| Zr63.68-x3.68-x Cu16.2+x6.2+x Ni10.12Al10?x=0,0.45,0.9,1.35,1.8,2.25,2.7?bulk amorphous alloy were served as the research object in this experiment,Rods of bulk amorphous alloy with diameters of 2,4,6mm were fabricated by copper mold suction casting method in argon atmosphere.The effects of Cu?Zr content on mechanical properties,amorphousforming abilityandthermalstabilityofZr63.68Cu16.2Ni10.12Al10amorphous alloy were investigated by X-ray diffraction?XRD?,universal testing machine,scanningelectronmicroscope?SEM?anddifferentialscanning calorimetry?DSC?.The results show that the specimens with diameter of 2mm were completely amorphous with the increase of Cu content and the decrease of Zr content,and the plastic strain is increasing firstly and then decreasing.When x=1.8,the plastic strain reaches the maximum of 38.74%,which is about 4.3 times of Zr63.68Cu16.2Ni10.12Al100 bulk amorphous alloy with the plastic strain of 9.10%.The elastic modulus is 51757MPa,the yield strength is 2079MPa,the compressive strength is 3861MPa,and the fracture strength is 3861MPa.Obvious serrated flow behavior and work hardening phenomenon are observed in the course of plastic deformation.With the increase of specimen size,there is obvious scale effect of plastic strain.It is also found that the plastic strain is up to 30.94%for specimens with diameter of 4mm and showing a great plasticity.The supercooled liquid region??Tx=Tx-Tg?and parameter gamma??=Tx/?Tg+Tl??both increase first and then decrease with the increase of Cu content and the decrease of Zr content,it means that the thermal stability and amorphous forming ability of bulk amorphous alloy first increase and then decrease.The Zr-Cu-Ni-Al-Er alloy system was chosen for this study and the composition is(Zr0.6336Cu0.1452Ni0.1012Al0.12)100-x00-x Erx?x=06?.The effects of proper amount of rare earth element Er on the mechanical properties,amorphous forming ability and thermal stability of Zr-based bulk amorphous alloys were studied.The results show that all the alloy specimens with diameter of 2mm were completely amorphous with the increase of Er content,and the alloy specimens with diameter of 3,4,6mm were slightly crystallized after x=5.The compressive plastic strain of the specimen with diameter of 2mm is?p=35.06%when the Er content is x=2.6,which is about 8 times than the bulk amorphous alloy with Er free.The compressive strength of the specimen is 2513MPa,which is much higher than the compressive strength of the bulk amorphous alloy with Er free.The addition of Er element can obviously improve the plasticity and increase the compressive strength.A(Zr0.6336Cu0.1452Ni0.1012Al0.12)97.4Er2.6.6 bulk amorphous alloy was carried out for the thermal compression experiment because of its excellent room temperature compression plasticity.The rheological behavior and processability of bulk amorphous alloy in the supercooled liquid region were studied.The results show that in the low stress region(5×10-4s-110-3s-1)with temperatures of 410 and 420?,the range of processing efficiency is 70%85%,and the stress range is 60120MPa.The fluidity of the sample is better under the circumstances,so thermoplastic forming can be done under less stress.Therefore,the low stress region(5×10-4s-110-3s-1)and temperatures of 410 and 420?are optional process parameters for thermal processing.When the temperature is 430?and the strain rate is 5×10-4s-110-2s-1,the processing efficiency range is 75%85%,the stress range is 16106MPa,which shows excellent fluidity and can be formed under very low stress.The strain rate of 5×10-4s-1110-2s-11 and the temperature of 430?are also optional process parameters for thermal processing.This study provides some experimental data and theoretical basis for the research of thermal processing map and processing technology of Zr-based bulk amorphous alloys,also provide a new method and thought for the manufacture of micro parts with special properties. |
PDF Full Text Request