LASER MICROSTRUCTURE MODIFICATION OF METALLIC MATERIALS

Structure changes in laser constituted surface layers of aluminium all oys of the systems: Al-Zn, Al-Fe, Al-Fe-Ni, Al-Si were examined. Signi ficant structure refinements and even formation of characteristic prec ipitates for rapidly quenched microstructure were found. Fine martensi tic microstructure was observed in constructional steels of the types: X45CrSi92 (H9S2) and C50 (50G) subject to a laser modification. The s tudy of influence of the chemical composition on the solidification st ructure and hardness was carried out on a steel 45, as well as on a hi gh speed steel M2 (SW7M), by laser alloying using carbides of the type s: VC, Mo2C and the borides of the types: CrB, VB2, B-4 C. Thermodynam ic calculations of phase diagrams were made to predict the changes of the constitution due to laser alloying. A comparison of tile solidific ation structures and the calculated phase diagrams revealed a good agr eement, especially for carbides. Boride alloying led to very complex m icrostructures consisting of various metallic and intermetallic phases .