Sheng Li

With surging demand for oil and gas resources, staged fracturing is becoming extremely important, and fracturing material is the key factor in exploration. Recently developed Mg-Al alloys cannot simultaneously achieve high strength and rapid degradation, limiting their widespread application in the exploration. To address this issue, this study utilized the rapid densification technology of spark plasma sintering (SPS) to sinter Mg, Al, and Fe powders at a ratio of Mg-5Al-Fe (0, 2, 4, 6 wt.%) under a temperature of 510 °C and a pressure of 35 MPa for 800 s. And this study conducted investigations on the microstructure, mechanical strength and degradation rate of the alloy through scanning electron microscope, hardness and compression tests, as well as immersion experiments. The results indicated that SPS enabled rapid powders densification and grain refinement, and the addition of Fe particles formed a second-phase strengthening which could block dislocation, thereby increasing mechanical strength. The ultimate compressive strength (UCS) was increased from 189.37 ± 6.12 MPa for Mg-5Al to 421.21 ± 12.31 MPa for Mg-5Al-6Fe. Furthermore, the addition of Fe accelerated the degradation rate, with the Mg-5Al-6Fe alloys reaching 45.26 ± 2.6 mm/year. Meanwhile, the alloys also had a low density of 1.38 ± 0.027–1.53 ± 0.030 g/cm³, which could effectively reduce the pumping energy consumption of fracturing fluids. These characteristics met the core requirements of degradable fracturing balls, showing the great potential of Mg-5Al-Fe alloys for staged fracturing.

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.