Study On Thermal Deformation And Heat Treatment Properties Of ZL114A Alloy

The cast ZL114 A alloy was investigated in this paper.At the condition of deformation temperature of 350 ?-470 ?,strain rate of 0.001 s^-1-10 s^-1,deformation of 50 %,hot compression tests for ZL114 A alloy were carried out by Gleeble^-1500 D thermal simulation testing machine.The true stress-true strain curve showed that flow stress of the ZL114 A alloy decreased with the reduction of strain rate and the increase of deformation temperature.The other curves showed obvious dynamic recovery characteristics except that the curve of strain rate 10s^-1 exhibited dynamic recrystallization characteristics.The constitutive model of peak stress and flow stress of ZL114 A alloy was established based on Arrhenius hyperbolic sine equation,and the verification results showed that the model could accurately reflect the change of flow stress.The microstructures of the alloys after hot compression deformation were observed and analyzed.The results showed that the softening mechanism of ZL114 A alloy during hot working was mainly dynamic recovery.Dynamic recrystallization occurred only at 10 s^-1,which was consistent with the true stress-true strain curve.With the increase of the deformation temperature or the decrease of the strain rate,the distribution of the second phase in the alloy is more uniform.The hot working map of ZL114 A alloy was established based on the material dynamic model theory.The processing instability zone was mainly concentrated at high strain rate of 1 s^-1-10 s^-1,and gradually increased from low temperature to high temperature as the amount of deformation increased.The machinable area of the alloy was large,indicating that the hot workability of ZL114 A alloy was better.Based on the hot working map of ZL114 A alloy,hot extrusion deformation test was carried out.The microstructure observation showed that the three-dimensional stress in the extrusion process caused the coarse eutectic silicon phase to be remarkably refined,and distributed along the extrusion direction,organizations hadbeen significantly improved.At the same time,the fractures of the extruded alloy were dominated by dimples,and the elongation increased from 2.5 % of as-cast to19.5 %,tensile strength of 208 MPa,slightly improved.The heat treatment of extruded ZL114 A alloy was studied by orthogonal test.The results showed that the effect of solution temperature and aging temperature on the alloy was the most significant,and the optimal heat treatment of the extruded ZL114 A alloy was 525 ?×8 h+190 ?×7 h.The Si phase in the alloy was uniformly rounded after the heat treatment in this process,and aging phase was mainly composed of acicular ??.The tensile strength of the alloy was 350 MPa,elongation of 11 %,far meet the actual production and use requirements.