Microstructure And Solidification Simulation Of Φ480 ZK60 Mg Alloys Cast Ingot

This paper aims at the properties of Φ480 ZK60 Mg alloy ingot. The macrostructure and microstructure of the ingot have been studied. Further more, the dependence between cooling rate (v) and dendrites space (λ) of ZK60 Mg alloy has been researched in Gleeble solidification experiment.Optical microscope is used to study ingot macrostructure. The results show that the ingot is made up of almost entire equal-axed grains. The grains grow in a dendrite-like way during the early stage of solidification and in a cell-like way during the later stage. As a result, the grains' shape appears to be anthoid. This has been contrasted with Φ405 AZ31 Mg alloy ingot made by same casting procedure, and with Φ130 ZK60 Mg alloy ingot. Grain size has been measured by quantitative metallographical method, the average grain chord length is about 160 for the whole ingot, the corresponding ASTM Grain Size Number is 2. Therein, the grain chord length in the center region of the ingot is about 230, which is as 2.3 times long as it in the ingot edge region.Metallographical microscope and transmission electron microscope (TEM) have been used to observe the microstructure and to discover new alloy phases. Electron diffraction patterns have been used to calculate out the phase that found during the former experiments. Groundmass was found to be -Mg. Pseudo- eutectoid structure composed of -Mg + Mg3Zn2 is found in the small area between grain boundaries. It's discovered that -MgZn2 congregats along grain boundaries as tiny pots. The precipitated particles inside grains proved to be -MgZn. Otherwise, a novel etched pattern is found during metallographical experiment, it's supposed to be microsegregation of Zn and Zr. Electron probe (EPMA) line scanning experiments has been conducted to verify the presumption. The conjecture proved correct by the experimental results. In addiyion, Zr-rich Cores are found inside grains and grain boundaries.Gleeble1500 thermal simulation instrument is used to obtain ZK60 Mg alloy samples with various cooling rate (v) that can be calculated out according to the data recorded by the instrument. Primary Dendrites Space (λI) and Secondary Dendrites Space (λII) are measured for each sample. Empirical formulas about v-λI and v-λII are regressed with mathmatical method. Therange of the formulas' application is also analyzed.In addition, the dependence between micro-hardness (HV) and Secondary Dendrites Space (λII) for ZK60 cast alloy proved to be similar with Hall-Petch formula. And the empirical formula forλII-HV has been put forward in this paper either.All results have been discussed in this paper. Suggestions for further research also have been brought forward either.