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Sherstnev P.,LKR Leichtmetallkompetenzzentrum Ranshofen GmbH
Materials Science Forum

The present work focuses on a physical description of phenomena occurring during the heat treatment of a cold deformed aluminium sheet. The major practical interest lies in the prediction of microstructural changes and their impact on the yield strength. The material softening part was described due to thermally activated glide of dislocations. The precipitation kinetics are calculated by using the computational thermodynamics program MatCalc (MATerials CALCulator). The model was validated by comparison with experimental data from tensile tests of cold deformed and heat treated sheets. Finally, it was shown that the model can be used to predict the yield strength during heat treatment of Al-Mg-Si alloys. © (2011) Trans Tech Publications. Source

Voyer J.,LKR Leichtmetallkompetenzzentrum Ranshofen GmbH
Materials Science Forum

Partially amorphous iron-based coatings were produced onto aluminium using a powder flame-spraying process with a commercially available feedstock powder (Nanosteel SHS-7170) obtained from the Nanosteel Company Inc.. Several coating properties such as the microstructure, porosity, phase content, micro-hardness, and wear resistance were evaluated in the as-sprayed condition. As shown by the results obtained, the powder flame iron-based coatings perform relatively well in term of wear resistance in comparison with similar coatings produced using other expensive thermal spray techniques. Furthermore, this study shows that all the coating properties (microstructure, porosity, phase content, hardness and wear performance) depend strongly on the flame spraying parameters used. Finally, this paper demonstrates clearly that the flame-spray process may be used to produce amorphous iron-based coatings having a good wear resistance, and that this process appears to be a suitable inexpensive alternative to plasma or HVOF processes based on the present results. © (2011) Trans Tech Publications. Source

Kumar M.,LKR Leichtmetallkompetenzzentrum Ranshofen GmbH
Materials Science Forum

The aluminium alloy AW-6016-T4 sheet is the most widely used alloy for simple-shape outer body parts for passenger vehicles at room temperature. However, for complex parts, such as the B-pillar, the room temperature formability of AW-6016-T4 sheet is not sufficient. Simultaneous hot stamping and quenching is a viable alternative, but there is still limited information about the influence of process parameters on both the formability during the process and the part strength at the end of the process. A combination of thermo-kinetic simulation and experiments were used to investigate the influence of process parameters in the simultaneous hot stamping and quenching process. Increasing the heating rate from 1 to 100 K s-1 during heating to the solution heat treatment (SHT) temperature was found to have no significant influence on the UTS. However, a SHT time of 4 min is required to achieve highest strength by the end of the process chain. Increasing the amount of deformation and cooling rate after SHT have a positive influence on the finished part. Predicted DSC curves and Yield strength values from MatCalc were in good agreement with the experimental results. © 2016 Trans Tech Publications, Switzerland. Source

Horr A.M.,LKR Leichtmetallkompetenzzentrum Ranshofen GmbH
Key Engineering Materials

There have been many efforts to investigate and develop a numerical damage and failure models during metal forming process of lightweight alloys. Due to the difficulties experienced during experimental determination of the incurred damage during forming of lightweight alloys, many researchers have sought to predict the damage, failure and forming limit curves using numerical simulations. Conventional finite element analysis of metal forming processes for lightweight parts which have been subjected to a nonlinear strain history often breaks down due to numerical difficulties. Many scientific research works have attempted to use different mathematical methods to model the damage progression and failure of alloying material under large deformation. The damage initiation, progression and also failure of alloys are a result of accumulated damage under plastic deformation [1-3]. These models (single and multi-damage parameters) are generally based on energy and constitutive equations to simulate the fracture and failure processes in metal alloys. However, these methods have serious short comes in predicting the damage and failure in metal forming process with strain rate effects. In the present study, following the in-depth study of damage initiation and progression in lightweight alloys, a frame work has been setup to develop a numerical model for damage accumulation during forming process. Based on the existing damage theory, a mathematical extension for damage initiation and also damage accumulation under wide range of stress triaxiality (including near pure shear) has been developed. An experimental program has also been carried out using samples made from lightweight alloys. One of the main contributions of this paper is to show the advantages of using plasticity-based modified damage models to investigate the damage accumulation in cast aluminium alloys. © (2015) Trans Tech Publications, Switzerland. Source

Ucsnik S.,LKR Leichtmetallkompetenzzentrum Ranshofen GmbH | Scheerer M.,ARC Seibersdorf Research | Zaremba S.,FACC AG | Pahr D.H.,Vienna University of Technology
Composites Part A: Applied Science and Manufacturing

An integrative joining technology between steel and carbon fibre-reinforced plastics (CFRP) is presented for lightweight design applications in aviation industries. Small spikes are welded onto metal surfaces via "cold-metal transfer" which then build up a fibre-friendly fixation through form-closure with co-cured composites. Manufacture of such reinforced hybrid specimens and results of static tensile testings are discussed. Video-extensometry is applied to characterize the hybrid joints in terms of strength and failure history. Comparisons with epoxy bonded references show improvements in ultimate load, maximum deformation and energy absorption capacity. © 2009 Elsevier Ltd. All rights reserved. Source

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