| As the main die casting trademark ,AZ91D magnesium alloy has advantagesof low density ,high specific strength and high damping capacity .These make AZ91D magnesium alloy be extensively applied in auto, meter, aviation etc. It is important to investigate the machining properties of the die casting AZ91D magnesium for big scale production. Drilling is one of the most important means in machining. So we will study its drilling properties in this paper. The material composit-ion(quality percent): Al:9.068%,Zn:0.726%,Mn:0.131%, the other is magnesium.A drilling force measurement & control system is developed including the hardware and software according to the research requirements. The hardware system bases on the SDZ-E multicomponent dynamometer , CA electric charger enlarger , PCI7483 data acquisition card and computer . The software based on VC++6.0. Several key problems including the data acquisition card class , the setting of the programmable timer , data storage have been resolved .In the experiment , we use the multimedia timer to achieve a precise time ,and we use timeGetTime() and timeSetEvent()to achieve timer accuracy of 1ms. The function of multi-channel data acquisition card with a high frequency has been implemented . The assessment of the performance of the system with the input range of ±5kN(8kN after enlarging capacity ) ,the error of 1.078% and the sample frequency of 100HZ meets the requirements of the experiment. In this paper, we discuss the organization traits of the diecasting AZ91Dma-gnesium alloys . Its organization is made up ofα-Mg matrix,βphase(Mg17Al12) and crystal integration in the crystal boundary .In order to research drilling properties of the die casting AZ91D magnesium alloys , we carried out drilling experiment of the overall three elements and three levels .When the horizontal edge is located in 2.3mm to the sample face , the axial force is maximal ; when the horizontal edge is in the sample center(the midpoint of unbroken string of the corresponding point in two opposite surfaces), the axial force is minimum.The range of moment is small. When the axial force is maximal , the main cutting edge is in the sample just completely and the HB is 60.As the horizontal is advancing ,the sample temperature is rising ,but it can not give rise to the cutting tumors , the axial force is reduced . When the horizontal edge gets to the sample center, he axial force becomes minimum.Under the different drilling factors ,we determine the amount of the drilling force(or moment). We get the relationship between the drilling factors and drilling force(or moment);F=6.246d1.1079f0.7643v0.2328;M=0.045d2.0716f0.8894v0.4607. We test the formula ,in the table F,α=0.01,F=4.76 ,the F is far less than F of the two formula ,so the two formula is notable .Under the identical machining condition , we compared the drilling force ,moment and power of the die casting AZ91D magnesium alloys with 45# steel,s, and we findthat the biggest of them is 12.22%,9.8%,9.8% of the 45# steel,s .so the die casting AZ91D magnesium is a kind of easily cutting material .According to the experience of the experiment , we find the rotation velocity would better be 5000 r/min, the proceeding velocity is about 0.20mm/r.In this paper , we also study the temperature trait of the tool in the process ofdrilling die casting AZ91D magnesium alloys .The cutting temperature is rising very fast . In the experiment , we find that the cutting scrapes is still contacted with cutting edge ,this makes the cutting temperature raised further.Because of the plastic deformation of material and friction force , the heat center is at the edge of tool and the total heat quantity q=[(6.246d1.1079f0.7643v0.2328)2+(0.09d1.0716f0.8894v0.4607)2 ]0.5 ×v. These factories are harmful to the drilling machining :1) Accelerating the wear and tear of the tool .2) Because of the low melting point of AZ91D magnesium alloys ,the cutting scraps maybe be melted.
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