Multi-directional Forging of Large-Scale Mg-9Gd-3Y-2Zn-0.5Zr Alloy Guided By 3D Processing Maps And Finite Element Analysis

The three-dimensional (3D) processing maps of cast Mg-9.0Gd-3.0Y-2.0Zn-0.5Zr alloy were established based on isothermal compression tests and dynamic material model (DMM). The stable and power efficient forming domains were determined by considering both the instability and power dissipation efficiency maps. Multi-directional forging (MDF) was then simulated by employing finite element (FE) analysis in the Deform-3D software, using the 3D power dissipation efficiency maps as input. The optimal forging parameters were thus obtained for a large-scale ingot with 430 mm in diameter and 440 mm in height, i.e. a forging temperature of 450 ℃ and forging speed of 10 mm/s. Finally, a Mg-9.0Gd-3.0Y-2.0Zn-0.5Zr cake-shaped forged part with 900 mm in diameter and 100 mm in height was produced. After T6-heat treatment, the edge and center of the forged part exhibit homogeneous microstructure and relatively consistent properties, with the tensile strength, yield strength and elongation being about 400 MPa, 320 MPa and 14.0% respectively. Using transmission electron microscopy, the main strengthening phases were revealed to be the dense nano-scale β' phases that are uniformly distributed inside the material.

3D processing map and high-temperature deformation behaviour of Fe–0.05C–0.015N–0.13P Steel

Steels alloyed with high phosphorus should be developed for those applications where both strength and corrosion resistance are required. Structural steels such as rebars are manufactured using high-temperature deformation. Hence, thermo-mechanical behaviour of Fe-0.13P-0.05C -0.015N steel is considered using high temperature compression experiments after austenitization at 1050 °C for 10 s. The temperatures selected were between 750 and 1050 °C and at intervals of 50 °C. The rates of strain varied from 0.001 to 10 s−1. Microstructural evolution was studied with the help of optical and scanning electron microscopy. Modified dynamic materials model is used to draw a processing map. The processing map helps in determining the domains which are safe for hot working. This alloy steel can be safely processed in the area confined by the rates of strain between 1 and 10 s−1 as well as the temperature interval of 900 to 1000 °C.

Metadata schema and ontology for capturing and processing of 3D cultural heritage objects

Motivated by the increased use of 3D acquisition of objects by cultural heritage institutions, we were investigating ontologies and metadata schemes for the acquisition process to provide details about the 3D capturing, which can be combined with preexisting ontologies describing an object. Therefore we divided the 3D capturing workflow into common steps starting with the object being placed in front of a 3D scanner to preparation and publication of the 3D datasets and/or derived images. While the proposed ontology is well defined on a coarse level of detail for very different techniques, e.g. Stucture from Motion and LiDAR we elaborated the metadata scheme in very fine detail for 3D scanners available at our institutions. This includes practical experiments with measurement data from past and current projects including datasets published at Zenodo as guiding examples and the source code for their computation. Additionally, the free and Open Source GigaMesh Software Framework’s analysis and processing methods have been extended to provide metadata about the 3D processing steps like mesh cleaning as well as 2D image generation. Finally, we discuss the current limitations and give an outlook about future extensions.

Detection and analysis of photo-acoustic emission in Direct Laser Interference Patterning

Functional laser texturing by means of Direct Laser Interference Patterning is one of the most efficient approaches to fabricate well-defined micro textures which mimic natural surfaces, such as the lotus effect for self-cleaning properties or shark skin for reduced friction. While numerous technical and theoretical improvements have been demonstrated, strategies for process monitoring are yet to be implemented in DLIP, for instance aiming to treat complex and non-plane surfaces. Over the last 35 years, it has been shown that the sound pressure generated by a laser beam hitting a surface and producing ablation can be detected and analysed using simple and commercially available transducers and microphones. This work describes the detection and analysis of photo-acoustic signals acquired from airborne acoustic emission during DLIP as a direct result of the laser–material interaction. The study includes the characterization of the acoustic emission during the fabrication of line-like micro textures with different spatial periods and depths, the interpretation the spectral signatures deriving from single spot and interference ablation, as well as a detailed investigation of the vertical extent of the interference effect based on the ablated area and its variation with the interference period. The results show the possibility to develop an autofocusing system using only the signals from the acoustic emission for 3D processing, as well as the possibility to predict deviations in the DLIP processing parameters.

3D Processing Maps of Cast Mg-9Gd-3Y Alloy and Numerical-Experimental Verification

The hot compression behavior of Mg-9Gd-3Y (GW93) alloy was investigated by carrying out isothermal compression tests at the deformation temperature range of 300–450°C and strain rate range of 0.001–1s−1. Considering the influence of the strain on the formability of the GW93 alloy, three-dimensional (3D) processing maps were established based on the dynamic material model. The 3D processing maps indicate that the formability of the material improved with the decrease of the strain rate and the increase of the heating temperature, and the material at lower heating temperature mostly underwent flow instability. The formable processing region of the hot deformation of the GW93 alloy was concentrated within the temperature range of 380–450°C and the strain rate range of 0.001–0.01 s−1. Subsequently, the 3D processing maps were embedded into the finite element (FE) software DEFORM-3D by means of user subroutines, and the formability of GW93 alloy during the isothermal plane strain forging process was predicted. The FE simulation results revealed that the formability of the material at low strain rate improved compared with that at high strain rate under the same temperature. Finally, an isothermal plane strain forging technological experiment was carried out, and the microstructure of the formed sample was analyzed. The experimental result is in good agreement with that of the numerical simulation. Combined with microstructural observation, the accuracy of the simulation results and the 3D processing maps of the GW93 alloy was verified.

Flow Stress Modelling and 3D Processing Maps of Al4.5Zn4.5Mg1Cu0.12Zr Alloy with Different Scandium Contents

The hot deformation behaviour of an Al4.5Zn4.5Mg1Cu0.12Zr based alloy with 0.05, 0.1 and 0.15% Sc was investigated at temperatures between 300–450 °C and a strain rate of 0.1–15 s−1. The materials constants of a flow stress model based on the Zener-Hollomon parameter were determined (AARE was 5.8%). Three-dimensional processing maps were established by combining power dissipation efficiency and flow stability diagrams. Based on processing maps analysis and microstructures investigations, the optimal deformation parameters were determined as a temperature range of 350–400 °C and strain rates of 0.1–1 s−1 for the alloys with 0.05% and 0.1% Sc, and 0.1 s−1 for the alloy with 0.15% Sc.