Regulation Of Mechanical Properties For Several Typical Metal Films By Trace Light Element

Metal materials have obvious performance-price ratio superiority and broad development prospects in various fields involving national defense,industry and electronic information,by virtue of their intrinsically excellent ductility and simple processing process.To meet the high-speed development of aerospace,energy and other modern industries,it is urgent demand to develop advanced techniques in metal materials.In particular,for the service life of key components,researchers have focused on the material mechanical properties including hardness and toughness,since both are critical physical quantity against catastrophic failure.However,hardness and toughness are usually found to be incompatible,that is high hardness often coexists with high brittleness(poor fracture toughness).Thus,solving the hardness-toughness conflict and achieving the comprehensive properties increase is full of challenges but signifcance.In fact,there has been reported that a certain degree strengthening and toughening of metal materials can be achieved through alloying with heavier metallic aroms,but the strengthening effects is limited.Focusing on above questions,based on several typical metal materials(Group-VIB transition metals,Mg light metal,Cu conductive metal),here,we,from another perspective,carry out metal modification via ingenious introduction of light elements(B and C)using non-equilibrium magnetron co-sputtering technology.It is found that significant grain refinement and solid solution strengthening can be induced when B atoms doping into W lattice,resulting in the simultaneous increase of hardness and toughness,the hardness is more than double that of corresponding pure metal films.Furthermore,the tribology behaviors of suchlike small atoms doped metal film are investigated,it is suggested that the hard yet tough film can exhibit excellent tribological performences simultaneously.Subsequently,we present the universal strengthening and toughening phenomenon on metal films induced by suchlike small atoms,on the basis of the systematacial investigations of serial metal-small atom systems like W-B?Mo-B and Cr-C.Compared with traditional alloys containing heavier metallic atoms,such solid solution structure formed with small atoms dopants could induce more severe lattice distortion and thus greater solid solution strengthening to the maximum extent.Also,the obtained refined grains can benefit to obvious toughness increase.More importantly,non-equilibrium sputtering method is expect to induce larger impurities solute contents in metal lattice that far exceed equilibrium-state solid solubility limit,i.e.,supersaturated solid solution structure,which further facilitates the strengthening and toughening behavior.As for the Mg light metal,we develop a special nanostructure with ultrafine Mg(B)interstitial solid solution grains(~5 nm in diameter)embedded into narrow amorphous shell(2 nm thick)with small B addition(6.6 at.%),and achieve nearly 4× increase in hardness,but without much compromising the good ductility of pure Mg.On the other hand,we consider the incompatible small atoms-metal system and investigate the role of various B content in Cu film modification.Our results show that a special microstructure with ultrafine Cu(B)interstitial solid solution grains(~5 nm in diameter)embedded into turbulence-like B matrix can be designed and synthesized by introducting large-concentration B atoms into Cu matrix.This structure can combine the advantages from both phases and result in the achievement of ceramic-like high hardness(~10.3 GPa,two higher than pure Cu)and excellent wear resistance,meanwhile,good metallic ductility and high elastic recovery of Cu can be retained.What is more,the special structure applies negligible influence on the Cu electrical conductivity,making it the highly strong yet conductive Cu alloy.The findings,we believe,can provide a new idea to develop novel high-performance and multi-functional metal-based alloy materials.