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锥桶式流变成形机制备A356铝合金半固态浆料的研究 总被引:1,自引:0,他引:1
采用自主研发的锥桶式流变成形机(TBR),研究了浇注温度、内锥桶转速及剪切温度对A356铝合金半固态组织的影响规律。结果表明,适当降低浇注温度、提高内锥桶转速或降低剪切温度,均有利于获得初生相颗粒细小、圆整、分布均匀的半固态组织;当浇注温度为660℃、内锥桶转速为500r/min、剪切温度为590℃时,获得了理想的半固态浆料,其初生固相颗粒平均直径为41μm,形状因子为0.89;半固态组织的形成受到枝晶破碎和枝晶抑制生长两方面因素的共同影响。 相似文献
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A self-developed taper barrel rheomoulding(TBR)machine was introduced,and the rheo-diecasting process was implemented by combining TBR machine with the high pressure die casting(HPDC)machine.Microstructural characteristics of the rheo-diecasting components were investigated at different rotation speeds.Flow characteristics and microstructural evolution of the semi-solid slurry during the rheo-diecasting process were analyzed and the mechanical properties of the rheo-diecasting components were studied.The experimental results show that the process is able to obtain such components in which the primaryα-Mg particles are fine,nearly spherical and uniformly distributed in the matrix.When the rotation speed of internal taper barrel is 700 r/min,the primaryα-Mg particles get a mean diameter of about 45μm and a shape factor of about 0.81.The magnesium alloy melt has complex stirring-fixed flow characteristics when flowing in TBR machine.Compared with conventional die-casing process,the rheo-diecasting process can improve the mechanical properties of components;especially,the elongation is improved by 80%. 相似文献
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In this paper, the effects of pouring temperature of magnesium melt, preheating temperature of the barrel of the screw mixer, and shear rate on the solidified microstructures of semi-solid slurry were investigated by a mechanical stirring semi-solid process. The appropriate processing parameters of slurry preparation were obtained, and the mold filling ability of semi-solid slurry for thin-walled casting was examined. Results indicate that the solid volume fraction of non-dendritic microstructure increases with a decrease in pouring temperature of magnesium melt and the barrel preheating temperature of the screw mixer. Also the grain size of primary α-phase is reduced. Furthermore, the solid volume fraction of semi-solid nondendritic structure decreases with an increase of shear rate. The fine and round granular microstructure with 30~50 μm in size of semi-solid AZ91D magnesium alloy was presented. Finally, a 1.0 mm thin-walled casting with a clear contour and good soundness was successfully made by semi-solid rheo-diecasting. 相似文献
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自孕育半固态制浆技术的研究 总被引:8,自引:3,他引:5
分析了国内外制浆技术的现状及组织形成的理论,提出了一种新的半固态制浆技术——自孕育法,即采用与合金同成分的本体孕育并经过导流器进一步孕育的方法,并对AM60合金进行了浆料制备试验。通过控制合金熔体温度与局部过冷使之具有大量的晶核,再利用流动冲刷,获得具有非枝晶初生固相的固-液混合浆料。试验结果表明,经过自孕育处理,当温度为650℃、孕育剂加入量为熔体质量的11%时,制备的半固态浆料具有均匀、细小、非枝晶状的微观组织,晶粒平均尺寸仅为51μm。 相似文献
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AZ91D镁合金半固态浆料制备的研究 总被引:9,自引:9,他引:9
采用AZ91D镁合金为试验原料,用自行研制的新型半固态浆料设备及直接流变成形装置为试验设备,研究不同温度、剪切速率下半固态组织的变化规律,并与常规铸造组织相比较。研究表明:适量提高剪切速率或降低温度,半固态组织的固相颗粒会变得细小、均匀和圆整。同时,对新型装置制备半固态组织的机理进行了研究。 相似文献
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采用新型的自孕育法制备AZ91D镁合金半固态浆料,研究了导流器在半固态组织形成中的作用.结果表明,合金熔体加入孕育剂并经导流器浇注后,导流器吸收大量过热,使合金温度迅速降低至液相线附近;合金液在导流器表面流动时,导流器促进了熔体中非均质形核及游离晶粒的产生,使合金凝固时晶粒增殖.导流器表面凝固组织从上至下依次为树枝晶、细小树枝晶、等轴晶;倾斜角度影响合金流动方式及传热效果,角度过大和过小均不利于晶粒增殖,角度为45°时冷却效果和剪切作用最佳,此时合金有效形核数量最多,半固态浆料组织初生相细小且分布均匀. 相似文献
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蛇形通道浇注制备半固态7075铝合金浆料(英文) 总被引:4,自引:0,他引:4
采用蛇形通道浇注技术制备半固态7075铝合金浆料,研究浇注温度和弯道数量对半固态7075铝合金浆料微观组织的影响。结果表明:当浇注温度为680~700°C时,可以制备出质量较好的半固态7075铝合金浆料;在相同浇注温度条件下,随着弯道数量的增加,初生α(Al)的平均晶粒尺寸减小,形状因子提高。在浇注制备半固态7075铝合金浆料过程中,合金熔体在具有一定弧度且封闭的蛇形弯道内流动并多次改变流动方向,具有类似"搅拌"的功能,使得初生晶核逐渐演变为球形或近球形晶粒。 相似文献
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间接超声振动制备ZL201铝合金半固态浆料 总被引:1,自引:0,他引:1
采用间接超声振动方法,即工具头在盛熔体的金属杯外面进行超声振动,制备ZL201铝合金半固态浆料。主要研究了启振温度和振动时间对浆料微观组织的影响,以及超声振动作用下整杯浆料的初生晶粒分布。结果表明,在液相线以上附近温度,对熔体进行60s左右的间接超声振动,可以获得平均晶粒直径为67μm,形状系数为0.56的半固态浆料。在60s的振动时间内,晶粒平均直径和形状系数呈现出一直增大的趋势,但是60s后平均形状系数有所降低。整杯浆料中各处浆料组织基本均匀一致,顶部和底部晶粒的平均直径略大于中部。在靠近杯壁1~3mm的区域发现大量游离晶核,表明间接超声振动还具有高频机械振动的效果。 相似文献
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使用自制的交错式功率超声双振动头装置,处理A356铝合金流动熔体获得半固态浆料,研究了1000和1500W超声换能器前后排布流道、不同浇注温度和不同流道倾斜角度对A356熔体处理所获半固态组织的影响规律。结果表明,双振头斜流道对晶粒有细化作用,不同的倾斜角度对A356半固态组织细化程度不同。施振温度为620℃,流道倾斜角度为40°时,初生相晶粒最为细小,球化效果最好。 相似文献
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以A357铝合金为试验材料,利用双螺旋流变制浆设备进行了半固态浆料的制备工艺研究。考察了高剪切熔体处理,也即高强度的搅拌剪切和高强度的紊流作用下,搅拌速度和搅拌时间对铝合金非枝晶组织的形成以及组织特征的影响。结果表明:随着搅拌速度的提高,坯料组织中初生α-Al晶粒尺寸减小,形状变得圆整均匀,但是固相体积分数逐渐减小,搅拌速度的增大对球晶的生长起到了抑制作用;熔体在双螺旋设备中的凝固主要经历了连续冷却以及等温剪切两个过程,搅拌时间越长,晶粒越圆整均匀,尺寸越大,但晶粒密度会急剧下降,总的固相分数不会发生明显变化。 相似文献
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研究了熔体处理对A356合金半固态浆料组织的影响,结果表明,适当的熔体处理工艺具有一定的生成非枝晶组织的作用,但很难实现半固态浆料的快速制备;“熔体处理+双向电磁搅拌”复合技术具有较高的浆料制备效率,为流变成形的制浆提供了可能。同时,优化出A356合金的最佳熔体含量(质量分数),即0.6%的Al-5Ti-B和0.4%的A1-10Sr。 相似文献
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连续冷却条件下半固态AZ91D镁合金组织及流变特性 总被引:11,自引:0,他引:11
在自行设计的Couette型同轴双桶流变仪上对半固态AZ91D镁合金浆料的流变性能以及组织进行了研究。结果表明,连续冷却条件下,连续搅拌半固态AZ91D镁合金浆料的表面粘度随固相分数的增大先缓慢而后迅速增大。此外,冷却速率和剪切速率也都显著影响半固态AZ91D镁合金浆料的表面粘度,降低冷却速率和增大剪切速率,都将导致表观粘度下降,显微组织观察表明,降低冷却速率和增大剪切速率都有利于固相颗粒形态向非枝晶形态转变,从而导致表观粘度的降低。 相似文献
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半固态金属浆料制备技术的研究进展 总被引:1,自引:0,他引:1
总结了30余年来半固态金属浆料制备技术的研究和应用现状,分别介绍了压室浆料制备技术、单螺旋机械搅拌浆料制备技术、双螺旋机械搅拌浆料制备技术、低过热度倾斜板浇注浆料制备技术、低过热度浇注和弱机械搅拌浆料制备技术、连续流变转换浆料制备技术、低过热度浇注和弱电磁搅拌浆料制备技术、蛇形通道浇注浆料制备技术、熔体分散混合浆料制备技术、转桶搅拌浆料制备技术、波浪倾斜板浇注浆料制备技术、旋转倾斜圆筒浆料制备技术、超声振动浆料制备技术、熔体处理和双向电磁搅拌浆料制备技术、低于液相线温度浆料制备技术、偏旋热焓平衡浆料制备技术、气泡搅拌浆料制备技术及其发展前景。 相似文献
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通过建立A356铝合金的半固态表观粘度模型,采用计算机模拟方法对A356铝合金轮毂半固态挤压铸造成形工艺进行了研究.通过分析挤压速度、半固态浆料充填温度及模具预热温度对铝合金轮毂半固态成形性能的影响,探讨了不同条件下的金属流动特点和温度分布规律.结果表明,对该尺寸铝合金轮毂的最佳成形工艺:半固态浆料充填温度为600℃,模具预热温度为300℃,挤压速度为5 mm/s,保压时间为25 s. 相似文献
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Semi-solid metal processing is being developed in die casting applications to give several cost benefits. To efficiently apply this emerging technology, it is important to understand the evolution of microstructure in semi-solid slurries for the control of the rheological behavior in semi-solid state. An experimental apparatus was developed which can capture the grain structure at different times at early stages to understand how the semi-solid structure evolves. In this technique, semi-solid slurry was produced by injecting fine gas bubbles into the melt through a graphite diffuser during solidification. Then, a copper quenching mold was used to draw some semi-solid slurry into a thin channel. The semi-solid slurry was then rapidly frozen in the channel giving the microstructure of the slurry at the desired time. Samples of semi-solid 356 aluminum alloy were taken at different gas injection times of 1, 5, 10, 15, 20, 30, 35, 40, and 45 s. Analysis of the microstructure suggests that the fragmentation by remelting mechanism should be responsible for the formation of globular structure in this rheocasting process. 相似文献
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Degassing effect of ultrasonic vibration in molten melt and semi-solid slurry of Al-Si alloys 总被引:1,自引:0,他引:1
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. 相似文献