Investigation Of Structure And Mechanical Properties For ZLD106 Alloys Melted With Grain-refining Aluminum Ingots

In this paper, the influence of different refining and modifying elements on microstructures and mechanical properties of ZLD106 alloys melted by Grain-refining Aluminum Ingots(GRAI) have been studied, the results have an important theoretical meanings and practical meanings on the popularity of ZLD106 alloys and GRAI. The experimental results are as following:(1) With the addition of Ti melted by Al-Ti master alloys and GRAI, the grain refining effect is improved with the increase of Ti when the content of the titanium is less than 0.21% in ZLD106 alloys. Because Grain-refining Aluminum Ingots are of low production cost, the optimized content of Ti is 0.18%; The grain refining effect of boron(B) on ZLD106 alloys is obvious. The grain refining efficiency is improved with the increase of B, and the long axis and axis ratio ofα-Al decrease at the same time. The optimized content of B is 0.03%; The addition of zirconium(Zr) has no refining effect on ZLD106 alloys when the content of Zr is less than 0.11%. When the content of Zr is more than 0.11%, the grain refining effect is improved with the increase of Zr. The long axis and axis ratio ofα-Al decrease at the same time. The optimized content of Zr is 0.15%;(2) Strontium(Sr) has an obvious effect of modification on ZLD106 alloys. When the content of Ti is certain, it makes the lamella silicon change into fibre silicon with the increase of Sr, and the second dendrite spacing is decreased. The optimized content of Sr is 0.03%. when the contents of Ti(0.18%) and Sr(0.03%) are certain and the cerium-rich mixtures of rare earth (RE) are added from 0 to 0.3%, the effect of RE on the grain refining and the morphology of eutectic silicon have not been obvious with the increase of RE. The second dendrite spacing is decreased at first, and then increased rapidly with the increase content of RE. In view of the capability of purification, the optimized content of RE is 0.1% in this group; When the contents of B(0.03%) and Sr(0.03%) are certain and the RE is added from 0 to 0.3%, the effect of RE on the grain refining and the morphology of eutectic silicon have not been obvious with the increase content of RE. The long axis and axis ratio ofα-Al are less than the samples without RE. In view of the capability of purification, the optimized content of RE is 0.3%; When the contents of Zr(0.15%) and Sr(0.03%) are certain and the content of RE is added from 0 to 0.3%, the effect of RE on the grain refining and the morphology of eutectic silicon have not been obvious with the increase content of RE. The second dendrite spacing is increased obviously, and the second dendrite spacing is twice than the samples without RE;(3) Comparing the refining and modifying methods of 0.03%Sr+0.18%Ti(GRAI), 0.03%Sr+0.18%Ti(GRAI)+0.1%RE, 0.03%Sr+0.18%Ti(Al-Ti), 0.03%Sr+0.03%B and 0.03%Sr+0.03%B+0.3%RE in ZLD106 alloys, the sample which is added with 0.03%Sr and 0.18%Ti(GRAI) in ZLD106 alloys with T6 heat treatment has the best mechanical properties, and the yield strength, tension strength and elongation respectively reach 294.3MPa, 352.2MPa and 1.96%. The sample which is added with 0.03%Sr and 0.18%Ti(GRAI) in ZLD106 alloys with T5 heat treatment has the best mechanical properties. The yield strength, tension strength and elongation respectively reach 244.6MPa, 327.6MPa and 3.42%.