摘要:
为研究纳米颗粒增强铝基复合材料的高温蠕变特性, 基于6063Al-Al2(SO4)3体系, 采用超声化学原位合成技术, 制备出不同Al2O3体积分数(5%、7%)的纳米Al2O3/6063Al复合材料, 通过高温蠕变拉伸试验测试其高温蠕变性能, 利用XRD、OM、SEM及TEM分析其微观形貌。结果表明:施加高能超声可显著细化增强体颗粒并提高其分布的均匀性, 所生成的Al2O3增强颗粒以圆形或近六边形为主, 尺寸为20~100 nm;纳米Al2O3/6063Al复合材料的名义应力指数、表观激活能和门槛应力值与基体相比大幅提高, 均随着增强体体积分数的增加而提高, 表明纳米Al2O3/6063Al复合材料的抗蠕变性能提高;纳米Al2O3/6063Al复合材料的真应力指数为8, 说明复合材料蠕变机制符合微结构不变模型, 即受基体晶格扩散的控制;纳米Al2O3/6063Al复合材料的高温蠕变断口特征以脆性断裂为主, 高应力下形成穿晶断裂, 低应力下形成沿晶断裂和晶界孔洞;纳米Al2O3/6063Al复合材料的主要强化机制为位错强化与弥散强化。
Abstract:
In order to investigate the high temperature creep properties of nanoparticle reinforced aluminum matrix composites, the nano Al2O3/6063Al composites with different Al2O3 volume fractions (5%, 7%) were fabricated by in-situ synthesis technology via 6063Al-Al2(SO4)3 system assisted by ultrasonic chemistry. The high temperature creep tensile test was used to test the high temperature creep property of the prepared composites. XRD, OM, SEM and TEM were used to analyze micromorphology of the composites. The results show that with the help of the high-intensity ultrasoniy, the prepared Al2O3 reinforced particles mainly exhibit spherical or nearly hexagon shape with the size range from 20 to 100 nm, where the size refinement and dispersion uniformity of reinforced particles are elevated significantly. The apparent stress exponent, apparent activation energy and threshold stress value of nano Al2O3/6063Al composites increase gradually with the volume fraction increasing of reinforcement, and greatly compared with those of the corresponding matrix. The nano Al2O3/6063Al composites exhibit a significant improvement in creep resistance. The true stress exponent of nano Al2O3/6063Al composites is 8 and indicates that the creep mechanism of composites is in accordant to the substructure invariant model, i.e., controlled by the lattice diffusion. The high temperature fracture surface morphology of the nano Al2O3/6063Al composites indicates a brittle fracture of the composite and exhibits transcrystalline fracture under high stress condition, intergranular fracture and voids at grain boundary under low stress condition. The main strengthening mechanisms of nano Al2O3/6063 Al composites are dislocation strengthening and dispersion strengthening.
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