SiC_P/6061 Al合金复合材料的高温单轴棘轮行为及其时间相关特性

Uniaxial ratcheting of SiC_P/6061Al alloy composites and its time-dependence at high temperature

对T6热处理后的SiCP/6061Al合金复合材料的高温(300℃)单轴应变循环特性和棘轮行为进行了实验研究,讨论了具有两种颗粒体积分数的复合材料在高温下不同加载条件时的循环软/硬化特性和棘轮行为特征。实验研究表明:颗粒增强金属基复合材料宏观上表现出与金属材料相类似的应变循环特性和棘轮变形规律,即复合材料在非对称应力循环下也将产生一定的棘轮变形,并随应力幅值和平均应力的增加而增加;颗粒的引入使复合材料抵抗棘轮变形的能力增强,棘轮变形随颗粒体积分数的升高而下降;在高温下棘轮行为体现出明显的时间相关特性,即棘轮应变值明显依赖于加载率和峰值保持时间,并具有明显的蠕变-棘轮交互作用。在对该类复合材料的棘轮行为进行本构描述时必须考虑复合材料的微结构特征、加载条件以及时间效应等的影响。

The uniaxial strain cyclic characteristics and ratcheting behavior of T6-treated SiCp/6061Al alloy composites were experimentally studied at high temperature （300℃）. The cyclic softening/hardening feature and ratchering behavior of the composites containing two kinds of particulate volume fractions were discussed under different loading conditions at high temperature. It is shown that the particulate reinforced metal matrix composites show similar strain cyclic characteristics and ratcheting behavior to those of metals on a macro-scale. Namely, the ratchering also occurs in the composites under asymmetrical cyclic stressing, and the ratcheting strain increases with the increase of the stress amplitude and mean stress; however, the addition of SiC particulates into the matrix increases the resistance of the composites to ratcheting, and the ratcheting strain decreases with the increase of the volume fraction of SiC particulates; at 300℃, the ratcheting has great time-dependence, i. e. , the ratcheting strain depends greatly on the stressing rate and hold-time at peak stress, and an interaction of creep and ratcheting is remarkable. The effects of microstructure features of the composite, loading condition and time on the ratcheting should be well considered when trying to construct a constitutive model to describe such ratcheting.