Microstructure and Mechanical Properties of AZ31 Alloys Processed by Residual Heat Rolling

To produce high strength and ductility Mg alloys with high productivity and low energy consumption,the residual heat rolling (RHR) process was initially proposed.The microstucture and mechanical properties of AZ31 processed by RHR were investigated by optical micrscopy (OM),electron backscatter diffraction (EBSD),and electron universal testing machine.The yield strength (YS),ultimate tensile strength (UTS),and elongation to failure of RHRed AZ31 sheet were 194 MPa,311 MPa,and 22%,respectively.The RHRed AZ31 alloys after annealing have very fine and homogeneous grains.The symmetrical rolled (SR) and RHRed AZ31 exhibit typical {0002} basal textures.The RHRed AZ31 has double-peak basal texture distribution.The basal poles of RHRed AZ31 split from normal direction (ND) to rolling direction (RD).There are few hard orientation distributions on the basal slip and more soft orientation distributions on the prismatic slip in the RHRed AZ31 sheets than those in the SRed AZ31sheets.

Modeling of Heat Transfer and Solidification of Composite Roll

Modeling of heat transfer and solidification of composite roll was established and used to predict the thermal history and solidification process of roll during spray forming. Evolution of temperature field of the preform and cooling rate in the growing deposit during spray deposition and post-deposition were numerically simulated.

Optimized Tension for AZ31B Thin Sheets Rolled with On-Line Heating Rolling

On-line heating rolling mill which could efficiently preheat sheet and apply tensile force on both ends of the sheet along rolling direction(RD)was used to investigate the effect of tension on mechanical behavior and shape quality of magnesium sheets.For revealing the infl uence mechanism,many analysis techniques including optical microscope,electron backscattered diffraction,macrotexture and transmission electron microscope were performed.The shape defect,edge wave,could be eliminated under higher tension along RD,which was attributed to more uniform distribution of microstructure and microstrain.Nevertheless,it is undesirable that the forward tensile force exceeds 3 kN in present work because the strength decreased for high recrystallization level when the tensile force is beyond this value.Furthermore,the main deformation mode was still slip during rolling process despite of accompanying twining,e.g.,double twins,but more prismatic slip activated when tensile force exceeds 3 kN.The distribution of shear bands was affected by the applied tensile force that they appear as"V"shape along RD at a low forward or backward tensile force,while they appear as reticulate shape under applied tensile force of 5 kN.

Comparison of edge cracking and tensile cracking in in-situ deformation at 150℃of Mg-2Zn-1.5Mn alloy sheet

The Mg-2Zn-1.5Mn alloy(ZM21)sheets were hot-rolled in a single pass at 150℃with different reductions through on-line heating rolling.Microstructures and edge cracking behavior of the rolled sheets were investigated.The in-situ tensile tests at 150℃were also carried out,the crack initiation and propagation were compared with the edge cracking behavior of ZM21 sheets prepared by on-line heating rolling.The results reveal that the edge cracks are most likely to originate in the rolling direction and normal direction(RD-ND)plane due to the secondary tensile stress along RD.Edge cracking becomes more severe with an increasing reduction.The edge cracks mainly initiate and propagate in the fine recrystallized grain areas and the junction of recrystallized grains and sub-grains with hard orientation.The in-situ tensile test indicates that micro-cracks mainly initiate at the triple junction of grain boundaries where grains have hard orientation with low basal Schmid factor(SF).Meanwhile,those cracks are more likely to propagate along the grain boundaries with maximum difference in basal Schmid factor.Besides,the crack initiation and propagation during the in-situ tensile deformation at 150℃are found not to be associated with the recrystallization.

Manufacturing of Long Products Made of Innovative Lightweight Materials

The processing of innovative lightweight materials to sheet metal components and assemblies with globally or locally defined properties is the object of this work. It takes a load-dependent design of components and assemblies, for example, based on the composition of different construction materials or a targeted setting of component areas with specified characteristics to fully exploit the lightweight potential when substituting conventionally used materials. Different process chains for the manufacturing of roll-formed long products made of magnesium alloys and high-strength steels with locally defined properties will be presented in this paper. Depending on the kind of material to be formed and the desired product characteristics, different temperature managements are needed for capable processes. Due to limited formability at room temperature, magnesium alloys require a heating of the forming zones above 200–225 °C throughout the bending process in order to activate additional gliding planes and to avoid any failures in the radii. The realization of local hardening effects requires at least one process-integrated heat treatment when roll forming manganese–boron steels. For both processes, it is imperative to realize a heating and cooling down or quenching appropriate for the manufacturing of long products with the required quality. Additionally, proper line speeds that allow a continuously operated economical production have to be considered. Research results including design, FEA, realization and experimentation of the mentioned process chains and strategies will be described in detail.