| Microstructure of Mg-6wt%Zn-1wt%Y-0.6wt%Ce-0.6wt%Zr alloy fabricated by rapid solidification and forward extrusion was studied by optical microscope,scanning electronic microscope,transmission electronic microscope and X-ray diffraction.Mechanical properties of the alloy at different temperatures were also tested.The main results are as follows:(1)The alloy consists ofα,W and Mg17Ce2 phases,the grain size of the alloy is 0.7μm, and secondary phases dispersed in it evenly.The texture vertical to the extrusion direction is formed in the alloy,.(2)The maximum hardness,ultimate tensile strength,elongation,compression strength and compressibility of the alloy can reach 118HV5,506MPa,18%,470MPa and 12% respectively.The ratio of the tensile and compression yield strength is 0.9～0.95.As the extrusion temperature increases,the strength of the alloy decreases,and the structural homogeneity and property stability are improved.310～330℃is the favorable extrusion temperature for the alloy.(3)The compression strength of the alloy is～437 MPa when compression temperature is 120℃,and the fracture strain exceeds 0.15.The compression yield strength decreases to 360 MPa at 175℃and the alloy doesn't broken when the compression temperature is above 175℃. Two factors affect the compression process,that is strain-strengthening and dynamic recrystallization(DRX).The mechanism of dynamic recrystallization of the alloy at low temperature is attribute to the low temperature dislocation dynamic recrystallization(LTDRX).(4)The flow stress falls with increasing of deformation temperature if the same strain rate is same.Meanwhile,the resistance to deformation decreases and softening will occur in the alloy.The flow stress increases when the strain rate increases,so the alloy is one of the plus strain rate sensitivity exponent materials.(5)The compressive deformation activation energy and the corresponding stress exponent of the alloy were 151KJ/mol and 6.44 respectively at 150～175℃and strain rate10-2～10-3s-1.
|
PDF Full Text Request