Mechanical Properties And Interface Strengthening Behavior Of W-1TiC-xTi Alloy

Tungsten and its alloys are ideal plasma-facing materials in nuclear fusion devices materials owning to its high melting temperature,excellent thermal conductivity and resistance to high temperature corrosion.However,the drawbacks of pure tungsten bulk material,such as low strength and hardness,low relative density,and low-temperature brittleness,greatly limits its application.Carbides dispersion strengthening tungsten（CDS-W）is a proper way to modify its microstructure and improve its mechanical properties.However,some reports suggest that CSD-W alloys have some problems like the formation of sintering defects,the aggregation of the second phase particles,and tensile strength and microhardness need to be further improved.Therefore,it has great significance by introducing sintering activator like Ti in CDS-W alloys to modify its microstructure and mechanical properties.In this manuscript,the dissolved-segregation mechanism of sintering activator Ti is explored by introducing Ti in W-1TiC alloy.The influence of Ti content on microstructure and mechanical properties is systematically investigated.Meanwhile,the effects of the Ti-rich region on mechanical properties and interface strengthening of W-1TiC-x Ti（x=0.1,0.3,0.5,0.7,0.9 wt.%）are analysis in this work.The main innovations are as follows:（1）The balling milled Ti-doped W-1TiC alloy powder have good dispersibility and without obvious agglomeration.The average size of W-1TiC-x Ti alloy powder is 212 nm.By introducing Ti in raw powder,Ti partially dissolves in W powder,forming W-Ti solid solution powder,which increasing the of sintering activity the alloy powders.The fined and dispersed W-1TiC-0.5Ti alloy sintered at 1930°C is nearly full densification（over 99%）and its porosity is 0.12%.（2）The average grain size of W-1TiC-x Ti alloys presents decreased first and then increased with the increasing of Ti content.The W-1TiC-0.5Ti alloy has the finest grain size is 2.7μm（sintered at 1930°C）.The introducing of Ti in W-1TiC alloy can improve the dispersibility of TiC particles in tungsten bulk alloys and enhance the dispersion strengthening effect.（3）The W-1TiC-0.5Ti alloy formed Ti-rich region at the phase boundary between TiC particles and W matrix,which can modify the microstructure of phase boundary and decrease the formation of sintering defects（sintering pores）.Meanwhile,the W matrix and the TiC particles form semi-coherent interface（mismatch value is 10.19%）and the crystal orientation relationship（OR）is[1（?）12]（1（?）11（?））_TiC（fcc）|[1（?）11]（011（?））_W（bcc）.The OR decreases the elastic strain energy and then increases the strength of their interface.（4）The tensile strength and microhardness of W-1TiC-x Ti alloys increase first and then decrease with the increasing of Ti content,which is related to the effect of Ti content on the dispersion of the second phase particles and the modification of the interface.The W-1TiC-0.5Ti alloy（1930°C）has the highest tensile strength and microhardness are 426 MPa and 860±11 HV_0.2,respectively.Thus,the improvement of mechanical properties of Ti-doped W-1TiC alloys is attributed to the synergistic effect of fine-grained strengthening,second phase particle strengthening,and interface strengthening.There are 41 figures,5 tables,and 102 references in this manuscript...