Elemental titanium(Ti)and nickel(Ni)powders were consolidated by spark plasma sintering(SPS)to fabricate Ti-51%Ni(mole fraction)shape-memory alloys(SMAs).The objective of this study is to enhance the superelasticity o...Elemental titanium(Ti)and nickel(Ni)powders were consolidated by spark plasma sintering(SPS)to fabricate Ti-51%Ni(mole fraction)shape-memory alloys(SMAs).The objective of this study is to enhance the superelasticity of SPS produced Ti-Ni alloy using free forging as a secondary process.Products from two processes(with and without free forging)were compared in terms of microstructure,transformation temperature and superelasticity.The results showed that,free forging effectively improved the tensile and shape-memory properties.Ductility increased from 6.8%to 9.2%after forging.The maximum strain during superelasticity increased from 5%to 7.5%and the strain recovery rate increased from 72%to 92%.The microstructure of produced Ti-51%Ni SMA consists of the cubic austenite(B2)matrix,monoclinic martensite(B19′),secondary phases(Ti3Ni4,Ti2Ni and TiNi3)and oxides(Ti4Ni2O and Ti3O5).There was a shift towards higher temperatures in the martensitic transformation of free forged specimen(aged at 500°C)due to the decrease in Ni content of B2 matrix.This is related to the presence of Ti3Ni4 precipitates,which were observed using transmission electron microscope(TEM).In conclusion,free forging could improve superelasticity and mechanical properties of Ti-51%Ni SMA.展开更多
Computer modelling using an FEM-based program, i.e. Forge 2008, was carried out. Laboratory model-ling of the process of free hot forging in shaped anvils was conducted to close up metallurgical defects. Results ob- t...Computer modelling using an FEM-based program, i.e. Forge 2008, was carried out. Laboratory model-ling of the process of free hot forging in shaped anvils was conducted to close up metallurgical defects. Results ob- tained from the simulation modelling were processed by using a commercial statistical package, i.e. Statistica 6.0 PL. The influence of the anvil shape and main parameters of the forging process on closing up metallurgical defects were determined. On the basis of the investigation carried out, the optimal values of main forging technologieal parameters and suitable groups of anvils to be used in particular forging tages are proposed for the elimination of metallurgical defects.展开更多
The reliability and robustness of the electro-hydraulic servo control system for heavy-duty forging machine play an important role in forging processes.A mathematic model of 50 MN water press for free forging was crea...The reliability and robustness of the electro-hydraulic servo control system for heavy-duty forging machine play an important role in forging processes.A mathematic model of 50 MN water press for free forging was created in this research.The dynamic robust compensator integrating with PID control method is designed and applied to the mathematical model simulation.The simulated results approved that the dynamic robust compensator application restrains interference from extra load and improves the electro-hydraulic position servo control system accuracy and stability.展开更多
基金the Ministry of Higher Education of Malaysia for the Malaysian International Scholarship and research funding under FRGS vote No. R.J13000.7824.4F810
文摘Elemental titanium(Ti)and nickel(Ni)powders were consolidated by spark plasma sintering(SPS)to fabricate Ti-51%Ni(mole fraction)shape-memory alloys(SMAs).The objective of this study is to enhance the superelasticity of SPS produced Ti-Ni alloy using free forging as a secondary process.Products from two processes(with and without free forging)were compared in terms of microstructure,transformation temperature and superelasticity.The results showed that,free forging effectively improved the tensile and shape-memory properties.Ductility increased from 6.8%to 9.2%after forging.The maximum strain during superelasticity increased from 5%to 7.5%and the strain recovery rate increased from 72%to 92%.The microstructure of produced Ti-51%Ni SMA consists of the cubic austenite(B2)matrix,monoclinic martensite(B19′),secondary phases(Ti3Ni4,Ti2Ni and TiNi3)and oxides(Ti4Ni2O and Ti3O5).There was a shift towards higher temperatures in the martensitic transformation of free forged specimen(aged at 500°C)due to the decrease in Ni content of B2 matrix.This is related to the presence of Ti3Ni4 precipitates,which were observed using transmission electron microscope(TEM).In conclusion,free forging could improve superelasticity and mechanical properties of Ti-51%Ni SMA.
文摘Computer modelling using an FEM-based program, i.e. Forge 2008, was carried out. Laboratory model-ling of the process of free hot forging in shaped anvils was conducted to close up metallurgical defects. Results ob- tained from the simulation modelling were processed by using a commercial statistical package, i.e. Statistica 6.0 PL. The influence of the anvil shape and main parameters of the forging process on closing up metallurgical defects were determined. On the basis of the investigation carried out, the optimal values of main forging technologieal parameters and suitable groups of anvils to be used in particular forging tages are proposed for the elimination of metallurgical defects.
文摘The reliability and robustness of the electro-hydraulic servo control system for heavy-duty forging machine play an important role in forging processes.A mathematic model of 50 MN water press for free forging was created in this research.The dynamic robust compensator integrating with PID control method is designed and applied to the mathematical model simulation.The simulated results approved that the dynamic robust compensator application restrains interference from extra load and improves the electro-hydraulic position servo control system accuracy and stability.
