Multi-component Nb-(11,15)Si-5Hf-30Ti-4Al-4W-2B-(8,16)Cr alloys have been proposed, attempting to obtain the Nb-Si based alloys with a comprehensive property. The results show that three phases of NbSS, Nb5Si3 and Laves Cr2Nb exist in the alloys with a Cr content of 16 at%. With increasing Si and Cr contents the fracture toughness KQ decreases, while the oxidation resistance at 1250°C and strength at 1250°C and 1350°C exhibit an increasing tendency. The 15Si-16Cr alloy shows the highest strength and oxidation resistance, and the lowest toughness; they are 385MPa at 1350°C, 215mg/cm2 at 1250°C for 100 h, and 5.45 MPa•m1/2 at room temperature, respectively. The 11Si-8Cr alloy with an NbSS/Nb5Si3 microstructure only has the highest toughness of 11.87 MPa•m1/2, its strength and oxidation resistance are the lowest.

The multi-population coevolutionary differential evolution (DE) based on estimation of distribution algorithm (EDA) is proposed. DE completes optimum search using the difference information between the individuals in the population, but the global population evolution information can not be used sufficiently. In this paper, the multi-population co-evolutionary is introduced, which incorporate the merits of the DE and EDA. The elite mutation is proposed in DE. To overcome the greed characteristic, the chaotic initialization and replacement are introduced in DE and the individual diversity in EDA is adjusted based on the individual density. Simulation results show the good global search ability of the proposed algorithm.

The large airspace varying trajectory is modified to large airspace spiral maneuver trajectory, in order to improve the penetration effect of a supersonic anti-warship missile against enemy long-distance ship-to-air missile (LDSAM). In the descent phase the missile may suffer the interception of LDSAM, so the descent phase is modified to spiral maneuver descent trajectory. A variable structure guidance law is designed firstly. On the basis of it, a variable structure guidance law with spiral maneuver is proposed, in order to realize the large airspace spiral maneuver trajectory. The simulation results show that the proposed guidance law can guide the supersonic anti-warship missile to realize the large airspace spiral maneuver trajectory. The entire missiles performance indexes satisfy the flight requirement.