镁合金焊接技术研究进展

介绍了镁合金先进焊接工艺,包括A-TIG、电子束焊、激光焊、激光-电弧复合焊和搅拌摩擦焊。针对镁合金焊接的特点,提出了有效的焊接工艺。实践表明,上述几种焊接方法均具有独特的优越性,可有效地解决镁合金焊接所面临的难点。     

深度塑性变形法的研究现状和前景

深度塑性变形加工与传统变形方法相比具有很大的优点,可得到超细晶金属和合金,其微观组织结构和性能也发生很大的变化.通过介绍累积轧合法、等通道角挤压法和高压扭转法等3种目前最主要的深度塑性变形方法,分析了深度塑性变形法的特点和现状,并对其未来进行了展望.     

镁及其合金导热研究进展

本文简要回顾了国内外镁合金导热行为和导热机制的研究工作，梳理了影响镁合金导热的因素，如固溶原子、变形和温度等。在此基础上，归纳总结了高导热镁合金的发展，并讨论了导热与力学性能之间的倒置关系，最后提出高导热镁合金的设计思路和发展方向。主要结论如下：固溶原子会导致晶格畸变而降低镁合金热导率，与其化合价、原子半径和原子核额外电子有关；第二相与Mg基体的界面会对电子运动产生阻碍作用，进而削弱热导性能，具体与其形貌、尺寸、分布和含量相关；对于变形镁合金，沿径向或法向方向的导热性能往往优于挤压或轧制方向；温度是影响镁合金热导率的重要因素，在不同的温度区间内，热导率的主要散射机制不同，一般需要对各温度区间分开讨论。未来关于导热镁合金的研究仍有必要继续深入，可以重点聚焦于以下方面：镁合金显微组织与其导热性能的关系量化；多元镁合金的导热行为及其导热模型的建立；高导热镁合金成分设计与组织控制；镁合金导热行为的物理本质探究。     

Mg_2Ge合金表面性质的第一性原理计算

镁锗合金有着良好的耐腐蚀性能,与其表面性质有着密切关系,但具体机制不明确。因此,基于电子密度泛函理论,计算了Mg_2Ge(100),(110),(111)面的表面能和电子亲合能。结果表明,Mg_2Ge最稳定的表面为(111)中的一种,其表面原子全由镁构成,第二层原子由锗原子构成,与实验报道Mg_2Ge的解离面为(111)面吻合。不同表面构型的电子亲合能差异很大,说明Mg_2Ge的腐蚀行为如腐蚀电位等应存在较强的各向异性。在理想界面中,镁的费米能级位于Mg_2Ge的导带底的下方,形成的肖特基能垒会阻碍电子由镁基体转移到Mg_2Ge,从而使镁锗合金表现出更好的耐腐蚀性能。     

HRTEM studies of aging precipitate phases in the Mg-10Gd-3Y-0.4Zr alloy

Rare-earth(RE) element addition can remarkably improve the mechanical properties of magnesium alloys through precipitation hardening. The morphology, distribution and crystal structure of precipitates are regarded as major strengthening mechanisms in the Mg-RE alloys. In order to understand the formation of precipitates during aging at 225 oC in a Mg-10Gd-3Y-0.4Zr alloy(GW103K) with high strength and heat resistance, a high-resolution transmission electron microscopy(HRTEM) was employed to characterize the microstructural evolution. It was found that three types of precipitates were observed in the alloy at the early stage, named as: single layer D019 structure, one single layer D019 structure and one layer of Mg, two parallel single layers(containing RE) and Mg layer in between, which was regarded as ordered segregation of RE, precursors to form β′′ and β′ phase, respectively. Both of β′′ and β′ phase were transformed from the precursors. It was also found that large size of β′ phase and the small size of β′′ phase were constantly existent in the whole aging process. β′ phase played a major role in the strengthening of the GW103 K alloys and the decrease of the hardness was caused by the coarsening of β′ phase.     

A modified Johnson-Cook constitutive relationship for a rare-earth containing magnesium alloy

Lightweight magnesium alloy has recently attracted a considerable interest in the automotive and aerospace industries to improve fuel efficiency and reduce CO2 emissions via the weight reduction of vehicles.Rare-earth（RE） element addition can remarkably improve the mechanical properties of magnesium alloys through weakening crystallographic textures associated with the strong mechanical anisotropy and tension-compression yield asymmetry.While the addition of RE elements sheds some light on the alteration in the mechanical anisotropy,available information on the constitutive relationships used to describe the flow behavior of RE-containing magnesium alloys is limited.To establish such a constitutive relationship,uniaxial compressive deformation tests were first conducted on an extruded Mg-10Gd-3Y-0.5Zr（GW103K） magnesium alloy at the strain rates ranging from 1×10–1 to 1×10–4s–1 at room temperature.A modified Johnson-Cook constitutive equation based on a recent strain hardening equation was proposed to predict the flow stresses of GW103K alloy.Comparisons between the predicted and experimental results showed that the modified Johnson-Cook constitutive equation was able to predict the flow stresses of the RE-containing magnesium alloy fairly accurately with a standard deviation of about 1.8%.     

TiO2与MnCl2对Mg合金旧料组织性能的影响

测试了含有不同量的TiO2或MnCl2的熔剂对Mg合金废旧料的力学性能、组织、断口形貌以及腐蚀行为的影响．结果表明，TiO2和MnCl2均可以降低Mg合金废旧料中的Fe含量，TiO2的除Fle效果可达0．0053％以下，优于MnCl2的效果．通过降低Fe量可以提高试样的σb和δ，MnCl2的效果优于TiO2．采用含30％TiO2或MnCl2的熔剂对Mg合金废旧料进行净化处理后，其σb和δ可分别大于185．3MPa和3．71％，即达到了AZ91Mg合金新料的性能指标．研究还表明，Ti02或MnCl2加入量一定时，均可以提高Mg合金的耐蚀性．但当熔剂中MnCl2的含量高于30％时，Mg合金的耐蚀性反而下降．Ti02有助于使γ相成粒状或小岛状析出，并具有很好的细化晶粒的效果．     

AZ31B管材挤压数值模拟及挤压极限图的建立

采用Gleeble3000型热-力学模拟试验机,对不同温度和应变速率下的AZ31B镁合金的变形形为进行了研究,以得到材料的真实应力—应变曲线,导入专业成形数值模拟软件,对尺寸为尴40×3的AZ31B无缝管材,以坯料初始温度240℃～480℃、挤压杆速度2mm/s～80mm/s的条件进行了数值模拟,根据模拟数据建立了挤压极限图,并通过挤压工艺试验对所得的挤压极限图进行了验证,结果吻合的很好。     

富士康镁合金压铸产业发展特点分析

介绍了富士康的快速发展情况及其镁合金产业的布局，分析了富士康镁合金产业规模大、模具快速生产、竞争优势等几个方面特点。国内压铸行业可以借鉴富士康的成功经验，但很难照搬。应创新发展道路，制定正确的市场竞争策略。     

等通道角挤压对AZ91镁合金组织性能的影响

在对等通道角挤压中模具通道夹角、挤压路线和挤压温度研究的基础上,确定了实验中的理想工艺。研究发现,AZ91镁合金经过一个道次的等通道角挤压后,材料中就有大量的超细晶粒出现。随着道次数增加,超细晶粒比例逐渐增多。AZ91镁合金经过225℃四道次+180℃二道次的挤压后,屈服强度和抗拉强度分别达到290MPa和417MPa,伸长率达到8.45%。