The microstructural evolution and precipitation hardening of an Elinvar alloy doped with Tiand Al during isothermal aging at 700℃ have been investigated by atom probe field ionmicroscopy and microhardness measurements.The γ′ precipiates are spherical and coherentwith the matrix.The chemical composition of the precipitates are(Ni0.53Fe0.473 (Ti0.（?）Al0.4).During aging,a Lifshitz-Wagner type dissolution and coarsening reaction of the precipitateshas been observed,The hardness of the material varies with the aging time and reaches maxi-mum when the average diameter of the precipitates was about 11 nm.
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