Study On Grain Refinement And Properties Of 6082 And Al-9.5Si-1.5Cu-0.8Mn-0.6Mg Deformed Aluminum Alloys

The deformed aluminum alloy has the characteristics of high strength,good plasticity,good electrical and thermal conductivity,strong corrosion resistance and good processing and forming performance.It has great potential in the development of industrial lightweight,and is widely used in the production and manufacturing of aircraft,rockets,rail connections,modern cars and so on.The billet before extrusion deformation of deformed aluminum alloy is obtained by melting and casting.During this process,problems such as element segregation,dendrite development and coarse brittleness often occur,resulting in uneven subsequent deformation or easy formation of stress concentration around the coarse phase,which ultimately affects the mechanical properties of the alloy.Grain refinement can not only improve the deformation ability of aluminum alloy,but also improve its mechanical properties.Based on that,this paper takes 6082 and Al-9.5Si-1.5Cu-0.8Mn-0.6Mg deformed aluminum alloys as the research objects.By adding Al-Ti-C-B master alloy and Al-5Ti-1B master alloy respectively,the changes of microstructure and properties of the alloys are studied from the perspective of grain structure refinement.In order to find new ideas and methods to obtain better comprehensive properties of 6082 aluminum alloy and Al-9.5Si-1.5Cu-0.8Mn-0.6Mg alloy.The main research contents of this paper are as follows:(1)Study on grain refinement and properties of 6082 aluminum alloyAdding 0.5%Al-Ti-C-B master alloy and 0.5%Al-5Ti-1B master alloy to 6082 aluminum alloy,the research results show that the α-Al grains of 6082 aluminum alloy have been refined to different degrees.The average grain size of α-Al in as-cast state was reduced from 167μm to 100μm and 93μm,respectively,and the average grain size of extruded α-Al was changed from 18 μm to 12 μm and 10μm.On the basis of exploring the best heat treatment process of extruded 6082 aluminum alloy,it is found that the room temperature tensile properties of extruded 6082 aluminum alloy have been improved to different degrees,and the tensile strength has been increased to 315 MPa and 330 MPa,which are respectively increased by 5%and 10%,the yield strength increased to 287 MPa and 300 MPa,which increased by 13.2%and 8.3%,respectively,and the elongation increased to 17.0%and 16.4%.The analysis shows that the grain refinement strengthening played a major role.Compared with the alloy without refining agent,the α-Al grain size of 6082 aluminum alloy added with 0.5%Al-Ti-C-B seed alloy and 0.5%Al-5Ti-1B master alloy is obviously reduced,and the grain boundary Increase,the electrical and thermal conductivity of the alloy decreased slightly,but did not affect the service performance of the alloy;in addition,after adding Al-Ti-C-B seed alloy and Al-5Ti-1B master alloy,the corrosion potential of 6082 aluminum alloy increased to some extent,the corrosion current density is reduced,and the corrosion resistance of the alloy is further improved(2)Study on grain refinement and properties of Al-9.5Si-1.5Cu-0.8Mn-0.6Mg alloyAdding different amounts of Al-Ti-C-B master alloy and Al-5Ti-1B master alloy to Al9.5Si-1.5Cu-0.8Mn-0.6Mg alloy,it was found that when the addition amount of two alloys was 0.5%,α-Al grain structure of the as-cast alloy is obviously refined,and with the increase of the addition amount,the refining effect gradually declines.The as-cast Al-9.5Si-1.5Cu-0.8Mn0.6Mg alloy with the addition of 0.5%Al-Ti-C-B master alloy has the best room temperature tensile properties.The strength and elongation have been improved,and the improvement effect of Al-Ti-C-B on the properties of the test alloy is better than that of Al-5Ti-1B under the same amount of addition.The research results show that the optimum heat treatment process of the as-extruded Al-9.5Si-1.5Cu-0.8Mn-0.6Mg alloy is 525 ℃ × 5h solution treatment+190℃×10h artificial aging.The average grain sizes of the as-extruded alloys after refinement are about 31μm and 33 μm,which are lower than 35 μm of the original alloy without the addition of refiner.It was found that the Al-Ti-C-B master alloy had better grain refinement effect on the Al-9.5Si1.5Cu-0.8Mn-0.6Mg alloy.The mechanical properties test results show that the tensile strength,yield strength and elongation of the as-extruded alloy are increased to 3 80 MPa,330 MPa and 11.2%,respectively,compared with 360 MPa,307 MPa,9%of the unrefined original alloy,increased by 5.5%,7.5%and 24.4%respectively,while the tensile strength and the yield strength of the test alloy with the addition of Al-5Ti-B master alloy was basically the same,and the elongation increased the most,from 9%to 11.9%,it was found that more obvious complete recrystallization occurred in the process of extrusion heat treatment.