半固态A380铝合金浆料的蛇形通道制备及流变压铸工艺
发布时间：2018-11-12 18:00
【摘要】：本文以A380铝合金为研究对象,系统研究了蛇形通道浇注工艺参数和Si含量对半固态A380铝合金浆料组织的影响,并适度阐述了A380合金熔体在蛇形通道内的流动状态、边界层分布以及半固态浆料中初生a-Al晶粒的形成机制。在此基础上,深入探讨了流变压铸工艺参数对流变压铸充型性能和流变压铸拉伸试样力学性能的影响,并制定了合理的流变压铸拉伸试样热处理工艺。结果表明： (1)降低浇注温度、增加弯道数量或减小通道内径均可提高半固态A380铝合金浆料的品质,但凝固壳的质量比例增加。石墨质蛇形通道制备半固态A380铝合金浆料最佳匹配工艺参数为：D20-S5型蛇形通道在630-650℃范围浇注,浆料组织中初生a-Al晶粒平均直径为48μm,形状因子为0.81。铜质水冷蛇形通道制备半固态A380铝合金浆料最佳匹配工艺参数为：D30-T4型蛇形通道在冷却水流量为500L/h和浇注温度范围为630～650℃,浆料组织中初生α-Al晶粒平均直径为47μm,形状因子为0.86。A380铝合金中Si含量较高时不宜采用蛇形通道制备半固态浆料,可采用铜质水冷蛇形通道在低浇注温度或大冷却水流量下制备优质半固体浆料。 (2)透明蛇形通道模拟A380铝合金熔体在蛇形通道内的流动状态为层流和紊流相互交替。A380铝合金熔体通过激冷形核和异质形核发生一次凝固,一部分自由晶直接生长为球晶,另一部分自由晶生长为树枝晶。在紊流“白搅拌”下枝晶臂发生颈缩和熔断向蔷薇晶和近球晶演变。剩余液相在收集坩埚内发生二次凝固并在高固相率半固态浆料中成长为非枝晶。 (3)半固态A380铝合金浆料的充型能力随浇注温度、压射比压和模具温度的增加而增强,浇注温度为650℃、模具温度为200～250℃、静置时间为Os和压射比压为105MPa时充型能力最强,螺旋形模具型腔全部充满。随静置处理时间的延长而下降,静置60s处理后充型能力最弱。 (4)压射比压、静置时间和A380铝合金中的Si含量对拉伸试样的组织影响十分明显,而浇注温度和模具温度对拉伸试样的组织影响不大。拉伸试样的力学性能随浇注温度降低、压射比压增大或模具温度升高而增加,浇注温度为650℃、模具温度为200～220℃、静置时间为Os和压射比压为105MPa时,拉伸试样的抗拉强度为312MPa,对应延伸率为5.6%,显微硬度为111HV。半固态浆料静置处理后,拉伸试样的力学性能先提高后降低。 (5)流变压铸拉伸试样T6热处理工艺为490℃+2h和165℃+48h,拉伸试样经T6热处理后最大抗拉强度为326MPa,对应延伸率为7.03%,显微硬度为131HV。拉伸试样的断裂形式随时效处理时间的延长由解理断裂向韧性断裂转变。断口处脆性断裂面的析出物为富Fe相和富Mn相,严重降低拉伸试样的力学性能。
[Abstract]:In this paper, the effects of pouring process parameters and Si content of serpentine channel on the microstructure of semi-solid A380 aluminum alloy slurry were systematically studied, and the flow state of A380 alloy melt in serpentine channel was described. Boundary layer distribution and the formation mechanism of primary a-Al grains in semisolid slurry. On this basis, the effect of rheological die casting process parameters on the filling properties and mechanical properties of rheological die casting tensile specimens is discussed, and a reasonable heat treatment process for rheological die casting tensile specimens is established. The results show that: (1) the quality of semi-solid A380 aluminum alloy slurry can be improved by decreasing pouring temperature, increasing the number of bends or reducing the inner diameter of the channel, but increasing the mass ratio of solidified shell. The optimum matching process parameters for the preparation of semi-solid A380 aluminum alloy slurry by graphite-serpentine channel are as follows: D20-S5 serpentine channel is casted at 630-650 鈩，
本文编号：2327803
[Abstract]:In this paper, the effects of pouring process parameters and Si content of serpentine channel on the microstructure of semi-solid A380 aluminum alloy slurry were systematically studied, and the flow state of A380 alloy melt in serpentine channel was described. Boundary layer distribution and the formation mechanism of primary a-Al grains in semisolid slurry. On this basis, the effect of rheological die casting process parameters on the filling properties and mechanical properties of rheological die casting tensile specimens is discussed, and a reasonable heat treatment process for rheological die casting tensile specimens is established. The results show that: (1) the quality of semi-solid A380 aluminum alloy slurry can be improved by decreasing pouring temperature, increasing the number of bends or reducing the inner diameter of the channel, but increasing the mass ratio of solidified shell. The optimum matching process parameters for the preparation of semi-solid A380 aluminum alloy slurry by graphite-serpentine channel are as follows: D20-S5 serpentine channel is casted at 630-650 鈩，
本文编号：2327803
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