【摘要】 采用静态压力试验方法,在不同的温度和载荷下,对半固态ZA27合金的金属型和砂型试样的静态剪切应变特征曲线进行了测试和比较。发现在半固态温度高于430℃时,金属型试样的应力水平明显低于砂型,而且进入触变成型的时间短。比较481℃变形组织演变过程,发现起初金属型的液相转化速度慢于砂型,而保温15 min后液相较多,且枝晶明显细化。更多还原

【Abstract】 The shearing strain characteristic and microstructure of the semi-solid samples fabricated by sand mould and permanent mould were tested and compared by an improved compress testing equipment at different temperatures and loads. The results showed that the strain values of permanent mould s samples are much lower than sand mould s above 430℃ and the holding time is shorter when permanent mould’ s samples come into stage of the thixoforming. Compared with the microstructure of those samples after deformation at 481 ℃ , the rate of volume fraction of producing liquid for the samples fabricated by permanent mould is slower than that of the sand mould samples at the initial stage ,and the volume fractions of liquid increase rapidly and dendritic structures are becoming refining after 15 minutes.更多还原