Method for transforming columnar crystal-orienting isometric crystal of directional solidified alloy with strong static magnetic field induction

A technology of directional solidification and static magnetic field, which is applied in self-solidification, chemical instruments and methods, single crystal growth, etc., and can solve problems such as complex equipment, difficulty in implementation, and contamination of molten metal

Inactive Publication Date: 2012-10-03
SHANGHAI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this method has complex equipment and is difficult to implement in industrial production; the contact between the electrode and the melt will still pollute the molten metal; at the same time, high-frequency current needs to be passed through the electrode, which consumes a lot of energy, so there are obstacles to industrial promotion

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  • Method for transforming columnar crystal-orienting isometric crystal of directional solidified alloy with strong static magnetic field induction
  • Method for transforming columnar crystal-orienting isometric crystal of directional solidified alloy with strong static magnetic field induction
  • Method for transforming columnar crystal-orienting isometric crystal of directional solidified alloy with strong static magnetic field induction

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] (1) A lead-tin hypereutectic alloy whose alloy composition is Pb-80wt% Sn is selected. The purity of Pb and Sn are both 99.99%. After vacuum induction melting, the diameter is 3mm and the length is 20cm. Alloy rods, which are packaged in corundum tubes;

[0030](2) A directional solidification device using a typical Bridgman method (see figure 1 ), fix the above-mentioned corundum tube on the pull rod, and raise it into the heating furnace; adopt the longitudinal strong static magnetic field generated by the superconducting strong magnet, make the solid-liquid interface of the sample be in the stable magnetic field area, and control the magnetic field intensity to 12T (special Tesla);

[0031] (3) Turn on the power and turn on the heating furnace to heat the alloy rod. The central temperature of the heating furnace is 600°C and keep it warm for 30 minutes. After measurement, it is found that the temperature gradient in front of the liquid-solid interface is 52K / cm; th...

Embodiment 2

[0032] Example 2: The process and steps in this example are exactly the same as those in Example 1 above, except that the alloy is Al-4.5wt% Cu hypoeutectic alloy; the central temperature of the heating furnace is 900°C; The speed is 10μm / s; the temperature gradient at the front of the solid-liquid interface of the sample in the furnace is 62.8K / cm; the magnetic field strength generated by the superconducting magnet is 10T.

Embodiment 3

[0033] Example 3: The process and steps in this example are exactly the same as those in Example 2 above, except that the alloy system is an Al-7wt% Si hypoeutectic alloy; the central temperature of the heating furnace is 900°C, and the solid-liquid interface front of the sample The temperature gradient is measured as 40K / cm; the pulling speed of the rod is 120μm / s.

[0034] Microstructure Observation of Dendrites in Solidified Structure of Alloy Rod Samples

[0035] The sample obtained by directional solidification is cut symmetrically along the axial direction, and the sample near the solid-liquid interface is taken; it is ground and polished, and then corroded. The etchant used for the Pb-Sn alloy sample is a mixed solution of oxalic acid and hydrogen peroxide. The volume ratio is 3:1; the etchant used for Al-Cu and Al-Si alloy samples is H 2 O: HF mixed solution, the volume ratio of the two is water: HF=1000:5.

[0036] In order to make a comparison, during the detection...

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Abstract

The invention relates to a method for transforming a columnar crystal-orienting isometric crystal of a directional solidified alloy with strong static magnetic field induction and belongs to the technical field of an alloy metallographic structure controlled by a physical field. According to the method, the growth morphology of an alloy treelike crystal is controlled by utilizing a thermoelectric magnetic effect generated under the mutual action of the strong static magnetic field and a temperature gradient generated on a solid liquid interface during a directional solidifying process. The method provided by the invention is characterized in that a 10-14T strong static magnetic field is utilized; a typical Bridgman directional solidifying device is adopted; the solid liquid interface of a melt is designed as being in a central position of the strong static magnetic field; the whole solidifying process is finished under the strong static magnetic field; a lathy alloy bar is adopted; the temperature gradient of the solid liquid interface of a sample is changed following the change in furnace temperature and alloy variety; the directional solidifying is performed under the condition of a downward drawing speed of the alloy bar at 10-120 microns per second; and after a crystal grows to a stable stage, the crystal is quickly pulled into a cooling medium for quenching, so that a special isometric crystal alloy structure is finally obtained under the directional solidifying condition.

Description

technical field [0001] The invention relates to a method for inducing the directional solidification structure of alloys to change from columnar crystals to equiaxed crystals under a strong static magnetic field, and provides a method for inducing directional solidification structures that is different from the existing mechanical oscillation and electromagnetic oscillation methods. The invention relates to a new technology of crystal to equiaxed crystal transformation, which belongs to the technical field of alloy structure control research. Background technique [0002] Dendrite is the most common tissue pattern in the process of material preparation, and its size and shape have a very important impact on the final performance of the material. Under normal circumstances, people generally hope that dendrites can grow in the form of equiaxed crystals, because the polycrystalline material obtained by equiaxed crystal growth has non-anisotropic properties. When deformed by for...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C30B30/04C30B11/00C30B28/06
Inventor 李喜杜大帆侯龙于清晨卢振远
Owner SHANGHAI UNIV
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