Abstract

In this work, we study the influence of the local porosity in isotropic reactive cast particulate reinforced metal–matrix composites on the statistical amplitude distribution of backscattered broadband pulses of longitudinal ultrasonic waves. A special laser optoacoustic transducer is employed for this purpose, which makes it possible to achieve laser excitation and piezoelectric detection of ultrasound by one-side access to a sample or product. Two series of in-situ reactive cast aluminum–matrix composites were studied: reinforced solely with the Al₃Ti intermetallic particles (volumetric contents 0.04–0.115) and with combination of Al₃Ti and synthetic diamond nanoparticles (volumetric content 0.002). The last accelerate reactive synthesis of Al₃Ti particles and lead to modification of their shape and sizes. For both series of composites, the amplitude distribution of backscattered ultrasonic pulses has been approximated with the Gaussian probability distribution applicable for statistics of large number of independent random variables. The empirical dependence of the half-width of this distribution on the local porosity in composites of two series has been fitted by the same function close to the linear one regardless the size and content of reinforcing particles. This functional relationship can be used for quantitative evaluation of the local porosity of the composite material both at its manufacturing stage and during service of composite parts and products.

中文翻译：

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孔隙率对活性铸造金属基复合材料中反向散射超声脉冲统计振幅分布的影响

摘要

在这项工作中，我们研究了各向同性反应铸造颗粒增强金属基复合材料中局部孔隙率对纵向超声波的后向散射宽带脉冲的统计幅度分布的影响。为此，使用了特殊的激光光声换能器，这使得可以通过单侧访问样品或产品来实现超声的激光激发和压电检测。研究了两个系列的原位反应铸铝-基体复合材料：仅用Al ₃ Ti金属间化合物颗粒（体积含量为0.04-0.115）增强，并使用Al ₃ Ti和合成金刚石纳米颗粒（体积含量为0.002）进行增强。最后加速反应合成Al ₃钛颗粒并导致其形状和尺寸的改变。对于这两个系列的复合材料，已经使用适用于大量独立随机变量统计的高斯概率分布来近似估算了反向散射超声脉冲的幅度分布。无论增强颗粒的大小和含量如何，两个分布的复合材料中这种分布的半宽度对局部孔隙率的经验依赖性已通过接近线性线性的相同函数拟合。这种功能关系可用于在复合材料的制造阶段以及在复合零件和产品的维修期间定量评估复合材料的局部孔隙率。