassing, hot isostatic pressing and extrusion, followed by a subsequent heat treatment. The mechanical behavior and microstructure of the materials were analyzed and compared directly to the coarse-grained (CG) counterpart. Three-dimensional atom-probe tomography was utilized to investigate the intermetallic precipitates and oxide dispersoids formed in the as-extruded UFG material. UFG 7075 exhibits higher strength than the CG 7075 alloy for each equivalent condition. After a T6 temper, the yield strength (YS) and ultimate tensile strength (UTS) of UFG 7075 achieved 734 and 774 MPa, respectively, which are similar to 120 MPa higher than those of the CG equivalent. The strength of as-extruded UFG 7075 (YS: 583 MPa, UTS: 631 MPa) is even higher than that of commercial 7075-T6. More importantly, the strengthening mechanisms in each material were established quantitatively for the first time for this complex precipitation-strengthened system, accounting for grain-boundary, dislocation, solid-solution, precipitation and oxide dispersoid strengthening contributions. Grain-boundary strengthening was the predominant mechanism in as-extruded UFG 7075, contributing a strength increment estimated to be 242 MPa, whereas Orowan precipitation strengthening was predominant in the as-extruded CG 7075 (similar to 102 MPa) and in the T6-tempered materials, and was estimated to contribute 472 and 414 MPa for CG-T6 and UFG-T6, respectively. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.