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Porous metal materials are applied in various industries, among which powder rolling is the most widely used process for preparing porous metal materials. Then, metal porous materials prepared solely from powder as raw materials have the disadvantage of low mechanical properties, while wire mesh as reinforcement can effectively improve tensile strength. The preparation process of wire mesh powder composite is complex and requires the addition of adhesives. In this article, the mechanical properties of thin metal strips prepared by powder and wire mesh composite vertical rolling were much higher than those prepared by pure powder. Moreover, this thin strip had porous characteristics, and the preparation process was simple and easy to promote. This research could provide a reference for the powder metallurgy field, especially for the preparation of metal porous materials by vertical rolling.

The friction coefficient between the roller and the powder is one of the important factors affecting the rolling process. Since the friction coefficient is difficult to measure during rolling, it is usually regarded as a constant value in previous studies. However, the friction coefficient changes with the changes in process parameters such as the gap size and the rolling speed. In order to study the effect of the friction coefficient between the roller and the powder on powder rolling, the Drucker Prager Cap model for nickel powder rolling was established by ABAQUS. Firstly, the changes of contact stress (CPRESS) between the roller and the powder, the width (PE33), and relative density (SDV1) of the strip during rolling were analyzed. Then, the effect of the friction coefficient between the roller and the powder on the contact stress, the width, and the relative density of the strip was studied especially. The results show that during the rolling process, the contact stress remains basically unchanged. However, a large transverse deformation occurs on both sides of the strip, and the deformation in the middle is basically small. The relative density is greatest at the smallest seam between the rollers, and it decreases slightly after moving away from the roller, and then it remains stable. The coefficient of friction between the roller and the powder has an impact on the rolling result, in which the contact stress between the roller and the powder, the width, and the relative density of the strip will increase as the friction coefficient increases.

Semi-solid powder forming is a promising near-net-shaped forming technology, which has the advantages of powder metallurgy and semi-solid forming, such as fine grains, low forming pressure and short process flow. It was used to prepare wide solidification range alloys and its composites. Until now, there have been many studies on the parameters, microstructure and mechanical properties of this technology, but few on the forming principles. Because deformation, solidification and densification occur simultaneously, the forming mechanism is very complex. The liquid fraction is the key factor influencing the microstructure and mechanical properties. Semi-solid compression of porous materials was carried out to study the deformation mechanism of semi-solid powders. The combination mechanism and densification process for semi-solid powder rolling has been analyzed, and the compaction behavior of powders in the semi-solid state has been studied. Shima porous yield criterion and Doraivelu plastic yield criterion were applied in the simulation of semi-solid powder rolling. Based on the Fourier heat conduction equation and the related parameters of semi-solid powder, the rolling force and relative density were simulated by using the Marc finite element software platform. The simulation results are in agreement with the experimental results. Although some achievements have been made in the theoretical research and numerical simulation, the yield criteria and mathematical models suitable for semi-solid powder forming need to be further established. In addition, further optimization of this technology and its application in commercial applications should be the research direction.

Semi-solid powder rolling (SSPR) is widely used to produce alloy strips with fine grains and excellent performances in the automotive, aerospace and shipbuilding industries. During SSPR, powder temperature, as a very important parameter, greatly affects strips’ microstructures and mechanical properties, which have been investigated by many researchers, but its effect on the forming process and mechanism has rarely been studied. Therefore, based on online experimental detection and transient simulation, the microstructures, strip temperatures, relative densities and rolling forces at different conditions were, respectively, measured, calculated, compared and analyzed in order to study the deformation process and mechanism during SSPR. The result shows that with the increase in powder temperature, the strip temperature and relative density increase, while the rolling force decreases. The grains of the strips are refined after SSPR, and fine and dense microstructures are obtained at 600 °C, which is the optimum powder temperature. In the main deformation sections (II and III), when the contact normal force exists and reaches a maximum, the relative density and rolling force increase rapidly. At these sections, the strips rolled at 600 °C are mainly in a porous solid state, and powder crushing dominates the strip deformation. Therefore, SSPR at 600 °C and below can be considered porous or powder hot rolling, integrating powder crushing, solidification, deformation, densification and grain coarsening. Moreover, as the simulated values are basically consistent with experimental values, the thermomechanical coupling model based on the Fourier equation and its parameters are confirmed to be reasonable.

A systematic review of factors affecting the viability of direct powder rolling (DPR) as a process route for producing low-cost titanium metal strips was conducted by consolidating performance and process data from published research. Included is a market analysis that was performed by sourcing price points from powder and wrought product suppliers. As a result of the typical oxygen levels (>0.2 wt %) in low-cost powders, the performance of the DPR product is estimated at best to be comparable to ASTM grade 3 and 4 wrought products. Furthermore, evidence supporting chlorine levels >0.02 wt % in low-cost (non-melt) commercially available powders suggest poor weldability, which restricts the application of DPR titanium strips. A comparison of price points for powder and wrought products showed that the potential for commercial viability is likely to exist only for thin gauge strips of <1 mm thickness, as the cost advantage diminishes as the strip thickness increases. Based on the DPR product profile identified in this study (thin gauge, non-weldable, grade 3 or 4), the potential product applications are severely limited. The inability to reliably meet the properties of grade 2 metal strips excludes many uses of titanium metal strips. Consequently, it is emphasized that efforts need to be directed at improving the quality of low-cost powders and developing rolling practices to produce thicker gauge metal strips with desirable properties.

With advantages of powder metallurgy and semi-solid forming, Semi-solid powder rolling (SPR) as a novel technology was proposed and has been widely used to produce high-performance strips currently. As SPR is an extremely complex process and influenced by many factors, consequently it is necessary to be researched by the simulation method to study the forming process and various influence laws, in order to save experimental time and cost. Therefore, in this work, a two-dimensional model was built based on the Shima-porous yield criterion by using Marc software, considering the effect of temperature and relative-density on thermal conductivity, heat capacity, elastic modulus and Poisson's ratio. The semi-solid rolling process of Al–Cu–Mg alloy powder was simulated by the model, and the relative-density and rolling-force of strips were calculated and proven by experiments, which are basically consistent with the measured values. Based on this model, the influence of main parameters on SPR strips was analyzed. The results show that the rolling temperature of strips increases with the roller temperature increasing, and changes little with the variation of the compression ratio, rotational velocity and friction factor. The rolling-force reduces with the increase in roller temperature and the decrease in compression ratio, rotational velocity and friction factor. The relative-density rises as the four parameters increase. According to the results, it is suggested that a moderate roller temperature, a relatively large compression ratio and a small rotational velocity are recommended during the actual rolling, which provides a theoretical guidance for semi-solid powder forming experiments.

Semi-solid powder forming (SPF) as a novel technology has been widely used to prepare composite materials. However, most of the present models used to simulate the complicated SPF process are based on the constitutive relationship of single dense or porous material, which cannot well satisfy the actual conditions. In this study, the process of semi-solid powder rolling was simulated by the combined constitutive formula of sintered and dense Al-Cu-Mg alloy materials obtained from semi-solid compression experiments. The results show that the semi-solid compression curves of dense and sintered materials are similar, and their peak stresses increase with the decreasing porosities. The grain or particle size of sintered materials after semi-solid compression becomes finer as powders crushed, but the grain size of dense materials becomes larger due to grain coarsening and deformation, which is the key advantage of SPF with fine microstructures. The combined constitutive model of semi-solid powder materials was established and verified, and then the numerical simulation of semi-solid powder rolling based on the model was proved that can well describe the rolling process, which provides a guidance for process optimization.

For better clarifying the influence of processing factors on the forming quality of the direct powder rolling (DPR) process, finite element simulation based on the modified Drucker–Prager/Cap (DPC) model was established and the key physical parameters of the powder were confirmed by experimental measurements. Subsequently, the effect of the main factors in the DPR process, viz., powder gradation, rolling speed and rolling gap, on the density and morphology of a green sheet were discussed by using an orthogonal experiment design followed by experimental verification. The influence of DPR parameters on the density of the green sheet is examined by a range analysis, which can reflect the sensitivity of influencing factors to the forming quality of the green sheet. The larger the range value is, the more sensitive the influencing factor is. This suggests that the quality of the green sheet is mainly influenced by particle gradation. The results show that the density of the resulting DPR green sheet with optimal parameters is mainly 7.5~8.0 g/cm3, reaches 80% of the theoretical density, and the mechanical strength can also afford the transferring process of the green sheet for the next sintering craft. The methods for modeling, obtaining physical parameters and the numerical simulation results can be used to guide rapid formation of the metal sheet by using direct powder rolling craft.

Powder rolling is used for manufacturing long-length strip. For obtaining the product with high green density it is necessary to ensure shear strain in the deformation zone. Based on the principles of technologic adaptation the dual roll closed caliber with adaptively changed rigidity was constructed. It consists of upper bandage with shoulder, bottom bandage with groove in which the set of three rings (two aside and one central) is located. The pass is arranged by aside rings and outside surface of the central ring forming closed caliber while interacting with the shoulder of the upper bandage. The caliber output is equal to zero and the broadening at rolling is fully excluded. Such construction of the tool makes it possible to achieve high level of hydrostatic stress of tensor simultaneously with intensification of shear strains resulting in practically nonporous rolled strip. Taking into consideration peculiarities of calibre rolling the new criterion was proposed. This criterion enables to characterize roll system for each material, incompact materials in particular, considering retraction ability, to assess and identify the final square of the rolled material at different caliber configuration. Dependence of maximum value of powdered rolled strip thickness on dual roll closed caliber retraction surface value at different rolled strip width is presented.

Direct powder rolling (DPR) can be used to create metallic sheet at a reduced cost compared to traditional methods. The process is particularly relevant for metals that are beneficiated to a powder form. The DPR process, however, is not yet optimised and the material properties corresponding to DPR sheet do not compare well with sheet produced from rolled metallic billet. This study explores the effect of DPR input parameters on DPR aluminium sheet material properties. Roll speed, roll gap, sintering time and sintering temperature are shown to have an impact on the density, microstructure, hardness and ductility of DPR aluminium strip. It is shown that a low roll speed and a small roll gap produced the most dense strip. A roll gap of 0.7 mm and roll speed of 0.366 rpm produced green strip with a density of 90% of cast aluminium while a roll gap of 0.8 mm and roll speed of 0.73 rpm produced green strip with a density of 79.6% of cast aluminium. In addition, a Vickers hardness analysis and a three-point bending test show that increasing the sintering temperature of the green DPR strip will produce softer aluminium strips with higher ductility, as expected.