镁合金的塑性加工技术

分析了镁合金的塑性变形特点及应用前景，阐述了镁合金塑性加工研究现状及在材料，性能和加工制造方面的发展方向，分析了镁合金挤压，锻造，冲压，胀形等变形特点及工艺关键。讨论了镁合金的各种加工性能和环境影响，总结了镁合金塑性加工技术的最新进展。     

伺服冲床应用于镁合金温热成形冲压技术

伺服冲床的特色与金属手机外壳发展 伺服冲床．一般泛指利用伺服马达作为驱动源的；中压机械。从伺服冲床开始销售与应用，因其冲头速度具有得以控制的特性．很多冲压加工过程都在利用伺服冲床控制滑块运动来发展新的板材成形，如应用在超深拉深制程、减少噪音之冲剪下料制程、减少冲剪毛边之制程以及控制弹回的弯曲成形制程等．这些研究目前都有了突破性的发展。     

镁合金手机壳的温热液压成形实验及模拟研究

通过对镁合金手机壳进行温热液压成形实验及有限元模拟,分析了液压加载与冲头运动的不同匹配关系对成形结果的影响,以及成形过程中缺陷产生的原因,并确定了合适的成形工艺参数,即在170℃,控制冲头速度在0.2mm/s~1mm/s,液压载荷不低于5MPa,能一次完成成形底部带斜面,并具有较小圆角半径的镁合金手机壳。液压载荷应在坯料的拉深高度小于3mm时快速的施加,否则,在成形件的底部一平面和斜面与棱边交界处将形成难以消除的堆积缺陷。模拟结果与实验吻合良好。研究表明,温热液压成形可以实现常温或低温液压成形难以实现的复杂镁合金零件成形。     

板材零件局部体积成形技术研究

板材局部体积成形技术,或称为板材热冲锻成形技术,为近年来提出的一种板材零件成形方法,其特点是板材冲压成形时不但完成板材零件形状的成形,还兼有局部结构的体积成形,例如局部凸柱、凸台、凸筋等结构的成形,适合于成形镁合金、铝合金等金属的成形,尤其适于替代一些电子器件外壳的铸造加工产品。文章介绍了板材热冲锻成形技术的原理、主要工艺控制参数,并对镁合金盒形件的热冲锻成形过程进行了实验研究和计算机模拟分析。针对带有螺丝柱的典型AZ31B镁合金方盒件,通过实验和有限元模拟,研究了其热冲锻成形工艺。实验表明,在再结晶温度以上冲锻2mm或3mm厚的镁合金板材有很好的成形能力,盒形件的周边和内部凸柱都能同时成形。研究结果表明,合理的模具结构、摩擦润滑条件和加热温度等参数,可以获得侧壁高度均匀、凸柱高度合适、无吸孔和凸柱断裂等缺陷的工件。     

冲压板材的成形性

介绍了冲压板材的成形性直接影响到冲压件的质量，技术性能的评价指标也庆随着对冲压件的质量要求的提高进行更新和进步。为了与要求冲压件不破裂，形状精度高和尺寸精度高相适应，从抗破裂性能，抗起皱性能和抗弹复性能三方面衡量板材的冲压性能，比只考虑抗破裂性能更合理，更科学，更具有实用性。     

镁合金AZ31B板材热拉深成形工艺研究

镁合金(AZ3lB)板材的成形性能可以通过热拉深试验来进行观察评估。成形温度选择在100-400℃之间。以获得适合成形的最佳温度范围。使用有限元方法分析了主要工艺参数对坯料成形质量的影响。试验结果表明。成形温度低于200℃时坯料很脆，高于400℃叶坯料表面易发生氧化而不适合成形。当成形温度选择在300一350℃之间。压边力在6-15kN(单位压边力q为0．7—1．7MPa)之间时镁合金具有较好的成形性能，能成功拉深出质量好的筒形件。数值模拟结果表明，坯料与模具间的摩擦因数对产生破裂的影响较压边力的影响程度大。     

镁合金板材温热拉深成形工艺的研究

通过镁合金板材温热拉深试验确定适合板材成形的温度范围，分析了压边力对坯料成形质量的影响，选择适合成形的工艺条件来有效避免工艺缺陷的产生。试验采用刚性压边装置对压边力进行调整，润滑剂采用了液态的PTFE，通过对成形工艺缺陷的分析，确定适合成形的最佳工艺参数，以提高拉深件的极限拉深比。结果表明：成形温度选择在105～170℃范围内，此时镁合金轧制板材具有良好的拉深性能，极限拉深比可达到2．44；坯料的加热时间不宜过长，否则会严重降低板材的塑性变形能力。     

镁合金塑性成形技术研究进展

综述了镁合金塑性成形技术的研究现状,介绍了镁合金挤压、轧制、锻造、板料成形的成形特点及最新研究进展,探讨了关于镁合金塑性成形领域亟待解决的问题,展望了镁合金塑性成形技术的发展方向。     

AZ31镁合金板材超塑性气胀成形研究

研究了AZ31镁合金板材不同工艺条件下的气胀成形性能。实验表明，胀形高度随温度的升高而增大，且应变速率敏感指数值均大于0.3。在673K,0．7MPa下胀形25min所得的胀形件胀形高度达23．34mm，高径比为0．67。由金相及SEM电镜观察可知，在胀形件的顶端晶界处聚集了大量空洞。通过动态再结晶，晶粒得到了很大细化。并且随变形程度的增大，晶粒细化更明显。AZ31镁合金板材的超塑性胀形主要由晶界滑移控制，动态再结晶则为重要的辅助机制。     

元素粉末冷轧成形及反应合成制备Ti-Al合金板材

以Ti、Al元素粉末为原料,在粉末轧机上无包套冷轧成尺寸为500 mm×230 mm×1.5 mm的板坯,其相对密度达85.9%.研究了不同工艺参数对Ti、Al元素粉末轧制板材的影响.取小样在不同温度下进行真空无压烧结,研究了板坯的真空烧结行为.结果表明:Ti、Al元素粉末冷轧过程要求适中的粉末流动性、低的轧制速度以及一定大小且较稳定的轧制压力.真空烧结后,Ti-Al合金由Ti-Al和Ti3Al两相组成,Ti3Al相含量随烧结温度升高而增加.烧结坯孔隙度大幅度增加,增加量为21%～32%.原板坯中的孔隙及偏扩散是造成烧结坯孔隙的主要原因.低压(＜10 kPa)真空烧结过程中,外压仅有效作用于短暂的液相阶段,粉末粒度越粗,烧结温度越高,烧结坯孔隙度受这种低压强的影响程度越大.     

A study on the boss forming process of AZ31 Mg alloy sheet

A series of boss forming tests has been carried out using an AZ31 Mg alloy sheet at 250 °C, 300 °C, and 350 °C with various lubrication conditions to obtain optimum process conditions. The Mg alloy sheet had a homogeneous distribution of very fine sized grains. Surface defects generated during boss forming process could be reduced by changing the friction conditions, as prescribed by FEM analysis using the DEFORM 2D program. The modified boss forming process, lubricating only on the front side, was found to be successful in manufacturing the boss without defects.     

变压边力对铝合金板冲压成形的影响研究

通过数值模拟和实验,研究了变压边力对铝合金板成形过程中应变路径的变化规律,基于MK法研究应变路径的变化对铝合金板成形极限(FLC)的影响,通过比较不同随时间变化的压边力对铝合金成形极限的影响,揭示变压边力改善铝合金板冲压成形性能的机理。实验和数值模拟结果表明,变压边力改善铝合金板成形性能的主要原因是变压边力对应变路径的影响,对杯形拉深来说,渐增型随时间变化的变压边力可以改善铝合金板的成形性能。     

Superplasticity of fine-grained AZ31 Mg alloy sheets

Superplastic mechanical properties of fine-grained AZ31 Mg alloy sheets in the temperature range of 250 - 450 ℃ and strain rate range of 0.7 × 10-3- 1.4 × 10-1 s-1 were investigated by uniaxial tensile tests. The microstructure evolution during the superplastic deformation of AZ31 Mg alloy was examined by means of metallurgical microscope and transmission electronic microscope (TEM). It is shown that, fine-grained AZ31 Mg alloy starts to exhibit superplasticity at 300 ℃ and the maximum elongation of 362.5% is obtained at 400 ℃ and 0.7× 10-3 s-1.The predominate superplastic mechanism of AZ31 Mg alloy in the temperature range of 300 -400 ℃ is grain boundary sliding (GBS). Twinning caused by pile-up of dislocations during the early stage of superplastic deformation is the hardening mechanism, and dynamic continuous recrystallization (DCRX) is the important softening mechanism and grain stability mechanism during the superplastic deformation of the alloy.     

振动塑性加工及其在轻合金成形中的应用

振动塑性加工是将超声波等形式的振动施加在塑性成形的模具或坯料上,以达到提高坯料变形能力和加工质量等目的的一种塑性成形技术.回顾了振动塑性加工技术及其在铝、镁等轻合金塑性成形领域的理论研究和应用情况,探讨了利用该技术提高镁合金塑性成形性能与质量的可能性.     

变形镁合金温成形技术的研究进展

文章在阐述了变形镁合金的基本特性、分类、应用及其温成形技术的基础上,较为详细地论述了国内外温成形技术的发展及应用现状及变形镁合金温成形技术的研究现状,并对变形镁合金温成形技术的应用前景进行了展望.在温成形技术不断发展的基础上,变形镁合金的温成形技术也飞速发展,从而极大地促进了变形镁合金在工业中的广泛应用.     

有色金属板材若干温热加工成形技术的发展

介绍了有色金属材料加工先进新技术国内外发展和应用概况,包括近年来关于镁合金、钛合金、铝合金等典型有色金属材料领域出现的先进塑性成形技术,尤其温热加工成形技术。在镁合金板材冲压成形领域,介绍了镁合金板材温热冲压成形、差温冲压成形、温热液压成形和热冲锻成形以及镁合金型材温热拉弯成形等新工艺技术,为镁合金板材在汽车、电子、机车车辆等领域的应用奠定了技术基础。钛合金板材零件的热应力成形、热胀形成形、激光弯曲成形、高温蠕变成形技术都得到了发展和应用。随着铝合金的进一步应用和发展,一些低塑性难成形高强铝合金的用量在增加,应用领域在扩展。因此铝合金的温热液压成形、冲锻成形都有所发展。     

Ultrasonic welding between mild steel sheet and Al–Mg alloy sheet

Ultrasonic welding between SS400 mild steel sheet and aluminum alloy sheet containing magnesium (A5052) was conducted. In this study, authors investigated the influence of ultrasonic welding conditions on the mechanical properties and the interface microstructure of a joint, and the effect of insert metal was examined to improve the joint strength. The main results obtained in this study are as follows.It was possible to weld ultrasonically SS400 mild steel sheet to A5052 aluminum alloy sheet containing magnesium. The strength of the joints welded using various clamping forces and constant welding time of 1.0 s showed the maximum value at the clamping force of 588 N and decreased with the clamping force over 588 N because the excessively large clamping force reduced the frictional action at the interface. The strength of the joints welded using the constant clamping force of 588 N and various welding times showed the maximum value at the welding time of 2.5 s. However, the strength of the joint welded using the welding time of 3.0 s decreased due to the formation of Fe₂Al₅ intermetallic compound at the interface. Using the insert metal of commercially pure aluminum, the joint strength was successfully improved and the strength of the welded using 3.0 s welding time was about three times as large as that of the joint without the insert metal.     

Textural vs structural plastic instabilities in sheet metal forming

Negative work-hardening rates are precursors of plastic instabilities. The objective of the work is to determine the origin of the stress decrease in the case of prestrained sheet metals. Samples of low carbon steel and pure aluminium deformed in rolling and reloaded in simple shear exhibit softening for specific shear directions with respect to the rolling direction. Structural and textural evolutions are analysed with transmission electron microscopy and X-ray measurements, respectively. The low carbon steel shows clear evidence of intragranular structural destabilization while the Taylor factor, estimated by self-consistent calculations, remains nearly constant. It is deduced that for steel, the softening has a structural origin. By contrast the aluminium samples present identical structural changes whatever the sign of the work-hardening rate. It is shown that the latter is strongly correlated with Taylor factor evolutions. A textural instability is obtained in this case.     

Fabrication of supersaturated Cu-Sn alloy sheets and their antibacterial properties

Supersaturated Cu-Sn alloy sheets were successfully fabricated by hot-rolling mechanically alloyed (MAed) nanocrystalline powders within a range of up to 22 wt.% of Sn, and their antibacterial and ionization properties were investigated. While the pure Cu and hot-rolled Cu-Sn sheets using MAed powders show excellent antibacterial properties, the corrosion potential of the hot-rolled Cu-Sn using MAed powders is much less than that of the as-cast Cu-Sn and decreases as the Sn content increases, implying that the hot-rolled Cu-Sn alloy sheets using MAed powders have a more effective antibacterial property, mainly due to supersaturation.