Study Of The Fatigue Property Of Electrolytic Titanium-contained Aluminum Alloy

Electrolytic low content titanium aluminum alloy and electrolytic Al-Si-Ti alloy are two new alloy materials produced by new technique of production. It'll have very important practical value and referential significance in evaluating the properties of the two new materials and generalizing the new technique of production in industry to study and compare the fatigue properties and relevant mechanical properties of the applied cast alloys made from them and pure aluminum comprehensively.In this paper, current development of the titanium-contained aluminum alloys in industry and the gap between our country and advanced industrial counties were introduced first. The shortage of traditional technique for producing the titanium-contained aluminum alloy and the current research of the two new titanium-contained aluminum alloys produced in new technique were analyzed in detail. Then the significance of material's fatigue property in current engineering application was emphasized particularly.In order to study the influence of the existence and adding ways of trace titanium on the fatigue properties of aluminum alloys, three important common-used standard cast alloys ZL101A and ZL101 were prepared with electrolytic low content titanium aluminum alloy, electrolytic Al-Si-Ti alloy and pure aluminum respectively. The fatigue properties and relevant mechanical properties of these three cast alloys were tested and compared comprehensively. The analyses of their microstructure showed that comparing with ZL101 that contained no titanium, the trace amounts of titanium in alloys caused grain refining of Al-l%Si in ZL101A prepared from electrolytic low content titanium aluminum alloy (i.e. AlTi101A) and ZL101A prepared from electrolytic Al-Si-Ti alloy (i.e. AST101A), and the grain size distribution became more even, whereas the trace amounts of titanium have little influence on the size andshape of Si particles in these alloys.This paper studied the influence of different chemical components and microstructure in above aluminum alloys on their tensile properties and fracture toughness. The results showed that the grain refining by the trace amounts of titanium could improve the tensile stress, percentage elongation and fracture toughness, but had little influence on their yield stress. The trace amounts of iron hi AST101A could affect its elastic modulus, but not its tensile stress and yield stress, at the same time decrease its plasticity and fracture toughness notably.The abilities of resisting the incubation of fatigue crack in AST101A and AlTi101A were tested with the high-cycle fatigue method. A method combining the maximum likelihood estimation method with the correlation coefficient method was suggested to analyze the fatigue life experimental data some of which were incomplete. The S-N curve and P-S-N curves were presented, and the influence of the loading history and the defects in specimen on fatigue life was discussed.The remarkable differences of the fatigue crack propagating rates and the fatigue threshold among the above three alurninum alloys were studied and compared, which were caused by the microstructure based on alloys' chemical components. The results showed that the concentration, size and shape of Si particles in AlTilOlA, AST101A and ZL101 had some effects on the fatigue threshold, and the irregular shaped brittle phase of Fe intermetallics caused the fatigue threshold decreased. The fining grains of Al-l%Si could accelerate the fatigue crack propagation from the near threshold zone to Paris zone.The fatigue crack propagating rates of the above aluminum alloys in Paris zone had no remarkable differences. It was showed that fatigue crack propagating rates had little susceptivity to the microstructure of the above alloys in Paris zone. In contrast, the size and shape of Si particles and the phase of Fe intermetallics could affect the fatigue crack propagating rates beyond the Paris zone. The fatigue crack propagating rate of AST101A was the highest, and that of AlTilOlA was the lowest...