Ram Speed Research Articles

Influence of the press ram motion on the joining characteristics during indentation plastic joining using a servo press

A plastic joining method for fixing bars and hot plates, called “indentation plastic joining”, was carried out using a servo press with press ram speed control. The influence of the press ram motion control on the indentation joining characteristics of an aluminum alloy bar and plate was examined. The accelerated ram motion was effective in reducing the bar indentation pressure by approximately 15% and the bonding strength of the indented bar–plate was improved by approximately 7%. The bonding mechanism underlying the indention joining method under press ram motion control is discussed in terms of the seizure of the plate and the mechanical clamping associated with the process. It is found that the accelerated ram motion produces heavier seizure at the indented bar–plate interface, whereas the decelerated ram motion reduces the degree of the seizure.

Anomalous Strain Rate Sensitivity of $$ \{ 10\overline{1}2\} $$ $$ \langle 10\overline{1}\overline{1}\rangle $$ Twinning in a Magnesium Alloy at High Temperature

Anomalous strain rate sensitivity of \( \{ 10\overline{1} 2\} \)\( \langle 10\overline{1}\overline{1}\rangle \) twinning was observed in a Mg-Al-Mn magnesium alloy during extrusion around 723 K (450 °C). The density of \( \{ 10\overline{1}2\} \)\( \langle 10\overline{1}\overline{1}\rangle \) twins decreases as the ram speed increases. At 10 mm min−1, relatively high density twins are activated, but much fewer twins were observed at 30 mm min−1; at 50 mm min−1, twins were hardly seen. The negative strain rate sensitivity was ascribed to the interaction of \( \{ 10\overline{1}2\} \)\( \langle 10\overline{1}\overline{1}\rangle \) twinning with defects.

Materials flow for different lubricants during cold forming

PurposeBarreling contour variations on the free surfaces of cylindrical upset specimen are to handle measuring for different upsetting reductions and different lubrication conditions in this study. The purpose of this paper is to address this issue.Design/methodology/approachThe materials flow for various materials using different lubricants in upsetting was investigated in this study. SAE 1020 steel, commercially pure copper and CuZn40Pb2 brass were used as the test materials. Upsetting process was applied to the cylindrical specimens using flat end dies. Three types of lubricants, namely grease, graphite and SAE 40 oil, were used in this study. Experiments were performed using a hydraulic press, which has 5 mm/s ram speed, and with a capacity of 150 metric tons.FindingsVariations of barrel radius change clearly with increasing deformation ratio depending on lubricant type. Radius values are different to each other for SAE 1020, Cu and brass specimens. It was understood that surface roughness effect is negligible at material types. The highest radius values were obtained for the brass among all the materials for the same deformation ratio. The materials flow is hard for brass specimens because of its brittleness which is due to cold drawing so its barrel radii are high. On the contrary, SAE 1020 and copper are more suitable for the plastic deformation. As shown in the Figures, the higher radius values were obtained especially with grease lubricant for brass specimens.Research limitations/implicationsIt would be interesting to search material flow for different materials and lubricants. It could be a good idea for future work could be concentrated material flow on upsetting using different lubricants.Practical limitationsThe friction at the faces of contact retards the plastic flow of metals and the surfaces and in its vicinity. A conical wedge of a relatively undeformed metal is formed immediately below it, while the rest of the cylinder metal suffers high strain hardening and bulges out in the form of a barrel. This demonstrates that the metal flows most easily towards the nearest free surface which is the point of least resistance. However, the use of lubricants reduces the degree of bulging and under the conditions of ideal lubrication, the bulging can be brought down to zero.Originality/valueThe main value of this paper is to contribute and fulfil the detailed the dependency of barrel radius on material type by upsetting of specimen of various materials using different lubricants that are being studied so far in the literature.

Controlling heat balance in hot aluminum extrusion by additive manufactured extrusion dies with conformal cooling channels

To prevent overheating of the workpiece material, an extrusion die with integrated local cooling was designed and manufactured by selective laser melting (SLM) as an additive manufacturing technology. The major advantage of SLM is the geometric freedom of the components that can be manufactured, which has been used to produce a die with integrated multidirectional channels for a cooling medium and the integration of thermocouples for temperature measurement. To analyze the influence of the die cooling on the heat balance in hot extrusion, extrusion trials at different ram speeds and billet preheating temperatures with and without applying die cooling were performed. Compressed air was used as coolant. At lower ram speeds, a significant reduction of the profile’s exit temperature in hot aluminum extrusion was achieved without causing an excessive rising of the extrusion force. At higher production speeds, surface defects in the shape of stripes of rough surfaces occurred but could be prevented by applying internal die cooling. Due to focusing of the heat exchange on the area of the die bearings, only a little influence of the cooling on the microstructure can be observed.

Effects of extrusion speed on the microstructure and mechanical properties of ZK60 alloys with and without 1 wt% cerium addition

The effects of extrusion speed on the microstructure and tensile properties of the ZK60 and ZK60-1Ce alloys were investigated by performing indirect extrusion at three ram speeds (0.3, 1.0 and 3.0mm/s). All of the extruded alloys showed a bimodal microstructure consisting of equiaxed fine recrystallized (DRXed) grains and elongated coarse unDRXed grains. With increasing extrusion speed, the exit temperature increased due to deformation heating, resulting in a larger grain and a higher DRXed fraction. The yield and ultimate tensile strengths and elongation at RT decreased with an increase of extrusion speed. The ZK60-1Ce alloys exhibited a finer grain size, a higher DRXed fraction, and weaker texture intensity than the ZK60 alloys at the same extrusion speed due to the inhibition of grain growth by the pinning effect and the promotion of DRX by particle-stimulated nucleation. The yield and ultimate tensile strengths at room and elevated temperatures were increased by the addition of Ce, while elongation was decreased due to cracking at the Mg–Zn–Ce particles.

Numerical Simulation and Experimental Investigation on Thixo-Backward Extrusion of 7075 Aluminium Alloy

The thixoextrusion process could become an important technique to extend the complexity of extruded profiles. However, the complex thixotropic flow behavior of semi-solid, during thixoextrusion is still partly characterized. The study described in this paper investigates thixoextrusion for 7075 aluminium alloy at different temperature conditions. A complete die filling and a good surface state of parts was obtained at high solid fraction (fS = 0.70), in heated dies, for an extrusion ram speed of 416 mm/s. The thixoextrusion process is simulated using the finite element code Forge2009©. The constitutive equation used for these simulations is based on a micro-macro model for the semi-solid evolution. The tendency of the experimental curves evolution, preserving the same parameters of the micro-macro constitutive model, for each values of solid fraction, was reproduced, except the last step of the ram displacement.

The Effect of Ti on Mechanical Properties of Extruded In-Situ Al-15 pct Mg2Si Composite

This work was carried out to investigate the effect of different Ti concentrations as a modifying agent on the microstructure and tensile properties of an in-situ Al-15 pctMg2Si composite. Cast, modified, and homogenized small ingots were extruded at 753 K (480 °C) at the extrusion ratio of 18:1 and ram speed of 1 mm/s. Various techniques including metallography, tensile testing, and scanning electron microscopy were used to characterize the mechanical behavior, microstructural observations, and fracture mechanisms of this composite. The results showed that 0.5 pctTi addition and homogenizing treatment were highly effective in modifying Mg2Si particles. The results also exhibited that the addition of Ti up to 0.5 pct increases both ultimate tensile strength (UTS) and tensile elongation values. The highest UTS and elongation values were found to be 245 MPa and 9.5 pct for homogenized and extruded Al-15 pctMg2Si-0.5 pctTi composite, respectively. Fracture surface examinations revealed a transition from brittle fracture mode in the as-cast composite to ductile fracture in homogenized and extruded specimens. This can be attributed to the changes in size and morphology of Mg2Si intermetallic and porosity content.

The processing of NiTi shape memory alloys by equal-channel angular pressing at room temperature

The processing of NiTi alloys by severe plastic deformation (SPD) leads to significant grain refinement and improves both the mechanical properties of the alloy and also the shape memory effect and superelasticity. Nevertheless, it is generally not possible to process NiTi alloys by equal-channel angular pressing (ECAP) at room temperature because of low deformability and the development of cracking due to strain-induced austenite formation. It is shown in this investigation that near equi-atomic NiTi shape memory alloys may be successfully processed by ECAP at room temperature by containing the NiTi samples within Fe sheaths. Processing was performed successfully for up to two passes of ECAP by controlling the processing variables and the initial structure of the NiTi alloys. The results show that the austenitic transformation and cracking can be suppressed if adiabatic heating is minimized by reducing the processing ram speed and the specimen size.

Hydrogen storage properties of pure Mg after the combined processes of ECAP and cold-rolling

Abstract Commercial Mg was processed by two combined processes: ECAP and cold rolling. Samples were first processed by ECAP for four passes using route Bc, at 300 °C and ram speeds of 3 and 25 mm/min. The ECAPed samples were cold-rolled in several passes. The cold rolled samples, which presented a favorable (0 0 2) texture, presented faster hydrogen absorption kinetic than the just ECAPed samples. No significant changes of desorption temperatures were found. The good results observed in the ECAPed plus cold rolled samples were explained by the acquired preferred orientation and by the increase of defects after cold rolling.

Evaluating the effects of process parameters on maximum extrusion pressure using a new artificial neural network-based (ANN-based) partial-modeling technique

Metal extrusion process accounts for the production of the majority of industrial and domestic aluminum sections. A major limitation to the success of any extrusion operation is the capability of the particular extrusion press to meet the maximum pressure requirements for that operation. In the present work, the effects of industrial extrusion process parameters and their interactions on the resulting maximum extrusion pressure, of an industrially extruded aluminum alloy, have been studied using a newly devised ANN-based partial modeling technique. Two operating parameters (initial billet temperature and ram speed) and three geometrical parameters (extrusion ratio, profile average thickness, and number of die cavities) were investigated. The main objective for developing this modeling technique is to overcome the limitations of presently available statistical modeling tools, as foreseen by the modeling needs for a complex thermo-mechanical process such as extrusion. The main present limitations are accounting for non-linearity in the process behavior, incorporating interaction effects and a meaningful determination of the highly significant process parameters and/or interactions. These three features have been, collectively, incorporated into the present model by means of combining statistical analysis of variance into ANN and by using a partial sum of squares analysis, which we propose to call the “present factor analysis.” Normal linear regression has been also employed for comparison purposes. According to the present model, maximum extrusion pressure has shown various degree of non-linearity in behavior with respect to the different process parameters and their significant interactions. It has been found that variations in the maximum extrusion pressure are mainly a function of initial billet temperature and its interactions with other process parameters, especially the ram speed. The present ANN-based model has shown superior prediction capabilities compared to the linear model with a marginal overall prediction error value of ±2.5 %.

Effect of Process Parameters on Die Wear Behavior of Aluminum Alloy Rod Extrusion

In this article, a subroutine that calculates die wear depth based on modified Archard's wear model was developed and then embedded into DEFORM-3D, with which the extrusion process of an aluminum alloy 7075 rod was simulated. Useful information was obtained from the numerical simulation, including interface pressure, distribution of instantaneous temperature, required extrusion force, die wear depth, etc. The numerical result shows that extrusion parameters have multiple effects on die wear behavior. The severest die wear occurs at the bearing entrance due to the greatest deformation, highest pressure, and temperature in this area. It is found that ram speed has no single tendency on die wear, while die wear depth rises with the elevated initial temperatures of billet and extrusion tooling. In addition, the required extrusion force has strong dependence on extrusion parameters. The extrusion force rises clearly with an increase of ram speed and a decrease of initial temperatures of billet and extrusion tooling, which is totally accordant to practical observation. Therefore, the study in this work could provide useful and helpful guides for selecting reasonable extrusion variables, predicting die life and reducing production cost.

Ultrasonic assisted-ECAP

Equal channel angular pressing (ECAP) is one of the most prominent procedures for achieving ultra-fine grain (UFG) structures among the various severe plastic deformation (SPD) techniques. In this study, the effect of ultrasonic vibration on deformation behavior of commercial pure aluminum in the ECAP process is analyzed successfully using three dimensional (3D) by finite element methods (FEMs). The investigation includes the effects of die geometry, billet length, friction factor, ram speed, ultrasonic amplitude and ultrasonic frequency. Conventional as well as ultrasonic ECAP has been performed on aluminium 1070 alloy and the obtained data were used for validating simulations. It is observed that a 13% reduction in the average force was achieved when ultrasonic vibration with amplitude of 2.5μm at 20kHz is applied. Also, further reduction in ECAP forming forces are obtained with increase of vibration amplitude, vibration frequency, friction factor, billet length and die channel angle.

Influence of Rare Earth Elements on Microstructure and Mechanical Properties of Mg97Zn1Y1RE1 Alloys

Mg97Zn1Y1RE1 (RE=La, Ce, Nd and Sm, at. %) alloys were prepared by high-frequency induction melting in an Ar atmosphere. Rods were extruded at 623K and a ram speed of 2.5mm·s−1 using a circular die with an extrusion ratio of 10. The microstructure and mechanical properties of the extruded alloys were investigated. The Mg97Zn1Y1Nd1 and Mg97Zn1Y1Sm1 alloys consisted of only two phases: α-Mg and a Mg-RE intermetallic compound. The Mg97Zn1Y1La1 and Mg97Zn1Y1Ce1 alloys consisted of three phases: α-Mg, a Mg-RE intermetallic compound, and a Mg12ZnY phase with a long-period stacking ordered (LPSO) phase. Additionally, after extrusion, the three-phase Mg97Zn1Y1RE1 alloys, i.e., those with an LPSO phase, had a stratified microstructure and exhibited better mechanical properties than those without an LPSO. At room temperature, the yield strength and ultimate tensile strength of the three-phase Mg97Zn1Y1La1 and Mg97Zn1Y1Ce1 alloys were 381–384MPa and 427–429MPa, respectively, and yield strengths greater than 280MPa were observed at the elevated temperature of 523K.

The influence of Cu–15P master alloy on the microstructure and tensile properties of Al–25 wt% Mg2Si composite before and after hot-extrusion

This study was undertaken to investigate the effect of CuP master alloy on the microstructure and tensile properties of hot extruded Al–25wt% Mg2Si in-situ metal matrix composite. Cu–15wt% P master alloy was added to produce different levels of P (0–3wt%) in the composite. Then, these small billets were hot extruded by using a hydraulic press at a ram speed of 1mm/s with the extrusion ratio of 6:1 at 500°C. Microstructural examinations were carried out by using optical and scanning electron microscopy (SEM). The results showed that P addition changes the morphology of primary Mg2Si from large dendritic to polyhedral shape and its average particle size decreases from 220μm to 22μm in as-cast condition. Microstructural studies also showed that extrusion process not only refines the primary Mg2Si particles, but also fragments intermetallic phases to fine particles. Tensile testing results also revealed that the optimum P level for the improvement of both ultimate tensile strength and elongation values of hot-extruded specimens is 1wt%. The examination of fracture surfaces via scanning electron microscopy (SEM) revealed a transition from brittle fracture in as-cast to ductile fracture in hot-extruded and P-modified specimens. This can be attributed to the changes in the size and morphology of intermetallics and reduction in pore size after hot-extrusion.

Grain size evolution simulation in aluminium alloys AA 6082 and AA 7020 during hot forward extrusion process

The present paper investigates the grain size evolution in aluminium alloys AA 6082 and AA 7020 during hot forward extrusion process. The aim of the present work is the definition and implementation of a predictive algorithm that is able to compute the evolution of the grain shape during the process within the finite element method code Deform. Extrusion experiments were performed at two levels: at reduced scale for investigating and identifying the predictive equations and at industrial scale for validating the developed algorithm. At small scale extrusion, a complete factorial plan was performed for two alloys at three different temperatures, three extrusion ratios and two ram speeds: the discards and extrudates from the experiments were quenched immediately in order to avoid any potential recrystallisation, hence allowing measurements of transitional processing steps. At the industrial scale, instead, the 7020 alloy was extruded with two different die designs, thus producing a 20 mm diameter round bar under different extrusion ratios and strain paths. Finite element simulations were initially validated over visioplastic investigations in order to establish an accurate computation of the material flow, then experimental and numerical results were coupled, thus allowing the definition of the grain evolution model that was successfully integrated and validated on industrial scale trials.

Finite Element Analysis Using Dynamic Material Model to Design Process Variables of Radial Forging

In order to obtain a refined and uniform microstructure in the final billet, the radial forging process needs to be optimized and controlled with various process parameters such as temperature of ingot and die, die size, ram speed, upset ratio, etc. Grain size control is one of the most effective ways for the control of mechanical properties. The change in grain size is significantly related with strain, strain rate and temperature of forged part. To understand material properties and to analyze stability and instability area of forged workpiece, hot compression test of Ti-6Al-4V was carried out within the strain-rate range 10-2 to 10 s-1, and the temperature range 800 to 1100oC. And dynamic material map of Ti-6Al-4V was tabulated. In this study, a three-dimensional rigid-plastic finite element method(FEM) was used to analyze the radial forging process, focusing on the effects of feed rate and rotation angle for appropriate forging pass schedule. And the simulation result was confirmed with dynamic material model of Ti-6Al-4V. The optimal combination of feed rate and rotation angle has been determined by quantifying the radius profile in the longitudinal direction, roundness of the product and uniform strain distribution.

Aging Behavior of Semi-Solid Mg-10Al-0.3Mn Alloy by the Hot Extrusion

In present study, the aging behavior of the hot extruded semi-solid Mg-10Al-0.3Mn alloy was investigated. In order to obtain the extruded bar, we carried out the hot extrusion at 380°C with an extrusion ratio of 25 and ram speed of 2.4mms-1. Vickers hardness test, electrical conductivity measurements, scanning and transmission electron microscopy and tensile testing were performed to identify the aging behaviors and mechanical properties during the aging treatment. Observations of the aging behavior and results of the tensile tests after the T6 heat treatment at each aging temperature show that the optimum aging conditions was indicated by a hardness increment of 72% and a tensile strength of 340MPa in the extruded bar.

Effect of extrusion temperature on texture evolution and recrystallization in extruded Mg–1% Mn and Mg–1% Mn–1.6%Sr alloys

Alloys Mg–1% Mn (M1) and Mg–1% Mn–1.6Sr (M1–1.6Sr) were subjected to three extrusion temperatures of 300, 350 and 400°C at 8mm/s ram speed in order to investigate the texture evolution and recrystallization mechanisms. M1 alloy exhibits weaker texture after extrusion at 300°C, but develops strong basal texture at 350 and 400°C. The weaker texture of M1 at 300°C is partially due to random orientations created by CDRX mechanism. M1–1.6Sr alloy develops weaker textures at all extrusion temperatures as a result of particle stimulated nucleation promoted by Mg–Sr intermetallics which forms grains with random orientations.

An Investigation of Die Wear Behavior During Aluminum Alloy 7075 Tube Extrusion

During hot extrusion process, die wear shortens markedly the service life of extrusion dies under the high-pressure, high-temperature conditions. In this paper, based on modified Archard's wear model, a user-defined subroutine for calculating die wear depth was developed and implanted into DEFORM-3D. On the basis of the numerical model, the die wear behavior during aluminum alloy 7075 tube extrusion has been investigated. The numerical results show that process variables have multiple effects on die wear behavior. With the increasing ram speed, wear depth of die bearing rises and then tends to decline gradually. From the ram speed of 15 mm/s, die wear depth begins to increase again. Wear depth rises suddenly with the increase of friction coefficient, then gradually reduces. When friction coefficient is greater than 0.8, wear depth tends to be a constant. A maximum wear depth occurs at 430 °C of billet temperature, and a minimum wear depth occurs at certain die temperature in the range of 400–425 °C. In addition, the required extrusion force has strong dependence on process variables. The extrusion force rises clearly with the increase of ram speed and friction coefficient and with the decrease of initial temperatures of billet and die.

Inhomogeneity Through Warm Equal Channel Angular Pressing

In this study, the hardness inhomogeneity of billets during multi-passes of equal channel angular pressing (ECAP) at elevated temperatures is investigated and the effect of large strain deformation during ECAP on the hardness inhomogeneity characteristics due to dynamic aging of aluminum 6061 under a variety of temperatures and ram speed was studied by TEM and hardness measurements. The hardness results showed that the hardness distribution is more homogenous after four passes using the pressing route Bc. However, when the deformation temperature was considered, performing ECAP at 100 °C may provide the most homogeneous microstructure after multi-pressing as long as the total number of pressing passes is four. This indicates that a lower temperature (in the range of warm working) is favorable for achieving an ultrafine-grained/nanomaterial with a more homogenous microstructure. In order to quantify the inhomogeneity in the cross section of the as-pressed sample, an inhomogeneity index has been defined. The results show an increase in the hardness in the first pass with significant inhomogeneous deformation and a transition toward a more homogeneous structure with subsequent passes.