Dissertation > Excellent graduate degree dissertation topics show

Preliminary Resaerch on Anisotropy of Extruded-Rolled Sheet of Mg-Mn Alloy

Author: JiangTing
Tutor: PengJian
School: Chongqing University
Course: Materials Science and Engineering
Keywords: ME Department of magnesium alloy Extrusion cogging Rolling Anisotropic
CLC: TG146.22
Type: Master's thesis
Year: 2009
Downloads: 167
Quote: 0
Read: Download Dissertation

Abstract

The magnesium alloy lightweight advantage but forming lack, the sheet rolling cogging need huge investment in equipment and production costs are high due to the need to pass repeatedly rolling annealing. China currently only the field of national defense industry, aerospace high performance magnesium alloy sheet, still mainly rely on imports. Difficult to deform metal extrusion cogging then roll forming is a sheet processing pathway, magnesium alloy extrusion cogging rolling requires in-depth study This selection of medium-high strength plastic ZM21 magnesium manganese alloy, as well as in add the high and low content of Ce alloy as the research object, its extrusion - longitudinal rolling and extrusion - cross rolling process. By extrusion, rolling and other industrial test, the room temperature mechanical properties testing, microstructure analysis, scanning electron microscopy fracture morphology, comparative study squeezed - organizational performance anisotropic change in the rolling process, validated by squeezing blooming process feasibility, preliminary exploration of the basic law of the squeeze - rolled sheet organizational performance anisotropic effects of alloy content, the direction of rolling and rolling reduction. The test results show that: ME-based magnesium alloy after 420 ℃ × 12h homogenization treatment at 420 ℃ cogging 175 extrusion ratio extrusion, to obtain uniform and fine recrystallization organizations, with increasing Ce content, grain-Etsu small, excluding the grain size of the of the Ce ME0 alloy (ZM21) in 21UM about, low Ce (0.19%) Alloy ME3 size is 18um, high of Ce (0.57%) alloy ME7 13um; tensile strength: ME0 at 0 ° considerable strength and the direction of 90 °, the average is between 245MPa and 250MPa, higher than the 45 ° direction 10MPa above; addition ME7 increases very slightly in the direction of 0 °, add the alloy of the high and low two kinds of Ce content in each direction are more than 10MPa , the relative differences decreased. Yield strength: ME3 in the 0 ° direction and the outside in the direction of 90 ° close to 150MPa ME7 other direction in each alloy between 135-140MPa. Elongation: ME0 direction of 0 ° and 90 ° are around 10% to 22%, 45 ° direction; adding Ce direction were increased by 5-10%, but the ME7 direction of 90 ° down to 12%. Compare IPA Indices, ME3 having better strength isotropic and plastic combination of isotropic and anisotropic performance level of tensile strength IPA = 1.82% = 8.1%, the yield strength of the IPA IPA = 23%; elongation . The three alloys in the the ME7 plane anisotropy index value IPA too large a number, do not add of the Ce ME0 and low Ce content ME3 alloy better performance to performance consistency. ME0 alloy cross rolling and rolling and deformation organizations, have maintained a 31% reduction squeeze fibrous flow line features, side and face in the reduction of 44.8% equiaxed organization. After rolling, the grain size distribution in the 10-20 micron. ME0 alloy strength with the amount of deformation is gradually increased, the yield strength increases more evident; longitudinal rolling, the highest tensile strength and yield strength are in direction of 90 ° and 0 ° direction lowest difference are about 40MPa; elongation with the deformation increased first and then decreased, 45 ° direction is always higher than the other two directions by about 5%. Cross rolling, a small amount of deformation strength slightly higher in the direction of 90 ° about 40MPa, when the deformation amount is increased to 45%, a tensile strength of about 280, the yield strength at 220 or so, the direction of the difference does not exceed 10 MPa; elongation higher than the direction of 0 ° to 90 ° at low deformation amount nearly doubled, but the amount of deformation reached 45% in each direction are essentially completely equivalents. Cross rolling consistency compared to longitudinal rolling more conducive to ME0 alloy maintain to mechanical properties. ME3 alloy after rolling and cross rolling need more than 45% of the amount of deformation qualify for full equiaxed, and the organization is very small, the grain size distribution is about 5 microns; strength with cross rolling and rolling and the amount of deformation first increase over 44.8% performance reduction; the elongation rolling and consistency strong, in the amount of deformation of 66.5% to 17-18%, the cross rolling the elongation 45 ° direction is always and with the amount of deformation increased slowly up to about 16% from 12%, the lowest of the 90-degree direction before 44.8% reduction to the amount of deformation of 66.5% flat with 45 ° direction. Rolling and more conducive to the ME3 alloy comprehensive performance consistency. ME7 alloy with longitudinal rolling the increase in the amount of deformation, the tensile strength variation in the range of 270-310MPa, yield strength continue rolling to 66.5% from 44.8%, there was a 180-230MPa significantly improve; elongation with deformation increase in volume the large slightly weakened, but three more uniform size. ME7, the alloy with the increase in the amount of longitudinal rolling deformation, tensile strength, yield strength continue rolling to 66.5% from 44.8%, a significant increase from 180MPa to 230 MPa change in the range of 270MPa-310MPa; elongation with the amount of deformation is increased significantly weakened, the direction of 0 ° is particularly serious. After cross rolling strength extruded improve the average more than about 70MPa, but the strength and continue to improve with increasing the amount of deformation is not obvious, and after rolling extending rate decreased by about half, the particularly serious decline in the direction of 90 °. Comparative cross rolling and the vertical rolling, and found that the cross rolling to a certain extent can be obtained more uniform tissue sheet, especially cross rolling deformation is relatively small when its organization better uniformity conducive anisotropy control. The rolling and when the amount of deformation increases to a greater extent, is conducive various consistent performance. The three alloys rolled sheet IPA found the the ME7 anisotropy was significantly higher than the other two series, ME0 and ME3 little difference. ME0 alloy should be used in the manner of cross rolling, to achieve more than 44.8% of the various properties of each to a strong consistency in the amount of reduction, and the tensile strength of three distributed between 258Mpa-295MPa, yield strength is distributed in 173Mpa-203Mpa between distribution of elongation is between 11.2% -22%. ME3 alloy should adopt the way of rolling and, with the reduction increasing elongation each significantly improve the consistency and strength of each to the consistency better reduction of 66.5%, while the tensile strength of three-way 244 between-267MPa, the yield strength distribution between 135-138MPa, elongation of 17.3-18.1%.

Related Dissertations

CLC: > 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
© 2012 www.DissertationTopic.Net Mobile