Effects Of Mn Element And Heat Treatment Process On Microstructure And Properties Of ZA40

The effects of Mn element and heat treatment process on microstructure and properties of ZA40 alloy have been systematically studied in this paper, the best Mn addition and heat treatment process are obtained on the premise that hoping to get high mechanical property and the best wear resistance. Systemmatical researchs on the regularties of distribution and effect of Mn element have been studied. The effects of heat treatment on distribution of element have been discussed, advantages of solution and aging technology to solution technology are analysed. This provides a theoretical basis about heat treatment of alloys. Main conclusions obtained are shown below:(1) The microstructure of ZA40 alloy consists of dendritic a matrix,α+η eutectoid around grain boundary, ε phase and Mn-rich phase in this paper. The matrix structure of the alloy is significantly refined with little Mn addition, Mn-rich hard spots distribute in the shape of spot and grain. Mn-rich hard spots transforme into Mn-rich phase with 0.75% Mn addition. Mn-rich phase stacks and then distributes in the shape of strip and block in the grain boundary with more Mn addition. The Mn-rich phase distributes in the shape of sheet and intersects the grain with 1.5% Mn addition.(2) When the Mn content is between 0% to 1.0%, the hardness of alloy significantly increases with the increase of the Mn content. When the Mn content exceeds 1.0%, influence of Mn on the hardness is insignificant. The tensile strength of alloy increases with the increase of the Mn content. The tensile strength of alloy is the biggest with 1.25% Mn addition. When the Mn content exceeds 1.25%, The tensile strength of alloy begins to decline. The elongation of alloy decreases with the increase of the Mn content, it varies between 1.5% to 4%. The wear resistance of alloy can be significantly improved with Mn addition, the tribological properties of alloy also can be improved with Mn addition. Wear loss is the lowest with 1.0% Mn addition, friction and wear properties of the alloy perform best.(3) Solution heat treatment makes matrix structure of the alloy significantly refined. When the solution temperature is 380℃, the amount of a matrix grows, its dendritic becomes bigger and matrix structure is coarsend, ε phase and Mn-rich phase decrease with solution time increases. The hardness and tensile strength of alloy significantly increase, the elongation of alloy decreases slightly. In comparison with solution heat treatment, the hardness and tensile strength of ZA40 alloy decrease, the elongation of alloy increases after solution and aging treatment. The new phases Al8Mn5 and AlCu appear in the matrix structure.(4) In comparison with solution heat treatment, the coefficient of friction and Wear loss of ZA40 alloy are the lowest under different applied load and sliding speed after solution and aging treatment. The coefficient of friction and Wear loss have a small change with the change of applied load and sliding speed, the stability of firction and wear is good.(5) The sort of effect of each factor on the hardness of ZA40 alloy from primary to secondary is solution time, solution temperature, aging temperature and aging time, respectively. The sort of effect of each factor on the stable coefficient of friction of ZA40 alloy from primary to secondary is solution temperature, solution time, aging temperature and aging time, respectively. The sort of effect of each factor on the Wear loss of ZA40 alloy from primary to secondary is solution time, aging temperature, solution temperature and aging time, respectively. After solution treatment at 380℃ for 5 hours and aging at 100℃ for 3 hours, the hardness of ZA40 alloy is best, the stable coefficient of friction and wear loss of ZA40 alloy are lowest, the wear resistance of ZA40 alloy is best.