Modifying Effect Of Nano-Inoculant On ZL109 Aluminum Matrix Composites

Now the most popular piston materials in used are ZL109 Al matrix composites. But the microstructures of casting ZL109 alloys usually consist of needle-like or lamellar eutectic silicon, which greatly aggravated the mechanical properties of ZL109 alloys. So the control of the morphology and size of eutectic silicon have become the most important and necessary processing for ZL109 alloys.Generally, Al-5Ti-1B can refine primaryα-Al dendrite and improve the shape of eutectic silicon.Sr, RE (Rare Earth elements) are usually used to transform the morphology and size of eutectic silicon. In this paper, the Al-Ti-B-Sr system and the Al-Ce-Sr system are fabricated by rapid solidification respectively. Phase composition, microstructure and micro-morphology of rapidly solidified Al-Ti-B-Sr and Al-Ce-Sr composite modifier have been studied respectively. Effect of rapid solidified composite modifier on microstructure and mechanical properties of ZL109 alloy have been analysed.The results shown that rapidly solidified Al-Ti-B-Sr composite modifier refined the microstructure of ZL109 significantly and improved mechanical properties of ZL109 obviously compared with ZL109 alloy processed by bulk modifier under the same conditions. The strength increases from 372 MPa to 402 MPa, increased by 8%; the hardness increases from 77HRB to 83HRB, increased by 7%, wear rate decreases from 0.1324% to 0.102%, therefore, the wear resistance can be improved effectively. The results show that the ZL109 alloy processed by melt-spun Al-Ti-B-Sr modifier can refine the microstructure of ZL109 significantly, and mechanical properties increase obviously, compared with ZL109 alloy processed by bulk modifier under the same conditions, the strength increases from 375 MPa to 395 MPa, increased by 5%, the hardness increases from 70HRB to 77HRB, increased by 10%, wear rate decreases from 0.2918% to 0.1545%, therefore, the wear resistance can be improved effectively. Phase composition of rapidly solidified Al-Ti-B-Sr composite modifier involves Al3Ti,TiB2 and SrB6. Phase composition of rapidly solidified Al-Ce-Sr modifier is composed ofα-Al, Al4Sr and Al4Ce. Grain size of rapidly solidified composite modifier is up to nanometer grade.