软相尺寸对反贝壳复合材料压缩性能的影响

Effect of Soft Phase Size on Compressive Properties of Inverse Nacre Nanocomposites

文章采用一步球磨结合真空热压工艺制备了由Al_(2)O_(3)/Al纳米复合材料(硬相)和纯铝(软相)构成的反贝壳结构复合材料,研究了软相尺寸(从微米级到亚微米级)对复合材料压缩性能的影响,并对其变形失效机制进行了分析。结果表明:在保持高失效应变的前提下,抗压强度随软相尺寸的减小而逐渐提高,尤其是从微米级减小到亚微米级时,抗压强度达到494 MPa,比微米级时至少提高60%;当软相尺寸为微米级时,复合材料中的裂纹萌生于软硬相界面处,并沿着界面-硬相-软相扩展,最终形成沿着与加载方向呈45°的宏观主裂纹。同时,软相可有效阻挡二次裂纹的扩展,当软相尺寸减小到亚微米级别时,裂纹萌生于软相变形带附近并沿着变形带-硬相扩展,逐渐演变成与加载方向呈±45°的均匀分散于整个复合材料的微裂纹,即软相尺寸从微米级减小到亚微米级时,增韧机制由软相对裂纹的阻挡转变为微裂纹的增殖和均匀分散。该研究结果为制备高强韧铝基复合材料提供重要参考价值。

The inverse nacre composites composed of Al_(2)O_(3)/Al nanocomposite(hard phase)and pure Al(soft phase)are prepared by one-step ball milling and vacuum hot pressing.Influence of the soft phase size ranging from ten microns to sub-microns on the compressive properties of the resulting composites is studied,and their failure mechanism is analyzed.The results show that with the decrease of soft phase size,the compressive strength increases gradually accompanying with high failure strain,in particular when the soft phase size is reduced from micro-scale to submicro-scale,the compressive strength reaches 494 MPa,increasing by 60%by comparison with that of the composite with micro-scale soft phase.For the composites with micron-scale soft phase,the cracks originate from the interface between the soft and the hard phases and propagate along the interface-hard phase-soft phase,finally the macro crack at an angel of 45 degrees to the compressive axis is formed.The soft phase blocks the propagation of the secondary cracks.When the soft phase is reduced to submicron level,the cracks are initiated near the deformation band and propagate along the deformation band-hard phase,then gradually develop into microcracks having angles about 45 degrees or-45 degrees with the compressive axis and spreading throughout the composite.This means that when the soft phase size reduces from micro to submicro scale,the toughness mechanism changes from the blocking of the soft phase on the crack propagation to the multiplication and even distribution of the microcracks.The research results provide important reference value for the preparation of high strength and toughness aluminum matrix composites.