显微组织和织构对AZ31B镁合金成形性能的影响(英文)

通过单向多道次弯曲(RUB)工艺及随后的退火处理来改变镁合金的显微组织和织构,研究显微组织和织构对其成形性能的影响。RUB工艺和不同温度下的退火处理对显微组织有两方面的影响:粗化晶粒和削弱织构。经RUB处理并在300°C退火的板材表现出最好的成形性能。这主要归因于(0002)基面织构强度的削弱,而织构的削弱导致了较低的屈服强度、较大的断裂伸长率、较小的Lankford值(r值)和较大的加工硬化指数(n值)。与原始板材相比,经RUB处理并在400°C退火而产生的具有粗大晶粒的板材具有较低的拉伸性能,但却表现出较高的成形性能。这主要是由于粗大晶粒增强了变形孪晶,而变形孪晶可以协调厚向应变。     

AZ31镁合金热成形及退火过程的组织与织构

研究了热轧板及不同挤压比的热挤压棒的组织和织构特征 ,确定了热挤压时 <110 0 >织构随应变的加大取代 <112 0 >织构的原因。分析了退火对热成形组织及织构的影响 ,确定了 <110 0 >织构的消失与残余形变晶粒再结晶的联系。估算了退火时两类样品的平均晶粒长大速度并讨论了其与织构的关系。综合分析表明 ,AZ31镁合金热成形后总产生较强的织构 ,织构提高了热成形后的力学性能。高温退火虽使织构减弱 ,但伴随晶粒的明显长大。     

AZ31镁合金薄板经不同累积应变的连续弯曲变形后的显微组织与成形性能（英文）

对AZ31镁合金板材进行不同累积应变的连续弯曲变形及退火处理,随后对显微组织与力学性能的变化进行了研究。结果表明:经不同累积应变的连续弯曲变形后,镁合金板材的显微组织中没有发现孪晶,退火后,板材表层的晶粒异常长大,粗晶层的厚度随着累积应变的增加而增加,并且镁合金板材的织构朝RD方向偏转,偏转角度随累积应变的增加而增大;与原始板材相比,连续弯曲变形及退火处理使镁合金板材呈现出较好的室温成形性能(杯突值由2.3 mm提高到4.9 mm,提高了~113%),这主要归因于基面织构的改善使镁合金板材的r值减小与n值增大。     

织构与晶粒尺寸对AZ31镁合金薄板成形性能的影响

通过不同的轧制工艺,制备了4种具有不同晶粒尺寸和织构的镁合金板材;通过单向拉伸试验和室温埃克森试验,探讨了晶粒尺寸与织构对镁合金板材室温成形性能的影响。研究表明,晶粒细化虽然增强了板材的力学性能,但却不利于提高板材的胀形性能;基面织构减弱使板材沿厚向的变形能力提高,具有较好的胀形性能,但却造成板材屈服强度的降低。     

AZ31B变形镁合金压力成形

总结了AZ31B变形镁合金挤压、轧制和热冲压拉深的研究工作。AZ31B挤压板材无裂纹、无烧损,其组织呈晶粒细小的等轴晶;用分流挤压铝合金技术可生产挤压比不大于45,厚度不小于1 5mm的非薄壁镁合金管材;交叉轧制的镁合金薄板的A显著提高,Rp0.2和Rm明显下降;单向轧制时,则出现相反的结果。采用机械冲压法成功地热冲压出60mm×60mm×20mm的方形件,无裂纹现象。     

织构和晶粒尺寸对AZ31镁合金薄板成形性能的影响

采用不同的轧制工艺,制备4种晶粒尺寸为7~18μm和不同强度基面织构的AZ31镁合金板材,通过单向拉伸试验和室温Erichsen试验,探讨晶粒尺寸与织构对镁合金板材室温成形性能的影响。结果表明:晶粒细化虽然增强了板材的力学性能,但不利于提高板材的胀形性能;基面织构的减弱使板材沿厚度方向变形能力增强,具有较好的胀形性能,但另一方面使板材的屈服强度降低。     

挤压轮转速对AZ31镁合金连续挤压显微组织的影响

在250型连续挤压机上对挤压态AZ31镁合金进行连续挤压试验,观察比较挤压前后在纵截面上的组织变化,并研究挤压轮转速对AZ31镁合金显微组织的影响.结果表明:经过连续挤压后,AZ31镁合金晶粒得到细化;随着挤压轮转速的提高,在产品心部区域的晶粒尺寸逐渐增大;当挤压轮转速为7.0 r/min时产品的表层和心部区域的显微组织趋于均匀.     

异步轧制AZ31镁合金的微观组织与室温成形性能

探讨采用小异速比多道次异步轧制技术提高AZ31镁合金板材室温成形性能的可行性,研究异步轧制板材微观组织的特点、形成机理及其与成形性能间的内在联系。结果表明:多道次异步轧制所累积的剪切应变能有效促进压缩孪晶的交互作用,细化合金晶粒组织,削弱(0002)基面的织构强度;异步轧制AZ31镁合金板材后续退火处理后的室温伸长率和Erichsen值分别可达32%和6.14mm;(0002)基面织构减弱和塑性应变比的降低是板材室温成形性能提高的根本原因。     

喷射成形高强度AZ91镁合金的组织与力学性能

在保护气氛中采用喷射成形制备技术制备了形状完整的AZ91镁合金沉积圆柱坯.对沉积坯进行显微组织分析,结果表明:喷射沉积AZ91镁合金具有均匀、细小的等轴晶组织,平均晶粒尺寸约17 μm,有效地改善了离异共晶β-Mg17Al12相在晶界的偏析;挤压变形过程引发的动态再结晶使喷射成形AZ91镁合金的组织进一步细化;经175 ℃时效时,析出相中多数为不连续析出,连续析出所占比例很小;后期阶段时效过程加快,长时间时效未见片状及针状析出物球化现象.喷射成形AZ91 镁合金经挤压变形和T6处理后,抗拉强度和屈服强度分别达到435和360 MPa,伸长率为9.2%,实现了强度和韧性的同步大幅度提高.     

加热温度对AZ31镁合金连续挤压组织与性能的影响

采用连续挤压方法,开展AZ31镁合金工艺试验,研究加热温度对挤出产品微观组织和力学性能的影响。结果表明,加热温度对AZ31镁合金组织影响明显,坯料室温挤压时,产品的芯部组织均匀细小,而表层的晶粒大小不均。随着加热温度的升高,微观组织的均匀程度提高。当坯料加热到450℃时,挤出产品芯部的晶粒有长大的趋势。连续挤压后的晶粒相比坯料显著细化,这是由于坯料在连续挤压过程中经历了多种变形,使晶粒得到细化。随着加热温度的升高,抗拉强度增加,伸长率变化不大,这是由于温度的适当提高,使再结晶充分,晶粒均匀程度提高。     

Influence of initial texture on formability of AZ31B magnesium alloy sheets at different temperatures

Repeated unidirectional bending (RUB) process was carried out to improve the texture of AZ31B magnesium alloy sheets. Influence of initial texture on formability of AZ31B magnesium alloy sheets at different temperatures was investigated. Compared with the as-received sheets, the limiting drawing ratio of the RUB processed sheets increased to 1.3 at room temperature, 1.5 at 50 °C and 1.7 at 100 °C, respectively. The improvement of the press formability at lower temperatures can be attributed to the texture modification, which led to a smaller Lankford value and a larger strain hardening exponent. However, the press formability of the sheet with a weakened basal texture has no advantage at higher temperature. This is due to much smaller r-value that results in severe thinning in thickness direction during the stamping process which is unfavorable to forming. Anyhow it is likely that the texture control has more effect on the press formability at lower temperature.     

电脉冲连续退火对AZ91镁合金带材组织和性能的影响

研究了电脉冲连续退火对冷轧时效态AZ91镁合金带材显微组织和力学性能的影响。结果表明:电脉冲退火在较低的温度下快速完成了α-Mg基体的再结晶,可显著细化晶粒。当退火温度为210℃时,α-Mg基体发生完全再结晶,其平均晶粒尺寸由冷轧态的约30μm减小为约7μm,带材的抗拉强度由冷轧态的410 MPa减小至334 MPa,断后伸长率由冷轧态的3.7%增大至23%。电脉冲退火后带材的拉伸断裂方式由冷轧态的脆性沿晶断裂转变为韧性穿晶断裂。电脉冲在其热效应和非热效应的共同作用下快速完成再结晶过程以及β-Mg17Al12相阻碍α-Mg基体晶粒长大,是电脉冲退火细化晶粒的主要原因。     

Cold stamping formability of AZ31B magnesium alloy sheet undergoing repeated unidirectional bending process

The repeated unidirectional bending (RUB) process was carried out on an AZ31B magnesium alloy in order to investigate its effects on the cold stamping formability. The limiting drawing ratio (LDR) of the RUB processed magnesium alloy sheet with an inclination of basal pole in the rolling direction can reach 1.5 at room temperature. It was also confirmed that cell phone housings can be stamped successfully in crank press using the RUB processed AZ31B magnesium alloy sheet. The improvement of the stamping formability at room temperature can be attributed to the texture modifications, which led to a lower yield strength, a larger fracture elongation, a smaller Lankford value (r-value) and a larger strain hardening exponent (n-value).     

Deep drawing of square cups with magnesium alloy AZ31 sheets

The square cup drawing of magnesium alloy AZ31 (aluminum 3%, zinc 1%) sheets was studied by both the experimental approach and the finite element analysis. The mechanical properties of AZ31 sheets at various forming temperatures were first obtained from the tensile tests and the forming limit tests. The test results indicate that AZ31 sheets exhibit poor formability at room temperature, but the formability could be improved significantly at elevated temperatures up to 200 °C. The test results were then employed in the finite element simulations to investigate the effects of process parameters, such as punch and die corner radii, and forming temperature, on the formability of square cup drawing with AZ31 sheets. In order to validate the finite element analysis, the deep drawing of square cups of AZ31 sheets at elevated temperatures was also performed. The experimental data show a good agreement with the simulation results, and the optimal forming temperature, punch radius and die corner radius were then determined for the square cup drawing of AZ31 sheets.     

Influence of strain rate on microstructure and formability of AZ31B magnesium alloy sheets

The effects of strain rate on microstructure and formability of AZ31B magnesium alloy sheets were investigated through uniaxial tensile tests and hemispherical punch tests with strain rates of 10^?4, 10^?3, 10^?2, 10^?1 s^?1 at 200 °C. The results show that the volume fraction of dynamic recrystallization grains increases and the original grains are gradually replaced by recrystallization grains with the strain rate decreasing. A larger elongation and a smaller r-value are obtained at a lower strain rate, moreover the erichsen values become larger with the strain rate reducing, so the formability improves. This problem arises in part from the enhanced softening and the coordination of recrystallization grains during deformation.     

Influence of Continuous Bending Process on Texture Evolution and Mechanical Properties of AZ31 Magnesium Alloy

Mg–3Al–1Zn alloy sheets have been deformed by continuous bending(CB) to investigate the effects of pro cessing parameters(bending angle and repetitive passes) on the texture and formability. The samples exhibited a bimoda microstructure with abnormal growth grains in the surface region and fine grains distributed in the center after CB process followed by annealing. The texture evolution measured by XRD indicated that the basal poles were rotated from ND toward RD, and the texture intensity decreased with the bending angle decreasing and repetitive passes increasing Compared with the as-received sample, the yield strength of CBA-120-2 sample significantly decreased from 183 to112 MPa, and a smaller r-value and a larger n-value were obtained. The formability of CB processed samples in annealing condition was significantly enhanced with the highest of Erichsen value of 5.4 mm, increased by about 135%. The improvement of formability was likely attributed to the weakened and RD-tilt basal texture and coarse grains in the surface part.     

连续挤压工艺生产AZ31镁合金板材的实验研究

本文利用连续挤压技术的单、双杆进料方法试验生产了尺寸为160mm×8mm, 170mm×4mm和160mm×3mm的AZ31镁合金板材。分析了单、双杆进料方式,不同宽厚比和不同挤压速度等条件对镁合金板材横截面微观组织及力学性能的影响。讨论了应用双杆进料连续挤压工艺生产AZ31镁合金宽薄板的工艺可行性。结果表明：与单杆进料相比,双杆进料方式的连续挤压AZ31镁合金板材横截面微观组织均匀性较好,板材平均抗拉强度可达到239MPa,平均延伸率为15%。宽厚比由20增加到53,可获得5μm细化晶粒的镁合金板材。随挤压轮转速提高,板材抗拉强度降低,是由于温度升高会导致晶粒尺寸变大。     

Sn纳米粒子对AZ31镁合金组织和性能的影响

采用直流电弧等离子体法制备Sn纳米粒子,通过搅拌铸造的方法添加到AZ31镁合金当中。通过金相、扫描电镜和拉伸性能测试等技术,考察了添加不同量的Sn纳米粒子对AZ31镁合金铸态组织和力学性能的影响。结果表明,添加Sn纳米粒子可抑制共晶相以层片状析出,促进β-Mg_(17)Al_(12)相以骨骼状分布在晶界处。重要的是,观察到Sn纳米粒子在镁合金中生成了纳米尺寸的Mg_2Sn颗粒,但主要以颗粒团簇的形式存在。过量添加Sn纳米粒子,会使Mg2Sn纳米级颗粒团聚严重,降低AZ31镁合金的力学性能。结果表明,添加1%Sn(质量分数)纳米粒子,AZ31镁合金的力学性能最优。     

Improvement of formability of Mg–Al–Zn alloy sheet at low temperatures using differential speed rolling

The differential speed rolling (DSR) with a roll speed ratio of 1.167 was carried out on an AZ31B magnesium alloy in order to investigate its effects on the formability. Compared with the normal rolled sheet exhibiting approximately the same average grain size, the Erichsen values of the DSR processed sheet with an inclination of basal pole in the rolling direction significantly increased by about 1.5 and 1.9 times at room temperature and at 423 K, respectively. The deep-drawing temperature limit for a drawing ratio of 1.5 was also lowered from 443 K to 423 K. The improvement of the press formability at low temperatures can be attributed to the texture modifications, which led to a lower 0.2% proof stress, a larger uniform elongation, a smaller Lankford value and a larger strain hardening exponent.     

Effect of temperature,strain rate and fibre orientation on the plastic flow behaviour and formability of AZ31 magnesium alloy

The sheet formability of AZ31 magnesium alloy has been widely investigated by means of uniaxial tensile and hemispherical punch tests, performed at different temperatures and strain rates, using samples with different fibre orientations. The results of the uniaxial tensile tests were analysed in terms of flow curves, ductility and microstructural evolution. They show that the flow stress decreases and ductility increases as temperature rises and strain rate reduces; the ductility is almost independent of the fibre orientation that, however, slightly affects the flow stress values. The formability, described by the forming limit curves (FLCs), improves with increasing temperature and decreasing strain rate. Moreover, formability along the rolling direction (RD) is higher than that along the transversal one (TD), even if the FLCs obtained along the TD have a larger extension in the drawing side than the ones along the RD. Such behaviours were related to the constitutive parameters and microstructure developed during deformation.