Investigation On Structure And Aging Property Of Al-5Cu-Ti-B Alloy

Al-Cu alloy is a typical age-hardening alloy, when the solution treatment, Cu dissollve into the solid solution to improve the mechanical properties by the crystal lattice distortion, when the artificial aging, the precipitation separate out, greatly increased the strength of the alloy.adding the different alloying elements into the Al-Cu alloy, the precipitation is enhanced or inhibited on different degrees because of different influential mechanisms, the precipitation behavior of Al-Cu alloy is influenced on different degrees too. In this study, by adding different contents of Ti, B or both to join Ti, B into the Al-5% Cu alloy , test the hardness and tensile mechanical properties of alloys in different states, analyse the different microstructure of the cast and heat treatment states and observe the Precipitate morphology of the samples through the optical microscope, observe the sample surface element distribution of the sample using scanning electron microscopy , to study and discuss the related mechanism, get the following main conclusions:As cast condition of the Al-5Cu alloy: (1) Adding the different contents of B, the grain of samples is refinement on content of 0.42%B, tissue distribution of samples is more uniform too. the as-cast hardness and tensile strength of samples show rise and then decline ,but the effect is not obvious;(2) Adding the different contents of Ti, Reaction of titanium and aluminum to Al3Ti phase, Al3Ti as the crystallization of the core ofαphase, grain refinement. the grain boundary of samples is refinement on content of 1.0%Ti. The hardness is decreased obviously of the Al-5Cu cast sample on adding Ti, but the tensile strength has been enhanced;(3) When both to join the Ti and B, in the content of 0.67% B remains basically unchanged, specimens cast structure appears segregation phenomenon obviously with the Ti content increases,the as-cast hardness and the tensile strength both get increase.Heat treating state of the Al-5Cu alloy: (1) Adding the different contents of B, the age- hardening curves tendency of the sample similar to the Al-5Cu alloy, the aging peak is also no significant difference. The age- hardening curve of the sample on content of 0.42% B has been upward side. The aging tensile strength of samples have been improved;(2) Adding the different contents of Ti, the age- hardening curves tendency of the sample similar to the Al-5Cu alloy and containing 0.2% Ti , the aging speed of the other 3 group samples have been increased significantly and the aging peak time have been advanced significantly. The aging tensile strength of samples appear downward with the increase of the Ti; (3) When both to join the Ti and B, the aging speed of the samples can be further raised, the aging peak time is more advanced. The aging tensile strength of samples have been greatly improved than join Ti or B separately, but The aging tensile strength of samples appear downward with the increase of the Ti.