搅拌摩擦加工工具对镍铝青铜合金显微组织和机械性能的影响

Effect of Friction Stir Processing(FSP) Tool on Microstructures and Mechanical Properties of NiAl Bronze Alloy

目的掌握搅拌摩擦加工镍铝青铜合金的组织演变规律,获得机械性能最好的显微组织。方法基于搅拌摩擦加工热输入理论改善加工工具,采用改善前后的工具制备具有各种微观组织的镍铝青铜合金,并采用显微硬度仪测试合金的显微硬度,通过光学显微镜、扫描电子显微镜、透射电子显微镜观察加工合金的显微组织。结果搅拌摩擦加工的组织主要包括魏氏体α、带状α、溪流状α以及等轴状α组织,各组织形成的最高温度逐渐减小,其中等轴状组织具有最高的显微硬度,其微观组织主要包括大量的等轴状α晶粒、κ相和极少的β′相。结论通过减少工具轴肩直径,增加搅拌针的长度来改善加工工具,可以明显减少搅拌摩擦加工过程中的热输入。较低最高温度下制备的等轴状α组织具有最好的机械性能,其主要的强化机制为细晶强化、第二相强化和加工硬化。

The work aims to understand the law of microstructural evolution of FSPed NAB alloy and obtain the microstructures with best mechanical properties.Friction stir processing(FSP)tool was improved based on heat input theories of FSP,and FSPed NAB alloy with various microstructures were prepared by previous and improved FSP tool,respectively.Vickers microhardness of FSPed NAB alloy was tested by microhardness tester,and the microstructures were observed by optical microscope(OM),scanning electron microscope(SEM)and transmission electron microscope(TEM).The microstructures of FSPed NAB alloy were mainly Widmanstattenα,band-likeα,stream-likeαand equiaxedαmicrostructures.The peak temperature for forming the microstructures gradually decreased,and the equiaxedαmicrostructures prepared by improved tool had the best mechanical properties.The equiaxedαmicrostructure included moreαandκphases,and very fewβ′phase.The heat input during FSP can be significantly reduced by decreasing the diameter of the shaft shoulder and increasing the length of the stirring needle.The equiaxedαmicrostructure prepared at low peak temperature has the best mechanical properties,and the main strengthening mechanisms are fine grain strengthening,second phase strengthening and work hardening.