Effect Of Low Cost Alloying On Microstructure And Properties Of Titanium Alloy

Titanium alloys are widely used in the field of aerospace and other fields because of their low density,high specific strength,corrosion resistance,high temperature resistance,good welding performance,and so on.However,compared with aluminum alloy and magnesium alloy,titanium alloy is severely restricted to be utilized more widely,especially in the civil field,due to their higher cost of raw materials and processing.A new type of Ti-6A1-xFe-yCr low cost alloy was designed by replacing the more expensive metal element V in the TC4 alloy with the cheap Fe-Cr master alloy,as well as adding non-metallic element B to modify alloy.The alloys was prepared by non-consumable vacuum arc melting furnace and its microstructures were observed by using OM and SEM.The phase analysis was conducted by XRD.The performances of tension and compression were tested by electronic universal testing machine,and the microhardness of the alloy was measured by Vickers hardness tester.The alloy's high temperature compression experiments were carried out under different temperatures and compression rates by using Gleeble dynamic thermal simulator.The results show that a near beta low cost titanium alloy was prepared,and its microstructures are mainly equiaxed ? phases,and also the needle and globular ? phases are precipitated at grain boundaries.With increasing the proportion of Fe and Cr in the alloys,the tensile strength and the micro-hardness of the alloy are further increased.Among them,the effect of Fe element is more obvious than that of Cr element.When the contents of Fe and Cr reach 2% and 12%,respectively,the best performance of alloy is gained,and its tensile strength,elongation and microhardness reach973 MPa,3.9%,338 HV,respectively.After adding the element B,the microstructure of titanium alloy is changed,while without adding the element B the microstructure of titanium alloy is primarily ? phase,and as the amount of B element increasing,? phase increases significantly,mainly as a needle crystal and equiaxed crystal.With the addition of B element,? grain in titanium alloy has been refined.As increasing the amount of B element,the Vickers hardness of the titanium alloy is improved.If without adding the element B,the titanium alloy hardness is308.94 HV.However,when the proportion of B element reaches 0.04%,the hardness of titanium alloy climbs up to 476.38 HV.The compression performance of titanium alloy is improved along with the addition of B.As the content of B element increasing from 0.02% to 0.04%,the yieldstrength of titanium alloy is also significantly improved,whereas the compression ratio is reduced with the increasing of the B element.When the alloy is compressed at high temperature,with the increase of deformation temperature,the peak stress and the steady state stress in the stress-strain curve are decreased,and the peak stress decreases gradually.At 850?~900?,the peak stress and steady stress of the curve are close to the fixed value.With the increase of deformation at 850 ?,the ? layer of the alloy in the cast structure is broken.When the deformation rate reaches 50%,the phenomenon of spheroidization occurs,and the original lamellar ? phase becomes small,dispersed? phase particles,with the size of the particle similar to the width of the lamellar.