Effects Of Alloying Element Cr And Heat Treatment Process On Microstructure And Properties Of Powder Metallurgy TC4

Ti-6Al-4V alloy is widely applied in various different fields because of its uniquecomprehensive mechanical properties. In this thesis, by the use of density analysis,hardness analysis, optical microstructure, XRD, TEM, and fracture morphologyanalysis, the cold isostatic pressing(CIP)+vacuum hot sintering pressing was comparedwith the cold isostatic pressing (CIP)+vacuum sintering+hot isostatic pressingmethod (CHIP).The effects on microstructure and properties of TC4alloys withdifferent contents of Cr element were studied. To get the best heat treatment process,the influence of the various heat treatment on the Ti-6Al-4V-2Cr alloys was studies.The results show that the relative density of TC4alloy prepared by CIP+vacuumhot sintering pressing is low and have a lot of pores. The microstructure of TC4alloyprepared by CHIP is compact and have a higher tensile strength and plastic than tha ofthe TC4alloy prepared by CIP+vacuum hot sintering pressing. Optimization of thesintering temperature is1300℃,and hot isostatic pressing temperature is940℃. Withthe increase of Cr, the density of TC4alloy is gradually reduced. There is no eutectoidreaction to generate TiCr2eutectoid phase with Cr and Ti in high temperature sinteringprocess. With the increase of Cr, the tensile strength and compressive strength of thealloy increase gradually，but the elongation decrease. The fracture morphology of thetensile sample of TC4alloy is characteristic of dimples and a little cleavage planewhich indicate that the fracture belong to the mixed-rupture fracture of cleavage anddimples. The tensile strength, elongation and fracture morphology are analyzed in thisthesis. The result shows that the TC4alloy which has2%Cr prepared by CHIP methodhas good tensile strength, and also has excellent plasticity and good comprehensivemechanical properties.The Ti-6Al-4V-2Cr alloy was treated by solution heat treatment and agingtreatment at different solid solution temperature, aging temperature and aging time.The results show that with the increase of solution temperature and the other heat treatment process constant, the tensile strength of Ti-6Al-4V-2Cr titanium alloyincrease and the elongation decrease; with the increase of aging temperature, thestrength of alloy increase firstly and then decrease. When the temperature is510℃, thetensile strength of the alloy is relatively well. When the aging time is6h, the alloy hasbetter mechanical properties. In order to ensure titanium alloy has enough tensilestrength and plastic, the experimental data is analyzed and the optimized solid solutiontreatment process is930℃×30min×WQ；Aging treatment:510℃×6h×AC...