Fracture Failure Mechanism And Mechanical Property Modulation Of 90W-7Ni-3Fe Alloy Deposited By Laser Melting Deposition

Tungsten heavy alloys(WHAs)are widely used in aerospace and defense industries because of their excellent overall mechanical properties.At present,they mainly processed by traditional powder metallurgical methods.However,it is difficult,if not impossible,to manufacture WHAs with complex geometries using traditional methods.In recent years,laser melting deposition(LMD)technology has gradually become a new method to manufacture WHAs thanks to its inherent merits of short processing period,high material utilization and personalized customization,but its nonequilibrium solidification process makes the strong toughened mechanical properties of them low and cannot meet the application requirements.Based on this,the fracture failure mechanism and mechanical property regulation methods of LMD 90W alloy are studied in this paper,and two optimized heat treatment processes suitable for LMD 90W alloy are proposed,which laid a theoretical foundation for the preparation of high strength-tough tungsten-based alloys by subsequent additive manufacturing technologies.The main research results are as follows.(1)Clarify the fracture failure mechanism of LMD 90W alloyThe microstructure and mechanical properties of LMD 90W showed obvious inhomogeneity along the deposition direction,and the middle region showed best mechanical properties,the overall plasticity was poor and showed brittle fracture characteristics,and the cracks mostly originated from the W-M interface and microvoids.(2)Establish optimized heat treatment process for LMD 90WAfter heat treatment process exploration,two optimized heat treatment processes are proposed:one is the HT process(1450? for 2 h,furnace cooling)that can significantly improve the plasticity of LMD 90W alloy,and the elongation reached 17.46%±2.93%;the second is the CHT process(1400? for 20 min,5 times,furnace cooling)that can improve the strength and plasticity of LMD 90W alloy,and the ultimate tensile strength was increased from 834 MPa to 870 MPa,and the elongation was increased from 3.44%to 6.96%.