Effect Of Composite Modifiers On Microstructure And Mechanical Properties Of Al-7Si Alloy

Hypoeutectic Al-Si alloy has high specific strength,excellent casting performance,tuning performance,processing performance,and good wear resistance and corrosion resistance,and the price is relatively low,in the fields of aerospace,rail transit,automobile manufacturing,etc.is widely used.However,in the structure of the as-cast hypoeutectic Al-Si alloy,coarse needle-like eutectic Si severely reduces the mechanical properties of the alloy.In order to improve the strength and volume of the Al-Si alloy,the rare earth element Y in the Si phase must be compounded with the Al-5Ti-1B refiner and the two alloying elements of Mn and Ni,respectively.The influence of the size,morphology and distribution of eutectic Si in crystalline Al-7Si alloy improves the strength and strength of the alloy by modifying the Si phase,and explores the modification mechanism of the composite modification on the Si phase,thus the following views:(1)Y/Al-5Ti-1B composite modifier modifies the long needle-like eutectic Si in Al-7Si alloy into uniform and fine particles,the tensile strength is increased from 168.1MPa to 209.1MPa,and the elongation is increased from 6.32% To 9.02%.(2)The addition of Mn element changes the eutectic Si in the Al-7Si alloy into small flaky and massive shapes,and the strength and toughness of the alloy are improved to a certain extent.(3)The Y/Mn composite modifier modifies the eutectic Si in Al-7Si into uniform and fine fibrous form,the tensile strength is increased to 207.3MPa,and the elongation is increased to 11.20%.(4)After adding 1.5% of Ni element,the eutectic Si in Al-7Si alloy is modified into plate and short rods,and the mechanical properties of the alloy are slightly improved.(5)The Y/Ni composite modifier modifies the eutectic Si in Al-7Si into uniform and fine fibrous shape,the tensile strength is increased to 217.8MPa,and the elongation is increased to 10.84%.