Papers by Keyword: Cold Deformation

Abstract: In this paper, tests were performed by monitoring changes of strain amounts and their distribution by digital image correlation during static tensile testing of steel. The influence of different combination of speckles application on the sample surface (white speckles on the black sample surface and black speckles on the white sample surface) during cold deformation of steel was tested with the non-contacting digital image correlation. Strain amounts obtained by digital image correlation analysis of tested samples, with white on black and black on white painted speckle patterns, were compared. Different analysis for determining and monitoring strain amounts, provided by digital image correlation software, were used in this paper. The strain amounts were compared during cold deformation until the occurrence of sample fracture in both combinations of speckles application on the sample surface. Research has shown the importance of proper sample preparation for determination strain amounts and insignificant minor differences of strain amounts, between different sample preparations for digital image correlation, during cold deformation of tested steel.

Abstract: Adapter parts are common in hydraulic pipelines. They can connect pipes of different cross-sections. The article discusses the crimping of pipes. Its peculiarity is that the pipe section to be crimped undergoes thinning, which is ensured by the gap between the tools. This process was studied to determine the deformation forces and the influence of various parameters of the operation on its value.

Abstract: The rolling operation consists of deforming the material by passing it between two rolls whose spacing is smaller than the initial thickness of the sample, the reduction in thickness is obtained discontinuously by successive passes in the rolling mill whose spacing between the cylinders gradually decreases. This operation can influence on the mechanical and microstructural properties of the deformed materials The effect of cold rolled on microstructural evolution and precipitation sequence in Al-Mg-Si alloy has been investigated by using optical microscopy and Differential Scanning Calorimetry (DSC) in this study. The results revealed that the distribution of the grains are elongated along the rolling direction. We also noted that insoluble coarse particles that originated during the manufacturing process of the alloy have become visible after the rolling processes. The dislocations generated by the plastic deformation during cooled rolling constitute preferential sites for the germination and the growth of the phases, which accelerates the kinetics of the precipitation.

Abstract: This study is to investigate the phase stability, cold deformation, elastic strain recovery and mechanical properties of a new Ti-17Nb-6Ta-3Zr, at. %, alloy for biomedical applications. The alloy was produced by arc melting. A heavy cold-working up to 90 % was applied to the alloy to investigate the stability of the predominant β-bcc structure. Characterization of the deformed structures was performed by X-ray diffraction (XRD), hardness measurements and optical microscopy. Quasi-static compression testing was conducted to determine the yield stress for stress induced martensitic (SIM) transformation and the Young modulus. XRD analysis of the cold-worked structures revealed that α-martensite was induced after less than 5 % deformation. An outstanding combination of strength-elasticity properties with the yield strength of 600 MPa and a Young modulus of 37 GPa was achieved during the compression tests.

Abstract: 5083 aluminum alloy, due to moderate strength, good thermal conductivity and formability, is an ideal structural material for car production. Influence of cold rolling process on microstructures and mechanical properties of 5083 aluminum alloys is significant and research hotspots. In this paper, cold deformation and annealing processes on grains, tensile properties and anisotropies of 5083 alloy sheets were studied. Results showed that incomplete recrystallization occured on 5083 alloy sheets when annealing temperature was at 300°C. The degree of recrystallization increased slightly with the cold deformation raised from 30% to 50% and varied slightly with prolonged annealing time from 2h to 4h. Furthermore, fully recrystallization occurred on 5083 alloy sheets at the annealing temperature above 320°C. Tensile strength of 5083 alloy sheets reduced significantly when the annealing temperature was raised from 300°C to 320°C, while it varied slightly when the annealing temperature continued to rise to 380°C.

Abstract: In the present paper, an extended age hardening model for Al-Mg-Si alloys is presented. In this new approach the combined precipitation, yield strength and work hardening model, known as NaMo Version 1, has been further developed to account for the effects of room temperature storage and cold deformation on the resulting age hardening behaviour. Incorporation of these two new stages in NaMo largely increases the versatility of the model by allowing simulations of complex multi-stage industrial processing involving thermomechanical treatment as well. Part 1 of this work deals with the theoretical background and experimental validation of the extended version of NaMo, while Part 2 focuses on the new applications of the model by showing some numerical examples related to production of automotive body panels.

Abstract: The effects of cold deformation and low temperature aging on the microstructural stability of a peak aged (PA) Al 6061 alloy were investigated by means of DSC and microhardness measurements. During aging at a relatively low temperature (100 °C) of the PA material, a small increasing of the mechanical properties was detected, which was explained by the formation of atomic clusters, GP zones and β phase. The response to the aging treatment of the cold deformed materials depends on both the level of the cold deformation and the aging temperature. During aging at relatively low temperature (100 °C), in contrast to the 75 % deformed material that shows a small variation in their mechanical properties, the mechanical properties, of the 30 % deformed material, are almost constant. This was attributed to the higher driving force of the recovery reaction in the heavily deformed material. In the other hand, aging at relatively higher temperature (140 °C) of the heavily deformed material, leads to a fast softening due to an increasing of the recovery kinetics.

Abstract: The precipitation behaviors were investigated during isothermally aging at 700°C and 800°C after cold compressed by 30% in thickness in Fe-18Cr-12Mn-0.48N high-nitrogen austenitic stainless steel by using optical microscopy (OM), laser scanning confocal microscopy (LSCM) and transmission electron microscopy (TEM). The results show that precipitation morphology in cold-deformed sample is the same as non-cold-deformed sample, which also displays discontinuous cellular way. Cold deformation accelerates the precipitation of M2N phase. The precipitation occurs at not only grain boundaries but also twin grain boundaries in the experimental steel. In cold-deformed sample, besides the long-strip M2N precipitates, intermetallic phase-σ phase owning bct structure and lattice parameters of a=0.8800nm and c=0.4544nm were observed along grain boundaries and inside the grain.

Abstract: In order to research the cold deformation work hardening characteristic of new type low carbon bainitic steel, this article studies the effect of different degrees of cold deformation (elongation and compression) and different tempering temperatures on microstructure and mechanical properties of 15SiMn2Mo low carbon beinaitic steel. The results showed that with the tempering temperature increasing after 10% pre-tension deformation, the tensile strength and yield strength of the test material increased first and then decreased, and reached its peak value at 300°C, roughly the same as the strength of hot-rolling and 300°C tempering. With the compression deformation degree rising, the hardness of test material increased and showed the test material has good work hardening performance. Streamline and "z" shape ferrite banding appeared in microstructure. With the tempering temperature increasing, the microstructure of compressed deformation steel recoveried and recrystallized, the tendency of ferrite along the streamline was weakened, the new refining granular phase was enhanced and uniformity of microstructure was improved. The microstructure refinement was significantly increased with the compressive deformation degree rising.

Abstract: With cold rolling base plate of low carbon steel by CSP process, the cold deformation experiments were carried out by the two-roller reverse-mill in the laboratory. The work-hardening was studied for different deformation plates through the room temperature tensile and microhardness measured, and the microstructure was also studied after deformation. It was found that the steel yield and tensile strength increased and work-hardening marked with the deformation augment, the test steel microstructure is ferrite with mingle small amount pearlite, its grain is refined and elongated with deformation increasing.