Microstracture And Properties Of AlSi5Cu1Mg Alloy With Rare Earth And Laser Cladding

In this paper,AlSi5Cu1Mg alloy was modified with different content of rare earth La,and cast into AlSi5Cu1Mg+x La?x=0,0.3 0.6 0.9wt.%?alloy.Then,the microstructure,hardness,tensile properties and corrosion behavior of AlSi5Cu1Mg+x La alloy were tested.Subsequently,Ni60+20wt.%WC powder was laser-clad on the surface of the AlSi5Cu1Mg substrate at different laser scanning rates?150mm/min,200mm/min,250mm/min,300mm/min?.Then,the microstructure,hardness and corrosion behavior of cladding layers at different scanning rates were tested.The results show that the microstructure of AlSi5Cu1Mg+xLa alloy changes from coarse to fine as the La content increases from 0 to 0.9wt.%.When the content of rare earth La is increased to 0.6wt.%,the hardness value of AlSi5Cu1Mg+0.6La alloy is97.1HV?the maximum hardness in the test group?.The hardness of the AlSi5Cu1Mg matrix is increased by 23.2%.Furthermore,the tensile strength of AlSi5Cu1Mg+0.6La alloy is 224.13MPa and the elongation is 4.82%.The tensile strength and elongation were increased by 26.99%and 29.91%,respectively,with respect to the AlSi5Cu1Mg matrix alloy.The results of electrochemical measurement and immersion test in 3.5wt.%NaCl solution revealed showed that the corrosion resistance of AlSi5Cu1Mg+xLa alloy strongly depended on its microstructures.The AlSi5Cu1Mg+0.6La sample exhibited the highest corrosion resistance due to its fine cellular structure and the cathode phases coated by the La element.The covering film of La hindered the corrosion electron flowing between the cathode and the anode.As a result,the corrosion current density of the AlSi5Cu1Mg+0.6La alloy was only about 40%that of the matrix alloy in the electrochemical measurement.When the laser scanning rate is 150mm/min,the WC particles in cladding layer are uniformly dispersed,but a large number of microcracks are generated in the cladding layer.When the laser scanning rate is 250mm/min,the WC particles are evenly distributed in the middle and bottom of the cladding layer,and there is no obvious microcrack in the cladding layer.At this time,the dilution ratio of the cladding layer is 24%.The WC particles and the cladding Ni-based alloy in the cladding layer produce mutual diffusion of elements,forming a good metallurgical combination.The hardness value of the cladding layer from the top to the substrate increases first and then decreases.The average hardness of the top cladding layer?about 0²75?m?is about 647.5⁶93.1HV,which is about 9 times that of the AlSi5Cu1Mg alloy matrix hardness value?78.8HV?.The average microhardness of the middle cladding layer?about 275⁶16?m?is about 846.9 HV,which is about 11 times that of the AlSi5Cu1Mg alloy matrix hardness value?78.8HV?.The electrochemical test results show that the corrosion potential(E_corr)of the cladding layer at 250mm/min is about-318.09mV,which is 309.80mV higher than that of the AlSi5Cu1Mg substrate.The corrosion current density(I_corr)was 12.33?A/cm².The corrosion current density is about 20.97%of the AlSi5Cu1Mg substrate.