铸造Al-50Si合金组织和性能变化

Evolution of microstructure and mechanical properties

of as-cast Al-50Si alloy due to heat treatment and P modifier

content

Fuyang Cao a ,Yandong Jia a ,b ,Konda Gokuldoss Prashanth b ,Pan Ma a ,b ,Jingshun Liu a ,c ,Sergio Scudino b ,Feng Huang a ,d ,Jürgen Eckert b ,e ,Jianfei Sun a ,⇑

a

School of Materials Science and Engineering,Harbin Institute of Technology,Harbin 150001,China b

IFW Dresden,Institute for Complex Materials,P.O.Box 270116,D-01171Dresden,Germany c

School of Materials Science and Engineering,Inner Mongolia University of Technology,Hohhot 010051,China d

Hubei Key Laboratory of Advanced Technology of Automobile Parts,School of Automotive Engineering,Wuhan University of Technology,430070,China e

TU Dresden,Institut für Werkstoffwissenschaft,D-01062Dresden,Germany

a r t i c l e i n f o Article history:

Received 12September 2014Revised 4March 2015Accepted 7March 2015

Available online 9March 2015Keywords:Al–50Si alloy

Superheat treatment Microstructure

Mechanical property

a b s t r a c t

The effects of superheat temperature,content of modifier (P)and T6heat treatment on the microstruc-ture and mechanical properties of the Al–50Si alloy have been investigated systematically by scanning electron microscopy (SEM)and differential scanning calorimetry (DSC).The results indicate that the pri-mary Si exhibits a plate-like morphology,with average size decreasing with increasing of the superheat temperature for the unmodified alloy.The morphology of primary Si changes to small blocky shape at an optimal P content of 0.5wt.%,and the nucleation temperature increases for the alloy with 1.3wt.%P because of the ease of formation of the AlP phase.The nucleation temperature is lower for 0.5wt.%P due to lack of P atoms at relatively higher temperature.The ultimate tensile strength was enhanced by the addition of P followed by the T6heat treatment,and the maximum ultimate tensile strength ($160MPa)was observed for the sample containing 0.5wt.%P.

Ó2015Elsevier Ltd.All rights reserved.

1.Introduction

Electronic packaging materials are required to protect the elec-tronic components from physical damage,mechanical forces,atmospheric chemical contamination,etc.[1].As the electronic packaging requires increasingly smaller size,lighter weight and higher integration,new packaging materials have to be developed to improve the performance of electronic components.However,the properties of traditional packaging materials can no longer sat-isfy the practical requirements [2–4].Hypereutectic Al–Si alloys with high Si content (50–70wt.%)are one of the ideal candidates for electronic packaging application as a result of the positive combination of properties,such as relatively low coefficient of thermal expansion (CTE),which closely matches that of GaAs or Si semiconductor materials,high thermal conductivity,low density and superior strength [5].However,the main limitation of this type of material is the presence of the coarse,irregular,and brittle primary Si phase that can act as soft spots for premature crack initiation,deteriorating the overall mechanical properties of these materials [6,7].Therefore,it is essential to modify the microstructure of hypereutectic Al–Si alloy to optimize the mor-phology and distribution of the primary and eutectic Si [8,9].

Efforts have been made to modify the microstructure of hypereutectic Al–Si cast alloys in order to achieve a refined Si phase with beneficial shape and distribution [10–12].For example,Liu et al.[13]have investigated the modification of hypereutectic Al–24%Si alloys with Si–P,which leads to the formation of primary Si with size of 19l m.Choi et al.[14]have reported that the mor-phology of primary Si in hypereutectic Al–20%Si alloy can be modi-fied from star-like to the polygon or blocky shape by the addition of c -Al 2O 3nanoparticles.Moreover,the spray forming technology was also used to prepare the Al–35%Si alloy with size of the Si phase less than10l m [15].However,only little attention has been paid to the modification of Al–Si alloys with high Si contents (e.g.50wt.%).

The present study analyzes this mentioned above aspect by examining the potential of different superheat temperatures and phosphorus contents as modifying agents for simultaneous refine-ment of both the size and morphology of primary Si phase in the as-cast Al–50Si alloy.Additionally,the work investigates the effect of the induced microstructural modifications on the mechanical properties of the material.

/10.1016/j.matdes.2015.03.008

0261-3069/Ó2015Elsevier Ltd.All rights reserved.

⇑Corresponding author.

E-mail address:jfsun@ (J.Sun).