Non-Isothermal Crystallization Behavior of a Zr-Based Amorphous Alloy Composite Prepared by Selective Laser Melting

Zr₄₈Cu_47.5Al₄Co_0.5 bulk amorphous alloy composites were prepared by selective laser melting (SLM) technology under different processing conditions and their non-isothermal crystallization behaviors were systematically investigated. The results show that the crystallization phases are Cu₁₀Zr₇ and CuZr₂ for both gas-atomized powder and SLMed samples. The dependence of volume fraction of Cu₁₀Zr₇ and CuZr₂ on laser energy density can be fitted by an exponential function. The crystalline sizes of Cu₁₀Zr₇ and CuZr₂ linearly increase with increasing energy density. The thermal stability is larger for the gas-atomized powders than for the SLMed bulk samples. It is interestingly found that there is an exponential relationship between the crystallization enthalpy ΔH_x and the amorphous content. In addition, the glass transition is more difficult for the gas-atomized powders than for the SLMed bulk samples. The crystallization procedure is more difficult for the SLMed bulk samples than for the gas-atomized powders. The local activation energy E_α decreases with increasing α for the gas-atomized powder and the SLMed bulk samples. In addition, the E_α is larger for the SLMed bulk samples than for the gas-atomized powder at the corresponding crystallization fraction α. The dependence of the local Avrami exponent n(α) on the α is similar for both the gas-atomized powders and the SLMed bulk samples at studied heating rates. The crystallization mechanism is also discussed.