The Research On Organization And Performance Of Cast Piston Aluminum Friction Stir Processing

Friction stir processing (FSP) which put forward basing on friction stir welding is aplastic processing technology. The surface modification technology of friction stirprocessing can greatly refine the grain of material organization, eliminate the flaw oncasting metal, form the modification surface layer or the particles reinforced compositelayer which has a gradient of structure and free of interface. It can greatly improve thehardness and abradability on the surface of the light alloy, for example, aluminum alloy,magnesium alloy and titanium alloy. It also can greatly improve the strength and plasticityand toughness of meterial on the whole alloy. The unique and distinct advantage of thefriction stir processing technology is environmental protection and energy saving. Whetherthe working quality of piston which located in the important area of the engine is well or not,directly influence the performance of engine is good or bad. The piston is one of thereciprocating motion and continuous friction accessory. The important way to improve theefficiency of the piston and prolong its service life is improving the abradability of thepiston. This paper attempts to use the friction stir processing technology to modificate thesurface on cast aluminium piston, in order to improve its surface hardness and abradability.This paper focuses on the research about the influence on the structure of castaluminum alloy and the performance of the organization by the friction stir processingtechnology parameters. At first, thought the different test by using different processingparameters, for example, the rotating speed, the forward velocity, the grooves of workpieceand the adding powder, it gets different structure forms and distribution and microhardnessdistribution on processing zones. Secondly, it summarizes the characteristics of organizationdistribution and microhardness distribution on processing zone of the processed alloy, andanalyzes the formation mechanism of the phenomenon. Finally, the paper discusses theeffect on the modification of the structure of the organization and microhardness onprocessing zone in the process under different processing parameters. Then, it obtains theoptimization processing parameters of the friction stir processing.Research conclusions are as follows: the appropriate friction stir processing parameterscan effectively improve the processing of various regions of the tissue characteristics. If thestir tool rotating speed is too large, the regional matrix tissue will grow up. The forwardspeed of tool area has obvious influence the organization on the shaft shoulder pressurezone, and low effect on the friction stir zone. The increase in the number of processing canimprove the added powder distribution, make it more dispersion and homogenization, and the hardness on the processing zone has big promotion. But if it processed repeatedlywithout sufficient cooling, it is easy to make to reduce the hardness of the processing zone.It has a significant influence between the geometry of adding powder filled groove and theprocessing area of the microscopic features and performance. It is certainly that theprocessing zone hardness will be improved much more by adding Boron carbide powderthan adding Silicon carbide powder. For the addition of10micron Boron carbide, the tissueis dispersion, and the powder is relatively uniform, and the hardness on the friction stir zoneis high. For the addition of25micron Boron carbide, the hardness on the shoulder pressurearea is high.