Preparation of semi-solid 7075 aluminum alloy slurry by serpentine pouring channel

The semi-solid slurry of 7075 aluminum alloy was prepared by a serpentine pouring channel （SCP）. Influences of pouring temperature and the number of turns on the microstructure of semi-solid 7075 alloy slurry were investigated. The results demonstrated that the semi-solid 7075 aluminum alloy slurry with satisfied quality could be generated by a serpentine pouring channel when the pouring temperature was in the range of 680-700 ℃. At a given pouring temperature, the equivalent size of the primaryα（Al） grains decreased and the shape factor increased with the increase of the number of turns. During the slurry preparation of semi-solid 7075 aluminum alloy, the flow direction of alloy melt changed many times when it flowed in a curved and closed serpentine channel. With the effect of“stirring”in it , the primary nuclei gradually evolved into spherical and near-spherical grains.

Preparation of semi-solid A380 aluminum alloy slurry by serpentine channel

The semi-solid slurry of A380 aluminum alloy was prepared by the serpentine channel. The effects of pouring temperature, curve number and curve diameter of the serpentine channel on the microstructure of the semi-solid A380 aluminum alloy slurry were investigated. The results show that the satisfactory semi-solid A380 aluminum alloy slurry could be obtained when the pouring temperature ranged from 630 to 650 °C. Under the same conditions, increasing the curve number or reducing the curve diameter of the serpentine channel would decrease the average diameter and increase the shape factor of the primary α（Al） grains. The ＂self-stirring＂ of the alloy melt in the serpentine channel was beneficial to the ripening of the dendrites and the spheroidizing of the primary α（Al） grains.

Influence of serpentine channel pouring process parameters on semi-solid A356 aluminum alloy slurry

Semi-solid A356 aluminum alloy slurry was prepared by using serpentine channel pouring process, and the influences of the channel diameters and pouring temperatures on the semi-solid A356 aluminum alloy slurry were investigated. The experimental results show that when the channel diameter is 20 and 25 mm, respectively, and the pouring temperature is 640-680 ℃, the average diameter of primary α（Al） grains in the prepared A356 aluminum alloy slurry is 50-75 and 55-78 μm, respectively, and the average shape factor of primary α（Al） grains is 0.89-0.76 and 0.86-0.72, respectively. With the decline in the pouring temperature, the microstructure of semi-solid A356 aluminum alloy slurry is more desirable and a serpentine channel with smaller diameter is also advantageous to the microstructure imProvement. During the preparation of semi-solid A356 aluminum alloy slurry, a large number of nuclei can be produced by the chilling effect of the serpentine channel, and owing to the combined effect of the chilled nuclei separation and melt self-stirring, primary α（Al） nuclei can be multiplied and spheroidized finally.

Microstructure evolution of semi-solid 7075 Al alloy slurry during temperature homogenization treatment

Semi-solid 7075 Al slurry was prepared by inverted cone-shaped pouring channel process （ICSPC） and temperature homogenization （TH） treatment was combined to make the slurry uniform and have a controllable solid fraction suitable for the follow-up rheocasting. The influence of cooling rate on the microstructure evolution of primary α（Al） during TH treatment was investigated. The results show that as the cooling rate of the slurry after being prepared reduces, the growth of primaryα（Al） in the slurry tends to be nearly spherical and the uniformity of the organization is also enhanced. This may be due to the fact that lower cooling rate plays an important role in achieving the uniformity of temperature and composition in the remaining liquid, which is crucial to the formation of the spherical and homogeneous microstructure. However, a too low cooling rate will lead to a significant increase in grain growth time, which makes too coarse grains and more particles coalesce, so a certain abnormal growth of grain appears and the shape factor decreases slightly.

Preparation of semi-solid A356 Al-alloy slurry by introducing grain process

A preparation technology of semi-solid metal slurry introducing grain process （IGP） was developed. The effects of processing parameters on the microstructures of the semi-solid A356 Al-alloy slurries were investigated, and the formation mechanism and morphology controlling of the spherical primary a（A1） grains were discussed. The results show that when the preparing slurry is 4 kg, IG size is 10 mm, dosage is 3.5% and dumping temperature （DT） is 611-617 ℃, the mean diameter of the primary a（A1） grains in the semi-solid slurries can reach 40-75 μm and the shape factor can reach 0.82-0.89. When the IG size is 10 mm, DT is 613℃and dosage is 2%-4%, the mean diameter can reach 45-82 μm and the shape factors can reach 0.78-0.88. With decreasing DT or increasing dosage properly, the primary α（A1） grain morphology is better. When QR=QA and Rh=Rc, as long as the DT is suitable, excellent semi-solid slurry can be produced. As a result of the IG melting, a large amount of dendritic fragments can become the direct source of the primary a（A1） grains. Meanwhile, many undercooled areas are formed, where abundant primary α（A1） grains are multiplied by heterogeneous nucleation.

多弯道蛇形管浇注法制备半固态A356铝合金浆料

采用多弯道蛇形管浇注技术制备半固态A356铝合金浆料。结果表明:在浇注温度为640～680℃的条件下,当弯道数量为3且直径为20 mm时,可获得形状因子F为0.72～0.85和晶粒直径D为55～75μm的半固态浆料;当弯道数量为5且直径为20 mm时,可获得形状因子F为0.86～0.92和晶粒直径D为44～58μm的半固态浆料;当弯道数量为5且直径为25 mm时,可获得形状因子F为0.76～0.90和晶粒直径D为48～68μm的半固态浆料。弯道数量增加或弯道直径减小,可以改善初生α(Al)晶粒的形貌和尺寸。弯道内的合金熔体具有"自搅拌"的作用,可使初生晶核逐渐演变为球形或近球形晶粒。

紊流通道浇注制备半固态A356铝合金浆料

采用水冷紊流通道制备半固态A356铝合金浆料，研究了紊流叶片对通道内合金熔体径向温度和半固态浆料组织的影响，分析了球状初生α（A1）晶粒的形成机制。结果表明，合金熔体每流过一个叶片后，径向温差逐渐减小；当浇注温度为650℃时，流过最后一个叶片后，径向温差减小到0～2℃。紊流叶片增大了合金熔体与管壁接触的表面积，促进了初生α（A1）晶核的生成，因此改善初生仪（A1）晶粒的形貌。

半固态浆料的冷却速率对组织的影响

为了研究半固态浆料的冷却速率对微观组织的影响,采用水冷冷却斜槽来制备半固态A356铝合金浆料。结果表明:当冷却速率大于26.4℃/s时,半固态浆料中的初生α(Al)全部由细小的枝晶和蔷薇晶组成;当冷却速率为14.0～20.6℃/s时,初生α(Al)主要由球形、近球形晶粒和一些细小的蔷薇晶组成;当冷却速率为5.0～14.0℃/s时,初生α(Al)主要由球形和近球形晶粒组成。适宜的冷却速率为5.0～15.0℃/s。冷却速率越快,晶粒平均直径越细小,但形状因子越低。

工艺参数对引晶法制备半固态浆料组织的影响

采用引晶法（Introducing Grain Process,简称IGP）制备半固态金属浆料,研究了工艺参数对半固态A356铝合金浆料组织的影响,讨论了球状初生α（Al）晶粒的形成机制及形貌控制.结果表明：当合金温度为630℃、制备浆料为4 kg时,如果引晶尺寸为10 mm、加入量为3.5%（质量分数）和倾倒温度为611～617℃,半固态浆料中初生α（Al）晶粒的平均直径可达40-75μm,形状因子可达0.82-0.89.如果引晶尺寸为10 mm、倾倒温度为613℃、加入量为2%-4%,初生α（Al）晶粒的平均直径可达45-82μm,形状因子可达0.78-0.88.合金温度和倾倒温度适当降低、或者引晶加入量适当提高,组织越好.当QR=QA、Rh=Rc时,只要倾倒温度适宜就可以制备优质半固态浆料.引晶熔化时产生的枝晶碎块是半固态浆料中初生α（Al）晶粒的直接来源,引晶熔化时形成的温度过冷区也为异质形核提供了有利条件.