NiAl Multischichten

Influence of stress and deformation on phase formation in reactive Ni/Al multilayers

Contact person

Prof. Peter Schaaf
Group of Materials for Electricial Engineering and Electronics

Phone: +49 3677 69-3611

Funding information

Project leader: Deutsche Forschungsgemeinschaft 

Project number:

SCHA 632/29-1,
SCHW 855/8-1

Participating groups: Group of Materials for Electrical Engineering and Electronics, Electronics Technology Group

Period of funding: 01.07.2019 - 31.12.2023


Frames from a high-speed image of a reaction front of a nanoscale Al/Ni multilayer system under extrinsic tensile loading
Intrinsic stress state of nanoscale Al/Ni multilayers as a function of bilayer thickness

This project aims at identifying the effects of mechanical and thermomechanical stresses and constraints on the transformation reaction and phase formation in transformation imprinted materials. This includes intrinsic and extrinsic stresses resulitng from mechanical loading as well as stresses caused by geometrical confinements, such as passivation layers on multilayer films. As shown for various metal combinations, intrinsic stresses may effect the thermodynamics, which might be used to obtain metastable phases and microstructures. Whether similar effects can be observed under mechanical loads is the central question to be addressed by this project. The findings should be used to design and control the phase morphologies and micorstructures. Moreover, new or metastable phases and new process paths should be identified. The following factors effecting the phase transformations will be studied: (i) stress and deformation through external loads using different loading conditions, including uniaxial tensile loading, bending, compression and contact loading, (ii) internal stress caused by external confinements. The occurring instrinsic stresses will be further evaluated by thermomechanically coupled numerical simulations and parameter indentification by inverse modelling through a close collaboration with project P1. Figure P4.1 gives a graphical summary of the project. This project will answer the question of the influence of applied mechanical and thermomechanical stresses on the phase formation and stability at different temperatures for differnt morphologies and microstructures as well as on the self-propagating transformation. It contributes in cooperation with other projects to the development of models for the prediction of tranformation imprinted materials and to a succesful microjoining process.