Kugelstrahlen von Spaltbiegeprofilen mit ultrafeinkörnigen Gradientengefügen

Linear bend splitting and linear flow splitting are innovative methods to produce bifurcated profiles with ultrafine grained (UFG) microstructures in an integral style. Linear bend split profiles exhibit high potential for lightweight applications, due to their bifurcations and the high strength of the ultrafine grained microstructures, which develop at the surface of the work piece. The presence of the ultrafine grained microstructure is accompanied by a duplication of hardness and strength and a markedly increase of the fatigue properties, compared to the untreated material. Because of their high strength, ultrafine grained materials exhibit increased potential for the formation of compressive residual stresses. Therefore, shot peening of ultrafine grained microstructures could result in an increased fatigue resistance. The results clearly show that shot peening, despite optimized shot peening parameters, does not lead to an increase of the fatigue resistance. Compared to the untreated ultrafine grained microstructure, the fatigue resistance of shot peened material is even lower. The lower fatigue resistance is probably caused by the roughness of the shot peened surface, which overcompensates the compressive residual stresses.