Numerical simulation on the rheo-diecasting of the semi-solid A356 aluminum alloy

The effect of injection pressure, piston velocity, and the forming temperature of semisolid slurry on the filling behavior of the semi-solid A356 aluminum alloy was investigated by simulation methods. The simulation results show that these processing parameters have an important effect on the filling behavior of the semi-solid A356 aluminum alloy. The slurry flows steadily in the cavity when the injection pressure, the piston velocity, and the forming temperature are low, but it is prone to turbulent flow w...     

镁合金半固态流变压铸充型凝固过程数值模拟及试验研究

在前期平板模型流变压铸充型凝固过程数值分析的基础上,利用所建立的数学模型对镁合金压铸件中间轴螺塞进行了数值分析和实验研究,对比分析了零件成形时镁合金牛顿流体与镁合金半固态流体的充型特征及零件中存在缺陷的位置和大小。结果表明,与牛顿流体相比半固态流体更易实现铸液充型时的顺序填充,有利于铸型中的气体的排出和铸件成形质量的提高。模拟结果与试验结果吻合较好。     

Influence of rheo-diecasting processing parameters on microstructure and mechanical properties of hypereutectic Al–30%Si alloy

The effects of pouring temperature, vibration frequency, and the number of curves in a serpentine channel, on the microstructure and mechanical properties of Al–30%Si alloy processed by rheo-diecasting (RDC) were investigated. The semisolid Al–30%Si alloy slurry was prepared by vibration serpentine channel pouring (VSCP) process in the RDC process. The results show that the pouring temperature, the vibration frequency, and the number of the curves strongly affect the microstructure and mechanical properties of Al–30%Si alloy. Under experimental conditions of a pouring temperature of 850 °C, a twelve-curve copper channel and a vibration frequency of 80 Hz, the primary Si grains are refined into fine compact grains with average grain size of about 24.6 μm in the RDC samples assisted with VSCP. Moreover, the ultimate tensile strength (UTS), elongation and hardness of the RDC sample are 296 MPa, 0.87% and HB 155, respectively. It is concluded that the VSCP process can effectively refine the primary Si grains. The refinement of primary Si grains is the major cause for the improvement of the mechanical properties of the RDC sample.     

Numerical simulation on rheo-diecasting mould filling of semi-solid key-shaped component

Based on the experimental data of apparent viscosity about semi-solid A356 aluminum alloy,the apparent viscosity model was developed and inserted into a commercial software Castsoft6.0,and a key-shaped component filling process was simulated.The simulation results are in good agreement with the experimental filling results,which indicates that the apparent viscosity model established is effective and available.The process parameters on the cavity filling of the key-shaped components have been optimized.The injection pressure should be more than 15MPa.the slurry flowing velocity in the in-gate should be more than 1.73m/s,and the slurry temperature should be over 585℃.     

流变压铸成形镁合金AZ91D的显微组织与性能

采用双螺杆机械搅拌法制备半固态镁合金浆料,对比研究了液态压铸与半固态流变压铸成形镁合金AZ91D的组织与性能,探讨了半固态成形镁合金铸件的热处理强化机制.试验结果表明,流变压铸成形铸件与液态压铸成形铸件在铸态时的力学性能相当;由于半固态成形减轻了铸件内部气孔、偏析等铸造缺陷,因而T4和T6热处理均明显地提高了半固态成形镁合金铸件的力学性能.研究还得出,液态压铸成形镁合金铸件经过固溶处理之后,其抗拉强度和伸长率也有所提高,但是,时效处理明显地恶化了铸件的力学性能.     

Filling ability of semi-solid A356 aluminum alloy slurry in rheo-diecasting

The effects of slurry temperature, injection pressure, and piston velocity on the rheo-filling ability of semisolid A356 alloys were studied by the reho-diecasting methods. The results show that the slurry temperature of the semi-solid A356 aluminum alloy has an important effect on the filling ability; the higher the slurry temperature, the better is the filling ability, and the appropriate slurry temperature for rheo-filling is in the range of 585-595℃. The injection pressure also has a great effect on the filling ability, and it is appropriate to the rheo-filling when the injection pressure is in the range of 15-25 MPa. The piston velocity also has a great effect on the filling ability, and it is appropriate to the rheo-filling when the piston velocity is in the range of 0.072-0.12 m/s. The filling ability of the slurry prepared by low superheat pouring with weak electromagnetic stirring is very good and the microstructural distribution in the rheo-formed die castings is homogeneous, which is advantageous to the high quality die casting. 2008 University of Science and Technology Beijing. All rights reserved.     

Effects of Cu content on microstructure and mechanical properties of rheo-diecasting Al-6Zn-2Mg-xCu alloys

A systematic study on how Cu content affects the microstructure and mechanical properties of rheo-diecasting Al-6Zn-2Mg-xCu alloys during solution treatment and ageing heat treatment was conducted. The swirled enthalpy equilibrium device (SEED) was adopted to prepare the semi-solid slurry of Al-6Zn-2Mg-xCu alloys. The microstructure development and mechanical properties were studied using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), as well as hardness and tensile testing. The grain boundary and shape factor were calculated using image processing software (Image-Pro Plus 6.0). Results show that the alloys are composed of typical globular primary α-Al grains, eutectic phases, and smaller secondary α-Al grains. After solution and ageing heat treatment, the eutectic phases are dissolved into Al matrix when the Cu content is lower than 1.5wt.%, while some eutectic phases transform into Al₂CuMg (S) phases and remain at grain boundaries when Cu content reaches 2wt.%. T6 heat treatment significantly enhances the mechanical properties of rheo-diecasting Al-6Zn-2Mg-xCu alloys. When Cu concentration is 0.5wt.%–1.5wt.%, the ultimate tensile strength, yield strength and elongation of T6 treated alloys rise to around 500 MPa, 420 MPa, and 18%, respectively.

     

ZL201铝合金半固态流变压铸组织与性能

研究了ZL201铝合金半固态流变压铸组织与性能,包括半固态浆料的制备、压铸成形和固溶、时效处理。结果表明:在ZL201铝合金液相线温度附近施加交变电磁场,能够获得均匀、细小、近球形非枝晶组织的半固态浆料;半固态浆料经压铸成形后,零件具有等轴或蔷薇状晶粒组织;经T5热处理后,ZL201铝合金的抗拉强度为253N/mm2,伸长率为7%。流变压铸件的组织和性能优于半固态触变压铸件的。     

引晶法制备半固态A356铝合金浆料的流变压铸

将引晶法制备的A356铝合金半固态浆料进行流变压铸,研究铸件在铸态和T6热处理条件下的力学性能和微观组织。结果表明:在铸态下铸件的抗拉强度可达到250 MPa左右,伸长率为9%~13%;经过T6热处理后,抗拉强度可提高约30%,但伸长率略有下降。引晶法可制备出初生α1(Al)的形状因子为0.76~0.85和晶粒尺寸为20~40μm的优质半固态A356铝合金浆料。     

AZ91D镁合金强制对流流变压铸组织与性能

研究了流变压铸成形和传统压铸工艺下AZ91D镁合金连接压铸件的组织特征,分析了流变压铸过程中半固态浆料的形成和凝固行为,测试了FCR工艺下流变压铸拉伸件的力学性能。结果表明:FCR工艺下的流变压铸成形工艺不仅可以获得晶粒细小、形貌圆整的半固态组织,而且能够明显改善传统压铸成型件中的气孔缺陷,提高组织致密度。与传统压铸件相比,流变压铸拉伸件的抗拉强度和伸长率都有了明显的提高;T6热处理能进一步强化流变压铸拉伸件的性能,其抗拉强度和伸长率分别为286MPa和6.1%。