阻尼冷却管法制备A356铝合金半固态浆料的研究

介绍了阻尼冷却管法制备A356铝合金半固态浆料工艺的试验装置及其工艺流程,在不同浇注温度下进行了系列试验,并与冷却斜槽法进行了对比分析。结果表明,浇注温度越低,浇注的铸件晶粒尺寸和形状因子数值就越小,晶粒球化程度越高。与冷却斜槽法相比,同一工艺参数下阻尼冷却管法制备的铸件晶粒更为细小和圆整。     

铝、镁合金半固态浆料的制备与流变成形新工艺

介绍了阻尼冷却管法制备A356铝合金半固态浆料工艺的实验装置及其原理,并进行不同浇注温度的系列实验。结果表明:由于阻尼冷凝管的冷却和搅拌作用,熔体浇注温度越低,在两相温度区间内生成的游离晶核就越多,制备得到半固态铸件的晶粒尺寸就越小,且球化程度越高。在此实验原理及结果分析的基础上,设计真空吸铸-阻尼冷却装置,近液相线温度的AZ91D镁合金液在冷却、剪切的作用下,由液态转变为半固态浆料,然后进入模具完成充型,实现镁合金半固态浆料的制备与铸件流变成形一体化;半固态镁合金熔体具有触变性及更高的黏度,以平稳、层流的充型方式完成充型,能够有效地改善成形件的质量。     

S-EMS复合作用对A356铝合金半固态组织形貌的影响

研究了蛇形通道制备A356铝合金半固态浆料时，浇注温度和通道数量对半固态坯料中心和边缘微观组织的影响。并结合蛇形通道与螺旋磁场电磁搅拌，开发了一种新型的半固态制浆方法——S-EMS，研究了高过热度浇注对A356铝合金半固态浆料初生形貌和尺寸的影响。结果表明：在不加任何处理时，显微组织具有明显的枝晶特征，部分枝晶臂长度甚至超过200μm。采用蛇形通道制备半固态浆料时，随着浇注温度的降低或通道数量的增加，试样中心与边缘的平均晶粒尺寸均不断减小并趋于平缓，形状因子不断增加并逐渐趋于平缓，但从3个通道增加至4个通道时，心部形状因子略微降低。S-EMS法在浇注温度680℃下制备出平均晶粒直径78.68μm，形状因子0.65的微观组织，即使在高过热度浇注条件下也能制备出良好的半固态组织。当浇注温度降至660℃，制备出平均晶粒尺寸和形状因子分别为70.25μm及0.71的具有理想微观组织的半固态坯料。     

倒锥形通道浇注制备半固态7075铝合金浆料

采用倒锥形通道浇注方法制备了半固态7075铝合金浆料.试验结果表明,当浇注温度为660～690℃、通道内壁锥度在2°～6°之间时,采用锥形通道浇注方法可以制备出较高品质的半固态7075铝合金浆料,且通道内挂料较少;当通道内壁锥度一定时,随着浇注温度降低,初生α -Al的平均晶粒尺寸减小、形状因子提高;当浇注温度一定时,随着通道内壁锥度的增大,初生α -Al的平均晶粒尺寸减小、形状因子提高;在倒锥形通道浇注制备半固态7075铝合金浆料过程中,通道内壁的大量形核和晶粒游离及收集坩埚中的晶粒熟化是获得细小球状初生α-Al晶粒的主要原因.     

水冷铜质蛇形通道制备半固态7075铝合金浆料

采用自制的水冷铜质蛇形通道装置制备了半固态7075铝合金浆料,研究了浇注温度、弯道数量和冷却水流量对半固态7075铝合金浆料组织的影响。结果表明,当浇注温度为680~700℃时,能获得理想的半固态7075铝合金浆料,其初生α-Al的平均晶粒尺寸小于41μm,形状因子大于0.79。相同温度下,随着弯道数量增加,半固态浆料组织中初生α-Al的平均晶粒尺寸减小、形状因子提高;冷却水流量为450L/h时,获得的半固态浆料组织较好。采用低过热度浇注制备半固态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,具有类似搅拌功能,使得初生晶核逐渐演变为球形或近球形晶粒。     

水冷铜质蛇形通道制备半固态A380铝合金浆料

采用水冷铜质蛇形通道制备了半固态A380铝合金浆料,研究了浇注温度、弯道数量、冷却水流量对半固态A380铝合金浆料组织的影响。结果表明,随着浇注温度的降低,初生α-Al晶粒尺寸减小、形状因子提高;浇注温度在610~630℃时,可以获得理想的半固态浆料组织。随着水冷铜质蛇形通道弯道数量增加,半固态浆料组织中初生α-Al晶粒更加细小、均匀、圆整。水冷铜质蛇形通道冷却水流量为500L/h时,可以获得初生α-Al晶粒细小、圆整的半固态浆料组织。     

蛇形通道浇注制备半固态7075铝合金浆料(英文)

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。     

蛇形通道浇注制备7075铝合金半固态浆料

采用蛇形通道浇注制备7075铝合金半固态浆料,研究了浇注温度、弯道数量和弯道直径对7075铝合金半固态浆料组织的影响.结果表明,当浇注温度为660～675℃时,可以制备出质量较好的7075铝合金半固态浆料,且管道内挂料较少;在相同温度条件下,随着弯道数量增加或弯道直径减小,初生α-Al的平均晶粒尺寸减小、形状因子提高.在制备7075铝合金半固态浆料过程中,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”功能,使得初生晶核逐渐演变为球形或近球形晶粒.     

蛇形通道浇注法制备半固态A380铝合金浆料

采用石墨质蛇形通道浇注法制备半固态A380铝合金浆料,研究了浇注温度、弯道数量和弯道内径对半固态A380铝合金浆料组织的影响。结果表明,浇注温度在610~650℃范围时可获得理想的半固态A380铝合金浆料,半固态A380铝合金浆料组织随浇注温度的降低,由蔷薇晶组织向近球晶或球晶组织演变。在相同浇注温度条件下,弯道数量的增加或通道内径尺寸的减小都可细化半固态A380铝合金浆料组织中的初生α-Al晶粒,提高形状因子,进而优化其浆料组织。     

ZL104铝合金连杆半固态挤压铸造工艺实验研究

研究了传统液态挤压铸造与半固态挤压铸造成形ZL104铝合金连杆的充填状态、微观组织及力学性能。结果表明:传统液态挤压铸造成形连杆充填饱满,但其抗拉强度及伸长率低于半固态挤压铸造成形连杆。对于半固态挤压铸造成形,浇注温度高于565℃时,铸件充填性能良好;平均晶粒尺寸及形状因子随浇注温度的升高而逐渐增大;连杆抗拉强度及伸长率先增加后减小。挤压压力高于25MPa时,铸件均充填饱满;挤压压力升高,平均晶粒尺寸不断减小且形状因子不断增大,连杆机械性能不断提高。模具预热温度升高,平均晶粒尺寸和形状因子不断增大,连杆机械性能逐渐提高。但当模具预热温度超过300℃时,平均晶粒尺寸进一步增大而其形状因子减小,导致连杆的机械性能下降。     

Preparation of Al-Zn-Mg-Cu alloy semisolid slurry through a water-cooled serpentine pouring channel

The semisolid slurry of Al-Zn-Mg-Cu alloy was prepared through a self-designed water-cooled copper serpentine pouring channel(WSPC) machine. Influences of pouring temperature, the number of turns and the cooling water flow rate on the microstructure of the semisolid Al-Zn-Mg-Cu alloy slurry were investigated. The results show that the semisolid Al-Zn-Mg-Cu alloy slurry with satisfactory quality can be generated by the WSPC when the pouring temperature is in the range between 680 ℃ and 700 ℃. At a given pouring temperature, the average grain size of primary α-Al decreases and the shape factor increases with the increase of the number of turns. When the cooling water flow rate is 450 L·h~(-1), the obtained semisolid slurry is optimal. During the preparation of the semisolid Al-Zn-Mg-Cu alloy slurry with low superheat pouring, the alloy melt has mixed inhibition and convection flow characteristics by "self-stirring". When the alloy melt flows through the serpentine channel, the chilling effect of the inner wall of the channel, the convection and mixed inhibition of the alloy melt greatly promote the heterogeneous nucleation and grain segregation. This effect destroys the dendrite growth mode under traditional solidification conditions, and the primary nuclei gradually evolve into spherical or nearspherical grains.     

Efficient fabrication of semisolid nondendritic Al alloy slurry with high quality

Subjecting a normal mechanical vibration to a cooling slope plate,is a proposed method for preparing semisolid nondendritic slurry,named shear-vibration coupling sub-rapid solidification(SCS).Taking Al-8Si alloy as model material,the temperature field and distribution field of solid or liquid phase during SCS were simulated using COMSOL Multiphysics software to primarily choose the optimal processing parameters.Subsequently,the slurries were prepared with the parameters selected according to the simulation results and the microstructures of the slurries were experimentally investigated.Results indicate that the simulation results could provide a basis for roughly choosing the processing parameters,although the calculated solid fractions are always higher than the experimental ones.The processing parameters affect the primary grain size,shape factor and solid fraction mainly through altering the contact duration of melt on the plate,and thus affecting the cooling effect on the melt,nucleation rate,and grain dissociation and proliferation.Experiments with optimized processing parameters show that the primary grains in the slurry have an average size of about 32μm and shape factor of 1.38,and are quite uniform,even at the highest pouring rate of 2.81 kg·s^-1,the size and shape factor are about 46μm and 1.7,respectively,which implies that the proposed SCS is a promising technology for efficient fabrication of high-quality Al slurry available for engineering applications.     

Effect of pouring temperature on fractal dimension of primary phase morphology in semi-solid A356 alloy

The fractal dimensions of primary phase morphology in semi-solid A356 alloy prepared by low superheat pouring and slightly electromagnetic stirring were calculated, and the effect of pouring temperature on fractal dimension of primary phase morphology in semi-solid A356 alloy was researched. The results indicate that it is feasible to prepare semisolid A356 alloy slurry by low superheat pouring and slightly electromagnetic stirring, and there is an important effect of pouring temperature on the morphology and the grain size of the primary phase in semi-solid A356 alloy, in which the reduction of pouring temperature can obviously improve grain size and shape factor of primary phase in semi-solid A356 alloy under the condition of a certain stirring power. The primary phase morphology of semi-solid A356 alloy prepared by low superheat pouring and slightly electromagnetic stirring can be characterized by fractal dimension, and the primary phase morphology obtained by the different processing parameters has the different fractal dimensions. Solidification of semi-solid alloy is a course of change in fractal dimension.     

Microstructure of partially remelted billet of AM60 alloy prepared with self-inoculation method

The billets of AM60 alloy, prepared with self-inoculation method, were partially remelted into semisolid state. Effects of process parameters on remelting microstructure of semisolid billet were investigated. Experimental results show that the solid particles obtained with self-inoculation method are in smaller grain size and globular shape after partial remelting, compared with those prepared with other casting methods. In the optimized process conditions, the average size of solid particles of partially remelted billet is 65 μm, and the shape factor is 1.12. The process parameters, i.e. pouring temperature, addition amount of self-inoculants, and the slope angle of multi-stream mixing cooling channel have influence on the microstructure of partially remelted billet. The optimized temperature is from 680 °C to 700 °C, addition amount of self-inoculants is between 5% and 7% (mass fraction), slope angle of multi-stream mixing cooling channel is between 30° and 45°, with which the dendritic microstructure of as-cast billet can be avoided, and the size of solid particles of remelted billet is reduced.     

强制对流流变成形制备7075铝合金半固态浆料及其数值模拟(英文)

采用自主研发的强制对流流变装置,研究搅拌速度对7075铝合金半固态组织的影响规律。实验结果表明,随着搅拌速度的增加,半固态组织的晶粒尺寸减小,形状因子及粒子数增加。同时,对强制对流流变成形浆料制备过程进行数值模拟,研究熔体在筒体内的流动规律和搅拌速度对合金熔体温度场和固相率的影响。模拟结果表明,合金熔体在FCR筒体内存在复杂的对流运动,熔体对流极大地改变了合金熔体温度场和固相率的分布。增加对流强度有利于减小合金熔体的过冷度梯度和改善初生晶粒的分布。     

半固态过共晶高铬铸铁的制备及组织定量分析

为改善过共晶高铬铸铁组织中粗大初生碳化物的形貌,采用冷却体法制备了碳化物明显细化、圆整的半固态坯料.通过分别改变浇注温度、冷却体斜度获得六组不同半固态浆料温度的凝固组织,并借助Leica图像分析仪分别定量分析了初生碳化物的形状系数和等效直径变化特征.研究表明:采用本方法可明显改善碳化物的形象,改变浇注温度和冷却体的倾斜角度对半固态组织有较大影响.     

Globulization mechanism of the primary Al of Al−15Cu alloy during slurry preparation for rheoforming

Semisolid slurries of Al-15Cu alloy were produced for rheoforming by a low temperature pouring technique. To investigate the morphological change of the slurry in terms of the particle mean diameter and the roundness factor, samples were extracted during the continuous cooling and the isothermal holding stage of the slurry by a simple technique of interrupt quenching. Results demonstrated that the fine-grained equiaxed dendritic structure, which formed during low temperature pouring, is changed to a globular structure when held at a semisolid temperature for sufficiently long holding time. With regard to the globulization mechanism of the primary α-phase, local melting is considered to take place at the neck of equiaxed dendrites, leading to the separation of small new particles during continuous cooling. These newly formed particles eventually grow during isothermal holding in the semisolid temperature by obeying theD ³=Kt kinetic law, which suggests coarsening by Ostwald ripening.