Abstract
Thestudy concentrates on the formation of titanium alloy forgings by press& forging, quenching and tempering, aging thermal treatment process. The purpose of this technology is to improve the structure and properties of titaniumalloy forgings, thereby improving the strength and toughness and otherproperties of titanium alloys. The microstructure of titanium alloy forgings andthe process parameters of press& forging, quenching and tempering, agingthermal treatment were studied by optical microscope, scanning electronmicroscope and hydrostatic pressure experiment. The results showed thatappropriate press& forging process, reasonable quenching and temperingprocess and reasonable aging thermal treatment process were effective tooptimize the structure of titanium alloy forgings and to improve itsproperties.
Titaniumalloy is widely used in aerospace, petrochemical, naval ships, control systemdue to its excellent comprehensive performance such as high strength, anticorrosionand low density. Especially, the titanium alloy in aerospace and nationaldefense industry has been applied on the components with high strength, whichhas made a very important contribution to the progress of science andtechnology. In order to meet the requirements of complex parts, a large nunmberof researches have been carrid out on titanium alloy forgings .In this study,our aim is the formation of quality titanium alloy forgings by high precisepress& forging, which has become more and more important in theindustry of press& forging.The high precise press& forgingtechnology can improve the components mechanical properties, reduce theproduct production cost, improve the products dimensional precision, and ensurethe quality of the product.The press& forging of titaniumalloy forgings needs to be optimized on the process parameters andstructural control of the material, involving the press& forging process,quenching and tempering, and aging thermal treatment process.
Thepress& forging of titaniumalloy forgings was studied to analyze theformation of forgings.This study used 3A2-3.5V titanium alloy as the rawmaterial. The press& forging experiment was carried out by the 500ton press machine.Through the experiments,the controlling factors forpress& forging process was determined and the press& forgingparameters were determined.. After press& forging, the titanium alloyforgings were quenched and tempered according to the control system.Thewater quenching and tempering temperature was 860 ℃ and the temperingtemperature was 500-540℃. Afterwards, the titanium alloy forgings were agingtreated.The aging temperature was set as 515-520℃. The effects of thepress& forging process on the structure of titanium alloy forgings wereanalyzed by optical microscope, scanning electron microscope andhydrostatic pressure experiment and the properties improved were summarized.
Titaniumalloy forgings were cut in two parts by an electric saw and were treated by aboring process to remove the surface defects and remove scale from themicrostructure.The surfaces of the parts were polished with abrasivepapers and finally grinded with a polishing cloth. The surface was observedby optical microscope to investigate the surface defects and morphologies. TheSEM images and EDS of the titanium alloy forges were taken for analyzing themorphology of the inside and surface structures.The deformation andtensile strength of the titanium alloy forgings were tested byhydrostatic pressure experiment. The results of hydrostatic pressureexperiment were compared with those of tensile experiment to get the propertyof fatigue.
Theresults showed that the press& forging process is abasic factor Control method to improve the properties of titanium alloy forgings.The surface defects were reduced when the pressing force was bigger,resulting in smoother surface and better surface quality.Moreover, with the increaseof pressing force, the grains were refined and the cross sectionuniformity improved.In addition, appropriate pressing deformation can reducethe defects in the microstructure and increase the volume fraction of tertiaryphases, which can effectively improve the properties of titanium alloy forgings.
As far as the quenching and temperingprocess, the hardness of the titanium alloy forgings increased with theincrease of quenching and tempering temperature and time.The tensile properties of theforgings were improved by the increase of tempering temperature up to 540°C.The impact toughness of the titanium alloy forgings was effectively improved bythe aging treatment process.The optimal aging temperature was 515-520° C.Thehardness of the titanium alloy forgings increased with the increase of agingtime and reached the plateau at the aging time of 6 hours.
As a result,appropriate press& forgingprocess, reasonable quenching and tempering process and reasonable agingthermal treatment process were all effective to optimize the structure of titaniumalloy forgings and to improve its properties.By this technology, we were ableto improve the structure of titanium alloy forgings and to obtain the desiredmechanical properties such as strength, toughness, etc.
Conclusion
Titaniumalloy forgings were formed by press& forging, quenching and tempering,and aging thermal treatment process. The press& forging process was amajor factor to determine the surface quality of titanium alloy forgings.Inaddition, the quenching and tempering process significantly improved the hardnessand tensile property of titanium alloy forgings.The aging thermal treatmentprocess significantly improved the hardness and impact toughness of titanium alloyforgings.By this technology, we were able to improve the structure oftitanium alloy forgings and to obtain the desired mechanical properties such asstrength, toughness, etc.
