Effect of hot extrusion on microstructure and mechanical properties of quasicrystal-reinforced Mg-Zn-Y alloy

The microstructure and mechanical properties of as-cast and as-extruded Mg-Zn-Y alloy （Mg-11 %Zn- 0.9%Y, mass fraction） containing Mg3 YZn6 quasicrystal were studied. The eutectic icosahedral quasicrystal phase （I-phase） is broken and almost distributes along the extrusion direction, and fine I-phase with nano-size is precipitated during the extrusion. The a-Mg matrix grains are refined due to recrystallization occuring during the hot extrusion. Some {1012} twins are observed in the extruded ZW1101 alloy. And {0002}（1010） fiber texture is formed in matrix alloys after hot extrusion. The extruded alloy exhibits high strength in combination with large elongation at room temperature. The strengthening mechanism of the as-extruded alloy was discussed.     

Texture evolution of extruded AZ31 magnesium alloy sheets

The evolution of texture during the annealing and hot rolling process of extruded AZ31 magnesium alloy sheets was studied. There are two kinds of texture components in the extruded AZ31 sheets. One is {0002}<1-010> and the other is {1-010}<1-120>. The {0002}<1-010>component predominates. After annealing at 723 K for 3 h, both {0002}<1-010> and {1-010}<1-120> components are strengthened moderately. This indicates that grains with both two components mentioned above grow faster than those with other orientations. The {1-010}<1-120> component disappears and the intensity of {0002}<1-010> component decreases significantly after hot rolling with a 30% reduction at 623 K. This is mainly attributed to rotational dynamic recrystallization (RDX) during the hot rolling.     

轧制工艺对N36锆合金带材微观结构的影响

利用扫描电镜(SEM)、透射电镜(TEM)和电子背散射衍射(EBSD)等方法,对不同轧制工艺制备的N36锆合金带材中的第二相、晶粒尺寸和微观织构进行了研究。结果表明,锆合金带材中织构主要以{0001}$\bar{1}2\bar{1}0$和{0001}$01\bar{1}0$两类基面织构为主,第二相粒子主要为HCP型Zr(Nb, Fe)₂粒子。在热轧总变形量一致的情况下,热轧工艺道次变形量的变化对最终带材的晶粒尺寸和微观织构影响不大,但是对第二相粒子的尺寸有很大影响。热轧过程第一道次变形量越大,最终带材中第二相粒子尺寸越小。在热轧过程中,换向轧制会影响最终带材的织构组成,也会促进锆晶粒的[0001]轴平行于带材的ND方向;同时在带材的轧面(RD-TD 面)上,晶粒的取向性减弱,晶粒取向更加随机。终轧过程中的变形量增大,会使最终带材的晶粒尺寸减小,再结晶程度提高,使得最终带材中{0001}$\bar{1}2\bar{1}0$织构增强,而{0001}$01\bar{1}0$织构减弱。     

初始取向对AZ31镁合金微观织构演化的影响

将从挤压棒材中截取的长轴与挤压方向分别成0°,45°和90°的AZ31镁合金长方体试样在中、高温度(523-723 K)下沿长轴方向压缩变形,利用OM和SEM/EBSD技术观察和分析了初始取向对其微观织构演化的影响.结果表明,随着变形温度的降低,初始取向对变形行为的影响显著增加,在523 K时,长轴平行挤压方向的0°试...     

Rolling Texture in Ti_3Al

ＲｏｌｌｉｎｇＴｅｘｔｕｒｅｉｎＴｉ＿３ＡｌＭａｏＷｅｉｍｉｎ，ＹｕＹｏｎｇｎｉｎｇａｎｄＸｕＪｕｎ（毛卫民）（余永宁）（徐军）（ＤｅｐａｒｔｍｅｎｔｏｆＭｏｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，ＵｎｉｒｅｒｓｉｔｙｏｆＳｃｉｅｎ...     

MGH754合金挤压棒材的二次再结晶与织构

研究了ＭＧＨ７５４合金在二次再结晶过程中的组织和结构变化。结果表明，合金大热挤压状态具有细小的等轴晶组织，织构微弱，有利于进行殂变加工；二次再结晶后，组织为粗大的柱状晶，且出现强烈的织构；随着退火时间延长，「１１０」〈００１》和「１００」〈００１〉织构含量明显增加，而「１１０」〈１１１〉，「１１０」〈１１３〉和「１１２」〈１１１〉等织构的含量减少，合金棒材的纵向主要为〈００１〉取向。     

润滑对3104铝合金板变形织构的影响

在无润滑(WOL)和润滑(WL)2种轧制条件下,分别对2.3 mm厚的热轧3104铝合金板进行不同压下量的冷轧.应用取向分布函数(ODF)定量计算和分析在不同轧制压下量下润滑对3104铝合金板材沿板厚方向织构演变的影响.结果表明:随着轧制压下量的增加,样品各层的织构组分强度均逐渐增加;无润滑轧制时样品表面层主要织构组分取向密度普遍高于相同压下量下润滑轧制时的取向密度.导致表面层织构组分增强的原因是摩擦引起应变状态改变的结果.     

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.     

Effect of Zn and Y Additions on Grain Boundary Movement of Mg Binary Alloys During Static Recrystallization

Texture evolution in rolled Mg–1 wt% Zn and Mg–1 wt% Y binary alloys was analyzed by quasi-in situ electron backscatter diffraction (EBSD) during static recrystallization. Mg–1 wt% Zn and Mg–1 wt% Y alloys exhibited strong basal texture at the initial recrystallization state. After grain growth annealing, the basal texture component {0001} < $11\overline{2}0$ > was increased in Mg–1 wt% Zn alloy and that of Mg–1 wt% Y alloy was decreased to be a random texture. Zn and Y atoms segregated strongly to the recrystallized grain boundaries in Mg–1 wt% Zn alloy and Mg–1 wt% Y alloy, respectively. Thus, Zn and Y elements facilitated the grain boundary movements along contrary directions during grain growth. In Mg–1 wt% Zn alloy, due to the Zn element segregation on grain boundaries, the grains consisted of a strong texture grew more easily because the grain boundary migration tended to move from the orientation close to normal direction to the orientation near to transverse direction or rolling direction. Therefore, after grain growth, the volume fraction of texture component {0001} < $11\overline{2}0$ > was increased by consuming the neighboring grains, leading to a stronger basal texture. On the contrary, in the Mg–1 wt% Y alloy, the Y element segregation caused the opposite direction of grain boundary migration, resulting in a random texture.     

形变量对6111铝合金再结晶织构的影响

采用取向分布函数(ODF)法研究了冷轧形变量对6111铝合金再结晶织构的影响。结果表明:6111铝合金的再结晶织构主要由Cube ND15和{011}<111>织构组分构成;随冷轧形变量的增加,这两种织构组分的取向密度逐渐升高,但二者升高的速度并不相同,{011}<111>组分取向密度升高的速度比Cube ND15组分的快,当冷轧形变量大约为50%时,{011}<111>组分的取向密度超过Cube ND15组分的。     

Shear bands in magnesium alloy AZ31

During deformation of magnesium at low temperatures, cracks always develop at shear bands. The origin of the shear bands is the { 1011 } twinning in basal-oriented grains and the mobility of this type of twin boundary is rather low. The most frequent deformation mechanisms in magnesium at low temperature are basal slip and { 1012 } twinning, all leading to the basal texture and therefore the formation of shear bands with subsequent fracture. The investigation on the influences of initial textures and grain sizes reveals that a strong prismatic initial texture of (0001) parallels to TD and fine grains of less than 5 8m can restrict the formation and expansion of shear bands effectively and therefore improve the mechanical properties and formability of magnesium.     

横轧3105铝合金织构演变的定量分析

采用X射线衍射仪研究3105铝合金在横轧过程中织构的演变.结果表明:3105铝合金热轧板材具有强的β纤维轧制织构,在横轧过程中B'{110}<111>、S"{123}<17229>和C"{112}<110>取向是不稳定的,它们将逐渐向新的坐标系中β纤维的位置旋转;随横轧压下量增大,C(和S(取向强度快速降低,B(取向强度先增加后降低,而β纤维轧制织构的强度逐渐增加;β纤维和剩余组分织构体积分数的变化与轧制真应变的关系遵循Avrami方程,强的初始B'、S"和C"织构显著地提高了β纤维织构的形成速率.     

Tailoring Texture to Highly Strengthen AZ31 Alloy Plate in the Thickness Direction via Pre-tension and Rolling-Annealing

Conventional wrought Mg alloys, such as AZ31 and ZK60 rolled plates, usually exhibit significantly low tensile yield strength in the thickness direction. This can be attributed to the high activity of {10-12} tension twinning due to the strong basal texture (< 0001 > //ND, normal direction). In this work, the tensile yield strength in the ND of the as-rolled (AR) AZ31 plate increased from 50 to 150 MPa (increased by 200%) via simple processing, i.e., pre-tension and rolling-annealing (PTRA) treatment. The strong basal texture (< 0001 > //ND) of the AR plate was changed into a weakened fiber texture (< 0001 > ⊥ND). The evolution of microstructures during PTRA treatment and the activated deformation modes during uniaxial tension were studied quantitatively and statistically by the means of intergranular misorientation (IM) and in-grain misorientation axes (IGMA) analysis. The results indicate that various twin variants, as well as {10-12}-{10-12} secondary twins, were activated during pre-tension and rolling, and most residual matrix was consumed by twins after annealing. The dominated deformation modes in tension changed from {10-12} tension twinning (the AR sample) to prismatic slip (the PTRA sample) in the early tensile deformation. The underlying formation mechanism of the fiber texture and corresponding strengthening mechanism were discussed.     

锆合金挤压管坯的组织及织构研究

采用XRD和EBSD技术,对不同挤压温度(650和630℃)的2种锆合金管坯的显微组织和宏观织构进行研究。结果表明,管坯内发生了动态回复和再结晶,其组织由沿挤压方向拉长的大晶粒与近似等轴的再结晶晶粒组成,管坯内再结晶晶粒的平均尺寸相近,分别为0.44和0.41μm,温度对显微组织无显著影响;挤压温度为650℃的管坯的织构主成分为<1010>纤维织构及{0001}<1010>,630℃挤压管坯的织构主成分为<1120>纤维织构及{0001}<1120>,并且后者基轴在管材横向的分布强度略高于径向分布。     

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.     

Effects of die angle on microstructures and mechanical properties of AZ31 magnesium alloy processed by equal channel angular pressing

1　INTRODUCTIONMagnesiumalloysarethelightestmetallicstruc turalmaterialsandhencetheyprovidegreatpotentialintheweightsavingofautomotiveandaerospacecomponents ,materialhandlingequipment ,portabletoolsandevensportinggoods[1,2 ] .Duetotheirhexago nalclose packed (HCP)crystalstructure ,magnesiumalloysperform poorformabilityandlimitedductilityatroomtemperature ,thustheirproductsaremainlyfabricatedbycasting ,inparticular ,die casting ,andtheapplicationsofwroughtmagnesiumalloysarelim ited .Nowit…     

铸造冷却速度对Mg-4.4Zn-0.3Zr-0.4Y挤压态合金组织性能的影响

本文通过两种不同冷却速度制备成分相同、铸造组织特征不同的Mg-4.4Zn-0.3Zr-0.4Y铸态合金,研究不同铸造组织特征对挤压变形态合金组织和力学性能的影响。研究结果表明：与空冷铸造合金相比较,通过水冷冷却增大了熔体冷却速度,使铸态组织得到细化,抑制了W-相（Mg3Y2Zn3相）的形核,并促进了I-相（Mg3YZn6相）的生成,获得了更大体积分数的准晶相(I-相)。经过挤压变形后,水冷铸造合金中的再结晶晶粒细小均匀,经过挤压变形破碎的细小I-相颗粒弥散分布在基体上,{0002}基面织构得到弱化,而{101 ?2}织构强度增强,从而使挤压态Mg-4.4Zn-0.3Zr-0.4Y合金的强度和塑性都得到了大幅的提高。水冷铸造Mg-4.4Zn-0.3Zr-0.4Y合金经过挤压变形后,屈服强度和抗拉强度分别达到297.0MPa和327.3MPa,与空冷铸造挤压态合金相比分别提高了46.4MPa和21.4MPa。水冷铸造Mg-4.4Zn-0.3Zr-0.4Y挤压态合金的延伸率达到14.8%,与空冷铸造挤压态合金相比增大了4.7%。     

AZ31镁合金挤出板降温热轧的组织和织构的演变

研究AZ31镁合金挤出板坯在降温热轧过程中的组织和织构的演变规律.结果表明:退火前滑移和孪生是主要的变形机制和取向硬化机制;退火后长条晶的滑移和细小等轴晶晶界扩散迁移的共同作用成为主要的变形机制;随着压下量的增大,析出物开始破碎和分散,压下量在70%～80%之间时,基面织构组分的取向密度存在突变最大值,形成硬取向较强的{0001}基面织构,软化退火能大幅减弱硬取向;通过一道67%大压下量和一次软化退火可顺利地将AZ31镁合金轧制成厚0.5 mm的薄板.     

异步轧制对3004铝合金变形织构及制耳率的影响

以３００４铝合金为实验材料，研究了异步轧制对该合金的变形织构以及相应的制耳率的影响。实验表明：异步轧制和同步轧制板的主要变形织构是相同的，均为纯铜型织构｛１１２｝＜１１１＞＋｛２１３｝＜３６４＞＋｛１１０｝＜１１２＞，但异步轧制产生的变形织构较同步轧制的强度高，且随异步轧制速比的提高而增强。同时，异步轧制的板材中还出现｛００１｝＜１１０＞织构。另外，在相同压下率的情况下，异步轧制板材的深冲制耳率均大于同步轧制的制耳率     

搅拌摩擦焊焊接5083铝合金板材焊核区的晶体取向

采用搅拌摩擦焊焊接了5083铝合金板材,借助电子背散射衍射技术和取向成像分析软件,对比性地分析了母材和焊核区的晶粒形貌、取向差分布、织构组分及取向分布函数,分析了焊核区晶体取向的变化.结果表明,在热-力作用下,焊核区发生动态再结晶,显示等轴晶粒形貌,平均晶粒尺寸约为15.8μm,同时大角度晶界比例明显增加.母材的黄铜织构B{011} <211> 和S织构{123} <634> 的比例分别达到30.6%和13.6%以上;搅拌摩擦焊后,焊核区的B织构和S织构的比例分别降至4%和1.8%,原位再结晶形成的R{124} <211> 织构组分约为7.7%,焊核区其它常见面心立方金属织构组分的比例均低于8%,意味着焊核区由强取向组织转变为弱取向组织.