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Das Oxydationsverhalten hochkaratiger Gold-Legierungen mit Titangehalten zwischen 0,5 und 1,3 Ma.-% Titan in synthetischer und natiirlicher Luft wurde in Abhangigkeit von Oxydationstemperatur und Zeit untersucht. Es bildet sich keine geschlossene homogene Titanoxidschicht. Im oberflachennahen Bereich der Legierung entstehenTi02-Ausscheidungen (Rutil) The behaviour of oxidation and precipitation hardening of very goldrich gold-titan alloysThe oxidation behavior of gold rich Au-Ti alloys with contents of titanium between 0.5 und 1.3 weight-% was investigated in synthetic and natural air in dependence on the oxidation temperature and time. A closed homogeneous layer of titanium oxid was not formed. The nucleation of TiOz (Rutil) starts at prefered sites (grain boundaries, structure defects) below the surface of the alloys. The precipitations grow without formation a gapless cover of the grain boundaries. Between the precipitations the concentrations of titanium and oxygen are zero. The titanium is transported out of the interior of the specimen by volume diffusion. Based on an experimentally observed linear relationship between the oxygen uptake and the oxidation time the speed constants could be determined for 750 "C, 825 "C and 900 "C. Between the natural logarithm of the speed constant and the reciprocal temperature a linear connection exists. For this reason it is possible to calculate the kinetics by a well-defined mathematical expression for the speed constant of the titanium oxidation in dependence on the titanium content and the oxidation temperature. The connection between the speed constant and the optical outfit of the surface is illustrated.Furthermore the precipitation hardening of the alloys at temperatures between 100°C and 700°C is described. A noticable increase of the hardness is already produced at relatively low temperatures. Whith increasing temperatures the hardness maximum is shifted to shorter times. With increasing titanium content the hardness maximum increases and it is obtained after shorter times. Cold working before the ageing, raises the hardness maximum and accelerates the precipitation. The precipitations are formed to little plates with high coherency to the matrix preferentialy at the grain boundaries. X-ray analysis sensitively responds to the kinetics of precipitation and gives reliable information about the concentration variations of the matrix. The results concerning the oxidation behaviour and the precipitation hardening make it possible to find the conditions of an optimized heat treatment with high hardness but without negative changes of the surface.