Segregation in squeeze casting 6061 aluminum alloy wheel spokes and its formation mechanism

Segregation can seriously damage the mechanical properties of the aluminum alloys.6061 aluminum alloy wheel spokes were prepared by squeeze casting.To investigate the formation mechanism of segregation,the microstructure of the alloy was observed using scanning electron microscopy,energy dispersive spectrometry,X-ray diffraction and electron microprobe analysis methods.The Gibbs energy of each phase during solidification was calculated by JMat Pro.Results show that the segregation phases in the R-joint of the wheel spokes are mainly composed of Mg_(2)Si,β-Al Fe Si and Al_(5)Cu_(2)Mg_(8)Si_(6)intermetallics.During the solidification of the 6061 aluminum alloy wheels,Mg_(2)Si andα-Al Fe Si phases precipitate in the mushy zone at first.With the decrease of temperature,α-Al Fe Si transforms intoβ-Al Fe Si,while Al_(5)Cu_(2)Mg_(8)Si_(6)precipitates from the solid-state aluminum alloy after solidification.Segregation at the R-joint of wheel spokes is mainly caused by insufficient cooling,so the cooling during alloy solidification should be enhanced to avoid segregation.

Short Stroke Control with Gaussian Curve and PSO Algorithm in Plate Rolling Process

The precision width control is vital for product quality and production economy in plate width control process,so short stroke control method was used in plate rolling by opening or closing edger gap so as to avoid head end necking.Head end necking on different broadening ratio was analyzed,and sections of different elongations at edger rolling was calculated;based on the law of volume constancy,the adjustment functions were described by parabolic functions.Control curves were developed with three Gaussian curves by means of additional combining;SSC control curve was changed with different weights of those curves,w_1effect one-third of SSC length,w_2effect two-third of SSC length,w_3effect all three parts of SSC length.In order to adjust the amount of weights for precise quantification,PSO algorithm was used to build sufficiency function so as to obtain best rectangular degree by global optimization.Practical applications showed that the method proposed is available to improve the product rolling yields by 1.0%-2.0%and worthy to apply to plate rolling.

Effect of Si addition on microstructure and mechanical properties of Al-Mg-Si-Zn alloy

The effect of Si addition on the microstructure and mechanical properties of Al-Mg-Si-Zn aluminum alloys were investigated.Results show that the microstructure of Al-Mg-Si-Zn alloy with low Si contents is mainly composed of Mg2Si and Mg5Si6 phases.With the increasing of Si content,Si and Al3.21Si0.47 phases precipitate in the form of eutectic phases in the alloys,at the same time,the mean shape factor of the second phase firstly increases and then decreases.Regression analysis results show that the Si content has the main influence and the mean shape factor has the least influence on tensile strength.Tensile strength increases significantly with the addition of Si,however,there is a remarkable drop in the elongation of the alloys.Decreased elongation is related to the formation of monotonous Al(200)structure and the enlargement of interplanar spacing of(111)and(200)crystalline planes.

Microstructure and mechanical properties of Ti/Al/Ti clad plates prepared via powder-in-tube method

The Ti/Al/Ti clad plates exhibit a broad spectrum of potential applications.However,the conventional techniques of hot-pressing composite and explosive composite are intricate and environmentally hazardous.A novel method was introduced for preparing clad plates,namely,the powder-in-tube method.This method involves a combination of cold rolling,annealing at a temperature of 550℃,and double rolling.The morphology of the intermetallic compound layer was analyzed through the utilization of interface stripping test,tensile test,and microscopic characterization.The interface morphology,interface bonding properties,tensile fracture structures,and properties of plates under the first and second rolling were compared,along with the effects of intermetallic compounds on the interface properties.The results indicate that the powder-in-tube method,when annealed at 550℃,can produce a composite plate featuring a complete and uniform Ti/Al interface.The obtained plate exhibits a peeling strength of 21.5 N/mm,tensile strength of 424 MPa,and elongation of 11.5%.Furthermore,a systematic analysis was conducted to determine the causes of performance degra-dation observed during annealing at temperatures of 600 and 650℃.

Springback behavior of tailor rolled blank in U-shape forming

The springback of tailor rolled blanks with quenching and partitioning steels was investigated.In order to find out the springback behavior and related influence factors for the novel sheets,both experimental and simulation methods have been used to compare and analyze the springback characteristics of equal thickness blanks and tailor rolled blanks in U-channel forming.From the results,the overall springback angles of tailor rolled blanks at thin and thick sides are respectively 106.79° and 99.705°,which are both lower than those of the corresponding equal thickness blanks.Due to the existence of the thickness transition zone,the stress distribution in thin and thick sides of blanks is changed.The location of dangerous region in thin side of tailor rolled blanks is closer to the end of side,and the thick side moved to the middle of straight wall,which are different with the equal thickness blanks.Afterwards,the released quantitles of tangential stress and strain per unit section of blank are adopted to calculate relative springback angles and give novel evaluation criteria for qualitatively analyzing the amount of springback angles.By comparing the results,it shows that the tangential strain method is more suitable for the actual situation.