Influence Of Microalloying On Microstructure And Properties Of Brass

It is well known that brass has been widely used as plumbing fitting, heating equipment, instrument and so on due to its great mechanical properties, electrically and thermally conductive properties, formability and high resistance to corrosion. But there is a problem that dezincification or the preferential dissolution of zinc from brass happens when the brass is under corrosive environment, which leads to a porous and friable layer of copper at the surface, it declines the mechanical properties of brass, shortens the service life and brings the security hidden danger.In order to solve this problem, researchers adopted a lot of measures, among which alloying was the most effective, such as adding arsenic,boron or rare earth to brass.Arsenic is used widely to refrain the dezincification of brass, but it has two important limitations. On the one hand, it is restricted to the α-brass and not effective to β phase. On the other hand, arsenic is venomous, which is harmful to health if volatilize during manufacture and use, so arsenic should be avoided using in the future. The present research is thus designed to use other elements instead of arsenic for enhancing the resistance to corrosion of brass. A new As-free and high-zinc complex-brass with La、La2O3 and Sb was investigated in present paper.The corrosion property, mechanical properties and microstructure of the alloy have been studied by means of electrochemical experiments, XRD, SEM, EDS, static corrosion experiments and tensile test. In the meanwhile, the influence of different annealing temperature and time to microstructure and properties of brass was investigated in this paper. The main results are as follows:By adding La、La2O3 and Sb to brass, the microstructure of brass,especially the shape and content of β phases have changed obviously,the resistance to corrosion of brass was improved,and its comprehensive mechanical properties were good.In terms of improving the corrosion resistance,the better content of La、La2O3 or Sb is 0.06%,0.8% and 0.02%,respectively,the corrosion rate of the sample is 9.91g·m-2·h-1,12.59 g·m-2·h-1 and 25.56g·m-2·h-1, respectively.The reason is that La deprives harmful elements from brass, which leads to decreasing of microbattery numbers in microstructure, Sb can form oxidation film, which prevents the dezincification of brass. La2O3 particles can decompose into the dissociated La and O under high temperature, so its function is similar to puer La.In terms of improving the corrosion resistance, La is better than combined addition of La and Sb, the minimum corrosion rate of the sample is 15.8g·m-2·h-1, besides its comprehensive mechanical properties were not good.Annealing with 450℃ and 60 min is the better heat treatment process for mechanical properties of the brass dealed with combined addition of La and Sb,the tensile strength is 375.06 MPa,hardness is 104 HB,elongation is 40.63%;Annealing with 500℃ and 90 min is the better heat treatment process for the corrosion resistance, the minimum corrosion rate of the sample is 8.39g·m-2·h-1。...