The Effects Of Trace Elements ER And ZR On The Microstructure And Properties Of ZA43 Alloy

In this paper, by adding the trace elements of Er and Zr into the ZA43 alloy, the effects of Er addition, Zr addition and combination of them on the microstructure and mechanical properties of the ZA43 alloy were studied, and the strengthening mechanism were discussed.As far as the Er addition is individually concerned, the refinement result of the ZA43 alloy with 0.4% Er addition is comparatively best. The coarse dendrite microstructure of the ZA43 alloy is refined and transformed to the uniform and small floccus microstructure, and shrinkage porosity are improved. The tensile strength of the alloy is up to 329MPa. In the ZA43 alloy, the trace element of Er combines with Al form the Al3Er particles, the lattice (LI2-type) and the cell size of which are extremely similar to the Al matrix. So these particles play the role of heterogeneous nucleation, refining the microstructure of the alloy and improving the mechanical properties of the alloy. At the same time, the particles in the grain boundary pin the grain boundaries, and restrain grain growth.When the trace element of Zr is individually added, the refinement result of the ZA43 alloy with 0.3% Zr addition is relatively the best. The coarse dendrites of the ZA43 alloy are refined to the uniform and small floccus microstructure. The tensile strength of the alloy is 326MPa. In the ZA43 alloy, the trace element of Zr combines with Al to form the Al2ZnZr particles, the lattice of which is LI2-type and similar to the Al matrix. Appropriate amount of these particles can play the role of heterogeneous nucleation, refining the microstructure of the alloy and improving the properties of the alloy.The combination of minor Er and Zr has refinement effect on the as-cast microstructure of the ZA43 alloy. In the microstructure of the ZA43 alloy with 0.2%Er and 0.1% Zr additions, the thick dendrites are almost disappeared. As for the ZA43 alloy with 0.2% Er and 0.1% Zr additions, the refinement result of its is relatively the best, the coarse dendrite microstructure of the alloy is refined and transformed to the uniform and small floccus microstructure, and the tensile strength of the alloy is up to 323 MPa. After adding appropriate amount of minor Er and Zr into the ZA27 alloy, the primary Al3Zr and Al2ZnZr particles can be formed, which has the lattice type of LI2 and is completely coherent with the matrixα(Al), playing the part of heterogeneous nucleation and promoting the fine crystalline strengthening of the alloy. They block the grain boundary sliding, the subgrain merger, and restrain recrystallization.ZA43-0.2%Er-0.1%Zr alloy is solid solution treatment at 380℃for 3 hours and then is air-cooled, which can make the phase of the unbalanced eutectics among the grain boundaries into the matrix and thus to form the supersaturated solid solution. After solid solution treatment, the hardness is up to 128HB. After ZA43-0.2%Er-0.1%Zr alloy being ageing treatment at 120℃for 1 hours, the strengthening phase separate out in the supersaturated solid solution, tiny dispersion, strongly pin the dislocation, and prevent the grain growth. After the ageing treatment, the hardness is up to 132HB.