Preparation And Properties Of Rare Earth Lu Strengthened Plasma Facing W-based Composites

Tungsten(W)and its alloys have been regarded as the most potentially suitable plasma-facing materials(PFMs)in fusion devices because of its remarkable properties.However,W shows some brittleness characteristics,including embrittlement induced by low-temperature,recrystallization and irradiation.In the present study,W-based composites with different rare-earth Lu contents were fabricated by mechanical alloying(MA)and spark plasma sintering(SPS)process.The effects of Lu addition on the microstructure and mechanical properties of the W composites were investigated.The transient heat load resistence and D retention properties of W-Lu composites were also researched.The main results of this research are as follows:(1)The addition of Lu dramatically enhanced the microhardness of the obtained bulk materials,whereas the density initially increased and then decreased with increasing Lu content.The grain size of W refined from 10 ?m to 2-3 ?m.The Lu second phases were completely distributed over the W grain boundaries and resulted in an effective grain refinement.Transgranular and intergranular fracture modes were observed on the fracture surface of the sintered W-Lu samples.(2)The surfaces of W-Lu samples were covered with various damages,such as cracks,pits,melting layers,Lu-rich droplets,recrystallization,and thermal ablation after exposed to high energy laser beam.The extent of damage was comparatively lower for W-2%Lu and W-5%Lu samples.The melting of low-melting-point second phases absorbed considerable shock energy hit on the surface and protected the W matrix from further damage,but causing material sputtering.Excessive Lu led to a decrease of W properties.The damage extent of W-10%Lu sample was next only to pure W.Appropriate Lu addition dramatically improved the thermal shock resistence of W-Lu composites.Besides,the crack and melting thresholds of W under heat load were effectively improved.(3)Suitable Lu element was beneficial to the D retention properties of W material.The D retention of W decreased first and then increased with increasing Lu contents.W-5%Lu sample presented the lowest D retention.He ion irradiation resulted in the formation of a new type of D trapped defect and dramatically increased the D retention of W.Fe ion irradiation with high energy increased the dislocation density inside W and also dramatically increased the D retention.