The invention relates to a method for evaluating the intercrystalline stress of a cubic structure polycrystalline alloy, and belongs to the technical field of material characterization. The method of the present invention uses the difference between the lattice strain of the {200} crystal plane and the {220} crystal plane in the TD direction of the cubic structure polycrystalline alloy under the action of specific applied stress, combined with the definition formula of elastic modulus E=σ/ ε and Poisson's equation μ=ε_transverse/ε_axial, the formula for evaluating the relative intergranular stress value of the sample to be tested is deduced σ'=|A _sample-A _{standard sample}|·E/μ,σ' and the test sample The actual intergranular stress value is proportional to the relationship, so the intergranular stress of the cubic structure polycrystalline alloy can be qualitatively evaluated. The method of the present invention is simple to operate, the test process will not cause damage to the test sample, the result is accurate, the test efficiency is high, and the cost is low, and it is suitable for testing all cubic structure polycrystalline alloys.

The invention relates to a copper alloy lead frame material with high strength, high conductivity and stress relaxation resistance and a preparation method thereof, belonging to the field of Non–ferrous metal processing. The weight percent composition of the material is: Ni 3.0-4.0%, P 0.3-0.5%, Si 0.2-0.4%, Sn 0.03-0.1%, Fe 0.5-1%, Co 0.05-0.2%, the rest is Cu. By melting and casting, hot rolling, rough rolling, intermediate annealing, pickling, intermediate rolling, solid solution treatment, pickling, finishing rolling, aging treatment and other processing. The lead frame material of the invention has tensile strength of 700-850 MPa, electrical conductivity of 40-50% IACS, elongation of 6-10%, stress relaxation resistance of 88-92%, and high strength, high conductivity and high stress relaxation resistance, the utility model can meet the application requirements of the medium and high end lead frame materials for large scale integrated circuits.