| A new type of near-α titanium alloy is developed to meet the requirement ofNO.3Academy of CASIC. In this thesis, both effects of traditional heat treatmentand dual heat treatment including a step of solution treatment and a step of agingtreatment to alloy microstructures are studied. The mechanical properties ofnew type of titanium alloy under annealing and other heat treatment conditions.Electron beam welding and argon arc welding are applied to this new alloy andinfluences of different welding processes to mechanical properties are studied.β transforming temperature of this alloy is1005℃~1010℃, measured bymetallography method. A solution treatment in α+β phase section followed byannealing in α phase section can lead to duplex microstructure of alloy, whileWidmannstatten structure can be created using a solution treatment in β phasesection. Solution treatment followed by aging that both in α+β phase section cancontrol the microstructures and phase contents effectively. The temperatu res ofsolution and aging both affect the contents of equiaxial α phase but solutiontemperature is more effective. Aging temperature and time effect size and contentof banded α phase. Effective controlling of microstructures makes it possible tocontrol the properties of alloy.The results of high temperature mechanical property test show a goodperformance of the new alloy under high temperature. Strength of alloy reducesobviously with the temperature increasing, while the speed of strength reducingdecreasing. Yield ratio shows unobvious change with the change of temperature.The yield strength of the alloy still remains a value of590MPa at650℃. Shorttime test under high temperature is taken to study creeping property of alloy. Theresults show reduced creeping properties with temperature increasing. A sharpingreduce happens when the temperature reaches650℃. With test strength of450MPa, the two specimens failed respectively at25and26minutes. Whilespecimens with teat temperatures below600℃didn’t fail in1h, with elongationof2.2%.Results of normal tensile test indicate that annealing treatment can improve thestrength of alloy within10%while reductive property reduces a number of10%. Duplex microstructure, Widmannstatten structure and solution-aging structure allhave much higher strength than original and annealing structures. Process ofduplex microstructure and solution-aging structure can improve reductive property,while reductive property of Widmannstatten structure is very low.Tensile strength and elongation of electron beam welding specimens performwell. There is unconspicuous change in tensile strength after annealing in air,while the value of elongation reduces. With the increasing of temperature,elongation increases while both tensile and yield streangth decrease under hightemperature. Test results of manual argon arc welding specimens show wellbehavior of tensile strength and elongation. There is unconspicuous change intensile strength after vacuum annealing, while the value of elongation reduces.With the increasing of temperature, elongation increases while both tensile andyield streangth decrease. With the increasing of temperature, elongation increaseswhile both tensile and yield streangth decrease under high temperature. |
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