A method of manufacturing an aerofoil structure to have a portion with an increased erosion resistance, the method comprising: providing one or more titanium elements (2, 4, 6) and a beta-stabilizing material (8); wherein the one or more elements (2, 4, 6) have an alpha-beta microstructure; assembling the one or more elements (2, 4, 6) and the beta-stabilizing material (8) such that the beta-stabilizing material (8) is adjacent to the one or more elements (2, 4, 6); and heating the assembly such that the beta-stabilizing material (8) diffuses into an adjacent portion of the one or more elements (2, 4, 6), causing the adjacent portion of the one or more elements (2, 4, 6) to have a beta microstructure which provides an increased erosion resistance.