Effect of Extrusion Strain Path on Microstructure and Properties of AZ31 Magnesium Alloy Sheet

The mechanical properties of AZ31 magnesium alloy sheets processed by different extrusion strain paths were examined in correlation with concurrent microstructure and texture evolution. The conventional extrusion(CE) and asymmetric extrusion(ASE) paths were performed on Mg alloy sheets. The textures at near surface and mid-layer of ASE sheets were various throughout sheet thickness direction as a result of extra asymmetric shear strain. This can stimulate the orientation of(0002) basal planes to incline approximately 12° toward the shear direction. Moreover, the basal texture of ASE sheet was weakened compared with CE one. Enhancing the ambient formability of extruded Mg alloy sheet fabricated by ASE path was accomplished by the tilted weak basal texture.     

连铸AZ31镁合金的热挤压变形组织与性能(英文)

文章研究了电磁连铸AZ31镁合金经热挤压变形后的微观组织和力学性能。结果表明,挤压过程中的动态再结晶能够显著细化晶粒,局部细晶区的平均晶粒为2μm。与铸态合金相比,挤压后的AZ31镁合金具有更细小的晶粒和更均匀的微观组织。挤压变形后产生强烈的基面织构;挤压后材料的力学性能显著提高。屈服强度、抗拉强度和断面收缩率随着挤压比的增大而增大。挤压比为25时,屈服强度、抗拉强度和断面收缩率分别为259MPa,357MPa和30.5%,比铸态合金分别提高了86.33%,64.52%和67.40%。随着挤压比的增大,晶粒细化效果更为明显,微观组织更均匀。断口形貌分析表明,挤压变形后材料由韧脆混合型断裂,转变为韧性断裂。     

Microstructure,Mechanical Properties and Texture Evolution of Mg-Al-Zn-La-Gd-Y Magnesium Alloy by Hot Extrusion and Multi-Pass Rolling

A high-ductility Mg-8.10Al-0.42Zn-0.51Mn-1.52La-1.10Gd-0.86Y (wt%) alloy was developed by hot extrusion and multi-rolling processes. Relationships between microstructure, mechanical properties and texture evolution of the extruded and rolled alloy were investigated. The rolling process had significant effect on grain refinement of the extruded plate. The grain size reduced from 12.3 to 4.9 μm with the increasing rolling pass. With the increase in rolling pass, the proportion of dynamic recrystallized (DRXed) grains increases due to particle-stimulated nucleation, grain boundary nucleation and twin induced nucleation. In the process of multiple rolling, the basal pole gradually tilted from normal direction to transverse direction due to the asymmetric deformation and irregular grain deformation, resulting in the weakening of the base texture. The results showed that grain refinement and texture weakening were the main reasons for the good ductility of the alloy.     

A High-Ductility Mg–Zn–Ca Magnesium Alloy

A new kind of Mg–2 Zn–0.6 Ca(wt%) alloy was fabricated by casting and hot extrusion as a high-ductility structural material. The extruded alloy exhibits a superior elongation of ～30%, yield strength of 130 MPa and ultimate tensile strength of 280 MPa along the extrusion direction at room temperature. Microstructure, texture and tensile properties of the extruded alloy were investigated in details. The remarkable improvement of ductility is ascribed to the weakened basal texture, refined grains and a small number of second phase in the alloy.     

常化工艺对高牌号无取向硅钢组织和织构的影响

以Si质量分数为3.3%的高牌号无取向硅钢为研究对象,研究了常化处理对试验钢厚度方向组织和织构的影响。结果表明：高牌号无取向硅钢热轧板沿厚度方向组织及织构不均匀导致常化板沿厚度方向出现织构梯度;常化处理可以明显改善热轧板组织和织构,促进晶粒粗大均匀,降低α纤维织构强度,增强λ纤维织构强度,减弱γ纤维织构强度。950 ℃常化时,常化板沿厚度方向晶粒粗大均匀,λ纤维织构强度最大。     

非对称挤压腔循环膨胀挤出法制备AZ31合金的显微组织和力学性能

研究AZ31合金在非对称挤压腔循环膨胀挤出(CEE-AEC)过程中的显微组织、织构演化和力学性能.结果表明,在CEE-AEC过程中发生连续动态再结晶(CDRX)和不连续动态再结晶(DDRX).经过3道次变形后,变形试样的显微组织得到细化,非对称型腔区域合金的平均晶粒尺寸为6.9μm.随着道次的增加,基体织构的最大强度增...     

Microstructure and Texture Evolution During the Direct Extrusion and Bending–Shear Deformation of AZ31 Magnesium Alloy

AZ31 alloys were extruded by direct extrusion and bending–shear deformation(DEBS). The microstructure characteristic and texture evolution of DEBSed AZ31 sheets were investigated by electron backscattered diffraction(EBSD). It is found that DEBS technique could effectively refine grains and weaken texture. Besides, we also investigate how twinning affects dynamic recrystallization during hot extrusion. {10–12} extension twins can offer nucleation sites and enough energy to trigger dynamic recrystallization. Moreover, the character of direct extrusion and bending–shear die can lead to the activation of non-basal slip system and further dramatically weaken the basal texture of the microstructure with many preactivated basal slip systems.     

挤压比对热挤压AZ80镁合金管材组织和性能的影响

选用不同的挤压比对变形镁合金AZ80进行管材热挤压工艺试验研究,对挤压前后材料组织与力学性能的变化进行分析。结果表明,热挤压可以显著细化AZ80镁合金的晶粒,而且随着挤压比的增加,晶粒变得更加细小;增大挤压比也可以提高AZ80镁合金的抗拉强度和屈服强度。结果表明,挤压比为18.2,坯料温度为390℃,模具预热温度为360℃,凹模的半模角为60°～70°,可得到均匀的合金组织和良好的力学性能。     

热挤压及固溶处理对AZ61镁合金组织和性能的影响

研究了不同温度下的热挤压工艺以及后续的固溶热处理对AZ61镁合金显微组织和力学性能的影响.利用扫描电子显微镜观察分析了AZ61镁合金拉伸断口形貌,探讨了其拉伸断裂机制.结果表明,热挤压可以细化晶粒、产生高密度位错从而有效提高合金的力学性能,试验发现在385℃下挤压AZ61镁合金组织均匀,塑性最好.经过热处理之后,370℃下挤压AZ61镁合金的强度有很大提高;385℃下挤压AZ61镁合金强度和塑性下降;400℃下挤压AZ61镁合金的塑性显著提高.     

Microstructure,texture and grain boundaries character distribution evolution of ferritic stainless steel during rolling process

In order to better understand the texture, microstructure and grain boundaries character distribution evolution of ferritic stainless steel, the texture, microstructure and grain boundaries character distribution of ferritic stainless steel (hot rolled sheet, cold rolled sheet and annealing sheet) with 11 wt%Cr content were studied using X-ray diffraction and electron back scattered diffraction technique. The texture of the hot and cold rolled sheets has a through-thickness texture gradient. In the center layer of the hot and cold rolling sheet, α-fiber texture was observed which was attributed to ideal plane strain deformation. Close to the surface a Gross orientation was detected which was attributed to shear deformation. During annealing, the γ-fiber was formed attributed to recrystallization process. The microstructure of the hot and cold rolled sheets was non-homogeneous through the sheet thickness, while, the microstructure of annealing sheets was homogeneous through the sheet thickness. Grain boundaries character distribution results show that there are many low angle grain boundaries in hot and cold rolled sheets and many high angle grain boundaries and coincidence site lattice after annealing. The above results indicated that the changes in texture are closely related to the grain boundaries type.     

高精度AZ31镁合金薄壁管件等温挤压后的组织与性能

研究了不同条件下AZ3l镁合金管材的等温挤压情况,并对挤压前后材料组织与力学性能的变化进行了分析.研究结果表明,AZ31镁合金热挤压时发生了动态再结晶,材料组织比铸态时细化,力学性能大幅度提高;在(653±10)K挤压温度范围内金属流动均匀,挤出管材尺寸精度较高,力学性能良好;从综合性能看,AZ31镁合金挤压产品的合适退火工艺为573 K × 2 h;此时管材的机械拉伸强度为260 MPa,伸长率为23%.     

Evolution of microstructure and texture of AZ61 Mg alloy during net-shape pressing of extruded perform

The micro orientation theological behavior of AZ61 Mg alloy during net-shape forming of tensile specimens via close-die pressing of extruded preformed and the effect of the press deformation rate on the microstructure characteristics were characterized with electron back-scattering diffraction (EBSD) orientation imaging microscopy and metallography. The results indicate that the intensity distribution of basal {0001}<10(1)0 > texture on the cross-section of the extruded perform is uniform and parallel to the extrusion direction. Subjected to pressing in extrusion direction, deformation shear stress leads to grain rotation and basal texture {0001}<10(1)0> deviation from the extrusion direction, spreading in the direction perpendicular to pressing direction. The texture intensity increases with the press deformation rate and reaches its peak value at 50%, which is considerably lower than the value reached in extrusion deformation. Then, the texture intensity decreases with the press deformation rate reversely.     

Effect of Asymmetric Hot Rolling on the Texture Evolution of Fe–3%Si Steel

In Fe–3%Si steel, the hot rolling process affects not only the hot rolling texture but also the primary recrystallization texture. Here, the effect of asymmetric hot rolling was studied by comparing the difference in the texture evolved between asymmetric and symmetric hot rolling. The effect of asymmetric hot rolling on the texture of primary recrystallized Fe–3%Si steel was also studied. The symmetric hot rolling of Fe–3%Si steel produces a rotated cube texture at the center but Goss and copper textures near the surface. Asymmetric hot rolling tends to produce Goss and copper textures even at the center like the texture near the surface. After primary recrystallization, the dominant texture at the center changes from {001} <210> to {111} <112> and the new texture has a higher fraction of the grains which make the low energy boundary with Goss grains than that of symmetric hot rolling.     

Texture Evolution and Dynamic Recrystallization of Zr-1Sn-0.3Nb-0.3Fe-0.1Cr Alloy During Hot Rolling

In the present work,the sheets of Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy were hot rolled with different reductions(10%,30%,50%,and 60%) at 1023 K and 1073 K.The micro structure evolutions including grain micro structure,texture,and dislocation were investigated,using electron backscattering diffraction and transmission electron microscope.The results showed that dislocation slip,twinning,and dynamic recrystallization(DRX) were the main deformation mechanisms.DRX was found to be promoted by larger reduction and higher rolling temperature.The predominant texture formed during hot rolling was basal 0001//ND,whose intensity reached peak value after 30% reduction hot rolling.While the intensity of DRX texture 10-10//ND and1-210//ND increased with increasing reduction and temperature.This study provided an effective way to tailor the texture and microstructure of the alloy,for optimizing process parameters.     

高压开关静触头成形工艺分析与挤压模设计

分析了高压开关静触头成形工艺,设计了静触头热挤压成形模具。与传统生产工艺相比,新的热挤压工艺采用两工序反挤压成形静触头毛坯,使材料利用率和生产效率大幅提高。     

Microstructure and mechanical properties of as-extruded Mg-Sn-Zn-Ca alloy with different extrusion ratios

The effect of extrusion ratio on microstructure and mechanical properties of as-extruded Mg-6Sn-2Zn-1Ca (TZX621) (mass fraction, %) alloy was investigated. It is found that incomplete dynamic recrystallization (DRX) took place in as-extruded TZX621 alloy. As the extrusion ratio was increased from 6 to 16, both fraction of un-DRXed grains and average size of DRXed grains in as-extruded TZX621 alloy decreased and the basal texture was weakened. Coarse CaMgSn phase was broken into particles and fine Mg₂Sn phase precipitated from α-Mg matrix during hot extrusion. Yield strength, ultimate tensile strength and elongation of as-extruded TZX621 alloy with extrusion ratio of 16 reached 226.9 MPa, 295.6 MPa and 18.1%, which were improved by 36.0%, 17.7% and 13.5%, respectively, compared to those of as-extruded TZX621 alloy with extrusion ratio of 6.     

静态退火对Mg-Gd-Y-Zr挤压合金的微结构与织构影响

本文研究了Mg-9Gd-4Y-0.6Zr挤压合金在静态退火过程中的微结构与织构的演变。采用金相显微术、扫描电子显微术、透射电子电子显微术、差热分析仪、XRD织构测试仪及EBSD分析技术表征了合金的晶粒长大、析出相沉淀及织构改变。结果表明,退火初期的晶粒尺寸下降是由再结晶引起的;晶间不均匀变形诱发了晶间的局部析出,继而抑制了再结晶过程。织构分析表明,热挤压产生了常见的基面纤维织构和不常见的柱面纤维织构,即c轴平行于挤压方向;在静态再结晶过程中,新晶粒形核会弱化柱面纤维,而晶粒长大过程会强化柱面纤维。晶界与亚晶界上的大量析出相抑制了织构改变。     

Effect of extrusion ratios on hardness,microstructure, and crystal texture anisotropy in pure niobium tubes subjected to hydrostatic extrusion

Nb tubes were fabricated through hydrostatic extrusion at extrusion ratios of 3.1 and 6.1 at ambient temperature, and then their microstructure, texture, and Vickers hardness were investigated based on electron back-scattered diffraction (EBSD) data. The fraction of low-angle boundaries (LABs) largely decreased with a sharp decrease in mean grain sizes after hydrostatic extrusion and was not proportional to extrusion ratios, assuming that mixed-asymmetrical junctions forming LABs dissociate at high extrusion ratios from the external stress (>981 MPa) with thermal activation by the generated heat. The correlation between grain size and Vickers hardness followed the Hall?Petch relationship despite the texture gradient of the 〈111〉 cyclic fiber textural microstructure at low extrusion ratios and the 〈100〉 true fiber textural microstructure at high extrusion ratios. The increase in hydrostatic pressure on the Nb tubes contributed to texture evolution in terms of extrusion ratios due to the difference between {110}〈111〉 and {112}〈111〉 components based on EBSD data.     

Microstructure and texture gradient in copper deformed by equal channel angular pressing

The aim of this paper was to examine the gradient in the microstructure and texture that develops during equal channel angular pressing (ECAP). Copper of 4N purity was subjected to ECAP deformation at room temperature by using three passes of Route A. The local microstructure and texture were investigated by orientation imaging microscopy and high-energy synchrotron radiation, respectively. The refined microstructure consists of elongated grains inclined in the direction of extrusion. The texture is characterized by typical shear components of face-centred cubic metals which deviate from their ideal positions. Inclination of the grain long axis and the texture components with respect to the extrusion direction depend on the distance from the top of the extruded bar and change from pass to pass. The texture gradient is modelled with the flow line model using the viscoplastic self-consistent polycrystal approach. Microstructure formation and reasons for the texture gradient are discussed.     

Effects of dynamic recrystallization in extruded and compressed AZ31 magnesium alloy

Commercial AZ31 billets were extruded to round rods at three extrusion velocities of 0.8~m/min, 1.4 m/min and 2.2 m/min, at 643 K, 673 K and 703 K, respectively. The microstructure and texture evolution at different conditions were investigated by optical microscopy (OM) and electron backscattered diffraction (EBSD) techniques. The average grain size is reduced significantly after the hot extrusion, and the microstructure is obviously inhomogeneous due to dynamic recrystallization, which is confirmed by uni-axial compression experiments at elevated temperatures with different strain rates. The uni-axial compression leads to a fibre texture, and {1120}<0110> texture is the major texture in extruded rods due to non-basal slip. As the extrusion temperature is elevated, the main texture becomes weak and other texture components appear.