AZ31变形镁合金轧制工艺初探

研究了板坯加热温度、退火温度以及冷轧道次加工率对AZ31变形镁合金轧制能力的影响.结果表明,当加热温度为350℃,轧制速度为0.4m/s时,AZ31镁合金板材的热轧道次极限加工率可以达到34.62%(无裂纹)和59.23%(无表面裂纹);将热轧态板材分别在250℃～350℃温度,退火40min后,板材显微组织中晶粒大小均匀,维持在5μm～6μm水平;板材具有良好的综合力学性能,其抗拉强度为:230Pa～240MPa,屈服强度为:135MPa～175MPa,延伸率为:12%～15%.当采用350℃×40min退火后,板材在冷轧道次加工率为5%～10%时,总加工率可以达到40%以上.     

Formation of the Nanocrystalline Structure in an Equiatomic NiTi Shape-Memory Alloy by Thermomechanical Processing

The microstructural evolution during cold rolling followed by annealing of an equiatomic NiTi shape-memory alloy was investigated. The high purity Ni₅₀Ti₅₀ alloy was cast by a copper boat vacuum induction-melting technique. The as-cast ingots were then homogenized, hot rolled, and annealed to prepare the suitable initial microstructure. Thereafter, annealed specimens were cold rolled up to 70 % thickness reduction at room temperature. Post-deformation annealing was conducted at 400 °C for 1 h. The microstructure was characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and differential scanning calorimetry techniques. The initial microstructure was free from segregation and Ti- or Ni-rich precipitates and was composed of coarse grains with an average size of 50 μm. The cold rolling of NiTi alloy resulted in a partial amorphization and the deformation-induced grain refinement. A nanocrystalline structure with the grain size of about 20-70 nm was formed during the post-deformation annealing.     

Processing Effects on Grain Refinement of AZ31 Magnesium Alloy Treated with a Commercial Al-10Sr Master Alloy

The effects of Sr amount and melt holding time on the grain refinement of AZ31 magnesium alloy treated with a commercial Al-10Sr master alloy are investigated. The effects of solutionizing, rolling, and remelting of commercial Al-10Sr master alloy on the grain refinement of AZ31 magnesium alloy are also investigated. An increase in Sr amount from 0.01 to 0.1 wt.% or melt holding time from 20 to 80 min causes the grain size of AZ31 alloy treated with the commercial Al-10Sr master alloy to gradually decrease. In addition, the solutionizing, rolling, or remelting of commercial Al-10Sr master alloy can improve the refinement efficiency of the master alloy to AZ31 alloy, and the improvement resulting from the remelting is best obvious, followed by rolling and solutionizing, respectively.     

Microstructure and temperature monitoring during the hot rolling of AZ31

This study details the microstructural evolution during hot rolling of AZ31 alloy sheet using a pilot-scale rolling mill. The aim is to understand the deformation mechanisms leading to grain refinement under industrial processing conditions and to design and optimize the hot rolling schedule for AZ31 in order to produce sheet with a fine and homogeneous microstructure. The study examined three different hot rolling temperatures, 350, 400, and 450°C, and two rolling speeds, 20 and 50 rpm. A total thickness reduction of 67% was obtained using multiple passes, with reductions of either 15% or 30% per pass. It was found that the microstructure of the AZ31 alloy was sensitive to the rolling temperature, the reduction (i.e., strain) per pass and the rolling speed (i.e., strain rate). The results show that the large cast grain structure is broken down by segmentation of the cast grain through localized deformation in twin bands, where dynamic recrystallization occurs in these bands as well as at the grain boundaries (necklacing).     

Effects of cerium on the microstructure and mechanical properties of AZ31 alloy

AZ31 alloy with Ce addition was studied. The influence of Ce contents on the microstructure and tensile properties of the alloy was analyzed. Ce addition results in the formation of AlzCe and the annealed microstructure is improved by the addition. There was no recrystallization of the alloy after rolling, however, it did occur after annealing. The alloy can be strengthened by adding Ce and the alloy with 1.05 wt.% Ce possessed the best synthetical properties of all the tested alloys. As rolled, σb and δof this alloy are 321 MPa and 6.9%, and as annealed, they are 259 MPa and 21.8%.     

轧制温度和后处理方式对AZ31镁合金显微组织和力学性能的影响

在不同的轧制温度下,对AZ31镁合金板进行轧制,然后取出轧板立即进行水冷、空冷和退火3种不同的后处理。探究轧制温度和后处理对镁合金显微组织和力学性能的影响。结果表明,轧制温度为250、300℃时,水冷和空冷处理后板材存在着大量的孪晶,350℃时由于轧制温度较高,孪晶的数量很少;水冷处理后的平均晶粒尺寸要小于空冷,空冷处理之后的孪晶数量略少于水冷,当轧制温度为350℃时,退火处理后,晶粒尺寸减小,晶粒趋于等轴状,晶格畸变程度低。在相同的轧制温度下,水冷处理的镁合金板材的屈服强度、抗拉强度和硬度较高;退火处理后可以显著提高板材的伸长率,但屈服强度、抗拉强度略有下降。轧制温度升高时,3种后处理方式之间屈服强度和抗拉强度的最大差值会减小。     

AZ31镁合金差温热轧过程的晶粒细化

实验研究了经不同道次差温热轧AZ31镁合金的金相组织,结合对轧制过程,尤其是轧件温度场的数值模拟结果,分析了AZ31镁合金差温热轧过程晶粒细化机制与主要影响因素,获得了通过轧制过程动态再结晶,使轧材晶粒尺寸随轧制道次增加,而持续细化的工艺参数,并制备出平均晶粒尺寸为5μm左右的细晶AZ31镁合金板材。     

AZ31镁合金热轧变形的动态再结晶机制

在轧制温度603~703 K、轧制压下量20%~40%、应变速率4~16 s-1下对AZ31镁合金进行轧制变形,研究轧制压下量、应变速率和变形温度对AZ31镁合金变形组织的影响,分析了镁合金的动态再结晶机制。结果表明：应变速率和变形温度不仅影响动态再结晶进行的程度,而且能够改变再结晶的方式或形核机制。当轧制应变速率= 13.9 s-1,变形温度T=603 K时,再结晶方式为孪生动态再结晶;变形温度升高到703 K时,沿晶界有链状新晶粒出现。当变形温度T= 673 K,应变速率= 11.35 s-1时,再结晶方式以孪生动态再结晶为主;应变速率降低到= 4 s-1时,再结晶方式以旋转动态再结晶为主。     

退火温度对大变形热轧AZ31镁合金板材力学性能的影响

采用热挤压态AZ31变形镁合金板坯,研究了退火温度对大变形热轧AZ31变形镁合金板材力学性能的影响.结果表明:随着退火温度的升高,变形镁合金板材的抗拉强度和屈服强度减小,伸长率呈线性增加趋势,硬度和杯突值均降低.变形镁合金板材的力学性能与其晶粒尺寸和组织均匀性密切相关.     

The Effect of Texture on the Corrosion Behavior of AZ31?Mg Alloy

Magnesium (Mg) grains show anisotropic corrosion behavior, which implies that the single-phase, hot-rolled Mg alloy AZ31 sheet, if highly textured, will have different corrosion performance depending on its crystallographic orientation of the grains. Its rolling surface, dominated by (0001) basal crystallographic planes, is more corrosion resistant than its cross-section surface, which is mainly composed of $ \{ 10\overline{1} 0\} $ and $ \{ 11\overline{2} 0\} $ prismatic crystallographic planes. Furthermore, grain refinement by hot rolling is beneficial to the overall corrosion resistance of AZ31 because of the dissolution of AlMn(Fe) intermetallic precipitates in the alloy. Surface compressive deformation machining can lead to refined grains and an expected preferred grain orientation, thus improving the corrosion resistance of AZ31 alloy.     

异步轧制AZ31镁合金板材室温冲压性能研究

文章主要对异步轧制AZ31镁合金板材室温冲压性能进行了研究,以探讨提高镁合金板材冲压性能的途径。结果表明,异步轧制有利于板材的晶粒细化,其晶粒尺寸约为7.6μm,明显小于普通轧制板材的12.5μm;而由于异步轧制过程中剪切变形的作用,异步轧制使板材的(0002)基面晶粒取向减弱;与普通轧制相比,异步轧制板材的应变硬化能力增加,屈服强度降低,制耳参数减小,但塑性应变比也降低,这可归因于异步轧制所导致的晶粒细化和晶粒取向的改变。     

铈对镁合金AZ31晶粒大小及铸态力学性能的影响

试验采用普通的熔炼铸造方法，就稀土Ce对镁合金AZ31晶粒大小及其铸态力学性能的影响进行了研究。Ce含量＜1％时随着Ce含量的增加AZ31晶粒越来越细，超过1％时晶粒又变粗。对获得的细晶材料进行了铸态下力学性能的测试并与未加细化剂的材料进行比较，发现抗拉强度和塑性都明显提高。断口扫描分析证明拉伸时断裂为明显的沿晶断裂，压缩时为穿晶断裂。     

Hot-deformation behaviors of AZ31 alloys with different initial states

The hot-deformation behaviors of three types of AZ31 samples,extruded sheet,hot rolled sheet and cast rod were studied. These samples had different initial grain size and texture.Compression deformation of these samples was carried out using a Gleeble 1500D under a series of thermal deformation conditions.Microstructure and texture of the initial and deformed samples were examined using electron backscatter diffraction(EBSD) techniques.The flow curves for all these three types of samples shifted upward w...     

轧制工艺对双辊铸轧AZ61镁合金组织性能的影响

研究了利用双辊铸轧镁合金铸轧坯直接进行热轧的生产工艺,研究了不同热轧工艺过程对产品品质的影响.研究表明,在400℃热轧时,随着压下量增加,铸轧镁合金显微组织的再结晶程度提高,晶粒细化;随着轧制温度的提高,显微组织中孪晶减少,再结晶程度提高,晶粒变得均匀且细小;在400℃下连续热轧到1.5 mm,得到的板材力学性能最优.     

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.     

Effect of plane strain on microstructures and texture, through the reduction ratio of AZ31 Mg alloy

Structural evolution of warm-rolled AZ31 alloy sheets was investigated with respect to various reduction ratios. In order to examine the effect of rolling pass on deformation of the sheet, one-pass rolling was applied to the AZ31 alloys for various 6/1/2011reduction ratios. When the applied reduction ratio was ∼85% of the initial thickness, significant grain refinement and texture development were achieved with dynamic recrystallization. Moreover, with the increase of the rolling reduction ratio from 30% to 85%, the warm rolled sheets exhibit plane strain mode displaying uniform 〈0 0 0 1〉//ND basal textures throughout the whole sheet thickness. The two-dimensional finite element method simulation showed that the current lubrication rolling results in a uniform plane strain deformation through the whole warm rolled sheet.     

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.     

同步和异步轧制AZ31镁合金板材的织构及力学性能

采用同步轧制(NR)和异步轧制(AR)工艺对AZ31镁合金挤压板材进行了轧制,研究了轧制过程中组织和织构的演化,以及总压下量和异步比对轧材组织、织构和力学性能的影响。结果表明,在压下量为3%～15%的范围内,同步轧制与异步轧制板材在晶粒尺寸以及均匀性上有相似的变化趋势。轧制过程中,在变形初期,随压下量的增加,孪晶数量不断增加,孪晶使同步轧制与异步轧制板材中晶粒取向都发生偏转,即C轴趋向于垂直于法向(ND),从而使初始挤压板材的丝织构强度减弱;而当压下量达到24%时,孪晶大量减少或消失。在压下量为3%～24%的范围内,同步轧制对板材力学性能的影响并不明显,峰值应变呈交替变化;异步轧制板材在压下量达到24%左右时,表现出了良好的塑性变形能力,抗拉强度达到309MPa,峰值应变达到0.163。     

轧制工艺对AZ31B镁合金薄板组织与性能的影响

研究了轧制温度和轧制速度对AZ31B镁合金薄板微观组织演变和力学性能的影响。结果表明,轧辊加热有利于镁合金薄板成型;AZ31B镁合金在低温或低速轧制时薄板纵向组织为大量的切变带,切变带区域包含大量孪晶组织,横向组织为含极少量孪晶的等轴晶组织;在轧制温度为400℃和轧制速度为16m/min轧制时,由于动态再结晶,横纵截面组织均为等轴晶。AZ31镁合金薄板的最佳轧制制度为轧辊温度为70℃、轧制温度为400℃、轧制速度为6m/min,此工艺轧制的薄板横向抗拉强度、屈服强度和伸长率分别为350MPa、300MPa和12%,纵向为345MPa、290MPa和11.2%,纵向与横向性能差别明显减小。     

挤压AZ31B镁合金板材高温轧制变形行为研究

通过单道次轧制试验,研究了AZ31B挤压镁合金板材在温度为365℃和450℃时的轧制性能,其变形量范围为10%～60%,应变速率为2.1s-1～5.0s-1。通过光学显微镜和扫描电镜观察了轧制变形中的微观组织及其演变。结果表明,在变形的初始阶段,孪生为主要的变形机理和硬化机制。由孪生变形积聚的畸变能和非基滑移的启动,导致了动态再结晶的形核与长大,增大变形速率可以抑制晶粒长大,使平均晶粒尺寸细化到7μm～10μm。365℃温轧制变形使板材晶粒明显细化,温度较高时,晶粒细化作用有限。在同一变形量下,随着轧制温度的升高,板材的晶粒呈长大趋势,在365℃轧制温度下,随着道次变形量的加大,细晶百分含量随之迅速增加。当轧制温度提高到450℃时,晶粒细化有限,晶粒尺寸保持在20μm以上。