The Gleeble 1500 test machine was used to simulate the single-pass welding thermal cycle of BWELDY960Q steel under different heat input conditions. In this paper, microstructure observation and mechanical properties of BWELDY960Q steel specimens in coarse grain heat affected zone (CGHAZ) under different heat input conditions were investigated. The results show that under different heat input conditions, the microstructure of CGHAZ is lath martensite, granular bainite, or M-A constituent. As heat input increases, the number and size of the M-A constituent increase accordingly, and the microstructure gradually changes from lath martensite to granular bainite. Meanwhile, compared with the previous samples, the CGHAZ austenite grain diameter increases, and the grain size scale decreases. Furthermore, the value of the CGHAZ impact absorbing energy increases at first but then decreases, while microhardness monotonously decreases. At-20 • C compared with the base metal, the impact absorbing the energy of CGHAZ is significantly reduced, and embrittlement occurs. K e y w o r d s : BWELDY960Q steel, heat inputs, coarse grain heat affected zone, microstructure, mechanical properties
In this study, a tube extrusion-shear-expand (TESE) process is proposed for the preparation of thin-walled tubes of high-performance magnesium alloys, and a comparison with direct extrusion(DE) is used to verify the superiority of the new process. Numerical simulations of the mesh variation, forming load, and equivalent strain during the forming of magnesium alloy tubes were carried out in combination with DEFORM-3D software. The results of the study show that: under the TESE process, the equivalent strain and the forming load are larger, which makes the plastic deformation of the tube larger; the grain refinement effect of the tube prepared under the TESE process is more obvious than that of the DE; the yield strength of the tube under the TESE process is about 293MPa, the elongation is about 15%, and the base structure dispersion is higher under the dynamic recrystallization and larger shear effect, the strength is obviously weakened, and the comprehensive performance of magnesium alloy tube is improved.
To research the influence mechanisms of expanding angles on extrusion-shearing-expansion(ESE) process of AZ31 magnesium alloy thin-walled tubes,the effects of different expanding angles on microstructures and mechanical properties of AZ31 magnesium alloy during extrusion-shear-expansion process have been investigated by optical microscope(OM),scanning electron microscope (SEM),X-ray diffractometer(XRD).Three expanding angles 130°,140°,150° have been used.The forming loads varying with expanding ratios,and equivalent strains at various expanding angles have been simulated by Deform-3D software.The research results show that the qualities and mechanical properties of the formed tube are satisfactory, and extrusion-shearing-expanding process can refine the grain of AZ31 magnesium alloy thin-walled tubes.The grain sizes decrease with the decrease of expanding angles.When the expanding angle is 140°,the comprehensive mechanical properties are best,and yield strength is 122.3MPa,the tensile strength 288.6MPa,the elongation 15.2%, the texture intense is optimized due to the DRX.The deflections of basal plane for most grains are obvious relative to the extrusion direction(ED).
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