Simulation and experimental analysis of melt pool evolution in laser engineered net shaping

In this work,the evolution of melt pool under single-point and single-line printing in the laser engineered net shaping(LENS)process is analyzed.Firstly,the basic structure of the melt pool model of the LENS process is established and the necessary assumptions are made.Then,the establishment process of the multi-physical field model of the melt pool is introduced in detail.It is concluded that the simulation model results are highly consistent with the online measurement experiment results in terms of melt pool profile,space temperature gradient,and time temperature gradient.Meanwhile,some parameters,such as the 3D morphology and surface fluid field of the melt pool,which are not obtained in the online measurement experiment,are analyzed.Finally,the influence of changing the scanning speed on the profile,peak temperature,and temperature gradient of the single-line melt pool is also analyzed,and the following conclusions are obtained:With the increase in scanning speed,the profile of the melt pool gradually becomes slender;The relationship between peak temperature and scanning speed is approximately linear in a certain speed range;The space temperature gradient at the tail of the melt pool under different scanning speeds hardly changes with the scanning speed,and the time temperature gradient at the tail of the melt pool is in direct proportion to the scanning speed.

Comparative study on microstructure and electrochemical corrosion resistance of Al7075 alloy prepared by laser additive manufacturing and forging technology

Al7075 alloy is a typical aviation aluminum with good mechanical properties and anodic oxidation effect.Laser engineered net shaping technology has unique advantages in the integrated forming of high-performance large aircraft structural parts.The manufacturing of 7075 aluminum alloy structural parts by laser engineered net shaping technology has become an important development direction in the future aerospace field.Electrochemical corrosion resistance of aluminum alloys is of vital importance to improve reliability and life-span of lightweight components.A comparative study on microstructure and anti-corrosion performance of Al7075 alloy prepared by laser additive manufacturing and forging technology was conducted.There are hole defects in LENS-fabricated Al7075 alloy with uniformly distributedηphase.No defects are observed in Al7075 forgings.The large S phase particles and small ellipsoidalηphase particles are found in Al matrix.The corrosion mechanisms were revealed according to the analysis of polarization curves and corrosion morphology.It was found that compared with that prepared by forgings,the additive manufactured samples have lower corrosion tendency and higher corrosion rate.Corrosion occurred preferentially at the hole defects.The incomplete passivation film at the defects leads to the formation of a local cell composed of the internal Al,corrosion solution and the surrounding passive film,which further aggravates the corrosion.