Ultrafine-grained(UFG)/nanocrystalline materials possess novel properties. Refining as-solidified grains of metals to the ultrafine and even nanometer scale by nanoparticles via slow cooling has been recently discover...Ultrafine-grained(UFG)/nanocrystalline materials possess novel properties. Refining as-solidified grains of metals to the ultrafine and even nanometer scale by nanoparticles via slow cooling has been recently discovered. Here, we report that microparticles(CrB and CrB_(2)) with surface nanofeatures can also enable ultrafine/nano grains via slow cooling. CrB/CrB_(2) microparticles, formed by coalescence of nanoparticles in Cu matrix, display surface nanofeatures, which induce substantial grain refinement and stabilization down to the ultrafine/nano scale. The UFG Cu/Cr B and Cu/CrB_(2) samples exhibit exceptional thermal stability, comparable to UFG Cu induced by nanoparticles, without coarsening after annealing at 600°C for 1 h. The microhardness, strengths, and Young's moduli of the Cu/Cr B and Cu/CrB_(2) samples are significantly enhanced over pure Cu. This discovery has great potential to advance the mass production UFG/nanocrystalline for widespread applications.展开更多
文摘Ultrafine-grained(UFG)/nanocrystalline materials possess novel properties. Refining as-solidified grains of metals to the ultrafine and even nanometer scale by nanoparticles via slow cooling has been recently discovered. Here, we report that microparticles(CrB and CrB_(2)) with surface nanofeatures can also enable ultrafine/nano grains via slow cooling. CrB/CrB_(2) microparticles, formed by coalescence of nanoparticles in Cu matrix, display surface nanofeatures, which induce substantial grain refinement and stabilization down to the ultrafine/nano scale. The UFG Cu/Cr B and Cu/CrB_(2) samples exhibit exceptional thermal stability, comparable to UFG Cu induced by nanoparticles, without coarsening after annealing at 600°C for 1 h. The microhardness, strengths, and Young's moduli of the Cu/Cr B and Cu/CrB_(2) samples are significantly enhanced over pure Cu. This discovery has great potential to advance the mass production UFG/nanocrystalline for widespread applications.
