Study on the high cycle fatigue properties of in-situ TiB₂/7050 composite

In-situ TiB₂/Al composite is a new type of aluminum matrix composite, which has the advantages of high specific strength and specific stiffness, good performances on wear resistance, electrical conductivity and thermal conductivity, a variety of matrix alloy candidates, low raw material cost, simple and diversified manufacturing and heat treatment processes. The existing research on the fatigue of in-situ TiB₂/Al composites mainly focuses on the strengthening mechanism in micro-scale and the general understanding of its fatigue performance is not sufficient. It is also lack of fatigue test data of in-situ TiB₂/Al composite for the engineering use. High cycle fatigue properties of the in-situ TiB₂ particle reinforced 7050 aluminum alloy composite (in-situ TiB₂/7050-Al) with volume fraction of 3.67vol% was experimentally investigated with comparison to 7050-Al, the matrix alloy of the composite. The results reveal that the fatigue strength of the in-situ TiB₂/7050-Al is apparently higher than that of 7050-Al. The fatigue limits of in-situ TiB₂/7050-Al are improved by 24.59% and 13.56% for stress ratios 0.1 and 0.5 separately, resulting from the increase of fatigue resistance induced by the tiny TiB₂ particles. The results at different stress concentration levels show that the notch sensitivity of in-situ TiB₂/7050-Al is higher than that of 7050-Al, which may attribute to TiB₂ particles impeding the plastic deformation of the aluminum alloy matrix in the composite. Despite the higher notch sensitivity, the fatigue resistance of the notched composite is still higher than that of the 7050-Al. Therefore, in-situ TiB₂/7050-Al is a promising material for lightweight structure application to replace traditional aluminum alloy in certain circumstances and achieve the joint improvement of static strength and fatigue performance.