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In this study, the effect of electro-pulsing combining laser shock peening (EP-LSP) treatment on the microstructure and corrosion resistance of Ti-6Al-4V alloys was investigated, and the hardness, surface roughness, microstructure, and electrochemical properties of Ti-6Al-4V alloys after EP-LSP treatment were studied and compared with those of single EPed and LSPed samples. Also, to investigate the effect of the number of laser impacts on microstructure and corrosion resistance, changes in samples after one and three laser impacts were compared. The results showed that all treatments improved the hardness of as-received sample and three EP-LSPed (3 EP-LSP) samples had the maximum hardness which increased 24.3% compared with the as-received sample. As the number of laser impacts increased from one to three, the surface hardness increased, but the surface quality decreased, and the surface showed periodic protrusions. The one EP-LSPed (1 EP-LSP) sample showed the best corrosion resistance, with a 73.2% reduction in corrosion current density compared to the as-received sample. This is due to the grain refinement and the transformation of the α to β phase in the EP-LSPed samples. It has a beneficial effect on the formation of dense passive film. In addition, the sample surface with one impact has lower surface roughness and better surface quality compared to that of three impacts. [ABSTRACT FROM AUTHOR]

Titanium alloy threaded fasteners offer great advantages to the field of aerospace. But the use of cold rolling process when forming threaded fasteners has the disadvantages of short die life and high apparatus requirements because of poor plasticity of titanium alloy at room temperature. This paper uses a combination of axial infeed rolling process and intermediate frequency induction heating to fabricate thread with Ti6Al4V. First, the principle of hot rolling process is introduced, and then the characteristics of induction heating and the strain, displacement, and metal flow law of the thread during hot rolling process are analyzed by using finite element analysis. The influence of different forming temperatures on the rolling torque and the major diameter of the formed thread are analyzed. According to the results of finite element analysis, the best forming temperature for hot rolling process is 800 °C. Moreover, experiments are carried out on related equipment, and the experimental results are similar to the simulation results. The torque is reduced by 74% relative to that in cold rolling process. Finally, the microstructure and hardness of the formed thread are observed. A dense and directional microstructure appeared on the surface of the formed thread. The overall hardness of the thread after hot rolling is higher than that of cold rolling, and the maximum hardness of formed thread is increased by 35% relative to that of the original metal. [ABSTRACT FROM AUTHOR]

The thread cold rolling process is an advanced produce for manufacturing thread parts. During this process, friction between the rolling die and the workpiece significantly influences the deformation process and the quality of the formed thread parts. However, material deformation and contact conditions between the rolling die and workpiece are complex, posing challenges to the study of friction during the deformation process. A single-tooth rolling friction test (STRFT) was proposed to investigate friction properties in the thread cold rolling process and surface morphology of the formed part. Moreover, the effects of friction on material flow behavior and stress distribution characteristics were investigated. Experiments were performed under various lubrication conditions, and finite element simulation was used to calibrate the friction factor. Rolling torque was significantly affected by the friction factor and regarded as the sensitive parameter. The friction factor m was determined as 0.16 under lubrication condition by comparing the torque during the test and the simulation. A larger friction factor increased deformation stress and decreased material flow speed. The bottom of the formed groove under larger deformation stress exhibited greater roughness and more surface defects than the flank. [ABSTRACT FROM AUTHOR]

Forming process of internal thread is an advanced manufacturing process. A new planetary rolling process for forming the internal thread is proposed. The structures of rolling system and working process are described in detail. The finite element model of forming internal thread is established, and the forming experiments are conducted by a homemade experimental rig. The material displacement, microstructure, strain, and microhardness are investigated by finite element model and experiment. The results show that the formed internal thread meets requirements and the results of simulation and experiment are consistent. Through the planetary rolling process, the microstructure is stretched and forms the fibrous tissue at the bottom of tooth space of the internal thread. The maximum deformation is located at the bottom of tooth space, and the deformation characteristics are corresponding to the microstructure distribution. At the bottom of tooth space, the microhardness and the equivalent strain are also largest. The maximum microhardness of formed internal thread is improved 37.6%. The new planetary rolling process can improve the production performances and simplify the processing equipment. [ABSTRACT FROM AUTHOR]

In this paper, the self-infeed rolling process of thread shaft with medium carbon steel AISI 1045 is investigated. Firstly, the principle of the self-infeed rolling process is introduced and then the deformation mechanism is analyzed by finite element method. The numerical results show that deformation mainly occurs on the surface layer of blank, and the deformation degree is different in the tooth profile. The metal flows along both the axial direction and the radial direction. Next, the experimental studies of self-infeed rolling process are carried out. The numerical results are shown in good accordance with the experimental results. The grain at the top of tooth profile is refined, and the microstructures in the surface of tooth profile as well as bottom of tooth root are fibrous tissue which is dense and streamlined obviously. The hardness of the formed thread shaft is improved than that of the blank. [ABSTRACT FROM AUTHOR]