Limitation On The Organizational Structure And Properties Of Cu-zn-ni-al Alloy

By means of detecting and analyzing methods, such as hardness test, electric conductivity test, mechanical properties test at room temperature, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the relationship between microstructure and the mechanical properties of Cu-Zn-Ni-Al alloys with high strength, conductivity and elasticity was studied, changing mechanism of microstructure and the mechanical properties under thermomechanical treatment was analyzed and ageing strengthening mechanism was explored. The conclusions can be summarized as follows:1. The Cu-Zn-Ni-Al alloys have typical strengthening effect by ageing precipitation, which has a strong age hardening effect under high temperature solution treatment and low temperature ageing treatment. The suitable solution and ageing treatment of Cu-Zn-Ni-Al alloy are:solution at 850℃for lh and ageing at 450℃for 16h. Under the heat treatment conditions, the ageing hardness peak of the alloys can reach maximum and the hardness added-value that arise from hardening effect of the alloys was 112 Hv.2. During the ageing treatment of the Cu-Zn-Ni-Al solid solution alloys, the supersaturated solute atoms precipitated to be the y'phase at the early ageing proceeding, which will improve the strength of the alloys. The y'phase that resembles the CU3AU structure with an Ll2 ordered cubic is the Ni3Al with a small quantity of Cu and Zn, and has a definite orientation relationship of [-112]p/ /[-112]m, (110)p//(110)m with the a solid solution matrix. With the extension of ageing time, the volume fraction of theβphase will increase and the y'phase decrease gradually. The (3 phase with B2 structure is the NiAl with a small quantity of Cu and Zn, and may be written as a formula of (NixZn1-x)(AlyCu1-y).3. The strengthening effect by ageing precipitation of Cu-Zn-Ni-Al solid solution alloys resulted from deformation strengthening generated by matrix lattice distortion and precipitation strengthening generated by coherent precipitation of precipitated phases.4. The cold rolling process of Cu-Zn-Ni-Al solid solution alloys before ageing treatment improved ageing hardness rate and conductivity of the alloys. The suitable thermomechanical treatment of Cu-Zn-Ni-Al solid solution alloys are: 80% cold rolling and ageing at 450℃for 1h. Under the above treatment conditions, the alloy has a good comprehensive performance:the tensile strength σb, the yield strengthσ0.2, the elongationδand the electrical conductivity EC were 968MPa,953MPa,3.9% and 18.7% IACS, respectively.5. The second phase particles precipitated by Cu-Zn-Ni-Al alloy slowed the progress of recrystallization in the deformed structure, increased recrystallization temperature of the alloys and restrained the discontinuous precipitation behavior of grain boundaries.