Experimental study of the mechanical property of barrel processed by cold radial forging

The cold radial forging process usually introduces some changes of the material, such as the increased strength, the decreased plasticity and the introduction of anisotropic mechanical prop- erty. To obtain the changes of mechanical property of barrel processed by cold radial forging, the tangential mechanical properties of the barrel blank and the forged barrel are measured with a de- signed test based on the plastic deformation analysis for a barrel and by applying internal pressure, and their axial mechanical properties are measured by the tensile test. The changes of mechanical property of barrel processed by cold radial forging are obtained by comparing the mechanical proper- ties of the barrel blank and the forged barrel. The tangential and axial flow stresses of the barrel blank and the forged barrel are also presented.

Gradient microstructure and superior strength-ductility synergy of AZ61 magnesium alloy bars processed by radial forging with different deformation temperatures

Gradient microstructure modification is a cost-efficient strategy for high strength without compromising ductility,which is urgently needed in the fundamental science of engineering materials.In this study,heterogeneous structures of AZ61 alloy bars with anisotropic gradients(with different grain size distributions from the surface to the center)were observed to exhibit strong strength-ductility synergies under different deformation tem peratures.The results reveal that the grain refinement process under mediumlow temperature deformation conditions(≤350℃)consists of four transition stages along the radial direction,i.e.,twin activations and deformation band formations,dislocation cells and pile-ups,ultrafine sub-grains,and randomly orientated quasi-micron grains.Different deformation temperatures have a great influence on twin activations and deformation band formations,and the high temperature can easily provoke the initiation of non-basal slip.The deformation bands were determined as a primary nucleation site due to their highly unstable dislocation hindrance ability.Analysis in combination with the Radial forging(RF)deformation process,the differences of dynamic precipitates can be attributed to microstructural difference and solubility limit of Al at different tem peratures.By summarizing the tensile test results,the sample forged at 350℃exhibited the best strength-ductility synergy,exhibiting the highest elongation(EL)of 23.2%with a 251 MPa yield strength(YS)and 394 MPa ultimate tensile strength(UTS)in center region,and combined with the highest strength value of 256 MPa YS and 420 MPa UTS in the center region,while the EL was slightly degraded to 19.8%.

Evolution of inner wall wrinkle defects in the sinking zone of a thick-walled steel tube during radial forging

An axial wrinkle defect was observed in the inner wall of the sinking zone of a thick-wall steel tube processed by cold radial forging.Wrinkles can evolve into fissures.The present study focuses on the evolution of wrinkles and the effects of process parameters on them using a three-dimensional radial forging process finite element model,radial forging experiments,and surface morphology observations.The results indicated that the vertical section angle of the hammer die and the size of the tube blank significantly affect the evolution of wrinkles.The height-to-width ratioλwas introduced to describe the morphology of wrinkles.It had an approximately linear relationship with the radius reduction in the sinking zone.There was a linear correlation between the growth slope ofλand the axial to circumferential strain ratio|εr/εθ|,which can predict theλunder few process parameters.For the 30SiMn2MoVA steel,at the junction of the forging and sinking zones,the threshold ofλof the wrinkle that can evolve into a fissure is approximately 1.123.

Microstructural and mechanical response of ZK60 magnesium alloy subjected to radial forging

Radial forging(RF)is an economical manufacturing forging process,in which four dies arranged radially around the workpiece simultaneously act on the workpiece with high-frequency radial movement.In this study,a ZK60 magnesium alloy step-shaft bar was processed under different accumulated strains by RF at350℃.The deformation behavior,microstructure evolution,and mechanical responses of this bar were systematically investigated via numerical simulations and experiments.At the early deformation stage of forging,the material undergoes pronounced grain refinement but an inhomogeneous grain structure is formed due to the strain gradient along the radial direction.The grains in different radial parts were gradually refined by increasing the RF pass,resulting in a bimodal grained structure comprising coarse(~14.1μm)and fine(~2.3μm)grains.With the RF pass increased,the initial micro-sizeβ-phases were gradually crushed and dissolved into the matrix mostly,eventually evolving to form a higher area fraction of nano-sized Zn2 Zr spheroidal particles uniformly distributed through the grain interior.The texture changed as the RF strain increased,with the c-axes of most of the deformed grains rotating in the RD.Additionally,excellent mechanical properties including higher values of tensile strengths and ductility were attained after the three RFed passes,compared to the as-received sample.

Progress in the Research and Manufacture of GH4169 Alloy

GH4169 alloy has been widely used in fields such as aviation, aerospace, and petrochemical, because of its excellent combination of mechanical and processing properties. These properties include good high-temperature strength, excellent creep and fatigue resistance, and good processing and welding performance. The requirement for high performance, high reliability, and long service life of modem engines has led to the incentive to develop GH4169 alloys with improved performance, such as increased temperature-bearing capacity, improved creep endurance, and better fatigue resistance. Advances during the past thirty years in ba- sic research and industrial technology related to GH4169 alloy were systematically summarized, including advances in alloy modi- fication, melting process optimization, and hot deformation technology.