Effect Of Ga Addition On The Microstructure And Mechanical Property Of Nb-Si Alloy

In this paper, we study the influence of the Ga addition on microstructure andmechanical property of Nb-Si alloy. We study the formation of solidificationmicrostructure of Nb-Si alloy through OM, XRD and SEM. We test and compare themechanical property of arc melting alloy with different Ga addition and heattreatment through Gleeble-1500Thermal Simulator, Universal Testing Machinesand Micro Hardness Tester.The volatile components of Arc-melted Nb-16Si-xGa alloy are Si and Ga. Theevaporation rate of Ga is less than Si. Ga addition on Nb-16Si alloy is conducive tothe generation of Nbss+Nb₅Si₃eutectic. The microstructure of Nb-16Si-5Ga alloyconsists of Nbss+Nb₅Si₃eutectic. The room temperature strength and ductility isimproved with Ga addition on Nb-16Si alloy, but too much Ga will decrease theroom temperature strength. The variation of high temperature strength is similar tothe variation of room temperature strength. Too small Nb₅Si₃can not providesufficient resistance to deformation. The room temperature fracture toughness ofNb-16Si-xGa alloy increases with Ga addition. Small Nbss+Nb₅Si₃eutecticstructure is good for the fracture toughness.With the Ga addition on Nb-16Si-22Ti-2Hf-2Al-2Cr alloy, hypoeutecticcomposition is converted into hypereutectic composition. Nb₃Si is decreased andNb₅Si₃is gradually increased. The room temperature strength and ductility, hightemperature strength and room temperature fracture toughness is increased and thendecreased with Ga addition on Nb-16Si-22Ti-2Hf-2Al-2Cr alloy. Nbss+Nb₅Si₃eutectic structure is conducive to the fracture toughness. The block silicide is notconducive to the compression performance of materials at room or high temperature.The Ga causes Nb₃Si phase eutectoid transformation in Nb-16-xGa alloy at1250℃. Nbss+Nb₅Si₃eutectic provides the nucleation substrate for eutectoidtransformation. Heat treatment at1250℃for10hour enables the silicidephase ofNb-16Si-22Ti-2Hf-2Al-2Cr-xGa alloy to become smaller and round, but Nb₃Siphase eutectoid reaction does not occurs.