Effect of calcium addition on microstructure and texture modification of Mg rolled sheets

The mechanical properties and texture of AM60（Mg-6.0Al-0.3Mn,mass fraction %） and ZXM200（Mg-1.6Zn-0.5Ca-0.2Mn） Mg alloys subjected to multi-pass hot rolling were investigated.The finer recrystallized grains usually exhibit particular preferred orientations and then alter the total texture feature of rolled sheets.Ca solid solution into Mg matrix serves to the formation of texture component with c-axis rotated away from normal direction towards transverse direction and then weakens the overall texture intensity,resulting in a similar anisotropic characteristic to RE-containing Mg alloys.

FEM modeling of dynamical recrystallization during multi-pass hot rolling of AM50 alloy and experimental verification

The microstructure simulation during the multi-pass hot rolling of AM50 alloy was studied by DEFORM-3D. The excellent agreement with the experiment observations shows that the present modeling and user routine are feasible for the reproduce of the hot rolling process. The multi-pass hot rolling contributes to the achievement of a uniformly recrystallized microstructure with fine grains in the rolled sheet. The sheet temperature before the finish rolling strongly affects the final grain size, but hardly affects the grain size distribution. This modeling and the user routine also have a potential to be applied in the researches of the other multi-pass hot deformation process.

Effect of finish-rolling conditions on mechanical properties and texture characteristics of AM50 alloy sheet

The conventional hot rolling of AM50 alloy at different roll temperatures and speeds was performed to investigate the effects of finish-rolling conditions on the mechanical properties and texture of rolled sheet. The better combination between strength（ultimate tensile strength： 295 MPa; yield strength： 224 MPa） and ductility（22.9%） can be obtained for the AM50 sheet rolled at the roll temperature of 200 °C with the roll speed of 5 m/min. The yield stress depends strongly on roll temperature, while the texture intensity in rolled sheets is more sensitive to roll speed during hot rolling. Increasing rolling temperature or roll speed can improve the mechanical anisotropy of AM50 rolled sheets.

Effects of trace Gd concentration on texture and mechanical properties of hot-rolled Mg-2Zn-xGd sheets

The effects of Gd concentration(0.1,0.3,0.7 wt%)on the microstructure,texture and mechanical properties of rolled and annealed Mg-2Zn-xGd sheets have been investigated aiming to develop low cost and high ductile Mg-Zn-Gd sheets.Dynamic recrystallization,static recrystallization and grain growth during hot rolling process and annealing process were delayed with increase of Gd concentration,leading to fine grain microstructure.The rolled 0.1 wt%Gd sheet showed strong basal texture which remained stable after annealing process and exhibited medium elongation of about 25%.In contrast,the rolled 0.3 wt%Gd sheet had weak basal texture which transformed to non-basal texture with double peaks tilted about±48°to the transverse direction due to the static recrystallization during annealing process.Consequently,the annealed sheets exhibited higher elongation of 40%along the rolling direction and 50%along the transverse direction due to the existence of non-basal texture.It is suggested that the minimum effective concentration for texture randomization in the Mg-2Zn-xGd alloy is about 0.3 wt%.

Effect of Partially Substituting Ca with Mischmetal on the Microstructure and Mechanical Properties of Extruded Mg-Al-Ca-Mn-Based Alloys

Mg-2Al-1.2Ca-0.2Mn(at%)-based alloys with Ce-rich mischmetal(MM) substitution of 0–0.6 at% for Ca were hot extruded at 400 °C. The effect of MM substitution on the microstructure and mechanical properties of the extruded alloys was investigated. The as-cast Mg-2Al-1.2Ca-0.2Mn alloy is mainly composed of a-Mg, Mg_2Ca and(Mg,Al)_2Ca phases and Al_8Mn_5 precipitates, whereas the substitution of MM brings about the formation of Al_(11)MM_3, Al_2MM phases and Al_(10)MM_2Mn_7 particles with the absence of (Mg,Al)_2Ca phase. The volume fraction of MM-containing phases increases with increasing MM contents. All of the extruded alloys exhibit bimodal microstructure comprising fine dynamically recrystallized grains with almost random orientation and coarse deformed grains with strong basal texture. Dense nanosized planar Al_2Ca and spherical Al–Mn phases precipitate inside the deformed grains. High tensile yield strengths of~ 350 MPa and moderate elongations to failure of >12% are obtained in all extruded alloys; the MM substitution induces negligible difference in the tensile properties at ambient temperature, while the highest MM substitution improves the strength at 180 °C due to the better thermal stability of the fragmented MM-containing phases.

Influence of size and distribution of W phase on strength and ductility of high strength Mg-5.1Zn-3.2Y-0.4Zr-0.4Ca alloy processed by indirect extrusion

A high strength Mg-5.1Zn-3.2Y-0.4Zr-0.4Ca （wt%） alloy containing W phase （Mg3Y2Zn3） prepared by permanent mold direct-chill casting is indirectly extruded at 350 ℃ and 400 ℃, respectively. The extruded alloys show bimodal grain structure consisting of fine dynamic recrystallized （DRXed） grains and unre- crystallized coarse regions containing fine W phase and β2′ precipitates. The fragmented W phase particles induced by extrusion stimulate nucleation of DRXed grains, leading to the formation of fine DRXed grains, which are mainly distributed near the W particle bands along the extrusion direction. The alloy extruded at 350 ℃ exhibits yield strength of 373 MPa, ultimate tensile strength of 403 MPa and elongation to failure of 5.1%. While the alloy extruded at 400 ℃ shows lower yield strength of 332 MPa, ultimate tensile strength of 352 MPa and higher elongation to failure of 12%. The mechanical properties of the as-extruded alloys vary with the distribution and size of W phase. A higher fraction of DRXed grains is obtained due to the homogeneous distribution of micron-scale broken W phase particles in the alloy extruded at 400 ℃, which can lead to higher ductility. In addition, the nano-scale dynamic W phase precipitates distributed in the unDRXed regions are refined at lower extrusion temperature. The smaller size of nano-scale W phase precipitates leads to a higher fraction of unDRXed regions which contributes to higher strength of the alloy extruded at 350 ℃.