Thomas Witulski

OTTO FUCHS · Materials and Processes

The process–microstructure–property relationship of high-strength 7000 series aluminum alloys during fatigue crack propagation (FCP) is highly relevant for safety during the design and service of aircraft structural components. It is scientifically evident that many metallurgical factors affect FCP properties, but partly contradictory or inconclusi...

Since it affects, among other things, the mechanical properties, the creep behavior, but also the cyclic strength, the grain size is a key quality criterion in the manufacture of engine disks made of superalloys. Large quantities of microstructure samples are produced and a metallographer manually determines their grain size with the aid of standar...

Mechanical properties of Ti-17 are typically strongly influenced by different thermomechanical process parameters such as applied strain, cooling rates and heat treatment temperatures and times. A variation of theses parameters allows the optimization of material properties. Today Ti-17 is mainly used for aero engine applications, where a high stre...

Critical engine disks are typically die forged products due to the high demand on quality and reproducibility. Therefore, it is state of the art that the die forging process is well controlled by a closed loop controlled hydraulic press combined with a tight monitoring of process parameters, e.g. deformation velocity, press load, transfer time etc....

Alloy Ti-6246 has been developed for application as high strength/high fracture toughness material for engine compressor disks. To achieve a balanced combination of properties, the alloy is typically forged in the β-phase field. During this last forging operation the β-grains are deformed to a pancake geometry. The degree of deformation and the ori...

An investigation into the effect of temperature and strain gradients on recrystallization during solution heat treatment has been performed on Alloy 718 test pieces. High temperature compression experiments were carried out using a Gleeble, which generates strain and temperature gradients within the compression sample. The initial results have show...

Even though the phenomenon of abnormal grain coarsening (AGC) or "exploded grains" has been known to occur in Alloy 718 industrial forgings there is still no satisfactory explanation for it. For this reason, detailed microstructure analysis has been carried out in normal and abnormal regions. Electron Backscatter Diffraction (EBSD) was employed to...

A description is given of a method for the heat treatment of a workpiece produced from a titanium alloy for obtaining a fine-grained microstructure by annealing the same above its β-transus temperature Tβ. According to the invention, the workpiece is heated in a furnace to a temperature level TH above its β-transus temperature Tβ. Reaching the temp...

EinleitungAllgemeine Eigenschaften, AnwendungenThermomechanische Behandlung von Ti-Legierungen Herstellung von VormaterialSchmiedenWärmebehandlungProzessauslegung Geometrische AnforderungenArten von Schmiedeteilen und verwendete SchmiedeaggregateProzessfenster beim SchmiedenEinsatz der FEM-SimulationBeispiele für Prozessoptimierung und AnwendungenL...

IntroductionGeneral Properties and ApplicationsThermomechanical Treatment of Titanium Alloys Processing of Forging StockForgingsHeat TreatmentProcess Design Geometric RequirementsForged Components and Forging EquipmentProcessing Window for ForgingsFinite Element SimulationExamples for Process Optimization and ApplicationsReferenced Literature and F...

Recent thixoforming development work at EFU has been concentrated on: (1) improved machine concepts for serial production, (2) die design and prototype manufacturing from various light metals including magnesium and metal matrix composites, (3) numerical simulation for process optimization, (4) accessing process benefits through the appropriate use...

Research in the production of the semi-solid materials, process modeling and development of the constitutive flow behavior is required to assist the industrial application of Semi-Solid Forging (SSF) technology. This paper presents the results of the finite element simulations of semi-solid forging of A356 disks using DEFORM code. Although approxim...

The paper presents results from Semi Solid Forming (Mushy State Forming, Thixoforming) of various aluminum alloys including usually wrought alloys. Raw material production, reheating to semi solid state and semi forming of demonstrator parts has been performed in pilot scale. Mechanical properties close to those of typical forgings have been achiev...

Particulate reinforced aluminium alloys produced by powder metallurgy are relatively expensive and difficult to shape by cutting or milling. Therefore near net shape forming of complex shapes is of high economic and technical interest. However, the formability of these MMC's under conventional forming conditions is limited.The potential of isotherm...

A modified chemical grain refinement method has been developed to produce prematerial for semi solid forming. Billets which need a fine globulare microstructure to show the necessary thixotropic behaviour, were cast from a number of aluminium alloys including casting alloy A 356 as well as usually wrought alloys (2xxx, 6xxx, 7xxx series). It has be...