T6I6二次时效对A356铸造铝合金力学性能的影响

为了解决热处理后材料的强度和塑性变化规律相反的问题,在T6热处理制度的基础上开发了一种新型的T6I6二次时效制度.研究结果表明：采用T6I6热处理制度可以同时提高A356铝合金的强度、塑性、弹性模量和硬度.在相同的自然时效条件下,材料的强度、弹性模量和硬度随着第一次人工时效时间t1的增加呈现先增加后减小的趋势.延伸率既随着第一次人工时效时间的增加而增加,又随着中间自然时效时间的延长而增大.屈服强度和抗拉强度分别在t1为10min和20min时达到最大值237.38MPa和320.15MPa,增幅达到27.53%和15.24%;当t1=120min且t2=8周时,延伸率达到最大值13.63%.这主要是因为T6I6中的自然时效阶段形成大量的GP区,在随后的人工时效过程中析出大量细小高密度的β相.

Effect of T616 Secondary Ageing Processing on the Mechanical Properties of A356 Casting Aluminium Alloys

On the basis of traditional T6 heat treatment, a new T616 secondary aging process was developed in order to solve the problem of increasing the strength and ductile simultaneously. The results show that the strength, ductile, Young＇s modulus and Brinell hardness of the A356 aluminum alloy are all enhanced. As the first artificial ageing time increases, the strength, Young＇s modulus and Brinell hardness of the A356 alloy firstly increase and then decrease slightly under the same natural ageing time. However, the elongation percentage increases not only with the increase of first artificial aging time but also with the increase of natural ageing time. The yield strength and ultimate tensile strength of the materials reach the maximum values of 237. 38 MPa and 320. 15 MPa, when tl is equal to 10 min and 20 min respectively. The elongation percentage of the materials achieves 13. 63% with tl of 120 min and t2 of 8 weeks, which is associated with the formation of a great number of finer and more densely distributed β precipitates while a large number of GP zones are formed as precursors to β precipitates in the following artificial aging at elevated temperature.