Study On Liquid-solid Properties Of Quasicrystal Al-Cu-Fe Alloy

In this article, DSC, rapid solidification and the hot speed processing methods are used to study the liquid-solid properties of the quasicrystal Al₆₃Cu₂₅Fe₁₂. And make a research on the liquid-solid variation characteristics. The high temperature melt viscosity instrument and the four electrode resistance furnace are used to study alloy Al₆₃Cu₂₅Fe₁₂.The high temperature melt viscosity meter instrument was used to test the viscosity of the quasicrystal alloy. The results show that ,when the temperature reduce from1545K to 1365K, the viscosity rise by 3.9810 mPa.s to 5.1803 mPa.s, namely the viscosity value of Al₆₃Cu₂₅Fe₁₂ alloy increases with the temperature decreasing near the metal temperature. And the melt viscosity in the range 1401-1473K appear discontinuous changes. The high temperature DSC is used, the results show that except the quasicrystal phase transition point it appears the discontinuous change at the temperature of about 1120℃. This experimental result have very good control effect with the viscosity result. According to the analysis, in the temperature range 1365-1401K, the atomic clusters mostly existed by the form of Al-Fe, and with temperature rising the metallic bond Al-Fe fracture and form a new atoms cluster quickly. And this new atoms clusters are larger than Al-Fe. So it will produce more abnormal phenomena. And the temperature range 1401-1437K should be the transformation temperature range.The four electrode measuring resistance instrument is used to test the resistivity of the melt Al₆₃Cu₂₅Fe₁₂ and Al65Cu20Fe15. Through the resistivity testing it is found that the liquid-liquid structure change exist above the liquid line. And the temperature points should occur at the temperature of 1140℃. This result is some different from the results of viscosity and the DSC. It probably because of the different experimental instrument. And the kind of structure anomalous change but not reversible. That is to say in the quasicrystal melt exist sub-stable uneven phenomenon. And this phenomena can be eliminated by heating and preservation. Under the different speed of cooling, the Al₆₃Cu₂₅Fe₁₂ resistivity is measured. It is found that as the cooling rate faster, the resistivity value increase faster. And the I phase precipitate at the higher temperature points. And after another group of quasicrystal resistivity experiment, it found that the conclusion is reliability. It is believed that as long as cooling rate fast enough the liquid phase can form I phase without peristaltic reaction.It can be seen from the DSC curve of the alloy, theβphase change is a continuous absorption process with theλphase change, reflected on the curve is the same heat sink peaks. The abnormal sink peak appeared near the temperature of 1120℃account that there is structure transformation above the liquid phase line. Under the same speed quench, overheating by 1300℃, the solid organization is evener, and the content of I phase is increased, the impurity phase decreases. And after 1400℃overheating, the solid organization is more particular uniform, in the organization there is mainly I phase. It shows that in the same quench the higher overheat makes for the content of the I phase, and the solid organization is detailed.