An Investigation on the Effect of Heat Treatment on the Compression Behavior of Aluminum Matrix Syntactic Foam Fabricated by Sandwich Infiltration Casting

Abstract In this research, syntactic foams including Al-7075 matrix and 2-4 mm low-cost pumice particles were manufactured via a novel casting method called as sandwich infiltration. According to physical evaluations, thanks to extremely porous structure of pumice, density values of the fabricated foams varied between 1.42 and 1.61 g/cm3. Porosity values were between 40.62% and 47.39%. Microstructural observations showed that there was a perfect infiltration between Al matrix and pumice particles because of correct process optimization (process pressure of 0.1 MPa, matrix melting temperature of 720°C and filler pre-temperature of 500°C). Furthermore, T6 treatment was applied to samples to comprehend effect of the aging on mechanical properties. The results indicated that there was an affirmative relation between the heat treatment and quasi-static compressive properties of the fabricated foams. The highest compressive strength, plateau stress and energy absorption values were measured as 64.4 MPa, 74.3 MPa and 34 MJ/m3 for heat treated samples. It was also observed that although the highest energy efficiency of 0.89 was calculated for heat treated sample, there was no relation between the heat treatment and efficiency. As for failure modes, as-cast samples exhibited ductile barreling characteristic whereas T6 treated foams indicated brittle v-shape fracture.

摘要 本研究采用一种名为夹层渗透法（sandwich infiltration）的新型铸造工艺，制备了以Al-7075铝合金为基体、2~4 mm低成本浮石颗粒为填料的复合泡沫材料（syntactic foam）。经物理性能表征可知，得益于浮石本身的高孔隙结构，所制备泡沫材料的密度区间为1.42~1.61 g/cm³，孔隙率介于40.62%~47.39%之间。显微组织观察结果显示，通过优化工艺参数（工艺压力0.1 MPa、基体熔化温度720℃、填料预热温度500℃），Al基体与浮石颗粒之间实现了完美的渗透结合。此外，为探究时效处理对材料力学性能的影响，本研究对试样实施了T6热处理。结果表明，热处理与所制备泡沫材料的准静态压缩性能呈显著正相关关系。经热处理的试样，其最高抗压强度、平台应力与吸能量分别可达64.4 MPa、74.3 MPa和34 MJ/m³。研究同时发现，尽管经热处理试样的能量效率最高可达到0.89，但热处理与能量效率之间并未存在显著关联。就失效模式而言，铸态试样表现出韧性鼓胀特征，而经T6处理的泡沫材料则呈现脆性V形断裂。