高强韧活塞铝合金在高温时效过程中的组织与性能演变

Evolution of Microstructure and Properties of Piston Aluminum Alloy with High Strength and Toughness During High Temperature Aging Process

为了预测新型活塞铝合金在高温工况下的服役寿命,文中以Pandat软件平衡计算相图为基础,采用布氏硬度和拉伸性能测试分析了该合金在150~500℃下时效0~100 h后的力学性能变化规律,并利用金相显微镜、扫描电子显微镜和透射电子显微镜观察了其显微组织,研究了显微组织对力学性能的影响机理。研究结果表明:该合金在150~500℃时效后的力学性能先下降后上升,350℃时力学性能最低,150℃时硬度曲线出现强化双峰;时效温度为250~500℃时,析出相θ聚集长大,导致合金的力学性能下降;当时效温度达到425℃后,基体析出大量的粒状富镍相和纳米相,导致力学性能下降幅度变小;当时效温度达到450℃后,α-Al固溶体中脱溶析出细小硅相,并聚集长大,提高了合金硬度。

In order to predict the service life of the new piston aluminum alloy during the high temperature aging process,the paper makes an analysis of the mechanical properties of the alloy after 0~100 h aging at 150~500℃by means of the balance phase diagram calculated with the Pandat software and with Brinell hardness test and tensile test.The microstructure of the alloy was observed by a metallographic optics microscope,a scanning electron microscope and a transmission electron microscope and the effect of the microstructure on its mechanical properties was studied.The results show that the mechanical properties of the alloy reduce first and then rise up after being aged at 150~500℃,and are the lowest at 350℃.The hardness curve at 150℃shows enhanced double peaks.When the aging temperature is at 250~500℃,the precipitated phaseθaggregates and grows up,leading its mechanical properties to decrease.When the aging temperature reaches 425℃,a large number of granular nickel-rich phases and nanophases precipitate out of the matrix,resulting in a decrease in its mechanical properties.When the temperature reaches 450℃,the fine silicon phase is dissolved and precipitated in theα-Al solid solution,and aggregates and grows,thus increasing the hardness of the alloy.