AZ31镁合金熔体超声净化处理

利用超声处理AZ31镁合金熔体,考察了超声功率及静置时间对净化效果的影响,分析了超声熔体净化的机理。结果表明,超声处理可以加速熔体中夹杂物的凝聚,实现AZ31镁合金熔体的净化。AZ31镁合金熔体超声处理的最佳超声体积功率密度为0.30 W/cm3,适当延长静置时间对净化有利。铸锭中夹杂物越多,电导率越小,电导率可以表征铸锭的净化程度。     

超声场作用下镁合金熔体净化工艺

采用XRD、SEM和图像分析软件对AZ80镁合金中夹杂的种类和形态进行了研究,并采用施加超声场来实现AZ80镁合金熔体的净化,以达到提高镁合金熔体质量的目的。研究表明,AZ80合金中夹杂主要为MgO,夹杂主要以颗粒状、团絮状、长条带状和块状形式存在。含有夹杂的AZ80合金熔体经超声处理可实现良好的净化效果,净化程度与超声功率和熔体温度有关。AZ80合金熔体在650℃经80W超声功率处理60s可以获得理想的净化效果。超声功率过大或超声处理时间过长均不利于合金熔体净化。     

熔体超声处理对AZ91镁合金除气的影响

研究了超声处理对AZ91镁合金除气效果的影响。结果表明,采用超声波处理可以有效的去除镁合金熔体中的气体,从而提高铸锭的致密度。超声除气效果与施加功率和处理时间密切相关。在本实验条件下:超声功率105 W,处理时间60 s时除气效果最好,除气率可达73%。超声波不仅具有良好的除气效果,而且可以细化铸锭的铸态组织,均匀细小的组织则有利于气泡的上浮和熔体补缩;经过超声处理后,铸锭的硬度值可从未处理的30.7增大至74,提高了141%。     

超声振动对半固态AZ61镁合金微观组织的影响研究

利用自行设计和研制的一套超声振动装置,试验研究超声导入温度、超声输出功率和超声处理时间对半固态AZ61镁合金微观组织的影响。试验结果表明,在半固态区间,只有将AZ61镁合金熔体控制在合适的温度时,才能获得细小、均匀的半固态球状组织;当超声振动时间为60 s时,对半固态AZ61镁合金超声处理的效果最好;随着超声振动功率的增加,熔体中的颗粒直径呈不断下降的趋势,晶粒尺寸得到的明显细化,形状趋于圆整。     

超声处理对AZ31镁合金组织和性能的影响

通过在AZ31镁合金熔体中施加超声波,研究不同超声处理功率和施振时间对AZ31镁合金显微组织和性能的影响,探讨了超声波对AZ31镁合金晶粒细化的作用机理。结果表明,超声波在合金液中的各种效应能够使合金晶粒明显细化,晶粒尺寸均匀,提高了AZ31合金的力学性能。超声功率和施振时间都是影响合金组织和性能的重要因素,随着超声功率的提高,施振时间的延长,合金晶粒细化明显,抗拉强度提高,但当功率、时间达到一定程度时,晶粒细化趋势下降,抗拉强度下降。超声功率为600W,施振时间为100s时,晶粒尺寸、AZ31合金抗拉强度最佳。     

电磁场对镁合金熔体的净化作用

对无磁场与静磁场作用下AZ61镁合金的凝固组织进行了研究.结果发现,静磁场作用下的镁合金凝固组织中夹杂物明显减少或呈球状分布,说明静磁场对AZ61镁合金熔体具有净化的作用,因此,静磁场可以改善镁合金的性能.     

镁合金熔体净化工艺的研究

研究了镁合金再生过程中熔体内夹杂物含量、尺寸与静置时间的关系,以及主要合金成分和杂质元素含量的变化规律.应用Stokes公式模拟了夹杂物沉降距离与静置时间的关系,分析了影响夹杂物沉降速度的因素.结果表明:在镁合金废料完全熔解后静置5～10 min,可以将熔体内夹杂物的含量降至0.5%以下,夹杂颗粒尺寸小于0.3 mm.234熔剂的精炼效果好于RJ-1熔剂,经234熔剂精炼后静置8 min,镁合金熔体中的夹杂物含量降至0.02%以下,夹杂颗粒尺寸小于10μm.夹杂物沉降速度与夹杂半径的平方、夹杂密度成正比,与镁合金液粘性系数及镁合金液密度和夹杂密度的比值成反比.     

超声场作用下Mg-3Ca合金除气及细化的工艺研究

对Mg-3Ca合金熔体进行超声处理来研究超声功率、施振时间和施振温度对合金除气及凝固组织的影响。结果表明,采用超声波处理技术,可以有效去除Mg-3Ca合金熔体中的气体,从而提高铸锭的致密度。超声除气效果与施振功率、处理时间及处理温度密切相关。当施振功率过小、处理时间过短或过长及处理温度过高或过低均不会有良好的除气效果。熔体处理温度为:700℃,超声功率为150W,处理时间为120s时除气效果最好,除气率可达53.8%。另外,超声波在去除熔体中气体的同时,也使得铸锭的凝固组织变得细小、均匀。粗大的树枝晶不利于气泡的上浮和熔体补缩;而均匀、细小的等轴晶则有利于这一点。     

超声细化处理AZ80镁合金过程中的声场数值模拟

采用不同强度超声对AZ80镁合金熔体进行处理以改善合金的凝固组织。当施加的超声强度为30.48W/cm2时,合金的平均晶粒尺寸由未经超声处理时的303μm降低为148μm。为了进一步了解超声改善镁合金微观组织的机理,采用数值模拟的方法研究超声声压对空化泡行为的影响,并且对熔体中的超声场分布情况进行分析。结果表明,熔体内不同位置所受的声压是不同的,因此不同位置上的铸锭试样的晶粒细化程度也不同。随着超声强度的增加,声压值增加,而合金的晶粒尺寸则随之降低。     

高强超声对Mg-Ca合金凝固组织的影响

研制了镁合金熔体功率超声处理设备及附属装置.通过对镁合金熔体进行超声处理和改变熔体状态来研究超声功率、施振时间和施振温度等参数对镁合金微观组织的影响.结果表明,经功率超声处理后,镁合金的凝固组织细小,并随超声功率的增加,镁合金微观组织细化程度提高,但功率提高到一定程度时,组织有粗化的趋势;施振时间和施振温度等处理参数对镁合金凝固组织也有较大影响.同时也表明功率超声对镁合金熔体处理有良好的应用前景.     

Effect of ultrasonic power on grain refinement and purification processing of AZ80 alloy by ultrasonic treatment

Ultrasound with different powers was applied to treat AZ80 alloy melt to attain grain refinement or purification processing of the alloy. The influence of ultrasonic powers from 0 W to 1400 W on microstructures of the AZ80 alloy with ultrasonic grain refinement treatment was investigated. The average grain size of the alloy could be decreased from 387 μm to 147 μm after the ultrasound with the optimal power 600 W was applied to treat the melt. The effect of ultrasonic powers from 0 W to 230 W on the inclusion distribution in the ingot that was treated by ultrasonic purification processing was also studied. The optimal ultrasonic power in the ultrasonic purification processing was 80 W. In order to gain insight into the mechanism by which ultrasonic power affected the microstructure of the alloy or inclusion distribution in the ingot, numerical simulations were carried out and the ultrasonic field propagation in the melt was characterized.     

Numerical simulation of standing waves for ultrasonic purification of magnesium alloy melt

It was attempted to enhance and accelerate the separation of oxidation inclusions from magnesium alloy melt by virtue of ultrasonic agglomeration technology. In order to investigate the feasibility and effectiveness of standing waves for ultrasonic purification of magnesium alloy melt, numerical simulation and relevant experiment were carried out. The numerical simulation was broken into two main aspects. On one hand, the ultrasonic field propagations within the cells with various shapes were characterized by numerical solutions of the wave equation and with a careful choice of geometry a nearly idealized standing wave field was finally obtained. On the other hand, within such a standing wave field the agglomeration behavior of oxidation inclusions in magnesium alloy melt was analyzed and discussed. The agglomeration time and agglomeration position of oxidation inclusions were predicted with numerical simulation method. The results show that the oxidation inclusions whose apparent densities are close to the density of the melt can agglomerate at wave nodes in a short time which to a great extent enhances and accelerates the separation of oxidation inclusions from magnesium alloy melt.     

不同熔炼方法对Mg-Nd-Zn-Zr熔体品质影响

采用熔剂法(熔剂保护和熔剂精炼)和气体法(气体保护和气体精炼)两种熔炼方法制备Mg-Nd-Zn-Zr合金熔体,对Zr合金化阶段及最终熔炼效果进行对比研究。结果表明,熔剂法和气体法均能得到成分合格的镁熔体。两种方法都可以实现良好的晶粒细化效果,但气体法制备的镁熔体试样的晶粒比熔剂法更为细小。气体法与熔剂法均能有效保护熔体及降低镁熔体中夹杂,但与气体法相比,熔剂法对夹杂的控制效果更好。     

Assessment of solidification characteristics of carbon-inoculated Mg-3%Al melt by thermal analysis

The Mg-3%Al melt was inoculated by carbon with different holding time. The effect of holding time on grain refining efficiency was evaluated. The solidification characteristics of the carbon-inoculated Mg-3%Al melt with different holding time were assessed by computer-aided cooling curve analysis. The results showed that Mg-3%Al alloy could be effectively refined by carbon inoculation. Slight fading phenomenon occurred with increasing the holding time to 60 min. Carbon inoculation could significantly influence the shape of cooling curves of Mg-3%Al melt. The nucleation starting and minimum temperatures increased. The recalescence undercooling and duration decreased to almost zero after carbon inoculation. The grain refining efficiency of carbon inoculation could be assessed by the shape of the cooling curve and solidification characteristic parameters including nucleation starting and minimum temperatures, recalescence undercooling and duration.     

超声波处理对Al-Pb合金铸锭偏析及性能的影响

以Al-Pb合金为研究对象,研究了超声波处理对合金铸锭溶质分布的影响。利用BSE对试样进行了检测,且测试了试样的硬度以及磨损性能。结果表明：在铸造条件下,采用合适的超声波处理时间能够有效抑制Al-Pb合金的溶质偏析;溶质含量过高时,超声波处理熔体分散溶质效果不好,当处理时间为180s时,A1-1％Pb的分散效果最好;超声波功率对Pb溶质分散性有直接的影响,功率过大或功率过小都达不到令人满意的分散效果。最后,利用超声波的空化效应以及声流效应说明了产生上述现象的原因。     

Effects of processing variables on melt cleanliness of AZ31B magnesium alloy investigated by quantitative evaluation of Fe and non-metallic inclusions

Impurities such as Fe, Ni and Cu and non-metallic inclusions such as oxides, nitrides, carbides, sulfides and fluorides are harmful to the quality and various properties of magnesium alloy sheets produced by twin-roll casting. In this study, the changes of the content of Fe and non-metallic inclusions in AZ31B magnesium alloys with melt temperature and isothermal holding time were quantitatively evaluated using EPMA and the metallographic method. The Fe content did not increase above the Fe content in the raw material, which implies that the dissolution of Fe from a steel crucible was suppressed effectively. The content of non-metallic inclusions, mainly consisting of oxide, fluoride and Fe-rich intermetallic compounds, did not change remarkably with the melt temperature but it increased with the isothermal holding time due to the continuous oxidation of the magnesium alloy melt on the melt surface.     

Pb-Sn合金在功率超声场中的凝固过程研究

研究了功率超声在铅锡合金凝固过程的作用,分析了超声功率、施振温度、熔体的冷却方式等参数的影响机制。结果表明,在功率超声作用下,声空化效应和声流效应使含铅5%的铅锡合金的凝固组织明显细化,随着超声功率的增加,合金组织的细化程度提高,但功率提高到一定程度时,细化作用减弱;施振温度、熔体的冷却方式等参数对超声在铅锡合金凝固过程的作用有较大的影响。     

Degassing effect of ultrasonic vibration in molten melt and semi-solid slurry of Al-Si alloys

In the process of semi-solid slurry preparation with direct ultrasonic vibration (UV) by dipping the horn into the melt, one of the questions is whether the gas content in the melt would be increased or not by the cavitation effect of ultrasonic vibration. By application of quantitative gas content measurement technique, this paper investigated the effect of the ultrasonic vibration on the gas content of both the melt and the semi-solid slurry of Al-Si alloys, and the variations of the gas contents in two kinds of aluminum alloys, i.e., A356 alloy and Al-20Si-2Cu-1Ni-0.6RE alloy (Al-20Si for short). The results show that ultrasonic vibration has an obvious degassing effect on the molten melt, especially on the semi-solid slurry of Al-Si alloy which is below the liquidus temperature by less than 20 ℃. The ultrasonic degassing efficiency of the A356 alloy decreases with the reduction of the initial gas content in the melt, and it is nearly unchanged for the Al-20Si alloy. The gas content of both alloys decreases when the ultrasonic vibration time is increased. The best vibration time for Al-20Si alloy at the liquid temperature of 710 ℃ and semi-solid temperature of 680 ℃ is 60 s and 90 s, respectively; and the degassing efficiency is 48% and 35%, respectively. The mechanism of ultrasonic degassing effect is discussed.