Effects Of The B、Zn、Co On Microstructure And Properties Of Laves Phase Mgcu₂Alloy

Laves phase MgCu2has potential application as new type high temperature because of its excellent high-temperature properties, such as high melting point, high strength, high creep resistance, and good oxidation resistance at high-temperatures. However, and other intermetallic compounds Laves phase compounds room temperature brittleness greatly limits its application in various fields. In recent years, mainly from the Laves phase transition, crystal defects to explain its brittle at room temperature causes brittle at room temperature for improvement, and through grain refinement and alloying of these two aspects of the Laves phase, has made some progress.Samples were by mechanical alloying (milling time is10h, ball-to-powder is13:1and rotation speed is150r/min) and hot-pressing (hot-pressing temperature is680℃, hot-pressing time1h and pressure is25MPa). The effects ofB、Zn and Co on microstructure and properties of MgCu2-based Laves phase compounds are investigated systematically for the first time with optical microscope, scanning electron microscope, X-ray diffraction and energy disperse X-ray.1. The AB2Laves phase Mg(Cu1-xBx)2(0.05<x<0.20) was prepared with the method of mechanical activation combining with hot-pressed sintering. The phase, micro-morphology, and mechanical properties of hot-pressed products were analyzed. The results showed that, although part of the Cu atoms in MgCu2are substituted by B, the crystal structure is not changed, and the main phase is still the C15structure (MgCu2type) Laves phase. After adding B, Metallographic organization is more uniform, and the relative density is higher. With the increase of B content, the diffraction peak shift to the high angular position and the lattice constant gradually decreases. At the same time, with the increase of B content, the hardness and grain size increases, and the compressive strength and the flexural strength increase first and then decrease. The optimum content is6.67at%for Laves phase MgCu2in this research. The relativity density is95.1%, hardness is271HV, compressive strength is490.2MPa, flexural strength is22.2MPa, fracture toughness is2.29MPa· m1/2.2. The AB2Laves phase Mg(Cu1-xZnx)2(0.05<x<0.20) was prepared with the method of mechanical activation combining with hot-pressed sintering. The phase, micro-morphology, and mechanical properties of hot-pressed products were analyzed. The results showed that, although part of the Cu atoms in MgCu2are substituted by Zn, the crystal structure is not changed, and the main phase is still the C15structure Laves phase. After adding Zn, Metallographic organization is more uniform, and the relative density is higher. With the increase of Zn content, the diffraction peak shift to the low angular position and the lattice constant gradually increases. At the same time, with the increase of Zn content, the hardness increases, the grain size decrease first and then increase, and the compressive strength and the flexural strength increase first and then decrease. The optimum content is6.67at%for Laves phase MgCu2in this research. The relativity density is92.4%, hardness is273HV, compressive strength is435.7MPa, flexural strength is18.6MPa.3. The AB2Laves phase Mg(Cu1-xCox)2(0.05<≤x≤0.20) was prepared with the method of mechanical activation combining with hot-pressed sintering. The phase, micro-morphology, and mechanical properties of hot-pressed products were analyzed. The results showed that, although part of the Cu atoms in MgCu2are substituted by Co, the crystal structure is not changed, and the main phase is still the C15structure (MgCu2type) Laves phase. After adding Co, Metallographic organization is more uniform, and the relative density is higher. With the increase of Co content, the diffraction peak shift to the high angular position and the lattice constant gradually decreases. At the same time, with the increase of Co content, the hardness and grain size increases, and the compressive strength and the flexural strength increase first and then decrease. The optimum content is10at%for Laves phase MgCu2in this research. The relativity density is91.5%, hardness is295.1HV, compressive strength is425.3MPa, flexural strength is21.7MPa.