Study on Microstructure and Mechanical Property in Mg-Gd-Y Alloy by Secondary Extrusion Process

Extruded Mg-Gd-Y alloy tubes were obtained by using cast ingot and extruded bar billets. Microstructure and mechanical properties were also studied with two different cooling methods: air cooling and water cooling. The result shows that by using an extruded bar as billet extruded tubes achieves higher elongation comparing to using cast ingots due to favored texture for the activation of basal slip. Using the water-cooling method, extruded tubes achieve a higher yield strength compared to the air cooling method due to their fine grain size. Using cast ingot billets and the water-cooling method, the elongation is only 6% due to large unrecrystallized grains caused by inhomogeneous deformation and unfavored texture for the activation of basal slip. Using the extruded bar billet and the water-cooling method, the tube has uniformed small grains and much more randomized texture caused by the inhibition of preferred grain growth process. The highest texture intensity is only 1.852 in this kind of tube. Both high yield strength (195.3 MPa) and high elongation (23.9%) are achieved in this tube.

On the Impact of Microsegregation Model on the Thermophysical and Solidification Behaviors of a Large Size Steel Ingot

The impact of microsegregation models on thermophysical properties and solidification behaviors of a high strength steel was investigated. The examined microsegregation models include the classical equilibrium Lever rule, the extreme non-equilibrium Scheil-Gulliver, as well as other treatments in the intermediate regime proposed by Brody and Flemings, Clyne and Kurz, Kobayashi and Ohnaka. Based on the comparative analyses performed on three representative regions with varied secondary dendrite arm spacing sizes, the classical equilibrium Lever rule and non-equilibrium Scheil scheme were employed to determine the thermophysical features of the studied steel, using the experimentally verified models from literature. The evaluated thermophysical properties include effective thermal conductivity, specific heat capacity and density. The calculated thermophysical data were used for three-dimensional simulation of the casting and solidification process of a 40 metric ton steel ingot, using FEM code Thercast®. The simulations captured the full filling, the thermo-mechanical phenomena and macro-scale solute transport in the cast ingot. The results demonstrated that Lever rule turned out to be the most reasonable depiction of the physical behavior of steel in study in large-size cast ingot and appropriate for the relevant macrosegregation simulation study. The determination of the model was validated using the experimentally measured top cavity dimension, the thermal profiles on the mold outside surface by means of thermocouples, and the carbon distribution patterns via mass spectrometer analysis.

Study of Recrystallization Kinetics of 1565ch Aluminum Alloy during hot deformation

The present study addresses recrystallization process in Al-Mg-Mn-Zn-Zr system alloy samples. The samples are collected from cast ingot, produced by casting to industrial DC mold, and homogenized based on standard industrial practice. After that the samples were rolled with different hot rolling schedules. Rolled samples were annealed at different temperatures and their resultant microstructure was examined using optical microscope. During the study new grains nuclei generation rate and their growth rate were determined, analytical records, describing recrystallization kinetics, were obtained, main differences, specific to this alloy recrystallization in 350 ºС-450 ºС temperature range, were identified.

Effect of original grain size on microstructure and properties of extruded Mg-2Zn-0.2Mn biomedical alloy

Magnesium is a biocompatible and biodegradable metal, which has attracted much interest in biomedical engineering. Cast magnesium alloy shows the low strength and plasticity at ambient temperature. Microstructure, mechanical properties and degradation properties of the extrusion pressed magnesium alloy have been investigated for biomedical application in detail by optical microscopes, mechanical properties testing and corrosion testing. The magnesium alloy ingots were gained by different cooling rate. Then the ingots were extrude into bar at the same processing condition. The results show that the cooling rate of cast ingot is important factors that affect the properties of Mg alloy by dynamic recrystallisation extruding. The cooling rate of cast ingot has been successfully applied to control the microstructure, mechanical and degradation properties of the Mg alloy. Optical microscopy observation has indicated that the grain size of the dynamic recrystallisation extruding has been significantly decreased from fast cooling cast magnesium ingot, which has mainly contributed to the high tensile strength and good elongation. Fasting cooling rate of cast ingot and dynamic recrystallisation extruding has provided moderate corrosion resistance, which has opened a new window for materials design, especially for biomedical.

Effect of Ultrasonic Flexural Vibration on Solidification Structure and Mechanical Properties of Large-Size 35CrMoV Cast Ingot

In order to improve the performances of large-size 35CrMoV cast ingot, ultrasonic flexural vibration was guided into 35CrMoV steel melt through L-shaped ultrasonic waveguide rod during the solidification, and the effects of ultrasonic flexural vibration on macrostructure, microstructure, and mechanical properties of large-size 35CrMoV cast ingot were investigated. It is found that the columnar crystal zone has disappeared and the ingot is composed of the equiaxed crystals present in the ultrasonic ingot. The size of grains treated by ultrasonic are significantly smaller than conventional ingot. The distribution of ferrite in matrix structure is also more uniform than conventional ingot. The tensile strength is increased by 3.14%∼17.12%, and the elongation is increased by 39.13%∼287.50% compared with the conventional ingot at different positions.

Position Control and Alignment of the CCM Equipment

The improved technology of position control and alignment of the continuous casting machine (CCM) equipment based on high-precision online geodetic measurements is considered. The mathematical model for the technological axis of the continuous casting machine, the technique of the rational alignment of the machine’s equipment and the software implementing this technique are proposed. The application experience of the developed technique for control and aligning the equipment of continuous casting machines of different types is shown. The data on the efficiency of the technique for continuous casting machine equipment and its impact on the quality of a continuously cast ingot are presented.