激光沉积Ti60A钛合金的循环热暴露显微组织演变(英文)

Microstructure evolution of laser deposited Ti60A titanium alloy during cyclic thermal exposure

在激光沉积Ti60A合金片状试样(40 mm×12 mm×3 mm)上进行一系列的循环热暴露模拟实验,每个循环包括红外加热120 s至最高800℃,随后压缩空冷60 s至最低150℃。采用OM、SEM及EDS分析了合金α相体积分数和β相长度,并测试其显微硬度随热暴露循环次数的变化。结果表明,随着热暴露循环次数的增加,激光沉积Ti60A合金从初始的网篮状β相和体积分数为78.5%的α相逐渐向楔形β相和粗大α相过渡,750次循环后转变为极少量颗粒状β相和体积分数为97.6%的大块α组织。讨论了特殊粗大α和破碎β组织的形成机理。经750次热暴露循环后的合金最硬,其显微硬度比沉积态的高33.3%。

Cyclic thermal exposure tests of infrared heating to 800 ℃ in 120 s followed by compressed air cooling to 150 ℃ in 60 s were performed for the laser deposited Ti60A （Ti5.54Al3.38Sn3.34Zr0.37Mo0.46Si） alloy. The effects of thermal exposure cycles on length ofβphase, area fraction ofαphase and microhardness of alloy were examined by OM, SEM and EDS. The results indicate that thermal exposure cycles have significant effects on length ofβphase, area fraction ofαphase and microhardness of the alloy. The original fine basket-weaveβand 78.5%αtransform to transient wedge-likeβ, finally leaving granularβand 97.6%coarsenedαwith the increased thermal exposure cycles. The formation mechanism of coarsenedαand broken-upβmicrostructure is discussed. The alloy after 750 thermal exposure cycles has the maximum microhardness, 33.3%higher than that of the as-deposited alloy.