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The rolling direction (RD) and the transverse direction (TD) samples were obtained from an as-rolled ZK60 magnesium alloy sheet with strong anisotropy of initial texture and their mechanical properties were tested at various deformation temperatures. Meanwhile, the microstructure and texture of these samples after fracture were investigated. Results revealed that a higher flow stress along the RD than that along the TD at room temperature were ascribed to the strong anisotropy of transitional texture, and this texture effect was remarkably weakened with the increase of deformation temperature. Deformation structure was dominant at 100 °C, and was replaced by dynamic recrystallization structure when the deformation temperature increased to 200 °C and 300 °C. The texture presented a strong texture (transitional texture in the RD sample and basal texture in the TD sample) at 100 °C, but its intensity visibly decreased and texture components became more disperse at 200 °C and 300 °C. These microstructure and texture results were employed in conjunction with calculated results to argue that raising deformation temperature could increase the activity of non-basal slip by tailoring the relative critical resolved shear stress of each deformation mode and finally result in low texture effect on mechanical anisotropy.

The rolling direction (RD) and transverse direction (TD) samples with distinct difference in initial texture were cut from differential speed rolled ZK60 magnesium alloy sheet and were subsequently subjected to the bending process. The bending behavior, microstructure and texture evolution of the bending samples were investigated to argue the effect of initial texture during the bending process. Results revealed that conspicuous asymmetry in the bending behavior was ascribed to the initial texture, and weaker basal texture was favorable to improve the bending properties. Meanwhile, initial texture remarkably influenced the microstructure characteristics, especially the number and morphology of (10–12) tension twin. Texture results revealed that initial texture in conjunction with the deformation mode led to the difference in texture evolution by influencing the deformation mechanism: (10–12) tension twin for the inner region of the RD sample; basal slip and prismatic slip for the outer region of the RD sample; basal slip and (10–12) tension twin for the TD sample. In addition, the bending behavior was reflected well by finite element method, and was investigated by strain-hardening curves based on experimental tests. Results suggested that the priority of deformation mechanism was dependent on the initial texture.

ZK60 magnesium alloy sheets with various texture states were successfully fabricated by controlling the rolling temperature in multi-pass lowered-temperature rolling. The microstructure including texture and the mechanical properties of the resulting sheets were investigated. Results showed that dynamic recrystallization (DRX) during current rolling process could be realized at lower deformation temperature when the thickness reduction per pass was larger than 30%, and with its help, the grain size was significantly refined and the microstructure homogeneity strikingly improved. In this circumstance, deformation temperature mainly influenced the texture state of the resulting sheets, implying that with the increase of deformation temperature the distribution of (0002) basal planes remained stable along the rolling direction but gradually increased along the transverse direction. The calculation results about the friction stress for various deformation modes indicated that the changing ratios of the critical resolved shear stress (CRSS) for the non-basal slip to that for basal slip resulted in this texture difference. Additionally, for the samples with the dominant deformation mode of basal slip, the yield stress gradually decreased and the uniform elongation increased with the weakening of basal texture. However, if dominant deformation mode changed, an abrupt change would occur in their values. This change of yield stress came from the change of CRSS, while uniform elongation from strain hardening rate.

The effects of grain size on the tensile and compressive strain hardening behaviors for extruded ZK61 alloys have been investigated by uniaxial tensile and compressive tests along the extrusion directions. Cylindrical tension and compression specimens of extruded ZK61 alloys with various sized grain were fabricated by annealing treatments. Tensile and compressive tests at ambient temperature were conducted at a strain rate of 0.5 × 10−3 s−1. The results indicate that both tensile strain hardening and compressive strain hardening of ZK61 alloys with different grain sizes have an athermal regime of dislocation accumulation in early deformation. The threshold stress value caused dynamic recovery is predominantly related to grain size in tensile strain hardening, but the threshold stress values for different grain sizes are almost identical in compressive strain hardening. There are obvious transition points on the tensile strain hardening curves which indicate the occurrence of dynamic recrystallization (DRX). The tensile strain hardening rate of the coarse-grained alloy obviously decreases faster than that of fine-grained alloys before DRX and the tensile strain hardening curves of different grain sizes basically tend to parallel after DRX. The compressive strain hardening rate of the fine-grained alloy obviously increases faster than that of coarse-grained alloy for twin-induced strain hardening, but compressive strain hardening curves also tend to parallel after twinning is exhausted.

Multi-pass lowered-temperature rolling was applied on the friction stir welded ZK61 magnesium alloy sheets not only for fabricating wide high-performance wrought magnesium alloy sheets, but also for reducing the sheet inhomogeneity including the microstructure and mechanical properties induced by friction stir welding. Results showed that obvious microstructure inhomogeneity including plannar texture anisotropy between the base metal and the stir zone were introduced in the friction stir welded ZK61 alloy sheets, but can be strikingly weakened by hot rolling deformation via multiple dynamic recrystallization. These led to a uniform fine-grained structure of about 8 µm in average grain size and similar (0002) basal texture in the final 1.4 mm thick sheets, and brought a continuous improvement in the associated property differences, where the relatively lower yield strength in base metal zone was strongly correlated with spreading (0002) texture while higher values in stir zone with stable intense (0002) texture. Moreover, the experimental and calculated Hall–Petch relationships were investigated to explain the different evolution of yield strength between the base metal and the stir zone. Meanwhile, enhanced fracture elongations larger than 20% in both the base metal zone and the stir zone were primarily attributed to grain refinement.

Ductility enhancement up to about 28–39% in fracture elongation with simultaneous strengthening was achieved in fine-grained magnesium and magnesium alloy sheets by multi-pass rolling with lowered temperature suitable for industrial fabrication. Specifically, high strengths at yielding following slip-dominated Hall–Petch relations were achieved owning to the naturally twinning's replacement by pyramidal under intense basal texture. These Hall–Petch relations had a high slope of 190 MPa μm 1/2 and frictional stresses ranging from 40 MPa to 144 MPa. The variation in frictional stress matched well with solid solution hardening and/or precipitation hardening. Enhanced uniform elongation was strongly correlated with improved strain-hardening rate via introducing solid solution and/or fine precipitates in Mg alloys compared with pure Mg, and conversely post-necking elongation (local elongation) as well as cold-workability under compressive stress was strikingly weakened by the restriction of dynamic recovery.

An ultra-high strength and high ductility Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr Mg alloy sheet was fabricated by vertical direct chill casting, extrusion, hot rolling and peak-ageing treatment. The peak-aged sheet shows tensile yield strength of 416 MPa, ultimate tensile strength of 505 MPa and superior elongation to failure of 12.8% at ambient temperature. The remarkable improvement of strength is ascribed to the fine β′ phase precipitated within the grains, grains with strong basal texture and the dispersed long period stacking ordered (LPSO) phases located at the grain boundaries.

Mechanical properties of as-rolled magnesium alloy sheets show an obvious anisotropy during rolling. To get sheets with excellent performance and investigate the effect of microstructure, texture on mechanical properties and mechanical anisotropy, AZ31 magnesium alloy sheets with 4 mm in thickness were obtained by multi-pass hot rolling using different single pass rolling reductions. The texture evolution of the as-rolled AZ31 magnesium sheets was analyzed by the electron backscattered diffraction (EBSD) method. The Hall–Petch and Schmid law effect were discussed in detail on the basis of experiment. A revised form of Hall–Petch formula was proposed with the consideration of texture effect as σ s − t = ( 0.3 / m t ) ( σ 0 + k d − 1 / 2 ) . The mechanical properties were greatly enhanced by multi-pass hot rolling and the enhancement was attributed to both grain refinement and texture intensity. The results would provide useful guidance to design a rolling processing route for AZ31 Mg Alloys sheet.

The Mg-Gd-Y-Zn-Zr sheets with different accumulative rolling reduction were successfully prepared through the multi-passes hot rolling process. The accumulative rolling reduction significantly affects the mechanical properties of the resulting sheets through altering the fraction of dynamic recrystallization (DRX) grains and distribution of the broken interdendritic 14H-LPSO phase. In addition, the precipitated equilibrium β phase at grain boundaries can facilitate the DRX process through the particle-stimulated nucleation (PSN) mechanism. The sub-grain boundaries formed in the vicinity of the grain boundaries and within the coarse deformed grains, and then transformed into the high-angle grain boundaries (HAGBs) through incorporating the adjacent dislocation. The coarse deformed grains were also divided into several grains by the formation of HAGBs and the DRX grains at grain boundaries also spread into the coarse deformed grains, and thus the fraction of the DRX grains improved with the increase of the accumulative rolling reduction. The ambient temperature tensile strength anisotropy of the resulting sheets increases with further accumulative rolling reduction. The effectively broken interdendritic 14H-LPSO phases, which acts as the reinforcing short-fiber, significantly strengthen the tensile yield strength along the RD due to its decreased aspect ratio (d/l) and more dispersed distribution aligned along the RD. Thus, the tensile yield strength along the RD demonstrated the higher increment than that along the TD and 45° with increasing accumulative rolling reduction. The broken interdendritic 14H-LPSO phases aligned along the RD also contribute to the higher fracture elongation along the 45° due to its alignment parallel to the resolved maximum shear stress during tension. Furthermore, the larger accumulative strain is conducive to decreasing the tensile anisotropy of the resulting sheets at elevated temperature.

Pure magnesium sheets and wires with various microstructures and texture type were obtained using different deformation parameters and heat treatment methods. The work-hardening behaviors of pure Mg sheets and wires during tensile tests at room temperature were investigated. Effects of grain size, texture, twinning and alloying elements on work-hardening behaviors are discussed. The experimental results are analyzed by the Lukac and Balik hardening model: θ = A / ( σ − σ 0.2 ) + B − C ( σ − σ 0.2 ) − D ( σ − σ 0.2 ) 3 ; changes of parameters in the formula with the factors mentioned above are discussed in detail. Theoretical models for work-hardening rate with changing of grain size, texture, twinning and alloying elements are given in this article.

The W-30 wt%Cu composite bars and strips were obtained by hot extrusion with steel cup from spray-drying powders. The relative density of cold-compressed billets is about 71.4%, and after they are extruded by an extrusion rate of 8.35 at 1200 °C, it reaches 91%. XRD and metallographic microscope were used to study the properties and microstructures of the materials. After extruded at 1100 °C, the bars have good properties of which the conductivity is about 41%IACS and the hardness is about 287HV.

AZ31 magnesium alloy sheets were produced by conventional rolling at a temperature range of 433–523 K and subsequent annealing. The process could be optimized to produce sheets with grains as fine as 2.8 μm in average size. Obvious dynamic recrystallization was found to occur during rolling at temperature above 473 K. For the sheets rolled at temperature below 473 K, a subsequent annealing was needed to obtain a fine fully recrystallized microstructure, which gives rise to a significant increase in ductility as compared with the as-rolled state. The sheets produced by the processing route in the present study exhibit excellent mechanical properties, with the yield strength and tensile elongation achieving as high as 350 MPa and 35%, respectively. Their mechanical properties and the Hall–Petch relationship were compared with those magnesium alloys processed by other deformation methods. The results show that the present process offers a cost-effective way to produce high-performance Mg alloy thin sheets.

Recent research at Harbin Institute of Technology on the synthesis of nanocrystalline and untrafine grained materials by mechanical alloying is reviewed. Examples of the materials include aluminum alloy, copper alloy, Ti/Al composite, magnesium-based hydrogen storage material, and Nd2Fe14B/α-Fe magnetic nanocomposite. Details of the processes of mechanical alloying and consolidation of the mechanically alloyed nanocrystalline powder materials are presented. The microstructure characteristics and properties of the synthesized materials are addressed.

Nd2Fe14B/α-Fe nanocomposite powders with a nominal composition of Nd12Fe82B6 were prepared by HDDR combined with mechanical milling. The microstructure of both the as-disproportionated and the subsequently desorption-recombination annealed alloy powders was studied by Mössbauer spectrometry and TEM. The magnetic properties were investigated by VSM using bonded magnet samples. The results showed that the annealing temperature had significant influence on both the recombination kinetics and the grain size of the Nd2Fe14B/α-Fe nanocomposite phases, and the bonded magnet samples presented the best magnetic properties when the nanocomposite powders were prepared by annealing at 760°C for 30 min.

It is well known that the ductility of magnesium and magnesium alloy is too poor to be processed. After normal hot extrusion, the ductility of magnesium alloy will be improved, but not noticeably. In this paper, further extrusion (Extrusion Ratio is 6.25) is adopted to commercial AZ31 magnesium alloy rods (Extrusion Ratio is 2) at different temperatures in order to refine the size of grain, then the rods with the crystallite size between 4-10μm is obtained, and the influence of crystallite with different grain size on the ductility of this alloy is investigated further. A lot of experiments and research indicate that: the elongation of the initial billet with the grain size of 30μ m can reach about 12%; after extrusion at different temperatures, the grain size can be refined to below 10μm, and the ductility goes up to 24%-30%. It also shows that, when the grain size of AZ31 magnesium alloy is below 10μm, the ductility is effected obviously. Only when the grain size is about a few microns, the ductility of AZ31 magnesium alloy will be improved noticeably.

Interface characteristics of the deformation processed composite prepared by mutual insoluble elemental powders of Cu and Cr were investigated by SEM and HREM. The SEM results reveal that the interface between Cu and Cr phases is rough and beneficial to mechanical interlocking. The HREM results show that a significant diffusion exceeded mutual solubility between Cu and Cr exists in a range of 40 nm, and nano-crystalline microstructure of different phases is found at the interface. The formation of such interface structures is discussed and attributed to the manufacture process and different phase properties. Rather than a simple mechanical interlocking, the interface is an organic combination and can enhance the composite properties.

Equal-cross section lateral extrusion (ECSLE) is a special industrial process employed to make ultra-fine grain materials, and the structural change and properties of materials are strongly dependent on the stress–strain history of the process. The stress distribution of ECSLE has been simulated by finite element method in this paper, moreover, the factors which influence the stress distribution have been analyzed and discussed.

The microstructures of liquid phase sintered 93W-7(Ni/Fe/Co) tungsten-base alloys in the as-sintered and extruded conditions were investigated by transmission electron microscopy. It was found that there exists an amorphous phase in the extruded rods. A reasonable mechanism for the formation of this metastable phase is described.