Influence Of Deformation And Heat Treatment On Microstructure And Mechanical Properties Of Magnesium Alloy AZ91D

Magnesium alloy AZ91D is used widely in recent years. As the fast development of productive forces, it needs the material properties to be more advanced, especially the intensity. And one of the effective methods is to apply proper technologic process.Deformation intensifying and heat treatment strengthening are two ordinary intensifying mechanism. In this paper both of them were used. First compression and extrusion were carried out on the homogenizing annealing alloy. And then heat treatment T6 was adopted. In compression, five distortion ratio were chosen, which were 15%,30%,45%,60% and 75%, meanwhile there were five temperatures of 300℃,330℃,360℃,390℃and 420℃. In extrusion, only one distortion ratio of 75%, and the temperatures were the same to compression. Parameter of solution treatment was 410℃×3h, as for aging treatment, applied three schemes, which were 150℃×16h,170℃×16h,190℃×16h.The result indicates that:1,During the deformation dynamic recrystallization happens. Right distorting technology can receive symmetrical and fine recrystallized structure, and get better properties. In this trial, at compression of temperature 420℃and ratio 75% ,tensile intensity is 325.55Mpa, yielding intensity is 244.16Mpa.2,Extrusion is better than compression on mechanical properties. The grain size is about 17μm of extrusion, but it reaches 30μm by compression.3,Proper deforming technology prepares preferable structure for later heat treatment, and it's helpful for getting better properties, besides, the properties depend on final heat treatment T6.4,Heat treatment T6 increases the intensity and hardness, but decreases plasticity. Compression of temperature360℃and ratio 75% prepares well for T6, and gets better properties.5,After solution treatment of 410℃×3h, when aging time is 16h, 170℃～190℃is better aging temperature. 150℃aging gets lower intensity and hardness, but higher plasticity.6,On all accounts, when compressing distorting, the better process technics is: compression by 360℃temperature and 75% ratio+solution treatment of 410℃×3h+aging treatment of 190℃×16h(T6).By this process, tensile intensity reaches 350.97MPa,yielding intensity can be 270.24MPa,and hardness achieves 103HB.7,For extrusion of 75% ratio, 390℃is better distortion temperature, in which strengthening effect is better.