The Effect of Extrusion Temperatures on Microstructure and Mechanical Properties of Mg-1.3Zn-0.5Ca (wt.%) Alloys

The present work mainly investigated the effect of extrusion temperatures on the microstructure and mechanical properties of Mg-1.3Zn-0.5Ca (wt.%) alloys. The alloys were subjected to extrusion at 300 °C, 350 °C, and 400 °C with an extrusion ratio of 9.37. The results demonstrated that both the average size and volume fraction of dynamic recrystallized (DRXed) grains increased with increasing extrusion temperature (DRXed fractions of 0.43, 0.61, and 0.97 for 300 °C, 350 °C, and 400 °C, respectively). Moreover, the as-extruded alloys exhibited a typical basal fiber texture. The alloy extruded at 300 °C had a microstructure composed of fine DRXed grains of ~1.54 µm and strongly textured elongated unDRXed grains. It also had an ultimate tensile strength (UTS) of 355 MPa, tensile yield strength (TYS) of 284 MPa, and an elongation (EL) of 5.7%. In contrast, after extrusion at 400 °C, the microstructure was almost completely DRXed with a greatly weakened texture, resulting in an improved EL of 15.1% and UTS of 274 MPa, TYS of 220 MPa. At the intermediate temperature of 350 °C, the alloy had a UTS of 298 MPa, TYS of 234 MPa, and EL of 12.8%.

Micro-Extrusion Process And Microstructure Evolution of Miniature Heat Pipe In 6063 Aluminum Alloy

Micro-extrusion process of miniature heat pipe with axial micro grooves is particularly difficult due to ultra-large extrusion ratio and complex cross-sectional shape. In this study, the shape control of a miniature heat pipe in 6063 aluminum alloy with boundary dimension of 5×4 mm has been successfully realized during micro-extrusion. Micro-extrusion process and microstructure evolution of the miniature heat pipe were investigated by the combination of finite element (FE) analysis with experiments. The results show that material flow deformation behavior during micro-extrusion is highly affected by size effect, and lower ram speed is conductive to forming integrity, dimension accuracy and surface quality of the heat pipe profile. The primary mechanism for micro-extrusion failure of micro-grooves is severely more uneven material flow between the micro rib and base region at higher ram speed, which is caused by size effect and results in shear deformation and even fractures of micro rib. Further research shows that, compared to the extrusion using as-cast billets, much coarser grains were obtained after micro-extrusion using as-extruded billets at an ultra-large extrusion ratio of 205. Besides that, the entirely different texture components after extrusion were obtained instead of the typical < 100 > //ED or < 111 > //ED fiber texture components. These atypical texture components can be regarded as texture deviating from ideal texture by a certain angle (15° or 20°) along φ axis or φ1 axis.

Evaluation of Microstructure, Hardness, and Tensile Properties: A Comparative Study of Stir Cast and Extruded Al7005/Glass-/Fly-Ash-Reinforced Hybrid MMCs

The effect of extrusion ratio and addition of glass and fly ash on microstructural, mechanical properties, and fracture behavior of Al composites is examined. Both the composites and hybrid composites are prepared by the liquid metallurgical technique. Microstructure, extrusion effect on hardness, tensile properties, and fracture are studied using an optical micrograph, hardness tester, Universal Testing Machine, and scanning electron microscope, respectively. Experimental results show that increasing the extrusion ratio leads to a significant enhancement in mechanical properties such as tensile, compression, and yield strength and Young’s modulus, but results in a small reduction of ductility. It has been revealed that the presence of glass and fly ash improve the mechanical properties significantly with a slight reduction in ductility compared to the Al alloy. Fracture behaviour of the base alloy and composites show intergranular ductile and brittle cleavage mode failure as observed by SEM.

An Analysis for Magnesium Alloy Curvature Products Formed by Staggered Extrusion (SE) Based on the Upper Bound Method

Staggered extrusion (SE) is a new method to solve the bottleneck of traditional curvature products, such as long manufacturing cycle, many forming processes and difficult quality control. How to quantitatively control the curvature of extruded products is the key to implement this method. Herein, the upper bound method is used to calculate and analyze the power consumption of each characteristic zone in the SE process. The theoretical model of extrusion load and curvature is established. The results show that the staggered distance h has an important influence on the curvature κ. When the staggered distance h increases from 8 mm to 24 mm and other conditions remain unchanged, the curvature κ increases from 0.0546 to 0.1607. Any combination of the staggered distance h and the extrusion ratio λ corresponds to an eccentricity ratio ξ. The eccentricity ratio ξ decreases with the increase of the staggered distance h or the extrusion ratio λ. By comparison, it can be seen that the variation trend of the theoretical predicted value and the FE modelling in the steady-state extrusion stage is consistent. The experimental results are in good agreement with the curvature theory prediction model. These results provide a scientific basis for the formulation of the SE process and precisely controlling magnesium alloy curvature products.

Influence of the Microstructure of the Initial Material on the Zn Wires Prepared by Direct Extrusion with a Huge Extrusion Ratio

In this study, we prepared zinc wires with a diameter of 250 µm by direct extrusion using an extrusion ratio of 576. We studied the influence of the extrusion temperature and microstructure of the initial Zn billets on the microstructural and mechanical characteristics of the extruded wires. The extrusion temperature played a significant role in the final grain size. The wires extruded at 300 °C possessed a coarse-grained microstructure and the shape of their tensile stress–strain curves suggested that twinning played an important role during their deformation. A significant influence of the initial grain size on the final microstructure was observed after the extrusion at 100 °C. The wires prepared from the billet with a very coarse-grained microstructure possessed a bimodal grain size. A significant coarsening of their microstructure was observed after the tensile test. The wires prepared from the medium-grained billets at 100 °C were relatively coarse-grained, but their grain size was stable during the straining, resulting in the highest ultimate tensile strength. This preliminary study shows that strong attention should be paid to the extrusion parameters and the microstructure of the initial billets, because they significantly influence the microstructure and mechanical behavior of the obtained wires.

Piercing and Surface-Crack Defects in Cold Combined Forward-Backward Extrusion

Metal flow tends to be complex and difficult to predict in the combined forward-backward extrusion (CFBE) process. Piercing and surface-crack defects are phenomenal in forming fasteners featuring a forward extruded pin and a backward extruded cup. In this work, a series of the CFBE tests with various combinations of the forward extrusion ratio (FER) and the backward extrusion ratio (BER) were conducted. A forming limit diagram, detailed with the piercing and surface-crack defects on the forward extruded pin or the backward extruded cup, was developed to provide a conception in choosing appropriate extrusion ratios in forming fasteners with such pin-and-cup features. With the aid of the forming load-stroke curves and the finite element analysis of fracture damage, the fracturing mechanism for the CFBE process was provided.

On the Direct Extrusion of Solder Wire from 52In-48Sn Alloy

In this article, a technology for producing wire and rod solder from 52In-48Sn alloy has been developed and investigated in the conditions of small-scale production. The use of direct extrusion of wire and rods instead of the traditional technology for producing solder, which includes pressing, rolling and drawing, can significantly reduce the fleet of required equipment. Using only a melting furnace and a hydraulic press, solder wires and rods can be produced in various sizes. Shortening the production cycle allows you to quickly fulfill small orders and be competitive in sales. The article developed a mathematical model of direct extrusion, which allows you to calculate: extrusion ratio, extrusion speed and pressing force. The results of modeling the process of extrusion of wire &empty;2.00 mm and rods &empty;8.0 mm made of 52In-48Sn alloy are presented. The temperature of the solder and the tool is simulation in software QForm based on the finite element method. Experimental results of manufacturing &empty;2.0 mm solder wire and &empty;8.0 mm rods are presented. The microstructure of the direct extruded solder is a eutectic of phases &gamma; and &beta;. Energy-dispersive X-ray spectroscopy (EDS) mapping of the 52In-48Sn alloy showed that the solder obtained by direct extrusion has a uniform distribution of structural phases. The developed technology can be used in the manufacture of wires and rods from other low-melting alloys.

Extrusion and characterization of aluminum/graphene composites

Since its first synthesis in 2004 graphene was characterized intensively and exceptional properties in terms of e.g. mechanical strength, stiffness and electrical as well as thermal conductivity were revealed. These properties make graphene very attractive to be applied as additive in composite materials e.g. to increase strength and conductivity compared to the pure matrix material. In this study graphene nano platelets (GNP) in contents of 0. 5%, 1.0 % and 1.5 % were added to pure (99.7 %) aluminum powder and dispersed via EIRICH mixer method. This method is very appealing since homogenous mixtures can be achieved in significantly lower time when compared to e.g. the ball milling process. After subsequent cold compaction the composite materials were extruded with three different extrusion ratios. The influence of GNP content and extrusion ratio on the specific extrusion pressure is characterized as well the resulting rod surface quality, respectively. The effects of GNP content and extrusion ratio on homogeneity of graphene dispersion in the aluminum matrix, the relative density of the composite as well as hardness were also investigated.