Dissertation
Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Non - ferrous metals and their alloys > Light non-ferrous metals and their alloys > Magnesium

Study on the Microstructures and the Mechanical Properties of Mg-Gd-Y-Zr Alloys

Author HuangZhen
Tutor CuiJianZhong;LeQiChi
School Northeastern University
Course Materials processing
Keywords Magnesium alloy of Mg-Gd-Y-Zr Mechanical Properties Homogenization Extrusion Heat treatment
CLC TG146.22
Type Master's thesis
Year 2008
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Mg-Gd-Y-Zr alloy is the performance of high-strength magnesium alloy , with a wide range of applications in the defense and aerospace industries . However , the poor performance of the casting of the alloy and plastic processing . In this paper, the low-frequency electromagnetic casting technology to prepare a series of Mg-Gd-Y-Zr alloys , a detailed study of the microstructure and mechanical properties of cast homogenization heat treatment process , the hot compression behavior of the extrusion process and extruded bars after different heat treatment methods the treated alloy microstructure and mechanical properties . Provide a lot of basic work for the development of the alloy . Prepared using low-frequency electromagnetic casting technology Mg -Gd -Y -Zr alloy billets , the cast structure mainly composed of a-Mg, Mg24 (GdY) 5, Mg3 Gd, Mg2Gd and Mg5Gd ; Add Ag (1%) The new phase is formed is mainly present in a solid solution state . Second massive , particulate and lamellar phase mainly three kinds of patterns, which are mostly distributed in the grain boundary or dendrite boundaries , small distribution within the grain . The homogenizing annealing system alloy 500 ℃ × 8h. Mg-Gd-Y-Zr magnesium alloy ingot thermal compression rheological characteristics and microstructure observations suggest that the occurrence of dynamic recrystallization : thermal compression process . Experimental deformation true stress strain curve , and the constitutive equation fitting the apparent activation energy , temperature, strain rate , and strain microstructure . Hot compression results show that the , Mg - 10Gd - 3Y - 0.6Zr - 1Ag alloys plastically deformed the apparent activation energy of 180kJ/mol, thermal processing should be carried out in the temperature range of 360 ° C -400 ° C . Mg-Gd-Y-Zr alloy extrusion process , with the reduction of the extrusion temperature , grain refinement , aging mechanical properties improved. Through a series of secondary extrusion temperature comparison, determining 360 ℃ best secondary extrusion temperature . Significantly higher than the mechanical properties of the extruded alloy T5 state in the temperature secondary T4 and T6 condition . After 200 ℃, 68h of the aging treatment , the tensile strength of 465MPa, the yield strength of 398 MPa , an elongation of 8% . 3% -7.5 % pre-deformation , strain aging can significantly improve the mechanical properties of Mg-Gd-Y-Zr alloys . After 3 % pre-strain , 200 ° C x71h aging , the alloy tensile strength is 480 MPa , the yield strength of 431MPa , elongation of about 7% .

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