Aluminum becomes the most popular nonferrous metal and is widely used in many fields such as packaging, building transportation and electrical materials due to its rich resource, light weight, good mechanical properties, suitable corrosion resistance and excellent electrical conductivity. Grain refinement, which is obtained by changing the size of grain structure by different techniques, is a preferred method to improve simultaneously the strength and plasticity of metallic materials. Therefore, grain refining of aluminum is regarded as a key technique in aluminum processing industry. Up to now, there have been a number of techniques for aluminum grain refining. All the techniques can be classified as four categories as follows: grain refining by vibration and stirring during solidification, rapid solidification, the addition of grain refiner and severe plastic deformation. Each of them has its own merits and demerits as well as applicable conditions, and there are still some arguments in the understanding of the mechanisms of these techniques. In this article, the research progresses and challenges encountered in the present techniques and the future research issues and directions are summarized.

A Review on Grain Refinement of Aluminum Alloys: Progresses, Challenges and Prospects

In the present study, deep drawing process of brass-steel laminated sheets was investigated from the required forming load and thickness reductions points of view. Firstly, the process was simulated using finite element method (FEM) and then was verified using experimental data. For investigation of different process parameters since the implementation of fully experimental or simulation design is impossible, the design of experiments using response surface method (RSM) was carried out. The main effect of six considered parameters on required forming load and thickness reductions was studied and regression models for estimating the forming load and thickness reductions were represented in high reliability. The results showed that all terms of presented regression model were effective on response values. Also, the results of analysis of variance (ANOVA) illustrated that blank radius, steel friction coefficient, and punch nose radius with 53, 28, and 12% of contribution, respectively, were the most effective parameters on required forming load. It was illuminated that brass friction coefficient does not affect the forming load according to the obtained results. Also, according to the results, steel friction coefficient was the most important parameters on thickness reductions of both sheets with 41 and 39% contributions, respectively.

Finite element simulation analysis of laminated sheets in deep drawing process using response surface method

Multi-material lightweight designs are a key feature for the development of innovative and resource-efficient products. In the development of a hybrid composite, the interface between the joined components has to be considered in detail as it represents a typical location of the initialization of failure. This contribution gives an overview of the simulative engineering of metal-composite interfaces. To this end, several design aspects on the microscale and macroscale are explained and methods to model the mechanical behavior of the interface within finite element simulations. This comprises the utilization of cohesive elements with a continuum description of the interface. Likewise, traction-separation based cohesive elements, i.e. a zero-thickness idealization of the interface, are outlined and applied to a demonstration example. Within these finite element simulations, the constitutive behavior of the connected components has to be described by suitable material models. Therefore, inelastic material models at large strains are formulated based on rheological models.

On the Design, Characterization and Simulation of Hybrid Metal-Composite Interfaces

Tube forming technologies based on internal forming pressures, such as hydroforming or hot tube gas forming, are state of the art to manufacture complex closed profile geometries. However, materials with excellent specific strengths and chemical properties, such as titanium alloys, are often challenging to shape due to their limited formability. In this study, the titanium alloy Ti-3Al-2.5V was processed by superplastic hot tube gas forming to manufacture a helically shaped flex tube. The forming process was investigated in terms of process simulation, forming tool technology and process window for the manufacturing of good parts. Within a simulation study, a strain rate optimized forming pressure–time curve was defined. With the newly developed tool design, forming temperatures up to 900 °C and internal forming pressures up to 7 MPa were tested. A process window to manufacture good parts without necking or wrinkling has been successfully identified. The experiment data showed good agreement with the numerical simulations. The detailed study of the process contributes to an in-depth understanding of the superplastic forming of Ti-3Al-2.5V during hot tube gas forming. Furthermore, the study shows the high potential of superplastic hot tube gas forming of titanium alloys for the manufacturing of helical flex tubes and bellows.

https://www.mdpi.com/2075-4701/10/9/1150/pdf

Process Development for a Superplastic Hot Tube Gas Forming Process of Titanium (Ti-3Al-2.5V) Hollow Profiles

Forming of metal-based composite parts

Processing Q&P steels by hot-metal gas forming: Influence of local cooling rates on the properties and microstructure of a 3rd generation AHSS

The global trends towards improving fuel efficiency and reducing CO2 emissions are the key drivers for lightweight solutions. In sheet metal processing, this can be achieved by the use of materials with a supreme strength-to-weight and stiffness-to-weight ratio. Besides monolithic materials such as high-strength or light metals, in particular metal–plastic composite sheets are able to provide outstanding mechanical properties. Thus, the adaption of conventional, well-established forming methods for the processing of hybrid sheet metals is a current challenge for the sheet metal working industry. In this work, the planning phase for a conventional sheet metal forming process is studied aiming at the forming of metal–plastic composite sheets. The single process steps like material characterization, FE analysis, tool design and development of robust process parameters are studied in detail and adapted to the specific properties of metal–plastic composites. In material characterization, the model of the hybrid laminate needs to represent not only the mechanical properties of the individual combined materials, but also needs to reflect the behaviour of the interface zone between them. Based on experience, there is a strong dependency on temperature as well as strain rate. While monolithic materials show a moderate anisotropic behaviour, loads on laminates in different directions generate different strain states and completely different failure modes. During the FE analysis, thermo-mechanic and thermo-dynamic effects influence the temperature distribution within tool and work pieces and subsequently the forming behaviour. During try out and production phase, those additional influencing factors are limiting the process window even more and therefore need to be considered for the design of a robust forming process. A roadmap for sheet metal forming adjusted to metal–plastic composites is presented in this paper.

Process Design for Hybrid Sheet Metal Components

The usage of innovative lightweight materials and processing technologies gains importance in manifold industrial scopes. Especially for moving parts and mobility products the weight is decisively. The aerospace and automotive industries use light and high-strength materials to reduce weight and energy consumption and thereby improve the performance of their products. Composites with reinforced plastics are of particular importance. They offer a low density in combination with high specific stiffness and strength. A pure material substitution through reinforced plastics is still not economical. The approach of using hybrid metal-plastic structures with the principle of "using the right material at the right place" is a promising solution for the economical realization of lightweight structures with a high achievement potential. The article shows four innovative manufacturing possibilities for the realization of metal-plastic-hybrid parts.

http://iopscience.iop.org/article/10.1088/1757-899X/118/1/012042/pdf

Rico Haase

Papers

Processing Q&P steels by hot-metal gas forming: Influence of local cooling rates on the properties and microstructure of a 3rd generation AHSS

Process Design for Hybrid Sheet Metal Components

Process combinations for the manufacturing of metal-plastic hybrid parts

Tempered Forming of Magnesium Alloys Using the Example of Roll Forming

New metals remanufacturing business models in automotive industry