Effect Of Rare Earth (La?Nd?Y) And Al-Ti-C/B Master Alloy On The Microstructure And Mechanical Properties Of 6063 Aluminum Alloy

6063 aluminum alloy belongs to Al-Mg-Si series alloy,which is a widely used construction industry such as doors,windows,curtain walls,and automobiles and ships of some components with high strength,excellent plasticity and corrosion resistance.Grain refinement is a commonly used alloy strengthening method and one of the most effective methods to improve the toughness of aluminum alloys.In this study,the Al-Ti-C-La master alloy,Al-Ti-B master alloy,rare-earth Nd,and rare-earth Y were added into 6063 aluminum alloy,which are investigated the microstructure and properties of 6063 aluminum alloy.The effect of composite modification on the hot extrusion behavior and microstructure of 6063 aluminum alloy was analyzed.The main contents of the study are as follows:(1)The effect of Al-Ti-C-La master alloy on the microstructure and mechanical properties of 6063 aluminum alloy was studied.The experiment results show that:Al-Ti-C-La master alloy have good refinement effect on on 6063 aluminum alloy.When the addition 1%Al-Ti-C-La master alloy,the grain size is reduced from 482?m to 121?m.At this time,the rare earth La is mainly distributed near the Mg₂Si phase and?-Al Fe Si to fome the complex compounds such as Al Fe Si Mg La.After T6 heat treatment and natural aging for 270 days the tensile strength and elongation of 6063aluminum alloy increased with the increase of the amount of master alloy,but the hardness decreased slightly.The tensile strength,elongation and Vickers hardness of6063 aluminum alloy with 1%Al-Ti-C-La intermediate alloy added amounted to177.2 MPa,17.8%,and 60.9 HV respectively.The tensile strength and elongation were increased by 16.3%,50.8%,the Vickers hardness value decreased by 15.4%.The fracture of the alloy is mainly ductile fracture.(2)The effects of Al-Ti-B master alloy and rare earth Nd composite addition on the microstructure,mechanical properties and electrical conductivity of 6063aluminum alloy were studied.The results show that:Al-Ti-B master alloy and rare earth Nd composite modification have a good refining effect on 6063 aluminum alloy.As the amount of rare earth Nd added increases,the?-Al grain size gradually decreases,and some coarse crystals are refined into fine crystals.The addition of rare earth Nd has an impact on the microstructure of 6063 aluminum alloy.When the addition amount of rare earth is 0.1%,the grain boundaries are mainly composed of complex compounds of short rods or discontinuous particles of Al Si Fe Mg Nd.When the content of rare earth reaches 0.6%,the enrichment of rare earth Nd appears at the grain boundaries,with grid-like Al Si Nd phase.After T6 heat treatment and natural aging for 180 days,the electrical conductivity of 6063 aluminum alloy continues to increase,and the elongation of the alloy increases significantly with the increase of the amount of rare earth Nd added,but the tensile strength and dimension The hardness decreases.The tensile strength,elongation and Vickers hardness of 6063 aluminum alloy with the addition amount of Al-Ti-B+0.6%Nd master alloy reached 139.4 MPa,24.4%,and49.2 HV respectively.The tensile strength decreased by 34.6%and the elongation It increased by 70.6%and the Vickers hardness value decreased by 37.6%.The alloy is ductile fracture,and particles such as Al Si Nd and Al Si Fe Mg Nd exist on the fracture surface.(3)The effects of 0.1%Y,0.2%Al-Ti-B and 0.2%Al-Ti-B+0.1%Y master alloy compound addition on the microstructure and mechanical properties of 6063aluminum alloy were studied.Results revealed that the grain size of 6063 aluminum alloy with 0.2%Al-Ti-B+0.1%Y was 98?m.The rare-earth Y distributed mostly around Ti B₂particles and formed Al Ti Y particles.Some rare-earth Y also existed at the?-Al center as the form of Al₃Y,which increased the number of heterogeneous nucleation particles.Moreover,adding rare-earth Y decreased the Mg₂Si size,contributed to turn?-Al Fe Si phase into?-Al Fe Si phase,formed various complex compounds(e.g.,Al Si Y,Al Fe Si,and Al Fe Si YMg),and reduced the impurity of Fe-rich phase at the grain boundary.Furthermore,After T6 heat treatment,0.2%Al-Ti-B+0.1%Y compound addition makes the tensile strength,elongation and Vickers hardness of 6063 aluminum alloy reach 133.4 MPa,21.1%,45.4 HV,tensile strength and elongation respectively.It increased by 4.9%and 75.8%,but there was no significant change in hardness.The addition of rare earth Y changed the fracture morphology of the alloy from coarse irregular dimples to fine dimples,and the fracture mode was ductile fracture.Meanwhile,the rough and irregular dimples that formed in the fracture morphology became small dimples,and the form of fracture was ductile regardless of rare-earth Y or 0.2%Al-Ti-B+0.1%Y master alloy added to6063 aluminum alloy.(4)The effects of 0.1%Y,0.2%Al-Ti-B and 0.2%Al-Ti-B+0.1%Y composite addition on the microstructure and mechanical properties of 6063 aluminum alloy extruded material were studied.The results show that in the initial stage of hot deformation,the flow stress increases rapidly with the increase of strain,and gradually increases or decreases gradually when the stress reaches a relative peak.The addition of rare earth Y and Al-Ti-B master alloy is beneficial to improve the extrusion processability of aluminum alloy.Compared with the extruded 6063aluminum alloy without the addition of an intermediate alloy,the addition of rare earth can not only effectively refine the 6063 aluminum alloy,but also change the morphology and size of the second phase particles in the alloy to a certain extent,and improve the extrusion.Microstructure of the as-cast alloy,the addition of rare earth Y,Al-Ti-B master alloy,and 0.2%Al-Ti-B+0.1%Y have improved the elongation of the extruded 6063 aluminum alloy.The tensile strength of 6063 aluminum alloy after Al-Ti-B master alloy is the highest.The tensile strength of the extruded 6063aluminum alloy with 0.2%Al-Ti-B+0.1%Y was increased by 7.25%,and the elongation was increased by 45.9%.Compared with before extrusion,the tensile strength of 6063 aluminum alloy after extrusion has been significantly improved,but the elongation has been reduced to varying degrees.