Effect Of Y And V Elements On Hot Cracking Tendency Of Al-Cu-Mg Alloy

Al-Cu alloys are widely used because of their high plasticity,tensile strength,fatigue strength and heat resistance.However,Al-Cu alloys have wide crystallization range and mushy solidification,which make the hot cracking tendency serious.In this paper,the effect of Y and V content?0-0.25wt.%?on the hot cracking susceptibility of Al-4.4Cu-1.5Mg-0.15Zr alloy was studied.In the experiment,the samples were prepared by equal length metal mold.The prepared samples were analyzed by X-ray fluorescence.Based on the observation of cracks in hot cracking samples,the macro hot cracking sensitivity coefficient was calculated.The microstructure and grain size of the alloy were analyzed by Zeiss metallographic microscope.The phase composition of the alloy and the microstructure of the crack were observed and analyzed by electron probe and scanning electron microscope.The temperature of the alloy during solidification was measured by thermocouple,and the hot cracking tendency was predicted by Newton thermal analysis and Clyne-Davies model.The results show that the sensitivity coefficient of hot cracking is the smallest and the minimum average grain size of Al-4.4Cu-1.5Mg-0.15Zr alloy is 64.2±5?m and 71.2±5?m when the amount of Y element and V element is 0.15wt%and 0.20wt%.According to the analysis results of XRD and TEM,the addition of Y element can form Al₆Cu₆Y phase,which can produce the effect of feeding on the hot cracking.A small amount of V element will form Al₁₁V phase in the grain boundary to promote grain refinement and the formation of low melting point phase between grains,while excessive V element will gather at the grain boundary to intensify the hot cracking of the alloy.The addition of Y and V elements can refine the grain size of the alloy,prevent the expansion of hot cracks,and increase the number of low-melting phases between the alloy grains,increase the feeding capacity and thereby improve the hot cracking tendency of the alloy.Y element is more effective than V element in improving the hot cracking resistance of Al-4.4Cu-1.5Mg-0.15Zr alloy.