高压下Pd_（82）Si_（18）合金凝固过程中形成的亚稳相

FORMATION OF THE METASTABLE PHASES IN Pd-18 at.% Si ALLOY SOLIDIFIED UNDER HIGH PRESSURE

使用Ｘ射线衍射、差热分析、透射电镜及Ｘ射线能谱分析，研究了Ｐｄ＿８２Ｓｉ＿１８合金在高压下的凝固特点及所形成的相的结构和稳定性。在５．５ＧＰａ压力下以１００Ｋ／ｓ的冷却速率淬火，得到了面心立方结构钯硅固溶体（ＭＳ－Ⅰ），其点阵常数为ａ＝０．３８８３ｎｍ。与钯硅固溶体共存的还有另一未知结构亚稳相（ＭＳ－Ⅱ）。在７００Ｋ时上述亚稳相转变成平衡相Ｐｄ＋Ｐｄ＿３Ｓｉ。

The solidification characteristic of liquid Pd-18 at.%Si alloy under high pressurewas investigated by using X-ray diffraction,DTA,TEM,SEM and X-ray energy spectrum. Themixture of MS-Ⅰ and MS-Ⅱ metastable phases was obtained during the solidification of the alloyunder 5.5GPa with a cooling rate of 100K/s.The former has a fee structure with the lattice pa- rameter of a=0.388 3nm. MS-Ⅰand MS-Ⅱ will transform into the equilibrium phase Pd andPd_3Si above 700K.