Microstructure and properties of 35 kg large aluminum alloy flywheel housing components formed by squeeze casting with local pressure compensation

The squeeze casting method with local pressure compensation was proposed to form a flywheel housing component with a weight of 35 kg.The numerical simulation,microstructure observation and phase characterization were performed,and the influence of local pressure compensation on feeding of thick-wall position,microstructure and mechanical properties of the formed components were discussed.Results show that the molten metal keeps a good fluidity and the filling is complete during the filling process.Although the solidification at thick-wall positions of the mounting ports is slow,the local pressure compensation effectively realizes the local forced feeding,significantly eliminating the shrinkage cavity defects.In the microstructure of AlSi9Mg alloy,α-Al primarily consists of fragmented dendrites and rosette grains,while eutectic Si predominantly comprises needles and short rods.The impact of local pressure compensation on strength is relatively minimal,yet its influence on elongation is considerable.Following local pressure compensation,the average elongation at the compensated areas is 9.18%,which represents a 44.90%higher than that before compensation.The average tensile strength is 209.1 MPa,and the average yield strength is 100.6 MPa.The local pressure compensation can significantly reduce or even eliminate the internal defects in the 35 kg large-weight components formed by squeeze casting.

Preparation of large size ZTA ceramics with eccentric circle shape by microwave sintering

Ultra-large zirconia toughened alumina (ZTA,mass ratio of Al2O3 and ZrO2 is 78∶22) ceramics with eccentric circle shape were successfully sintered by microwave sintering with a multi-mode cavity at 2.45 GHz.The dimension of ZTA ceramics (green body) is 165 mm (outer diameter) × 25 mm (thickness).The optimized sintering temperature of microwave sintering is about 1500 ℃ for 30 min,and the total sintering time is about 4 h which is much shorter than that of conventional sintering.An auxiliary-heating insulation device was designed based on the principle of local caloric compensation to guarantee the intact sintered samples.With the increasing of sintering temperature,more and more microwave energy is absorbed within the entire sample,volumetric densification performs,and phases shift from m-ZrO2 phase to t-ZrO2 phase and cause Al2O3 grain growth.

Study of closed orbit response to magnet vibrations at the SSRF storage ring

This paper presents the analytical and simulation responses of the closed orbit distortion in the SSRF storage ring to random and plane wave like magnet vibrations respectively. It is shown that the use of girder is very beneficial in the view of suppressing this response function. Effect of the independently supported gradient bending magnets to the closed orbit response is given. An analytic formula is written to give a rough estimate of the closed orbit distortion due to ground motion, taking into account the closed orbit response function and girder transfer function. As an example, the result of SSRF case is given.