熔体处理温度对自孕育法制备AZ61半固态浆料的影响

采用自孕育法制备AZ61变形镁合金半固态浆料,研究了熔体处理温度对制备AZ61变形镁合金半固态浆料的影响。结果表明,自孕育铸造法制备AZ61半固态浆料在液相线以下凝固成形,可以获得近球状的初生相。适宜的熔体处理温度为700℃,对应的平均晶粒尺寸为39.8μm。熔体处理温度过低时,组织中的树枝晶减少的同时细小的近球状晶增多,但是其晶粒尺寸大小分布不均匀。熔体处理温度过高时,组织中树枝晶增多,晶粒平均尺寸显著变大。     

Mg-6wt%Zn-1wt%Mn镁合金均匀化处理研究

利用差热分析仪(DSC)、金相显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)和显微硬度测试仪,对不同的均匀化热处理工艺下铸态ZM61镁合会组织转变和成分均匀化效果进行了表征.并采用求显微硬度方差大小的方法对均匀化过程中的两个重要参数--温度和时间进行了深入探讨.结果表明:铸态ZM61镁合金显微组织中存在严重的枝晶偏析,枝晶问有粗大的呈网状分布的Mg-Zn相,枝晶内部和枝晶臂间也存在大块状化合物;温度是均匀化过程中的主导因素,过度延长保温时间对均匀化作用不大;ZM61镁合会较优的均匀化工艺:330℃×16h+420℃×2h.     

镀镍对镁合金AZ61耐腐蚀性能的影响

采用X射线衍射仪(XRD)、带有电子能谱仪(EDS)的扫描电子显微镜(SEM)等,研究了化学镀镍镁合金AZ61在NaCl溶液中的耐腐蚀性能。结果表明,化学镀镍在镁合金基体表面沉积了一层致密、均匀的镍-磷合金镀层,依靠镍-磷合金镀层的耐腐蚀性能来保护镁合金基体。腐蚀形貌与腐蚀速率的测定结果具有一致性。经化学镀镍后,镁合金AZ61的耐腐蚀性能有明显提高。     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Y对AZ61镁合金金相组织和力学性能的影响

研究了Y对AZ61镁合金金相组织和力学性能的影响。结果表明：Y能细化合金的组织,使AZ61中连续分布的β—Mg17A112相变成断网状分布,并在合金中形成块状的A12Y新相。少量的Y能提高合金的室温力学性能,当Y达到1％时合金的力学性能最佳,继续加Y后使合金的组织变的粗大,力学性能下降。     

热处理对挤压态AZ61合金力学性能的影响

对未均匀化处理的AZ61合金进行了热挤压及不同制度的热处理,采用拉伸试验、硬度及电阻率测试、显微组织观察等方法研究了退火及时效热处理对挤压态AZ61合金力学性能的影响。结果表明:低温退火未使合金的抗拉强度下降,而高温退火使合金的抗拉强度明显降低;退火后的时效由于有少量第二相析出,能显著提高合金的屈强比,同时降低了塑性。此外,热挤压后的直接时效对合金的力学性能几乎没有影响。     

安塞王窑南地区长612储层沉积微相研究

综合利用岩心,录井,测井及化验分析资料,以现代沉积学和层序地层学理论为基础,对安塞王窑南长612层沉积微相精细研究,搞清了骨架相砂体类型和几何形态,总结了长612小层各沉积期沉积微相平面时空演化规律,确定其为一套三角洲沉积,其中三角洲前缘较为发育,进一步可以划分为水下分流河道,河口砂坝,远砂坝,水下天然堤,席状砂,水下分流河道间6种微相类型。通过沉积相带对油气的控制作用分析,指出有利的油气聚集带,为油气开发提供了方向。     

Benefits and costs of transport

Abstract. This article aims to bring together insights from a broad body of recent literature concerned with the nature, the measurement and policy implications of benefits and costs of transport. It is argued that, for various reasons, transport cannot be treated as an'ordinary'economic sector, and the policy implications of a number of the sector's peculiarities are addressed. Explicit attention is given to spatial aspects and network elements, internal and external benefits and costs, and efficiency aspects and equity considerations in policy making.     

Energy policy scenarios to reach challenging climate protection targets in the German electricity sector until 2050

In this article we demonstrate how challenging greenhouse gas reduction targets of up to 95% until 2050 can be achieved in the German electricity sector. In the analysis, we focus on the main requirements to reach such challenging targets. To account for interdependencies between the electricity market and the rest of the economy, different models were used to account for feedback loops with all other sectors. We include scenarios with different runtimes and retrofit costs for existing nuclear plants to determine the effects of a prolongation of nuclear power plants in Germany. Key findings for the electricity sector include the importance of a European-wide coordinated electricity grid extension and the exploitation of regional comparative cost effects for renewable sites. Due to political restrictions, nuclear energy will not be available in Germany in 2050. However, the nuclear life-time extension has a positive impact on end consumer electricity prices as well as economic growth in the medium term, if retrofit costs do not exceed certain limits.     

Effects of grain size and precipitation on liquation cracking of AZ61 magnesium alloy laser welding joints

Abstract

Four kinds of wrought AZ61 alloy sheets with different microstructural features were successfully welded by CO₂ laser beam butt welding. Welding joints without visible pores were obtained under optimum process parameters. Effects of grain size and precipitation on liquation cracking behaviours of the laser welding joints were investigated. As far as the as rolled alloy sheets were concerned, liquation in the partially melted zone (PMZ) was visible along grain boundaries, and the extent of liquation was more serious in the alloy sheets with larger grains. As far as the as aged alloy sheets were concerned, plenty of precipitates (β-Mg₁₇Al₁₂) were involved and liquation in the PMZ was found both at grain boundaries and within grains. Moreover, the extent of liquation was more serious in the alloy sheets with more precipitates. It is promising to reduce liquation cracks in the PMZ of magnesium alloys by grain refinement, reducing the size and the quantity of the low melting point phase, and modifying its distribution.