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We elucidate the effect of lanthanum (La) on the grain refinement of Mg-3Sn-1Mn alloy during accumulative hot rolling. The lath-shaped Mg2Sn phase in the Mg-3Sn-1Mn alloy is firstly broken and spheroidized, and then the size increases and coarsens with the increase of rolling reduction, most of Mg2Sn move from grain boundary to grain and are homogeneously distributed within the matrix. However, the plate-shaped MgSnLa compound in Mg-3Sn-1Mn-1La gradually becomes fine, spheroidized, and homogeneously distributed. The grain sizes of Mg-3Sn-1Mn and Mg-3Sn-1Mn-1La alloys become fine through dynamic recrystallization (DRX), though the grain refinement of Mg-3Sn-1Mn-1La alloy is better compared to the Mg-3Sn-1Mn alloy. A large number of uniformly distributed spherical MgSnLa compounds pin the dislocations, thus increasing the dislocation density. Hence, the driving force for DRX increases and promotes the formation of deformation bands and more twins, providing the sites for DRX nucleation and growth.

This paper develops a new numerical analysis method to achieve rapid-hardening, early-strengthening, high-performance cement-based composite material preparation based on the Dinger–Funk equation of the closest-packing model with MATLAB and the Lagrange multiplier method, as several other methods, including theoretical calculations, have many constraints when obtaining a solution and direct determination methods that waste much time in evaluating the compactness of cement gel material based on the principle of closest-packing theory. To verify these theoretical results, orthogonal tests are used. The calculated results show that the resulting gradation curve is in good agreement with the theoretical curve from the Dinger–Funk equation for the densest packing state (R2 = 97.36%). Experimental results for the dosages of steel slag and fly ash need to be very close to those suggested by the theoretical calculations; however, proper adjustment of the content of silica fume is still necessary. Adjusted neat paste has the highest compressive strength of all tested materials. The research has concluded that the method is suitable and scientific for designing high-performance, cement-based materials.

Graphene has been successfully coated with a nano-Al layer through a novel activating treatment (i.e., organic aluminum reduction method). The nano-Al coated graphene was further processed into AlSi10Mg alloy based composites through a selective laser melting (SLM) process. During the nanocoating of Al on graphene, Al atoms deposited on the graphene through organic aluminum reduction gradually, via nucleation and growth process. There were two primary grain growth patterns: two dimensional (2D) layered growth and three dimensional (3D) island growth, until graphene was coated with Al. The Al-coated graphene was added to the AlSi10Mg alloy, refining the cell, increased the tensile strength, hardness and wear resistance of the alloy. Coating Al on the graphene improved the wetting between graphene and Al, and the addition of Al-coated graphene led to a high nucleation rate, which was responsible for refining the cell. This approach facilitated graphene homogeneous distribution in the Al alloy, the interface between graphene and Al was relatively stable, and the grapheme could pin the dislocation and grain boundary. All these attributes enabled superior mechanical properties to be obtained in the final alloy based nanocomposites.

The Mg-3Sn-1Mn-1La alloy sheets were prepared by a continuous rheo-rolling process, and the effects of the solution and aging treatment on the microstructures and mechanical properties of the alloy were studied. The tensile strength and elongation at room temperature and 150 °C of the Mg-3Sn-1Mn-1La alloy sheets were decreased with increasing the solution time. The grain size was increased gradually. The plate-shaped MgSnLa compounds composed of La5Sn3, Mg2Sn and Mg17La2 phases and Mg2Sn phase gradually disappeared. At the same time, new irregular MgSnLa compounds were formed in grains. Aging treatment of the alloy was performed after solution treatment. The new spherical MgSnLa compounds composed of La5Sn3, Mg2Sn and Mg17La2 phase were formed, increased and distributed gradually homogeneously in the matrix with increasing the aging treatment time. Meanwhile, the Mg2Sn phases with spherical, short-rod and lath-shaped were formed in the matrix. After solution treatment at 550 °C for 24 h, aging at 250 °C for 48 h, the tensile strength at room temperature and at 150 °C of the Mg-3Sn-1Mn-1La alloy sheet was increased to 270 MPa and 233 MPa, with 19% and 20% increase, respectively. The elongation at room temperature and 150 °C was increased to 7.9% and 67.5%, with 6% and 4% increase, respectively. The formed spherical MgSnLa compounds and Mg2Sn phases which were coherent with the matrix and effectively pinned the dislocations and grain boundaries were responsible for the enhanced mechanical properties of the alloys.

Due to the manufacturing ability of selective laser melting (SLM) in complex lightweight structures resulting from topology optimisation (TO), SLM and TO are considered to be the best combination. However, support structures are required for SLM processes because of the very complex lightweight structures resulting from TO. Support structures also help resist the thermal stress which can damage the part. On the other hand, support structures have some shortcomings including the difficulty of removing them from the original part and the increases in the total cost and manufacturing time. Because of the above-mentioned deficiencies, more research will be conducted in the near future to investigate the design of self-supporting components for SLM technology. Therefore, this study proposes a new design method, called topology optimisation design with draw constraint (TODDC). The proposed method can simultaneously realise lightweight and self-supporting design for SLM processes. The detailed design process is presented and its advantages are discussed. The most significant advantage of the proposed method is that topology optimisation will be the final design tool not only for the conceptual design but also for the industrial component. TO is applied in the design process to reduce weight and draw constraint is imported into the TO process to meet the self-supporting requirement. As for the industrial implications of the research, a control arm component is designed using the proposed method, and the final model is produced successfully using the SLM technology. Thus, the effectiveness of the proposed method in designing lightweight and self-supporting industrial metal components for SLM processes is verified through the case study.

A novel semisolid stirring and rheo-rolling process for preparing Mg–3Sn–1Mn–3SiC (wt%) composite strips was proposed, and the effects of process parameters of semisolid stirring on microstructures of Mg–3Sn–1Mn–3SiC (wt%) composite strips were investigated. The average grain size and roundness decrease, and the distribution of SiC becomes more homogeneous with the decrease in stirring temperature and the increase in the stirring speed. When the stirring time is increased, the distribution of SiC particles tends to be homogeneous, and the average grain diameter and roundness of α-Mg grain decrease. Under the following process parameters: the stirring temperature at 640 °C, the stirring speed at 1100 rpm, the stirring time at 30 min and the roll speed at 0.2 m/s, Mg–3Sn–1Mn–3SiC (wt%) strip with a cross-sectional size of 4 mm × 160 mm was prepared. The ultimate tensile strength and elongation of Mg–3Sn–1Mn–3SiC (wt%) composite strip reached 226 ± 6 MPa and (7.4 ± 0.2)%, which are obviously improved in comparison with Mg–3Sn–1Mn (wt%).

Martensitic transformation and matching fracture behaviors in lean duplex stainless steel 2101 (LDSS) during tension deformation at low temperature were investigated. The low-temperature tensile tests were conducted using tensile speed of 0.5 mm/min at − 30 °C, − 50 °C and − 70 °C. The results indicated that the stress–strain curves of lean duplex stainless steel 2101 at low temperatures show a work hardening and softening mode at different temperatures. The morphology of the strain-induced martensite is lath-like at − 30 °C, bow-like at − 50 °C and fold-like at − 70 °C. The e -martensite is not observed in the lean duplex stainless steel and the slip planes are high-index crystalline faces. The martensitic transformation mechanism is γ (fcc) → α′ (bcc) during the deformation of lean duplex stainless steel. Moreover, the strain-induced martensite improves the tension resistance by either hindering the crack propagation or reducing the crack growth rate. The fractography of matching fracture surfaces shows a mixture of dimple fracture in ferritic phase and austenitic phase.

TiC/316L stainless steel (316Lss) metal matrix composite parts have been formed using selective laser melting (SLM). In this study, we have investigated the influence of the TiC mass fraction on the microstructure evolution, microhardness, friction properties, wear properties, and corrosion resistance of the TiC/316Lss composites. The results show that the microhardness increased by the addition of the TiC mass fraction. In terms of friction and wear properties, the corrosion resistance initially increased, and then decreased. Compared with the pure 316Lss (298.3 HV0.2), the microhardness of the TiC/316Lss composites, which were formed with 2 wt% TiC, was raised to 335.2 HV0.2, which was a 12.4% increase, while the average friction coefficient was 0.123. The reason for this is that the addition of TiC can effectively refine the cell size, and as the TiC content increases, the refinement effect is more obvious. During the melting process, TiC particles act as nucleation centres, hindering the growth of crystal cells, promoting the formation of the austenite phase, and forming fine equiaxed structures, which increases the strength. However, excessive TiC particles aggravate the spheroidisation during the process of SLM, leading to increased defects, as well as a decrease in density and corrosion resistance.

The effect of Al2O3 content on ignition temperature and combustion temperature, the phase composition, the density of the products and the grain size of TiC was investigated by self-propagating high-temperature synthesis reaction of Al2O3–Ti–C system. The results show ignition temperature increases and combustion temperature decreases with the increasing of Al2O3 content; the density of the products varies with Al2O3 content, TiC and Al2O3 are the two stable phases after SHS, TiC particle size decreases with the increasing of Al2O3 content, furthermore, the fracture type of the sintered specimens is a nearly completely intergranular mode.

A novel preparing method of polymer-coated molybdenum powder was presented. A type of multi-component polymer-coated molybdenum powder was chosen for selective laser sintering. The effect of the process parameters on the part's characteristics is investigated. Based on our study for dynamic laser sintering process of polymer-coated molybdenum powder, its laser sintering mechanism was reported as follows: at the early stage of laser sintering, the viscous flow is the major mechanism; during the laser sintering, the melting/solidification is the major mechanism. Furthermore, a model corresponding to the mechanism was discussed schematically, which could be used to explain the material migrating mode during laser sintering process. The laser sintering experiments of polymer-coated Mo powder was conducted in the self-developed laser sintering machine, and optimized parameters have been acquired. At last, the post treatment process of laser sintered parts has been developed and refractory metal parts of Mo/Cu composites are gained. The post treatment process includes debinding, high temperature sintering and melting infiltration, which is sintering framework-Mo by high temperature combining with Cu impregnation method. It is found that the mechanical properties of parts have been greatly improved after the post treatment process.

Ti 2 SnC ternary compound was successfully synthesized utilizing laser ignited self-propagating high-temperature synthesis (SHS) of Sn–Ti–C system with the different C/Ti molar ratio. When C/Ti ratio is 0.7, Ti 6 Sn 5 as the main phase appears, and a small amount of TiC is also found, most of the Ti 6 Sn 5 phases synthesized exhibit the polygon-shaped coarse appearance with an obviously sintered morphology, and the distinct transgranular and intergranular microcracks can be observed. When C/Ti ratio increases over the range from 0.8 to 1.0, the relative content of Ti 2 SnC increase and the plate-like shape Ti 2 SnC appears. Furthermore, the sintered density increases firstly and then decreases with the increasing of C/Ti ratio.